• Journal of the Korean Wood Science and Technology
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• 제18권1호
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• pp.39-51
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• 1990

This research was carried out to offer the basis data for development of optimum drying schedule for a domestic oak species (Quercus grosseserrata B1.) by investigating drying rate. stress, defect, and moisuture gradient with board thicknesses and drying schedules (code number T4-C2 and T3-B1). The results were obtained as follows: 1. Average drying rate and total drying time from 52.2% to 5.8% were 0.105%/hr and 486 hours for drying schedule T4-C2 and those from 62.1% to 8.3% were 0.070%/hr. and 811 hours for drying schedule T3-B1. 2. Drying rates for 28mm- and 31mm-thick boards showed similar tendency, but were significantly different from 25mm- thick board in drying schedule T4-C2 and those for 22mm-, 25mm- 28mm- and 31mm-thick boards showed similar tendency but were significantly different from 19mm- thick boards in drying schedule T3-B1. 3. The moisture gradients for drying schedule T4-C2 were steeper than those for drying schedule T3-B1 during drying period. and especially in early drying stage slow slope of moisture gradients of drying schedule T3-B1 was effective in preventing serious problem of surface checks. 4. Drying stresses were lower in drying schedule T3-B1 than in drying schedule T4-C2 during drying period. 5. Drying schedule T4-C2 was appropriate for 25mm-thick board but not for 28mm- and 31mm-thick board because of strong drying condition. Drying schedule T3-B1 was appropriate for 28mm- and 31 mm-thick board but not for 19mm-, 22mm-, and 25mm-thick board because of weak drying condition.

• Journal of the Korean Wood Science and Technology
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• 제14권4호
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• pp.29-39
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• 1986

To investigate the effect of presurfacing, both 25mm rough and pre surfaced oak boards (Quercus grosseserrata BI.) were dried in the same dry kiln condition. Drying curves, drying strains and drying defects of rough and presurfaced boards were compared. The results obatained are as follows. 1. Average drying rate of rough and presurfaced boards from green to 10% M.C. was 0.276%/hr. and 0.284%/hr., respectively. 2. At the early stage of drying, in case of rough boards, maximum tensile strain of outer slices was $-24.2{\times}10^{-4}$mm/mm and maximum compressive strain of innermost slices was $13.0{\times}10^{-4}$mm/mm, and in case of pre surfaced boards, maximum tensile strain of outer slices was $-14.5{\times}10^{-4}$mm/mm and maximum compressive strain of innermost slices was $28.1{\times}10^{-4}$mm/mm. And in both cases, stress reversal occurred at about 40% M.C.. 3. Maximum surface checking appeared at about 40% M.C.. Of the 10 rough boards. 6 hoards contained surface checks, but presurfaced boards did not contained surface checks after drying. And the results of end checking were similar to those of surface checking. But, honeycomb was not found in both cases. 4. Board shrinkage. warp and casehardening of presurfaced boards were similar to those of rough boards. But, collapse of prsurfaced boards was less than that of rough boards.

• Journal of the Korean Wood Science and Technology
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• 제9권4호
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• pp.1-21
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• 1981

