• Title/Summary/Keyword: retarder

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Hygrothermal Performance Improvement Plan of Standard Model for Rural Housing and Wooden Housing (농촌주택 및 목조주택 표준모델 구조체의 습·열 환경 성능 개선 방안)

  • Yoo, Dong-Wan;Lee, Tae-Goo
    • Journal of the Korean Institute of Rural Architecture
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    • v.23 no.4
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    • pp.63-71
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    • 2021
  • The purpose of this study was to investigate whether the standard models for rural housing and wooden housing model have performance for hygrothermal and to propose a way of improvement relevant to hygrothermal performance for those models. All of the models to be analyzed were found to have some parts that were absent of stability in terms of performance for hygrothermal. In the process of analyzing the causes and proposing improvement measures, the following conclusions were derived. Fist, The exterior surface of the structure should be composed of a structure with good moisture permeability, and for the interior surface, a variable vapor retarder paper should be applied in consideration of the reverse condensation phenomenon in summer. Second, in terms of performance for hygrothermal, applications of external insulation plaster finish to the exterior wall or of ventilation method using a rafter vent on the roof should be avoided. Third, a rain screen method with a ventilation layer should be applied to the exterior wall, and a method of constructing ventilation layer separated from the insulation layer with a vapor retarder paper should be applied to the roof. Fourth, the application of insulation materials having capillary action, such as wood fiber insulation board or cellulose insulation board, contributes to more stable performance for hygrothermal.

Properties of Hot Weather Nuclear Power Plant Concrete with Water Cooling Method and Retarding used (배합수 냉각방법 및 지연제 사용에 따른 서중 원전콘크리트의 특성)

  • Lee, Seung-Han;Jung, Yong-Wook;Jang, Seok-Soo;Yeo, In-Dong;Choi, Jong-Oh
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.9
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    • pp.4602-4609
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    • 2013
  • In summer and winter, the difference between the temperature during the day and that during the night is high, which leads to various problems during concrete placement, such as cracks and defects in the concrete as well as low durability and strength. Although nuclear power plant concrete is widely used for placement in all seasons, particular attention must be paid to its quality during the summer. Therefore, we evaluated the effects of a cooling method for mixing water, which is a commonly used hot weather precooling method, and the use of a retarder, on the characteristics of Nuclear Power Plant concrete. In the cooling method for mixing water, cold water at 5 was used, with 50% of the water content consisting of ice flakes. The effects of using a retarder were evaluated by reviewing the characteristics of the cement at the unset stage and after hardening. To evaluate the characteristics of the unset cement, we measured the slump, air volumes, setting times, and pressure strengths after hardening. Furthermore, we measured the heat of hydration at different temperatures; the loss of heat was minimized using insulation. Both the slump time and the complete ageing time of the air volume were found to be 120 min at $20^{\circ}C$ and 40 min at $40^{\circ}C$. In the case when the cooling method for mixing water was used and in the case when a retarder was used, the initial and final sets by penetration resistance were delayed, and the delay decreased with increasing air temperature. For the heat of hydration, the cooling method for mixing water not only lowered the maximum temperature but also delayed its attainment. However, the use of a retarder had no effect on the maximum temperature. Moreover, in the early ages (e.g., 3 and 7 days), the pressure strength of the concrete was lower than that of plain cement. However, the strength of 28-day concrete met the standard construction specifications.

Study on Moisture Variation in Light Frame Wall with Different Wall Assemblies (II) - Moister Transfer of Light Frame Wall in Field Test - (벽체구성에 따른 목조벽체 내 수분변화에 대한 연구(II) - 외기에 노출된 목조벽체의 수분이동 -)

  • Kim, Se-Jong;Yeo, Hwan-Myeong;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.38 no.1
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    • pp.56-65
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    • 2010
  • The purpose of this study was finding out proper wall assembly to reduce moisture accumulation in light frame wall under outdoor air conditions. For the purpose, moisture transfer and accumulation in a wall were evaluated for five types of wall assembly; typical wall (T), addition of a vapor retarder (P1), addition of two vapor retarders (P2), addition of an open air gap for ventilation behind the siding (P3), and shift of vapor retarder with proposed wall 'P3' (P4). The moisture transfer and accumulation in the all walls were evaluated after applying the typical and proposed walls to the field test house. Performances of the typical and proposed walls were compared according to the season. Rank for effective wall on reducing moisture accumulation in wall was 1) shift of vapor ratarder and addition of open air gap (P4), 2) addition of vapor retarder (P1), 3) typical wall (T), 4) addition of open air gap (P3), and 5) the other (P2).

