• 한국융합학회논문지
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• 제13권3호
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• pp.281-289
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• 2022

플라즈마오존은 높은 살균성능으로 인해 다양한 살균분야에서 활용되고 있다. DBD(유전체 장벽방전)에 사용되는 유전체는 주로 석영, 세라믹, 폴리머 등이 주로 사용된다. 유전체로 이루어진 레이어는 공급되는 전하의 양을 제한시키고 플라즈마가 유전체 면 위에서 고르게 발생할 수 있도록 하는 역할을 한다. 이러한 DBD를 이용한 플라즈마, 오존살균은 살균대상이나 주변 환경이 복잡한 구조로 된 경우가 많아 공간살균에 대한 개념을 수립하고 이에 대한 연구와 학문적 체계가 필요하다. 본 연구에서는 플라즈마라디칼과 오존 생성을 위해 대기압에서 DBD방식을 이용한다. 플라즈마오존의 발생을 위한 반응기의 구조는 세라믹 튜브 유전체와 스테인리스 도체를 일정한 간격으로 배치하여 유전체 장벽방전을 발생시키는 형태이다. 공간살균장치로서의 플라즈마오존 발생은 성능 면에서 우수한 살균장치로 인식되고 있으므로 장치의 설계와 검증을 통해 공간살균장치의 최적설계를 확립하고자 하며 제안된 방법을 기반으로 다양한 살균 어플리케이션을 개발하는데 기초를 제공한다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권5호
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• pp.173-181
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• 2021

철근콘크리트 구조물은 다양한 환경에 노출되어 수분 침투로 인한 철근 부식이 발생하며, 부식으로 인한 구조물의 내구성능 저하 문제가 발생할 수 있다. 따라서 이러한 문제점을 해결하기 위해 철근에 비해 인장강도, 비부식성, 경량화 등 뛰어난 장점을 가진 FRP 보강근에 대한 연구가 활발히 진행되고 있다. FRP 보강근은 철근과 달리 항복 구간이 없으므로 파괴 시까지 선형탄성거동이 나타나고 탄성계수가 낮아 과도한 처짐이 발생할 수 있으므로 한계상태 조건에 대한 적용성 검토가 필요하다. 한계상태에서 FRP 보강 콘크리트 의 휨 설계 시 ACI 440.1R은 FRP 보강근의 재료적 불확실성을 고려하여 환경감소계수와 강도감소계수를 모두 적용하여 휨강도가 크게 낮아진다. 따라서 본 연구에서는 국내·외 다양한 문헌을 조사하여 유효단면이차모멘트 제안식의 처짐 해석 결과와 실험결과를 비교하였으며, ACI 440.1R 및 Fib bulletin 40의 설계휨강도를 분석하였다. 실험 결과에 따른 휨강도는 ACI 440.1R에 비해 Fib bulletin 40의 설계휨강도와 유사한 경향이 확인되었으며, 인장지배단면에서 ACI 440.1R은 설계휨강도를 보수적으로 평가하는 것으로 나타났다.

• 한국건축시공학회지
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• 제9권5호
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• pp.79-86
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• 2009