미송(美松) 및 포푸라 내수합판(耐水合板)을 내장용내화제(內裝用耐火劑)로 가압처리한 다음 저온(低溫), 중온(中溫) 및 고온건조상태(高溫乾燥狀態)에서 재건조(再乾燥)를 실시(實施)하였다. 붕사(硼砂)-붕산(硼酸), 크롬화(化) 염화아연, 미나리스, 파이레소오트 및 일종(一種)의 상업용(商業用) 내화제(耐火劑)로 내화처리(耐火處理)를 실시(實施)하였다. 건조방법(乾燥方法)은 키른건조(乾燥)와 열판건조(熱板乾燥)를 적용(適用)하였으며 건조속도(乾燥速度)와 건조결함(乾燥缺陷)에 관하여 검토(檢討)하였다. 붕사(硼砂)-붕산(硼酸)은 수분처리합판(水分處理合板)과 유사(類似)한 건조속도(乾燥速度)를 나타내었으나 기타(其他)의 내화제(耐火劑)는 일층(一層) 늦은 건조속도(乾燥速度)를 나타내었고 더 많은 건조결함(乾燥缺陷)을 일으키는 경향(傾向)이 있었다. 특(特)히 크롬화(化) 염화아연은 가장 건조속도(乾燥速度)가 느렸으며 가장 많은 건조결함(乾燥缺陷)을 일으키는 경향(傾向)이 있었다. 열판건조(熱板乾燥)는 키른 건조(乾燥)와 비교(比較)하여 같은 온도수준(溫度水準)에서 삼배(三倍)나 더 빨리 건조(乾燥)하였으나 열판압력을 50 $1b/in^2$(3.52$kg/cm^2$)를 적용(適用)하였기 때문에 두께 수축율(收縮率)은 이배(二倍)를 나타내었다.

• Journal of the Korean Wood Science and Technology
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• 제22권2호
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• pp.61-70
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• 1994

This study was executed to find the applicability of press drying of tree disk by investigating the shrinkage and drying defect and to form appropriate model by comparing the actual moisture content(MC) and internal temperature in respect of drying time with calculated values based computer simulation to which was applied finite difference method. In press drying disk, heating period, constant drying rate period maintained plateau temperature at 100$^{\circ}C$ and falling drying rate period were significantly distinguished. Actual MC and internal temperature were analogous to those calculated at comparing points. Heat transfer model formed by Fourier's law using specific heat of moist wood and conduction coefficient considering fractional volume of each element of wood cell wall, bound water, free water and air showed applicability as basic data to developing heat expansion, shrinkage and drying stress during press drying. Also mass transfer model formed by Fick's diffusion law using water vapor diffusion coefficient showed applicability. Longitudinal shrinkage was developed by pressure of hot press and tangential shrinkage was restrained by hygrothermal recovery. The heart check, surface check and ring failure were occurred differently in species, but V-shaped crack didn't develop.

• Journal of the Korean Wood Science and Technology
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• 제52권1호
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• pp.1-12
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• 2024

Betung bamboo (Dendrocalamus asper) is used as a building and handicraft material in Indonesia; however, bamboo needs to be dried to increase its stability. This study aimed to evaluate the efficiency of drying bamboo using solar energy and different drying oven designs. The betung bamboo pieces were dried using a direct solar dryer (direct drying) and an indirect solar dryer (indirect drying) and then the decrease in levels that occurred based on the relative humidity (RH) and temperature values achieved in the two dryers were compared. The highest average temperature in the direct indirect drying oven compartment was 60.1 ± 13.1℃ with 19.9 ± 16.4% RH and 60.2 ± 11.9℃ with 19.5 ± 15.5% RH, respectively. The drying defect in indirect drying was lower than that in direct drying, and indirect drying had a 61.7% greater average water loss than direct drying with significant difference (95%, analysis of variance) based on water loss/compartment volume parameters. Thus, the solar drying oven can be used to air-dry bamboo (14%) for 7 d from an initial moisture content of 70%-80% in bamboo strips. The results of this research can be used for small-scale bamboo processing industries that have limited use of electrical energy with quite good results.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.88-89
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• 2017

Curling is caused by the shrinkage difference between surface and bottom side of concrete, and the cracks can be occurred by vehicle load after curling. It is important to investigate and predict the curling behavior to minimize the quality defect of concrete due to the curling. Therefore, the experimental and analytical investigation was carried out.

