• Journal of the Korean Wood Science and Technology
• /
• 제21권2호
• /
• pp.39-48
• /
• 1993

End-matched disks of 7.7cm thickness were part-time dried in vacuum press dryer to investigate the drying characteristics by using drying schedules and end treatments. The ginkgo disks could be dried faster with severer end checks and ring failures by C schedule than by S schedule. There were no significant differences in drying rates and amounts of end checks, ring failures and V-shaped checks occurred between ginkgo disks end-taped with Korean traditional paper (KTP) and those untreated. The drying time of walnut disks was slightly reduced by end-taping with KTP. And the length of end checks and V-shaped checks and the frequency of defected disk were decreased more effectively than those untreated. The tangential strains and tangential drying stresses near bark sides of ginkgo and walnut disk untreated were developed in the early stage of drying and incresed slightly curvi-linearly above fiber saturation point (fsp) and more curvi-linearly below fsp. The influence of end-taping with KTP on the drying rate for impermeable walnut disk was stronger than that for permeable ginkgo disk.

• Journal of the Korean Wood Science and Technology
• /
• 제26권4호
• /
• pp.34-42
• /
• 1998

Three hardwood (ash, alder and black locust) and three softwood (Japanese red pine, radiata pine and Western hemlock) specimens were dried in microwave(MlW) oven and their drying rates were obtained. Their specific permeabilities were also measured by using a modified liquid permeability measuring device. The correlation between the M/W drying rates and permeabilities of six species were statistically analyzed. It was revealed that within a species there is a logarithmic relationship between the M/W drying rates and average moisture contents and that among species there is a linear relationship between the M/W maximum drying rates and the average specific permeabilities. A exception was Western hemlock, which was of low permeability and of high drying rate. A Me-time equation, which showed a good agreement with the actual data, was derived. Thus using this equation the moisture contents of wood and the drying end points of M/W drying could be predicted. Infrared images of the thermal distribution in wood were illustrated.

• Journal of the Korean Wood Science and Technology
• /
• 제25권4호
• /
• pp.99-107
• /
• 1997

This study was executed to test the possibility of replacement for domestic Japanese larch(Larix leptolepis) for hardwoods and to acquire the information about the effects of drying temperature on internal temperature, moisture content and drying defects. In high-temperature drying, internal temperature increased rapidly to boiling point, immediately after that point the internal temperature rising rate was reduced. In the case of drying at temperature of $125^{\circ}C$, internal temperature could reach at boiling point in a very short time. Moisture content in high-temperature drying showed constant drying rate period and first period of falling rate drying together in 4 hours since experiment begun. There was no strong correlation between initial moisture content and final moisture content. Average drying rate at $115^{\circ}C$, $120^{\circ}C$ and $125^{\circ}C$ was 1.42%/hr, 1.88%/hr and 2.02%/hr, respectively; the case of drying temperature of $125^{\circ}C$ showed most rapid drying rate. Drying rate of $125^{\circ}C$ was so rapid that it showed more severe shrinkage, bow, collapse, end check, and internal check development than in other drying conditions. The result of this study showed the strong possibility of high-temperature drying for Japanese larch, and to dry Japanese larch optimally, dry bulb temperature should not exceed $120^{\circ}C$.