철골구조에서 뿜칠내화피복재는 화재발생시 철골구조물의 내력이 저하되는 것을 방지하는 중요한 자재이다. 그러나 인력에 의한 작업 등으로 인하여 품질관리가 어렵고, 기능인력의 수급도 용이하지 않으며, 기능인력이 유해한 환경에 노출될 가능성도 높은 실정이다. 일반적으로 이와 같이 품질관리가 어렵고 인체에 유해한 건설작업들은 자동화 장비를 도입함으로써 문제를 어느 정도 완화할 수 있다. 그러나 기존의 건설현장은 환경이 비구조화되어 있기 때문에 장비의 주행이나 작업위치선정 등까지 자동화하기는 매우 어려웠다. 본 연구에서는 뿜칠내화피복 작업을 자동화하기 위한 기초연구로써, 자동화시스템과 첨단기술인 RTLS와의 연계성을 검토하고 내화피복 뿜칠 자동화작업의 시나리오, 시스템 구성요소 등을 제안하였다. 제안된 시스템은 아직 개념단계이므로 많은 제약조건들이 해결되지는 않았으나, 제안된 시스템으로 작업하면 내화피복의 균일한 피복두께를 유지할 수 있으며, 철골 구조물과의 일체성을 확보하며, 내화성능을 향상시킬 수 있을 것으로 기대된다. 또한 내화피복의 품질이 확보됨에 따라, 대형 철골 구조물에 화재가 발생하더라도 일정한 강도를 유지할 수 있어서, 화재의 전이를 방지하는 데에 효과가 있을 것으로 예상된다. 향후에는 첨단 IT인 USN등 첨단 모니터링 기술, BIM기술, 자재의 위치정보 인식기술 등과 연계하여 본 연구를 진행할 예정이다. 이와같은 기술과 본 연구가 연계되면, 국내 건설자동화 수준을 제고시키고, 건설 자원의 효율적 체계적 관리를 통한 비용절감, 공기단축, 정밀시공 등을 구현하는 데에 더욱 기여할 수 있을 것이다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권1호
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• pp.73-80
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• 2022

본 연구에서는 공장에서 L형강을 이용하여 선조립한 NRC 보와 NRC 기둥을 현장에서 볼트 조립하는 NRC 보-기둥접합부 상세를 개발하였다. 개발된 접합부 상세는 NRC-J형과 NRC-JD형이다. NRC-J형은 NRC 기둥 측면의 강재 플레이트와 NRC 보의 엔드플레이트의 측면과 하부면에 TS볼트로 인장접합하는 방식이다. NRC-JD형은 전단에 대해서 NRC 보와 NRC 기둥의 측면을 고력볼트접합하고, 휨에 대해서 접합부를 관통하는 철근연결재와 보의 보강재를 겹침이음하도록하는 강접합 방식이다. 접합부 내진성능평가를 위하여, 두 가지 NRC 보-기둥 접합부 상세를 가지는 NRC-J 실험체, NRC-JD 실험체와 RC 보-기둥 접합부 상세를 가지는 RC-J 실험체 등 3개의 실험체를 제작하였다. 반복횡하중가력 실험결과, 모든 실험체의 최종 파괴형상은 보-기둥 접합면에서 보의 휨파괴로 나타났다. 정가력에 의한 실험체 최대내력은 RC-J 실험체에 비하여 NRC-J 실험체와 NRC-JD 실험체가 각각 10.1%, 29.6% 크게 나타났다. 두가지 NRC 접합부 상세 모두 KDS 기준(KDS 41 3100)의 합성중간모멘트골조 모멘트접합부에서 요구되는 최소 총층간변위각 0.03 rad 이상의 연성능력을 확보는 것으로 평가되었다. 부재각 5.7%에서 NRC-J실험체, NRC-JD 실험체가 RC실험체에 비해 약 34.8%, 61.1% 큰 누적 에너지 소산능력을 보유하고 있었다. NRC 보-기둥 접합부의 실험내력이 KDS 기준식에 의한 이론내력에 비하여 30%~53% 큰 것으로 평가되어, 기준식이 보유성능을 안전측으로 평가하였다.

• KSBB Journal
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• 제14권3호
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• pp.328-336
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• 1999

