• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.105-114
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• 2007

Large span spaces have been widely used for various purposes including sports events in other countries. Due to increasing demands on multi-purpose use of such spaces, recently built large span sport facilities such dome stadiums have been required to accommodate sport events as well as performing events. Also, retractable ceilings and/or walls were generally adopted in those spaces for providing various event conditions. It seems obvious that the openings between diffuse fields and free field may cause difficulties in the acoustic design of such spaces In the present work, the acoustic characteristics of non-diffuse field has been investigated using 1/10 acoustic scale models. It was found that RTs at low- and mid-frequencies decayed faster than those at high-frequencies as the percentage of opening area increased. The decay rate of RTs at high frequencies were not influenced by increasing the area of an opening. Also high dependence of EDT on the percentage of opening area was observed at all frequency range. D50 was not improved by increasing the area of an opening up to 12.5% and then sharply increased. The application of Schroeder integration to evaluate the reverberation charateristics of coupled spaces may not be proper, since non-exponential decay process with double or triple decays of those spaces can not be properly defined. EDT seems more appropriate to predict reverberation at the early acoustic design stage of acoustically coupled spaces.

• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.235-240
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• 1991

Starch phosphates were prepared from the corn starch mixed with 2% sodium tripolyphosphate by twin-screw extruder with a feed rate of 20 kg/hr and an extrusion temperature of $130^{\circ}C$, and the effects of extrusion variables on the physicochemical properties (target parameters) of starch phosphates were investigated. Interrelations of system parameters (specific mechanical energy and extrudate moisture) and rheological properities of starch was analyzed by using the response surface analysis. Degree of substitution (DS) was increased with increasing the feed moisture, and showed the maximum value at the screw of near 250 rpm, Degree of gelatinization was proportionally increased with increasing the screw speed and decreasing the feed moisture. Apparent viscosity of the paste was increased with increasing the feed moisture, but it was not significantly affected by the screw speed. It was found by scanning electron microscopy that the starch microgranules were much more degradaded, and as consequent result, the intrinsic viscosity was decreased, whereas, water solubility index was increased. The rate of retrogradation of the gels was retarded with increasing DS and decreasing viscosity.

• Journal of Animal Science and Technology
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• v.53 no.5
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• pp.441-450
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• 2011

This study was conducted to determine the effects of partial replacement of corn grain and soybean meal with agricultural by-product feeds on in vitro rumen fermentation characteristics and optimum levels of mixing ratio. The agricultural by-products to examine the effectiveness of the partial replacement of concentrate were wheat bran, corn gluten feed, bakery waste, soybean curd, rice bran, green kernel rice, soybean hull, distillers' grain, and mushroom substrate. In the first experiment, in vitro ruminal fermentation characteristics of feedstuffs were evaluated at 0, 3, 6, 12, 24, and 48 hours after incubation. In the second experiment, fermentation characteristics were investigated with green kernel rice and soybean curd which replaced corn grain or soybean meal. Feed were formulated with 40% corn grain + 20% soybean meal (T1), 40% corn grain + 17.5% soybean meal + 2.5% soybean curd (T2), 25% corn grain + 20% soybean meal + 15% green kernel rice (T3), and 30% corn grain + 15% soybean meal + 6% green kernel rice + 9% soybean curd (T4), respectively, with forage source of 10% alfalfa hay, 20% timothy hay, and 10% corn silage as fed-basis. In 24 and 48 hour cultivations, T4 showed significantly lower pH compared to T1, whereas in 3 and 24 hour cultivations, T4 showed significantly higher DM degradation compared to T1. In addition, the gas production of T3 was also higher than T1 (p<0.05). Overall results of the present experiments indicated that green kernel rice and soybean curd as agricultural by-products have the possibility of partial replacements of corn grain and soybean meal.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.100-107
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• 2007

People have spent lots of time inside building about 90% of these day. Industry has been developed rapidly after I960. Construction materials had changed from natural materials to chemical materials and confidentiality of building has been more higher than before by policy of saving energy. These have caused sick-building syndrome (SBS) for us. So people want environmental construction materials for their house. We designed a environmental loess (yellow soil) finishing material which was composed of loess, water, water-soluble resin, hardener and filler. The purposes of this study were that making an environmental loess finishing material with optimum ratio, evaluating the usability of loess finishing material for wall. Furthermore it was suitable for wall to evaluate mechanical properties that are impact test, cracking test, abrasion test and de-bonding test, environmental properties that were emission of VOCs, formaldehyde and far infrared radiation.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.374-384
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• 2022