• 한국세라믹학회지
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• 제16권4호
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• pp.213-224
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• 1979

The present work was undertaken: (1) to determine if CaO-partially stabilized $ZrO_2$ prepared by Hot Petroleum Drying Method would show better ionic conductor as an oxygen sensor in molten metals than that prepared by Oxide Wet Mixing Method and than CaO-fully stabilized $ZrO_2$, and (2) to understand the nature of conduction mechanism of CaO-partially stabilized $ZrO_2$ by a comparison of measured electrical conductivity data with theory on defect structure of pure monoclinic $ZrO_2$ and fully stabilized cubic $ZrO_2$. The DC electrical conductivity was measured by 3-probe technique and the AC electrical conductivity by 2-probe technique as a function of temperature in the range 973-1373 K and oxygen partial pressure in the range 10-1-10-25Mpa. The results of the experiments were as follows: 1. CaO-partially stabilized $ZrO_2$ prepared by Hot petroleum Drying Method showed at T=1094-1285 K and $Po_2$=10-7-10-25 MPa a nearly ionic conduction with 4 times higher conductivity than that prepared by Oxide Wet Mixing Method. 2. High-oxygen pressure conductivity tends toward a Po_2^{+1/5}-Po_2^{+1/6}$dependence. An analysis of possible defect structures suggests that CaO-partially stabilized $ZrO_2$ has an anti-Frenkel defect in which singly or doubly ionized oxygen interstitials and defect electrons predominate at T=1094-1285 K and $Po_2$=10-1-10-7MPa. 3. The activation energy for pure electron hole-conduction and ionic conduction of CaO-partially stabilized $ZrO_2$ was found to be 130 KJ/mol at T=973-1373 K, $Po_2$=2, 127 10-2 MPa(air) and 153KJ/mol at T=1094-1285 K respectively.

• Journal of the Korean Wood Science and Technology
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• 제44권5호
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• pp.726-735
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• 2016

본 연구는 두께 15 cm와 18 cm 크기 Douglas-fir, Hemlock, Radiata pine 정각재의 고온건조 특성을 평가하기 위해 수행되었다. 수종에 따른 최종함수율은 시험재의 두께에 관계없이 Radiata pine, Douglas-fir, Hemlock 순으로 Radiata pine에서 가장 낮았으며, 배할처리를 하였을 때 무처리재보다 낮은 함수율을 나타내었다. Radiata pine과 Hemlock의 경우 배할처리를 하였을 때 함수율과 뒤틀림 발생을 감소시키는 효과가 있는 것으로 나타났다. Douglas-fir는 수를 포함하지 않는 정목형태로 가공될 때 건조결함의 감소가 가능하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.61-64
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• 2006

Comparing with traditional high performance concrete, ultra high performance concrete (UHPC) has the property of high-tenacity. However, drying shrinkage and autogenous shrinkage can be arisen as the major defect to UHPC. In this study, therefore, it was tested to reduce drying shrinkage and autogeneous shrinkage by adding expanding admixture (EA) and shrinkage reducing agent (SRA). As a result, for a case drying shrinkage, the shrinkage was decreased by 94% when EA was exchanged, and it was decreased by 64% when SRA was added. For the case of autogenous shrinkage, the mortar was expanded at early age and the shrinkage was decreased by 87% when EA was exchanged, and the shrinkage was decreased by 70% when SRA was added.

• 펄프종이기술
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• 제41권1호
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• pp.52-60
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• 2009

A printing defect known as fluting (or waviness) of the web printed by heatset web offset printing process is one of the chronically serious problems deteriorating print quality. In this paper, fluting occurrence on uncoated papers was explored in terms of many printing conditions including drying temperature, fountain solution amount, ink supply, and press configurations. For this purpose, fluting on prints from real press runs was appraised in a quantitative manner. As results, ink supply was a distinctive factor for fluting such that the lower ink amount, the milder fluting. However increase in fountain solution seemed to make fluting severer while the effect of drying temperature was inconsistent for each paper. This result might indicate variable drying requirements for each paper. Thereby it was suggested that the optimum drying conditions related to the printabilities of each paper need to be established to minimize fluting potential. A press with short dryer and drastic cooling unit produced higher fluting. Suggestions for future work were given along with interpretation for the results.