• 한국축산식품학회지
• /
• 제18권2호
• /
• pp.164-175
• /
• 1998

The objective of this study was to investigate the effects of freezing rate on ice crystal size and freeze-drying rate. Our experiments were carried out with self-manufactured freeze-dryer. Gelatin gels (2% w / w, 80$\times$20mm) were frozen unidirectionally (Neumann's model) from the bottom at -45, -30, -20, and -15$^{\circ}C$ and followed with freeze-drying. Under the upper conditions we measured freezing rate and the change of temperature and pressure during freeze drying. Freeze-dried gelatins were cut horizontally into 5 mm thickness from the bottom and measured their pore sizes. Also freeze-drying rate(primary drying) is estimated by measuring the temperature of sample and pressure of vacuum chamber. During freeze-drying, profiles of pressure and temperature were shown constant tendency regardless of freezing temperature and we could expect the end-point of freeze drying by considering pressure and temperature together. In temperature profiles, the point which temperature increased significantly was observed during freeze-drying. There is no relationship between freeze temperature and drying rate of primary drying in our model system. As freezing temperature increased, ice crystal size(X*) which correspond to 63.2% of cumulative frequency was increased and at the same freezing temperature ice crystal size(X*) was decreased with distance from the bottom of the sample. Freezing conditions have a strong influence on the quality of the final freeze-dried products in freeze-drying system.

• Journal of the Korean Wood Science and Technology
• /
• 제2권2호
• /
• pp.5-7
• /
• 1974

본 논문은 필자가 미국 미쉬간대학에 유학중 실시된 연구로서 동대학 목재가공학과에 설치된 소형 목재인공건조장치를 사용하여 일정한 건조조건(건구 온도 $150^{\circ}F{\risingdotseq}65.5^{\circ}C$, 습구온도 $1250^{\circ}F{\risingdotseq}51.7^{\circ}C$, 관계습도 48%, 평형함수율 6.9%)하에 공기 순환속도를 매분당 250ft., 400ft, 및 650ft.로 변경할 때 얻어지는 건조속도를 측정하고, 시간당 건조율을 산출하여 비교 검토한 것이다. 본 실험에 사용한 수종은 북미산소나무 Northern white pine (Pinus strobus L.)로서 시편의 크기는 길이 60cm, 넓이 12.5mm(5in.), 두께 18.7mm(3/4in.)이며 공시목의 표면은 증발조건을 균일히 하기 위하여 포삭하였으며, 마구리(end grain)에는 end coating 하였다. 또한 공기순환속도 측정은 상기대학에 비치된 velometer를 사용하였다. 1. 목재의 섬유포화점(함수율 30%) 이상에 있어서 공시목의 건조율은 건조실내 공기순환속도의 증가에 따라서 증가된다. 즉 공시목의 건조율 증감은 공기 순환속도에 대략 비례한다. 그러나 섬유포화점 이하에 있어서는 공기순환속도의 증강은 건조율 증감에 거의 영향을 이치지 아니한다(그림 1, 2 참조). 2. 실험한 건조조건하에 있어서는 공시목의 초기 함수율이 높을수록 높은 건조율을 얻을 수 있다. 즉 공시목의 초기 함수율(MC30% 이상)이 동일하지 아니한 경우에도 공기순환속도를 증가하면 건조 최종기에 있어서 비교적 빨리 대체로 같은 함수율의 공시목을 얻을 수 있다(실험한 초기 함수율, 건조조건 및 공기순환 속도등은 심한 건조 결함을 유발하지 아니하였음). 3. 본연구 결과에 의하면 공시목의 건조율은 섬유포화점(대략 MC30%)에 있어서 현저한 변화를 나타내고 있다. 즉 공시목의 함수율에 대한 건조율 곡선은 그림 3으로 표시된 바와 같이 섬유포화점 이상에 있어서는 건조율 곡선은 X축(MC)에 대하여 요(凹)형(concave)을 나타냈는데, 섬유포화점 이하의 함수율 범위 30%에서 20%에 있어서는 건조율 곡선은 X축에 대하여 철(凸)형(convex)을 나타냈으며 함수율 20% 이하에 있어서는 재차 심한 요(凹)형을 나타내고 있음을 알 수 있다. 이와감은 결과를 요약표시한 원문 그림4에 있어서, 건조율 곡선의 반곡점은 대략 섬유포화점인 MC 30%와 MC 20%에 위치하고 있음을 알 수 있다. 이와같이 섬유 포화점으로 알려져 있는 MC 30%와 20%에 있어서 건조율이 급변하는 반곡점 즉 한계점을 표시하는 것은 다음과 같은 야유에 의한 것으로 고려된다. 즉 세포막에 흡수된 결합수의 증발은 세포강, 세포간격 및 기타의 미세한 공간에 존재하는 자유수의 증발보다 훨씬 곤란하므로, 함수율 30%에서 20%의 범위에 있어서는 철(凸)형을 나타낸다. 즉 함수율 30%에서 20% 의 범위에 있에서 세포막의 모세관 응축수(capillary-condensed water)의 증발은 대략 동일한 감소율을 나타내나, 공시목의 함수율이 20%에 접근됨에 따라서 한층 강한 결합상태하에 있는 수분(표면 결합수 및 그 부근에 있는 수분)이 증발하게 되나, 그와 같은 수분의 증발은 한층 곤란하므로 함수율 20% 이하에 있어서 건조율곡선은 재차 요(凹)형을 표시하는 것으로 사료된다. 이상의 관계를 요약 표시한 원문 그림 4에 있어서, 반곡점을 가지지 아니한 점선 곡선 AC 와 2개의 반곡점을 가지는 실선곡선 BD를 비교하면, BD곡선은 AC곡선보다 함수율범위 30%에서 20%에 있어서 그 건조율은 현저히 감소되고 또한 D점을 반곡점으로 해서 그 건조율은 가일층 감소되고 있음을 알 수 있다. 이상을 요약하면 생재에서 함수율 30%(섬유포화점)까지는 큰 건조율을 표시하니 함수율 범위 30%에서 20%에 있어서는 그 건조율은 점감되고 함수율 20% 이하에 있어서는 그 건조율은 현저히 감소됨을 표시한다.

