• 제목/요약/키워드: expansion and weight

검색결과 390건 처리시간 0.033초

Expansion ratio estimation of expandable foam grout using unit weight

  • WooJin Han;Jong-Sub Lee;Thomas H.-K. Kang;Jongchan Kim
    • Computers and Concrete
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    • 제33권4호
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    • pp.471-479
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    • 2024
  • In urban areas, appropriate backfilling design is necessary to prevent surface subsidence and subsurface cavities after excavation. Expandable foam grout (EFG), a mixture of cement, water, and an admixture, can be used for cavity filling because of its high flowability and volume expansion. EFG volume expansion induces a porous structure that can be quantified by the entrapped air content. This study observed the unit weight variations in the EFG before and after expansion depending on the various admixture-cement and water-cement ratios. Subsequently, the air content before and after expansion and the gravimetric expansion ratios were estimated from the measured unit weights. The air content before expansion linearly increased with an increase in the admixture-cement ratio, resulting in a decrease in the unit weight. The air content after the expansion and the expansion ratio increased nonlinearly, and the curves stabilized at a relatively high admixture-cement ratio. In particular, a reduced water-cement ratio limits the air content generation and expansion ratio, primarily because of the short setting time, even at a high admixture-cement ratio. Based on the results, the relationship between the maximum expansion ratio of EFG and the mixture ingredients (water-cement and admixture-cement ratios) was introduced.

사전 의미 기반의 질의확장 검색에서 추가 용어 가중치 최적화 (Optimizing the Additional Term Weight Ratio in Query Expansion Search based on Dictionary Definition)

  • 최영란;전유정;박순철
    • 한국산업정보학회논문지
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    • 제8권2호
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    • pp.45-53
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    • 2003
  • 본 연구가 갖는 중요성은 두 가지로 요약된다. 첫째는 질의 확장 검색 방법으로 사전에서 나타나는 용어를 질의의 추가용어로 채택하는 것이다. 이 방법은 기존의 피드백 확정 방법이 갖는 2차적 검색 과정을 줄인다. 둘째는 초기 질의어와 추가용어 사이에 가중치를 달리 적용하여 재현율과 정확률을 동시에 높일 수 있는 최적의 모델을 제시하였다. 이렇게 함으로써 정보 검색의 성능을 크게 향상시킬 수 있는 방법을 제시하고 있다.

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Analysis of Excluded Volume Effect in Theta Solvent Systems of Polymethyl Methacrylate and Polystyrene by Means of a Modified Scaled Temperature Parameter

  • 김명주;박일현
    • Bulletin of the Korean Chemical Society
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    • 제22권11호
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    • pp.1255-1260
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    • 2001
  • The expansion of two different kinds of hydrodynamic size of polymethyl methacrylate (PMMA Mw: 1.56- 2.04 ${\times}$ 106 g/mol) has been measured by dynamic light scattering and viscometry above the Flory $\theta$ temperature of the variou s solvents such as n-butyl chloride, 3-heptanone, and 4-heptanone. The expansion of PMMA chains was analyzed in terms of universal temperature parameters and also compared with previous results of polystyrene (PS) system. First it was found that simple $\tau/{\tau}c$ parameter no longer had its universality for the expansion behavior of hydrodynamic size in the chemically different linear polymer chains. However after modifying ${\tau}/{\tau}c$ parameter into $(Mw/Ro2)3}2(\tau/\tauc)$, we observed a much better universality for both PMMA and PS systems. Here Mw, Ro, $\tau[=(T-{\theta}$)/${\theta}$]$, and ${\tau}c[=({\theta}-Tc)/Tc]$ are defined as the weight average molecular weight, the unperturbed end-to-end distance, the reduced temperature and the reduced critical temperature, respectively.