Characteristics of Chloride Diffusion and Compressive Strength in the Mortar containing C12A7 based Binder and Anhydrite (C12A7계 바인더와 무수석고를 혼입한 모르타르의 염화물 확산 및 압축강도 특성)

  • Byeong-Cheol, Lho;Yong-Sik, Yoon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.4
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    • pp.450-456
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    • 2022
  • In this study, as the preliminary research on the development of heating concrete members, compressive strength and accelerated chloride diffusion behavior in the mortar specimens containing C12A7 based binder and anhydrite was evaluated. Also, the effect of the mixing ratio of the citric acid based retarder was quantitatively evaluated by considering 4 levels of mixing cases. The compressive strength tests of the mortar specimen were performed referred to KS L ISO 679, and the accelerated chloride diffusion tests were performed according to NT BUILD 492 and ASTM C 1202. In the mortar with 0.3 % of retarder, the highest compressive strength was evaluated, which showed the strength development ratio of 127.6 % compared to the control case. It was considered that engineering performance was improved by effectively securing setting and curing time with 0.3 % of citric acid based retarder. As the result of the evaluation of the passed charge and the accelerated chloride diffusion coefficient, the evaluation results had similar behavior with the results of compressive strength. According to the previous study, the strength behavior and the chloride diffusion behavior had a linear relationship. The mixture showing the highest strength performance had the highest durability performance for chloride ingress, and the heating concrete development from this study will be performed in the future.

A Study on the Analysis of Faraday of Single Mode Optical Fiber. (단일 모드 광섬유의 Faraday Rotation 해석에 관한 연구)

  • 김기영;양길호;김은수;양인응
    • Proceedings of the Korean Institute of Communication Sciences Conference
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    • 1982.10a
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    • pp.67-70
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    • 1982
  • In this paper, the intrinsic birefringence and Faraday rotation of the single mode optical fiber have been investigated. On the analysis, the optical fiber has been modeled as a linear retarder and the intrinsic linear retardation of the fiber is approximatly found to be 2.57 deg/m from the measurement. Faraday ratation was analyzed as perturbation theory and Jones matrix.

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Design of a Reflective STN LCD On the Poincare Sphere (뽀앙까레 구면을 이용한 반사형 STN LCD의 설계)

  • 김도연;이서헌;심사용;이기동;김재창;윤태훈
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.140-141
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    • 2001
  • 반사형 STN-LCD (supertwisted nematic liquid crystal display) 는 많은 display에서 사용되고 있는 LCD mode 중의 하나이다. 그러나 현재 많이 사용되는 반사형 STN-LCD는 그림 1과 같이 한 장의 polarizer와 두장의 retardation film을 사용하는 구조이므로 각각의 component에 대한 parameter들에 의해 display의 표시 성능이 좌우된다. 먼저 Reflective STN-LCD의 보상에 필요한 parameter를 살펴보면, 그림 1과 같이 5개 ( $\alpha$, ø$_1$, ø$_2$, 각 retarder의 retardation : Δnd$_1$, Δnd$_2$)의 parameter의 결정이 필요하다. (중략)

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Design of wide-band 3/4 $\lambda$ retarder (광대역 3/4 $\lambda$ 위상지연판의 설계)

  • 박원상;전철규;강진우;김도연;최덕운;이서헌;윤태훈;김재창
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.268-269
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    • 2001
  • 반사형 액정표시장치는 저전력 휴대용 표시장치 시장이 급격하게 성장함에 따라 큰 주목을 받고 있다. 현재 반사형 액정표시장치는 밝기면에서 우수한 특성을 갖는 mixed mode TN(MTN)과 reflective TR(RTN)과 같은 단일편광자를 이용한 액정모드를 기본적으로 사용하고 있다. 그러나, 이러한 액정모드는 이중편광자를 이용한 액정모드와 비교해서 dark 상태에서 누설광이 많이 발생하여 대비비가 저하되는 단점이 있다. (중략)