• 설비공학논문집
• /
• 제27권12호
• /
• pp.645-651
• /
• 2015

This paper presents an experimental study on the freeze drying process for poly ${\gamma}$ glutamic acid. The physical properties of poly ${\gamma}$ glutamic acid are measured during the freeze-drying process. The moisture contents of poly ${\gamma}$ glutamic acid according to the glass transient temperature are obtained by DSC (Differential Scanning Calorimetry) analysis. The end point of primary drying for the poly ${\gamma}$ glutamic acid with a thickness of 3 mm is obtained by measuring the thickness of the dried layer, the amount of moisture evaporation, the moisture content, and the pressure in the drying vacuum chamber during the freeze-drying process. By considering the variation in the glass transient temperature with respect to the moisture content of the material, a control schedule for the heating plate temperature is suggested during the secondary drying process.

• 한국가구학회지
• /
• 제21권6호
• /
• pp.499-504
• /
• 2010

한국의 전통가옥인 한옥은 대각재와 원형목으로 만든다. 이들은 열기건조하면 심각한 결함이 발생하기 때문에 보통 수개월에서 1년까지 천연건조하는데 그래도 사용중 결함이 생긴다. 열처리기술을 이용하여 이들을 $170^{\circ}C$이상에서 건조하면서 건조결함을 조사하였다. 온도곡선은 모두 하나 또는 두개의 변곡점을 나타냈다. 표면에서 37.5mm 깊이지점이 $100^{\circ}C$에 도달하는데 걸리는 시간은 열처리온도 $170^{\circ}C$ 과 $190^{\circ}C$가 두 배의 차이를 나타냈다. 열처리 후에 $148mm{\Phi}$ 원형목에 내부할렬이 많이 발생한 것이 발견되었으나, 이에 빈해 표면할렬은 거의 닫혀 있었다. 이러한 표면할렬의 변화를 $300{\times}300mm$ 대각재의 사진을 통해 관찰하였다. 중공재와 무중공재의 건조시간을 비교하였더니 두 배의 차이를 나타냈다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2017년도 추계 학술논문 발표대회
• /
• pp.139-140
• /
• 2017