본 연구에서는 제철소에서 배출되는 산업폐수를 이용하여 미세조류를 성공적으로 배양하였으며 이에 대한 모델링 연구를 통해 이산화탄소의 고정화 및 암모니아의 제거효율에 미치는 환경인자에 대하여 살펴보고 실제 옥외배양에서의 성능을 평가하고자 하였다. Bottle에서의 배양을 통해 산업폐수에서 미세조류가 성장하면서 암모니아를 완전히 제거할 수 있음을 확인하였다. 또한 이때 타양미생물의 성장은 미세조류의 성장에 비해 미미하였으므로 건조중량으로부터 고정화된 이산화탄소를 계산할 수 있었다. Raceway pond의 회분식운전 결과로부터 조류성장에 대한 모델을 구축하고 관계되는 parameter를 결정할 수 있었으며 이로부터 실제 옥외에서의 빛의 세기에서 고정화된 이산화탄소의 누적량 및 암모니아의 제거를 계산할 수 있었다. 그 결과 60 klux이상의 빛에서는 암모니아가 완전히 제거될 수 있다는 결과를 얻었으며 빛의 세기가 증가할 수록 성능이 향상되지만 빛에너지에 대한 효율은 감소하는 경향을 발견하였다. Raceway pond의 실제 옥외운전을 모사하기 위한 반연속식 배양실험에서는 dilution rate이 증가할 때 이산화탄소의 고정화율 및 암모니아의 제거율이 증가하나 암모니의 제거효율은 감소하는 경향을 얻었다. 또한 raceway pond의 옥외배양시 빛의 세기 및 폐수의 깊이, dilution rate에 따른 성능변화를 모델로 이용하여 계산하였는데 결과적으로 하루에 12시간동안 100klux의 태양빛이 공급되는 조건에서 raceway pond를 운전할 때 최적의 dilution rate은 0.425$day^{-1}$이며 이러한 조건에서 24.7 g$m^{2}day^{-1}$의 속도로 이산화탄소를 고정할 수 있는 것으로 평가되었다. 또한 이러한 조건에서 암모니아는 0.52 g $NH_3-Nm^{-2}day^{-1}$의 속도로 제거될 수 있으며 배출수증의 암모니아농도는 폐수의 깊이에 따라 크게 변화하는 것으로 나타났다.

• Journal of Biosystems Engineering
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• 제1권1호
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• pp.15-15
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• 1976