There is an increasing demand for Tetradium daniellii seedlings due to their uses as alternative energy, for ecological restoration, and as a honey plant. This study was conducted to determine the optimum container for superior seedling production of T. daniellii. Experiments were performed using five plastic container types (500, 350, 320, 300, and 250 ml) for forestry facility cultivation. The height and root collar diameter growth of T. daniellii seedlings were significantly high in the 350-ml container. High growth appeared primarily in the container with a larger cavity volume and lower growing density. Root development was most active in full sunlight. The maximum dry matter production was observed in the 350-ml container, which was similar to the results of height and root collar diameter growth. QI, an index showing the quality of a seedling, was maximum at 0.97 in the 350-ml container. In conclusion, the 350-ml container is optimum for superior seedling production of T. daniellii.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.301-306
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• 2018

Urbanization causes urban floods and urban heat island in the summer, so it is necessary to understanding the changes of the thermal environment through urban climate and energy balance. This can be explained by the energy balance, but in urban areas, unlike the typical energy balance, the storage heat flux saved in the building or artificial land cover should be considered. Since the environment of each city is different, there is a difficulty in applying the method of retrieving the storage heat flux of the previous research. Especially, most of the previous studies are focused on the overseas cities, so it is necessary to study the storage heat retrieval suitable for various land cover and building characteristics of the urban areas in Korea. Therefore, the object of this study, it is to derive the regression formula which can quantitatively retrieve the storage heat using the data of the area where various surface types exist. To this end, nonlinear regression analysis was performed using net radiation and surface temperature data as independent variables and flux tower based storage heat estimates as dependent variables. The retrieved regression coefficients were applied to each independent variable to derive the storage heat retrieval regression formula. As a result of time series analysis with flux tower based storage heat estimates, it was well simulated high peak at day time and the value at night. Moreover storage heat retrieved in this study was possible continuous retrieval than flux tower based storage heat estimates. As a result of scatter plot analysis, accuracy of retrieved storage heat was found to be significant at $50.14Wm^{-2}$ and bias $-0.94Wm^{-2}$.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.530-534
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• 2006

조류발전은 조류 유속이 빠른 곳에 수차발전기를 설치하여 해수의 운동에너지로부터 전기를 생산하는 발전방식이다. 2001년부터 해양연구원에서는 울돌목의 우수한 조류발전 개발 여건을 바탕으로 조류에너지 실용화 기술을 개발하고 있다. 본 연구에서는 조류발전 시스템에 사용되는 헬리컬 수차의 효율을 현장실험을 바탕으로 판단하고자 하였다. 현장실험을 위하여 지름 2.2 m, 높이 2.5 m의 수차를 제작하고, 울돌목 협수로의 한 쪽 면에 쟈켓구조물을 설치하여 수차를 거치한다. 수차가 회전함에 따라 회전봉에 일정 마찰을 주어 토크와 RPM을 측정하고, 함께 측정된 유속자료를 이용하여 수차를 효율을 산정한다. 유속-수차효율, TSR(수차의 날개속도와 유속의 비)-수차효율의 상관관계로 실험결과를 고찰하였다. 1중 날개 수차인 경우에 유속 1.4에서 2.6 m/s 사이에서 최대효율이 30 - 35 % 정도였고, 2중 날개 수차에 대한 실험에서는 유속 1.4에서 2.6 m/s 사이에서 최대수차효율이 25 - 35 % 사이임을 알 수 있었다. TSR과 최대수차효율의 상관관계는 실험 case별로 조금씩 다르다. 전체적으로 1중 날개의 경우가 최대수차효율에서 2중 날개보다 TSR 값이 조금 큰 경향을 나타냄을 알 수 있다. 이것은 1중 날개가 2중 날개보다 가벼워 좀 더 큰 RPM을 발생시켜서 나타난 현상으로 생각된다. 현재의 실험결과들을 이용하여 TSR과 최대수차효율을 상관관계를 나타내는 모델식을 도출하였다. 현장시험결과를 종합하면, 현장조류발전 시설이 최소 600 kW의 전력이 생산되기 위해서는 지름 3 m, 높이 3.6 m 인 수차 3개가 하나의 축에 설치되어야하는 것으로 계산되었다. 정격유속이 4.8 m/s이고 수차의 지름이 3m 라면, 최적 전력발생시의 RPM은 1중 날개의 경우 79이고 2중 날개의 경우는 63정도임을 추정할 수 있었다.촬영하여 실시간으로 전송하기 때문에 홍수시 하천 상황에 대한 모니터링 목적으로 사용될 수 있다. 영상수위계는 우물통 등을 이용하는 기존 방법과 비교하여 구조물이 필요 없어 설치 비용이 저렴하고, 영상에 의한 하천 모니터링 기능을 자체적으로 가지고 있기 때문에 효율적이라고 할 수 있다.따른 4개의 평가기준과 26개의 평가속성으로 이루어진 2단계 기술가치평가 모형을 구축하였으며 2개의 개별기술에 대한 시범적용을 실행하였다.하는 것으로 추정되었다.면으로의 월류량을 산정하고 유입된 지표유량에 대해서 배수시스템에서의 흐름해석을 수행하였다. 그리고, 침수해석을 위해서는 2차원 침수해석을 위한 DEM기반 침수해석모형을 개발하였고, 건물의 영향을 고려할 수 있도록 구성하였다. 본 연구결과 지표류 유출 해석의 물리적 특성을 잘 반영하며, 도시지역의 복잡한 배수시스템 해석모형과 지표범람 모형을 통합한 모형 개발로 인해 더욱 정교한 도시지역에서의 홍수 범람 해석을 실시할 수 있을 것으로 판단된다. 본 모형의 개발로 침수상황의 시간별 진행과정을 분석함으로써 도시홍수에 대한 침수위험 지점 파악 및 주민대피지도 구축 등에 활용될 수 있을 것으로 판단된다. 있을 것으로 판단되었다.4일간의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주식시장에 적합한 거래전략은 반전거래전