팽창재를 포함한 시멘트 모르터의 팽창 요인 (Expansion Factors of Cement Mortar Containing Expanding Admixture)

  • 황인동;염희남;정윤중
    • 한국세라믹학회지
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    • 제37권6호
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    • pp.576-582
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    • 2000
  • Two type of expanding cement generally referred to as CSA with Hauyne(3CaO 3Al2O3 CaSO4) and Quick lime(CaO). Hauyne is formed to ettringite when there are presented with CaO and CaSO4, and CaO reacts wtih water to form Ca(OH)2. REcently, the mechanism of compensation and expand mortar or concrete tend to same and it has been used improving on its shrink property. The volume of cement paste varies with its water content shrink with drying and re-wetting. Concrete and mortar works are required shrinking compensation and expansion properties to reduce of potential crack. The use of expansion cement may improve on its shrinking volume changes. CSA dosages for shrinking compensation limited by cement weight, but obtained difference expansion rate with varied W/C or inorganic admixture. This paper studies expansion rate according to expansion cement dosages, water and inorganic admixtures as Silica fume. Therefor, the expansion factor has to considered before the application.

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하중조건에 따른 경량골재 콘크리트의 열팽창변형 특성 (Properties of Thermal Expansion Strain of Light Weight Aggregate Concrete with Loading Conditions)

  • 윤민호;김규용;이태규;남정수;신경수;이상수
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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    • pp.255-256
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    • 2012
  • In this study, strain properties of high strength concrete using light weight aggregate which is widely used in recent years are evaluated. For these purpose, thermal strain, transient creep were measured in prestressed condition as 0, 20, 40% of specimen strength at target temperature with 60MPa specimens which was using normal and light weight aggregate. As a result, light weight aggregate is more advantageous for the control of strain than normal aggregate because of its low thermal expansion.

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반응표면법을 사용한 고 중량물 낙하시험기의 충격에너지 흡수량 예측 연구 (Prediction of Impact Energy Absorption in a High Weight Drop Tester by Response Surface Methodology)

  • 강훈;장진석;김다혜;강지헌;유완석;이재욱
    • 한국기계가공학회지
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    • 제15권3호
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    • pp.44-51
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    • 2016
  • This paper presents the characteristics of the energy absorption in an expansion tube type impact absorber that is applied to a high weight drop tester and the use of a response surface methodology to predict the impact energy absorption. In order to identify the characteristics of the energy absorption, a set of finite element analysis was conducted with Abaqus Explicit. Moreover, the ISCD-II sampling method and a first order polynomial were used to build a response surface. As a result, we demonstrated that the impact energy could be controlled by four main design variables, namely an expansion pipe's thickness, inner radius, pressing die's expansion angle and expansion ratio. Additionally, we observed the relationship between the four main design variables and the impact energy absorbing time, displacement, and maximum impact force.

Biomass Expansion Factors for Pinus koraiensis Forests in Korea

  • Li, Xiaodong;Yi, Myong-Jong;Jeong, Mi-Jeong;Son, Yo-Whan;Park, Pil-Sun;Lee, Kyeong-Hak;Son, Yeong-Mo;Kim, Rae-Hyun
    • 한국산림과학회지
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    • 제99권5호
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    • pp.693-697
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    • 2010
  • Biomass expansion factors that convert the timber volume (or dry weight) to biomass are used to estimate the forest biomass and account for the carbon budget on a national and regional scale. This study estimated the biomass conversion and expansion factors (BCEF), root to shoot ratio (R), biomass expansion factors (BEF) and ecosystem biomass expansion factor (EBEF) of Korean pine (Pinus koraiensis) forests based on direct field surveys and publications in Korea. The mean BCEF, BEF, and R was 0.6438 Mg $m^{-3}$ (n = 7, SD = 0.1286), 1.6380 (n = 27, SD = 0.1830), and 0.2653 (n = 14, SD = 0.0698), respectively. The mean EBEF, which is a simple method for estimating the understory biomass in Korean pine forest ecosystems, was 1.0218 (n = 6, SD = 0.0090). The values of the biomass expansion factors in this study estimated the Korean pine forest biomass with more precision than the default values given by the IPCC (2003, 2006).