In analyzing the operational characteristics of a rice whitening machine, the internal radial pressure of the machine was measured using strain gage equipment. Changes in cylinder and feed screw configurations, screen type, cylinder speed and counter-pressure levels were examined to determine their impact on the quality and quantity of milled rice and the performance of the machine. The results are summarized as follows: 1. The internal radial pressure in the whitening chamber varied with the surface condition of the grain being processed. During the first or second pass through the machine, pressure was relatively low, reached a maximum after two to three passes with combinations I and II, three to six with combination III and then began to fall. 2. The pitch of the feed screw and the size of the feed gate opening which determine the rate of entry of grain into the whitening chamber, appeared to be the most important factor aff-::cting the degree of radial pressure, quality and quantity of milled rice and the efficiency of the machine. Using a feed screw with a wide pitch (4.8cm), radial pressure was relatively high and head rice recovery ratio \vere quite low. In this case capacity and machine effic?iency were much higher than obtained when using a feed screw with a narrow pitch (2.3cm). Very significant responses in radial pressure, head rice recovery rates and machine capacity were observed with changes in cylinder speed and counter-pressure levels when using the wide pitch feed screw. 3. The characteristics of the screen which surrounds the whitening chamber had an important effect on whitening efficiency. The existence of small protuberances on the original screen resulted in significant increases in both machine capacity and efficiency but without a significant decrease in head rice recovery or development of excessive radial pressure. Further work is required to determine the effects of screen surface conditions and the shape of the cylinderical steel roller on the rate of bran removal, machine efficiency and recovery rates. The size of the slotted perforations 0:1 the screen affects total milled rice recovery. The opening size on the original screen was fabricated to accommodate the round shape of Japonica rice varieties but was not suitable for the more slender Indica type. Milling Indica varieties with this screen resulted in a reduction in total milled rice recovery. 4. An increase in cylinder speed from 380 to 820 rpm produced a positive effect on head rice recovery for all machine combinations at every level of counter-pressure used in the tests. Head rice recovery was considerably lower at 380rpm using a wide screw pitch when compared to the results obtained at speeds from 600 to 820 r.p.m. The effects of cylinder speed On radial pressure, capacity and machine efficiency showed contrasting results, depending on the width of the feed screw pitch. With a narrow feed screw pitch (2.3cm), a direct proportional relationship was observed bet?ween cylinder speed and both radial pressure and machine efficiency. In contrast, using a 4.8 centimeter pitch feed roller produced a series of inverse relationships between the above variables. Based on the results of this study it is recommended when milling Indica type long grain rice varieties that the cylinder speed of the original machine be increased from 500-600 rmp up to a minimum of 800 rpm to obtain a greater abrasive effect between the grain and the screen. The pitch of the feed screw should be also reduced to decr?ease the level of internal radial pressure and to obtain higher machine efficiency and increased quality of milled rice with increased cylinder speeds. Further study on the interaction between cylinder speed and feed screw pitch is recommended. 5. An increase in the counter pressure level produced a negative effect On the head rice recovery with an increase in radial pressure, capacity, and machine efficiency over all combinations and at every level of cylinder speed. 6. Head rice recovery rates were conditioned primarily by the pressure inside the whitening chamber. According to the empirical cha racteristics curve developed in this study, the relationships of head rice recovery ($Y_h$) and machine capacity ($Y_c$/TEX>) to internal radial pressure ($X_p$) followed an inverse quadratic function and a linear function respectively: $$Y_h^\Delta=\frac{1}{{1.4383-0.2951X_p^\ast+0.1425X_p^{\ast\ast}}^2} , (R^2=0.98)$$$$Y_c^\Delta=-305.83+374.37X_p^{\ast\ast}, (R^2=0.88)$$The correlation between capacity and power consumption per unit of brown rice expressed in the following exponential function: $$Y_c^\Delta=1.63Y_c^{-0.7786^\{\ast\ast}, (R^2=0.94)$$These relationships indicate that when radial pressure increases above a certain range (1. 6 to 2.0 kg/$cm^2$ based On the results of the experiment) head ricerecovery decrea?ses in a quadratic relation with a inear increase in capacity but without any decrease in power consump tion per unit of brown rice. On the other hand, if radial pressure is below the range shown above, power consumption increases dramatically with a lin?ear decrease in capacity but without significant increases in head rice recovery. During the operation of a given whitening machine, the optimum radial pressure range or the correct capacity range should be selected by controlling the feed rate and/or counter-pressure keeping in mind the condition of the grain, particulary the hardness. It was observed that the total number of passes is related to radial pessure level, feed rate and counter-pressure level. The higher theradial pressure the fewer num?ber of pass required but with decreased head rice recovery. In particular, when using high feed rates, the total number of passes should be increased to more than three by reducing the counter-pressure level to avoid decreaseases in head rice recovery (less than 65 percent head rice recovery on the basis of brown rice) at every cylinder speed. 7. A rapid rise in grain temperature seemed to have a close relationship with the pressure generated inside the whitening chamber and, subsequently with head rice reco?very rates. The higher the rate of increase, the lower were the resulting head rice recoveries.

• Journal of Biosystems Engineering
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• 제1권1호
• /
• pp.17-48
• /
• 1976

