• 한국기계가공학회지
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• 제20권5호
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• pp.61-68
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• 2021

Movable weirs with multi-stage control are necessary in many Korean rivers to actively control the water storage level. A mesh dependency test was performed to determine the appropriate number of meshes for structural analysis of movable weirs. The standing angles of movable weirs were set to 60°, 45°, 30°, and 15° for stress analysis. The standing angle of 0° was excluded from the analysis because it was unloaded. Changes in the standing angle led to changes in the water depth, maximum pressure, maximum strain, and maximum stress. The maximum average stress and the structural safety of the multi-stage control movable weir were computed and tested using the Ansys FEA software package.

• 항공우주시스템공학회지
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• 제15권2호
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• pp.10-15
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• 2021

The propeller wake of tiltrotor-type aircrafts, such as TR-60 and quad tilt propeller (QTP) UAV, in hover substantially impinges the upper surface of the primary wing and generates a downward load. This load is directly proportional to the thrust of the propeller and reduces the available payload. Therefore, wing and nacelle mechanisms should be carefully designed to reduce downward load. This study conducted a numerical analysis of the rotating propeller in hover to predict the downward load of a QTP UAV. An unsteady three-dimensional Navier-Stokes solver was used along with a sliding mesh for the simulation of the rotating propeller. To reduce the downward load, the tilting mechanisms of the partial wing and nacelle were simultaneously introduced and numerically analyzed. Finally, the downward load was predicted by 14% of isolated propeller thrust; further, the downward load could be reduced by adopting the partial wing and nacelle tilting concept.

• 대한화학회지
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• 제29권2호
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• pp.178-182
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• 1985

비철특수합금중 아연(II) 구리(II)와 마그네슘(II)을 양이온 교환수지(Dowex 50w${\times}$8, 80-100 mesh)와 음이온 교환수지(IRA-400)을 이용하여 이온교환크로마토그라프로서 분리하는 방법을 연구 하였다. 이온교환수지는 25 ${\times}$ 2cm ID 칼럼에 넣고 흐르는 속도는 0.30 ml/min으로 조절하였다. 아연(II), 구리(II), 마그네슘(II)와 같은 비철금속 이온들을 분리하기 위한 좋은 용리액의 조건은 다음과 같다. 0.5M $NaNO_3$ (pH 3.1), 0.2~0.5M HCl + 50~90% Acetone과 1M HAc + 0.1M NaAcf(pH 3.7)였으며 0.1M NaAc + 1M NaAc(pH 3.7), 0.5M HCl + 50% Acetone이 가장 좋은 용리액으로 판명되었다. 분리된 용출액은 원자흡광 광도계로 측정하였으며 특히 아연 (II)은 음이온 교환수지에서 0.12N HCl과 1.5N $NH_4OH$ 수용액으로 분리하고 E.D.T.A로 적정하였다.

• 한국지반환경공학회 논문집
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• 제21권12호
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• pp.17-21
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• 2020

낙석방지울타리의 지지능력은 철망, 지주, 와이어로프의 성능을 합친 것으로 정의되며, 기존에 시공되고 있는 낙석방지울타리는 도로안전시설 설치 및 관리지침 중 낙석방지시설 편에는 48~61kJ의 에너지를 흡수할 수 있는 지주, 와이어로프, 철망의 규격이 제시되어 있다. 그러나 흡수에너지에 대한 각 요소들의 상관관계가 명확하게 제시되어 있지 않아 불확실하다(Ministry of Land, 2008). 본 논문에서는 수직 낙하시험을 이용하여 낙석방지울타리의 성능평가 시험을 수행하던 중 복잡한 꼬임으로 이루어져 체결 조건 등이 중요한 낙석방지망이 흡수하는 에너지를 확인하기 위해 실물낙석시험을 수행하였다. 시험결과를 이용하여 낙석방지망의 변위량 산정요소인 𝛿의 적절성을 판단하고 국외 성능평가 기준을 이용하여 낙석방지망의 흡수가능에너지를 평가하였다. 변위량 𝛿의 경우 명시되어 있는 1/4보다 1/2로 사용하는 것이 적합하다고 판단되며, 낙석방지망은 30kJ 정도의 에너지를 흡수한다는 결과를 도출하였다.

• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• 생약학회지
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• 제33권4호통권131호
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• pp.364-371
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• 2002

Yew (Taxus cuspidata Sibe) selected cultivation as drug, food and decorative plant in Gyong-gi province in Korea. To extract the water soluble active ingredients, as a extracting method, there was extracted with 20g of dried seeds with each 20g of butylene glycol(BG) and propylene glycol(PG), and 40 mL of water mixing 72 hours at $40{\pm}5^{\circ}C$, and then they were filtrated by 400 mesh. Appearance of extract of seeds was pale brown, $pH=4.5{\pm}0.5$, $gravity=1.013{\pm}0.05$, a reflective $index=1.373{\pm}0.05$, and yield=75%. Also, to extract the high purity oil from seeds, it minutely pulverized the dried seeds and added the hexane, mixing 2 hours at $20{\pm}57^{\circ}C$. And then, this filtrated it with 400-mesh. It got the purified oil through evaporating them at $55^{\circ}C$ during under vacuum. As the results, appearance was slightly brown, gravity=0.922 acid value=0.12, saponification value=192, and it should be obtained the $40{\pm}5%$ of yield. As the efficacy evalution of cosmetic field, the antioxidative activities by NBT method were stronger 86.0% from extract of talus seeds than 52.0% from green tea extract and 35.0% from skullcap extract as well as the antioxidative activities by DPPH method were stronger 93.7% from extract of seed than 60.3% from extract of green tea and 27.1% from extract of skullcap. These are more effective than other plant extracts. The collagen synthesis rate on the activating fibroblast for Taxus cuspidata Sibe extract showed 35.43%. As the activity of the skin elasticity, PPE(porcine pancreatic elastase)-inhibitory activities of talus extract was 50.8%. Anti-inflammatory activity was more effective to be taken 41.1% of taxus seed oil than 24.2% of steady glycyrrhetinate (SG) as a control.

• 수산해양기술연구
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• 제54권4호
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• pp.279-286
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• 2018

The objective of this study was to quantitatively evaluate the influence of the netting hanging ratio on fishing performance of gillnet. A total of six tests was carried out using three kinds of gillnets with different horizontal hanging ratios (0.3, 0.5 and 0.7) on the basis commercial gillnet of mesh size of 60 mm used in Yeosu Dolsan. As a result of the test fishing operation, catches of the net with hanging ratio 0.3 and the shortest float length was 1.34 times larger than the net with hanging ratio 0.7. The caught species in experimental testes was lager in the net with hanging ratio 0.3 than the net with hanging ratio 0.7. The catch rate per unit area (CPUE) is on the silver croaker with the largest catches in tests as follows. The net with hanging ratio 0.3 net was $89.45g/m^2$, hanging ratio 0.5 net was $41.63g/m^2$, and hanging ratio 0.7 net was $24.50g/m^2$. The net with hanging ratio 0.3 (float line length of 45 m) exhibited the largest CPUE value.

• 한국지열·수열에너지학회논문집
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• 제17권4호
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• pp.79-90
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• 2021

This paper presents a study to reduce the effect of blast pressure on the blast valves installed in protection tunnels, where the shape of the tunnel entrance and the blast pocket is optimized based on the predetermined basic shape of the protective tunnels. The reliability of the numerical tunnel models was examined by performing analyses of mesh convergence and overpressure stability and with comparison to the data in blast-load design charts in UFC 3-340-02 (DoD, 2008). An optimal mesh size and a stabilized distance of overpressure were proposed, and the numerical results were validated based on the UFC data. A parametric study to reduce the blast overpressures in tunnel was conducted using the validated numerical model. Analysis was performed applying 1) the entrance slope of 90, 75, 60, and 45 degrees, 2) two blast pockets with the depth 0.5, 1.0, and 1.5 times the tunnel width, 3) the three types of curved back walls of the blast pockets, and 4) two types of the upper and lower surfaces of the blast pockets to the reference tunnel model. An optimal solution by combining the analysis results of the tunnel entrance shape, the depth of the blast pockets, and the upper and lower parts of the blast pockets was provided in comparison to the reference tunnel model. The blast overpressures using the proposed tunnel shape have been reduced effectively.