This technology employs a method of forming a single-ply PLUS waterproofing sheet layer comprised of applying a single-ply synthetic polymer layer on a vibrating structure (steel frame, RC) or an inclined surface by using a T joint lap-filling coil and an embedded metal coated sheet. The T - joint reinforcing lap-filling coil was used to block the ingress channel of the rainwater by applying the material in the vulnerable area where the three sides of the waterproof sheet overlapped. Conventional waterproofing techniques have a problem in that the waterproof sheet is pierced because the end portion of the waterproof sheet applied to the vertical portion is fixed by a nail, and the sealant applied to the end portion of the sheet cannot easily secure long-term waterproof durability due to the influence of the external environment. Therefore, the developed technology secured the waterproof durability against the vertical part by using the embedded metal sheet. In addition, automatic hot-air fusing is used to improve the quality of waterproof construction and point fixation method using fixed hardware. This is a technology that is not significantly restricted in the high degradation level regions of domestic waterproof construction environments in Korea such as low-temperature environment, wet floor.

• Applied Microscopy
• /
• 제12권2호
• /
• pp.11-22
• /
• 1982

Mycoplasma pneumoniae의 형태적(形態的) 분화과정(分化過程)을 광학(光學) 및 Carbon replication과 critical point drying 전자현미경 기술(技術)을 이용하여 관찰(觀察)하였다. 단세포(單細胞)로 부터 시작하는 전분화(全分化) 과정에서 이 세균(細菌)은 구형(球形)과 방추형(紡錘形)의 세포형태(細胞形態)로 특유(特有)한 분화(分化)를 하며 이 과정은 배양액(培養液)의 pH변화(變化)와 일치(一致)하여 진행(進行)되었다. 본(本) 연구(硏究) 결과(結果)로 부터 M. pneumoniae의 단세포(單細胞)에서 시작되는 새로운 생활회로(生活回路)를 다음과 같이 제기(提起)하였다. 단세포기(單細胞期)를 지나 제1분열기(第1分裂期)에는 구형세포(球形細胞)가 주로 대수증식기(對數增殖期)의 초기에 이분법(二分法)에 의하여 분열하고 그 후에 방추형 세포(細胞)가 분절법(分節法)에 의하여 분열하는 제2분열기(第2分裂期)가 뒤 따른다. 방추형(紡錘形)의 긴 세포(細胞)는 극성(極性)을 갖고 세포 한쪽 끝으로 부터 성장(成長)하여 수 많은 방추형세포에 의한 망상기(網狀期)가 된다. 이와 같은 생장회로(生長回路)는 좋은 생장(生長) 환경에서는 반복되지만 pH가 6.8 이하로 떨어지거나 다른 조건(條件)들이 나빠지면 세포표면(細胞表面)이 조악(粗惡)한 구형(球形)으로 변형(變形)되어 사멸기(死滅期)에 들어가 모든 세포(細胞)는 생명력(生命力)을 상실하게 된다.

• Journal of the Korean Wood Science and Technology
• /
• 제18권4호
• /
• pp.26-40
• /
• 1990

The plane trees(Platanus occidentalis L.) have been grown in Korea very widely as ornamental garden or street trees but they have not been used as manufacturing materials The proportion of imported wood has been now over 85% of raw materials needed in the wood industry, and therefore, many of studies on the substitution of domestic wood for imported wood and on the increasing the utilization rate of domestic species have been attempted and considered as very important projects to solve. From a this point of view, this study was carried out to investigate solid wood bending properties of plane trees and then to develop their end-uses, and the size of specimens tested was $15\times15\times350mm$ for steaming treatment and they were dried to $15\pm1%$ before bending. The results obtained were as follows: 1. The optimum conditions for solid wood bending processing of Platanus occidentalis are showed in Table 7. 2. The minimum solid-bending radii of Platanus occidentalis were 40mm in steaming treatment. 3. The effect of knots, diagonal grain and decay on the degradation of bending processing properties were very severe. 4. The bending stress was setted successfully through $80^{\circ}C$-15hrs drying after bending and the spring back for 24hr-exposing time was only about 1%.