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The Development of a Motor and Controller for Hybrid System (하이브리드 시스템용 모터 및 제어기 개발)

  • Ha, Hoi-Doo;Park, Jung-Woo;Kim, Jong-Moo
    • Proceedings of the KIEE Conference
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    • 1995.07a
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    • pp.231-233
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    • 1995
  • The new hybrid scheme for electric bus is presented in this paper. This system is composed of a three-phase AC induction motor, one inveter and one system controller. The motor can be acted as starter, motor itself, alternator, generator and retarder. Various functions are simulated. The design stage has been finished. And the various experimental tests are undertaken now.

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A Study on the effect of bread quality by thawing temperature of frozen dough (냉동생지의 해동온도가 품질에 미치는 영향에 관한 연구)

  • Lee, Jeong-Hoon;Kim, Hyun-Whae
    • Culinary science and hospitality research
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    • v.7 no.1
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    • pp.91-105
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    • 2001
  • Chou-cream bread and Red bean paste bread were made by sponge & dough method with the sweet dough formula. The bread quality was studied by the measurements of the temperature variation, the fermentation level of frozen dough in the special condition(dough conditioner of 5$^{\circ}C$, 10$^{\circ}C$, 15$^{\circ}C$, 20$^{\circ}C$ and 30$^{\circ}C$), the product volume and thesensory evaluation with frozen dough thawed, fermented and baked. When thawing temperature was low, the core temperature of frozen dough increased slowly and the time for thawing and fermentationwas long. In thawing and fermentation, the core temperature of Red bean paste dough increased faster than that of Chou-cream dough. When the thawing conditions of dough conditioner(retarder) were 20$^{\circ}C$ and 30$^{\circ}C$, the level of total time decrease for thawing and fermentation was 55 and 86 min in Chou-cream dough and 62 and 90 min in Red bean paste dough respectively in comparison to dough conditioner of 5$^{\circ}C$. In volume of baked products, they showed no significant difference for three weeks of storage, but slight difference for four weeks of storage. The result was that Chou-cream bread was larger than Red bean paste bread in the decrease of volume. In sensory evaluation, the bread quality became low according to the time. When stored for four weeks in the freezer, significant differences were found in Chou-cream vread, but slight difference appeared in Red bean paste bread. The research identified that Red bean paste dough was more effective in manufacturing time than that of Chou-cream dough, when thawing temperature was high, and if frozen dough was thawed in the retarder of lower than 20$^{\circ}C$, the bread quality in terms of volume and sensory evaluation had no significant difference in comparison to the none-freezing Red bean paste bread.

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Fresh and Strength Properties of Mortar Produced with Recycled Cactus Stem Powder (자원순환형 선인장 줄기 분말을 혼입한 모르타르의 굳지 않은 특성과 강도)

  • Kim, Hyo-Jung;Kwon, Ki-Seong;Lee, Ka-Youn;Lee, Geung-Joo;Kim, Yun-Yong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.3
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    • pp.365-371
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    • 2020
  • In this study, in order to recycle the stems of opuntia cactus discarded after harvesting the fruit, the cactus stems were powdered and applied as a cement-based admixture. The powder of cactus stem was mixed into the mortar, and its effect on the fresh properties and strength of the mortar was studied. The results were compared with the properties of mortars produced by mixing with a retarder sugar and a viscosity agent methyl-cellulose, which are conventional saccharide-based admixtures. Based on the test results, the cactus stem powder did not clearly show the effect as a retarding agent, whereas the flow and the air content were similar to those of the mortar mixed with methyl-cellulose. This indicated that the cactus stem powder can be used as a viscosity agent. It was found that the strength of the mortar tended to increase when the mixing ratio of the cactus stem powder was lower than 0.3%.