• Journal of the Korean Wood Science and Technology
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• 제51권5호
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• pp.334-344
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• 2023

Dregs from the sugar palm (Arenga pinnata) starch industry are considered a waste product of the agricultural industry and have not yet been optimally utilized. Therefore, this study aimed to manufacture particleboards from dregs using different amounts of adhesive and particle size ratios. Sugar palm dregs, which had been separated into fibers and powder/fine particles, were used as raw material for making particleboards. The fiber had an average length of 6.84 ± 3.23 cm, while the fine particles were of a size that passed through size 10 mesh and remained in size 60 mesh. Three ratios of fiber to fine particles (100:0, 75:25, and 50:50 wt%) with three different amounts of sucrose-citric acid adhesive (10, 15, and 20 wt%) were used in this study. Increasing the amount of fine particles and the resin content can improve the physical properties and the internal bond strength of boards made from sugar palm dregs. The fine particles possibly filled the gap between the fibers in the particleboard, while the fibers exhibited a high bending strength. As a result, a high-performance particleboard can be attained by combining the composition ratio of fiber/fine particles and resin content. In this study, particleboards made from fiber/fine particles (75:25 wt%) and adhesive content of 15 wt% and 20 wt% had the mechanical properties that met the requirements of Japanese Industrial Standard (JIS) A 5908 type 18. Sugar palm dregs have the potential to be used as raw materials to create value-added particleboards.

• 한국산림과학회지
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• 제41권1호
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• pp.1-6
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• 1979

1. 본시험(本試驗)은 당화기질(糖化基質)로 산오리나무재(材)를 묽은황산(黃酸)으로 전처리(前處理)한 후(後) Trichoderma viride 16374호균(號菌)에서 얻은 cellulase를 작용(作用)시켜 환원당(還元糖)을 생성(生成)할 수 있는 최적조건(最適條件)을 조사(調査)한 것이다. 즉(卽) 산오리나무(10~15년생(年生))의 톱밥을 전처리(前處理)할 때 황산농도(黃酸濃度) 0.3%, 0.6%, 0.9%, 1.2%, 1.5%로 구분(區分)하고 열압시간(熱壓時間)은 $1.5kg/cm^2$에서 15분(分), 30분(分), 45분(分), 60분(分)으로 각각(各各) 구분(區分) 처리(處理)하여 건조(乾燥)시킨것을 다시 $190^{\circ}C$에서 30분간(分間) 열처리후(熱處理後) 60mesh로 분쇄(粉碎)한 것을 당화기질(糖化基質)로 사용(使用)하였다. 그리고 cellulase 반응조건(反應條件)은 0.1M황산완충액(黃酸緩衝液)(pH 5.0) 50ml, 기질량(基質量) 0.5g, 고근효소액(盬析酵素液) 0.5ml를 100ml용(用) 삼각(三角) flask에 넣고 잘 혼합(混合)한 후(後) $40^{\circ}C$에서 96시간(時間) 반응(反應)시켜 이때 생성(生成)된 환원당량(還元糖量)을 조사(調査)하였다. 2. 고근효소액(盬析酵素液)의 조제(調製)는 밀기울액체진탕배양법(液體振盪培養法)에 의(依에) 하여 생성(生成)된 조효소액(粗酵素液)을 유안절포도(硫安飽和度)에 의(依)한 고근효소액(盬析酵素液)을 만들었다. 3. 환원당정량(還元糖定量)은 DNS법(法)에 의(依)하였다. 4. 묽은황산(黃酸)으로 처리(處理)한 톱밥의 환원당(還元糖) 생성량(生成量)은 황산농도(黃酸濃度) 1.5%, $1.5kg/cm^2$에서 열압시간(熱壓時間)은 45분(分)으로 처리(處理)한 것이 16.0%로 최대량(最大量)을 나타냈으나 작용(作用)함으로서 생성(生成)된 환원당량(還元糖量)은 황산농도(黃酸濃度) 0.9%, 열압시간(熱壓時間) 60분(分) 처리(處理)한 것이 23.6%로(본시험(本試驗) 범위(範圍)에서는 47.5% 증가(增加)) 나타났다.