• Journal of Animal Science and Technology
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• v.49 no.6
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• pp.819-828
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• 2007

Two experiments were conducted to observe the effects of direct fed microbials on metabolic characteristics in sheep and milking performance in dairy cows. A metabolic trial with four ruminally cannulated sheep(60±6kg) was conducted in a 4×4 Latin square design to investigate the supplementation effects of Saccharomyces cerevisiae, Clostridium butyricum or mixed microbes of S. cerevisiae and C. butyricum on ruminal fermentation characteristics and whole tract digestibility. Sheep were fed 1.25 kg of total mixed ration(TMR, DM basis) supplemented with S. cerevisiae (2.5g/day), C. butyricum (1.0g/day) or its mixture(S. cerevisiae 1.25g/day+C. butyricum 1g/day), twice daily in an equal volume. But control sheep were fed only TMR. A feeding trial with 28 lactating Holstein cattle was also conducted for 12 weeks to investigate the effects of the same microbial supplements as for the metabolic trial on milking performance. The cows were fed the TMR(control), and fed S. cerevisiae(50g/day), C. butyricum(15g/day) or its mixture (S. cerevisiae 25g/day + C. butyricum 7.5g/day) with upper layer dressing method. Total VFA concentration and the digestibility of whole digestive tract in the sheep increased by supplementation of S. cerevisiae, C. butyricum or their combined microbials compare to control group. The proportion of propionic acid at 1h(P<0.039) and 3h(P<0.022) decreased by supplementation of S. cerevisiae while tended to increase acetic acid proportion at the same times. Daily dry matter intake(DMI) was not influenced by the microbial treatments, but milk yield(P<0.031) and feed efficiency(milk yield/DMI, P<0.043) were higher for the cow received C. butyricum than those for other treatments. The milk fat content was higher (P<0.085) when cows fed S. cerevisiae(4.11%) than that fed the control (4.08%), the diets with C. butyricum (3.85%) and the microbial mixture. Based on the results obtained from the current experiments, supplementation of C. butyricum or mixture with S. cerevisiae might be increased milk fat content and milk productivity of lactating daily cows. (Key words:Saccharomyces cerevisiae, Clostridium butyricum, Fermentation characteristics,

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• Journal of Bio-Environment Control
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• v.29 no.2
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• pp.130-140
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• 2020

This study was conducted in order to closely examine about optimum shading for superior seedling production a container seedling of Tetradium daniellii, which is being increased the demand for a seedling due to being used for alternative energy, ecological restoration and honey plant. The experiment of investigating the optimum shading on T. daniellii was carried out by using plastic container types (350 ml/cavity) for the forestry facility cultivation. The shading level was treated with full sunlight and with 35%, 55%, 75% of the full sunlight. As a result of having surveyed height and root collar diameter growth of a containerized seedling in T. daniellii, a case of the shading experiment showed a noticeably high value was indicated in the full sunlight. It was surveyed that the stronger shading level leads to the lower growth value. Root development was most active in full sunlight. Dry matter production, it was investigated to be the highest in full sunlight. It was surveyed to be the similar tendency to the outcome of height and root collar diameter growth. QI, which is index of showing the quality of a seedling, stood at 0.98 in full sunlight, thereby having been investigated to be the highest. As for the chlorophyll content in a seedling, the highest chlorophyll content was indicated in the 75% shading treatment with the relatively highest shading level. The photosynthetic rate and the water use efficiency were surveyed to be the highest in full sunlight with 8.48 μmolCO₂·m^-2s^-1, 1.40 μmolCO₂·mmolm^-1H₂O, respectively. As a result of surveying the whole experiment, optimum shading level for superior seedling production a container seedling of T. daniellii is determined in full sunlight (0%). It is expected that this will be used as a basic data for mass production.