고장력강의 구멍 확장 실험을 이용한 자동차부품 설계연구 (A Study of Automobile Product Design using Hole Expansion Testing of High Strength Steels)

  • 박병철;배경운;구선모;장승현;홍성훈;김영석
    • 소성∙가공
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    • 제19권6호
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    • pp.337-343
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    • 2010
  • Current need of weight reduction in automotive part increases the application for high strength steel (HSS). The various types of high strength steels have been used to produce chassis part, control arms and trailing arms for weight reduction and increasing of fatigue durability such as dual phase steel (DP) and ferrite bainite steel (FB). But, DP and FB steels have proven to show inferiority in durability as well as press formability. Edge cracking occurred often in flange forming and hole expansion processes is the major failure encountered. This paper discussed the behavior of edge stretchability of high strength steel of DP and FB steels. Experimental works have been conducted to study the effect of punch clearance and burr direction on hole expansion ratio (HER). Also finite element simulation (FEM) has been preformed to clarify the mechanism of flange crack and support the experimental results on HER of DP and FB steels. It was simulated the whole process of blanking process following by hole expansion process and ductile fracture criterion named the modified Cockcroft-Latham model which was used to capture the fracture initiation. From the hole expansion tests and FEM simulation studies it was concluded that ferrite bainite steel showed better stretch-flangeability than dual phase steel. It was attributed to the lower work hardening rate of ferrite bainite steel than dual phase steel at the sheared edge.

서로 다른 열환경에 노출된 고분자 소재의 열팽창계수 측정에 관한 연구 (A study on the Measurement of the Coefficient of Thermal Expansion of Polymer materials Exposed to Different Thermal Environments)

  • 김동주;박설현
    • 한국기계가공학회지
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    • 제20권4호
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    • pp.80-86
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    • 2021
  • Plastics are widely used in mechanical and other fields due to their light weight, design flexibility, and molding processability. In processing plastics, defective products are mixed and reprocessed to improve production efficiency and reduce costs. In this study, an experiment was conducted to confirm the coefficient of thermal expansion of HDPE during this reprocessing. The coefficient of thermal expansion was measured at different measurement directions and heating rates. As a result, we observed that the coefficient of thermal expansion in the direction perpendicular to the injection direction is greater than that in the horizontal direction.

대도시권 화물 기종점 통행량 전수화에 관한 연구 - 수도권 지역을 중심으로 - (A Study on the Weighting and Expansion of Sample O-D Freight Data, Focusing on the Seoul Metropolitan Area)

  • 김강수;조혜진
    • 대한토목학회논문집
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    • 제26권5D호
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    • pp.755-761
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    • 2006
  • 대도시 화물 기 종점 통행량(O/D) 자료는 각종 교통계획 및 물류계획의 효과적인 수립, 시행, 평가를 위해 필수적으로 요구되는 기초자료이나 우리나라의 경우 이에 대한 조사 및 연구가 매우 미약한 실정이다. 특히, 조사자료를 이용하여 기종점 화물통행을 구축하는 전수화 방법에 대해서는 외국의 경우나 국내의 경우 연구가 모두 매우 미흡한 실정이다 본 논문의 목적은 우리나라의 수도권의 화물통행실태 조사자료를 이용하여 화물기종점 통행량을 구축하기 위한 전수화 방법을 소개하는데 있다. 즉, 대도시권 화물통행 조사를 이용하여 기종점 통행량 전수화 과정 및 방법을 설명하고 구축된 대도시권 화물 기종점 통행량 통행 특성을 분석하였다. 특히, 본 연구에서는 화물자동차와 품목별 기종점 물동량을 개별적으로 분리한 전수화한 방법에서 벗어나 이를 동시에 고려하는 전수화 방법론을 제시하였다. 본 연구를 통해 그동안 공개되지 않았던 화물통행 전수화 상세과정을 통해 좀 더 신뢰성 있고 정확한 전수화 연구에 대한 초석이 되기를 기대한다.