In analyzing the operational characteristics of a rice whitening machine, the internal radial pressure of the machine was measured using strain gage equipment. Changes in cylinder and feed screw configurations, screen type, cylinder speed and counter-pressure levels were examined to determine their impact on the quality and quantity of milled rice and the performance of the machine. The results are summarized as follows: 1. The internal radial pressure in the whitening chamber varied with the surface condition of the grain being processed. During the first or second pass through the machine, pressure was relatively low, reached a maximum after two to three passes with combinations I and II, three to six with combination III and then began to fall. 2. The pitch of the feed screw and the size of the feed gate opening which determine the rate of entry of grain into the whitening chamber, appeared to be the most important factor aff-::cting the degree of radial pressure, quality and quantity of milled rice and the efficiency of the machine. Using a feed screw with a wide pitch (4.8cm), radial pressure was relatively high and head rice recovery ratio \vere quite low. In this case capacity and machine effic\ulcorneriency were much higher than obtained when using a feed screw with a narrow pitch (2.3cm). Very significant responses in radial pressure, head rice recovery rates and machine capacity were observed with changes in cylinder speed and counter-pressure levels when using the wide pitch feed screw. 3. The characteristics of the screen which surrounds the whitening chamber had an important effect on whitening efficiency. The existence of small protuberances on the original screen resulted in significant increases in both machine capacity and efficiency but without a significant decrease in head rice recovery or development of excessive radial pressure. Further work is required to determine the effects of screen surface conditions and the shape of the cylinderical steel roller on the rate of bran removal, machine efficiency and recovery rates. The size of the slotted perforations 0:1 the screen affects total milled rice recovery. The opening size on the original screen was fabricated to accommodate the round shape of Japonica rice varieties but was not suitable for the more slender Indica type. Milling Indica varieties with this screen resulted in a reduction in total milled rice recovery. 4. An increase in cylinder speed from 380 to 820 rpm produced a positive effect on head rice recovery for all machine combinations at every level of counter-pressure used in the tests. Head rice recovery was considerably lower at 380rpm using a wide screw pitch when compared to the results obtained at speeds from 600 to 820 r.p.m. The effects of cylinder speed On radial pressure, capacity and machine efficiency showed contrasting results, depending on the width of the feed screw pitch. With a narrow feed screw pitch (2.3cm), a direct proportional relationship was observed bet\ulcornerween cylinder speed and both radial pressure and machine efficiency. In contrast, using a 4.8 centimeter pitch feed roller produced a series of inverse relationships between the above variables. Based on the results of this study it is recommended when milling Indica type long grain rice varieties that the cylinder speed of the original machine be increased from 500-600 rmp up to a minimum of 800 rpm to obtain a greater abrasive effect between the grain and the screen. The pitch of the feed screw should be also reduced to decr\ulcornerease the level of internal radial pressure and to obtain higher machine efficiency and increased quality of milled rice with increased cylinder speeds. Further study on the interaction between cylinder speed and feed screw pitch is recommended. 5. An increase in the counter pressure level produced a negative effect On the head rice recovery with an increase in radial pressure, capacity, and machine efficiency over all combinations and at every level of cylinder speed. 6. Head rice recovery rates were conditioned primarily by the pressure inside the whitening chamber. According to the empirical cha racteristics curve developed in this study, the relationships of head rice recovery ($Y_h$) and machine capacity ($Y_c$/TEX>) to internal radial pressure ($X_p$) followed an inverse quadratic function and a linear function respectively: $$Y_h^\Delta=\frac{1}{{1.4383-0.2951X_p^\ast+0.1425X_p^{\ast\ast}}^2} , (R^2=0.98)$$ $$Y_c^\Delta=-305.83+374.37X_p^{\ast\ast}, (R^2=0.88)$$ The correlation between capacity and power consumption per unit of brown rice expressed in the following exponential function: $$Y_c^\Delta=1.63Y_c^{-0.7786^\{\ast\ast}, (R^2=0.94)$$ These relationships indicate that when radial pressure increases above a certain range (1. 6 to 2.0 kg/$cm^2$ based On the results of the experiment) head ricerecovery decrea\ulcornerses in a quadratic relation with a inear increase in capacity but without any decrease in power consump tion per unit of brown rice. On the other hand, if radial pressure is below the range shown above, power consumption increases dramatically with a lin\ulcornerear decrease in capacity but without significant increases in head rice recovery. During the operation of a given whitening machine, the optimum radial pressure range or the correct capacity range should be selected by controlling the feed rate and/or counter-pressure keeping in mind the condition of the grain, particulary the hardness. It was observed that the total number of passes is related to radial pessure level, feed rate and counter-pressure level. The higher theradial pressure the fewer num\ulcornerber of pass required but with decreased head rice recovery. In particular, when using high feed rates, the total number of passes should be increased to more than three by reducing the counter-pressure level to avoid decreaseases in head rice recovery (less than 65 percent head rice recovery on the basis of brown rice) at every cylinder speed. 7. A rapid rise in grain temperature seemed to have a close relationship with the pressure generated inside the whitening chamber and, subsequently with head rice reco\ulcornervery rates. The higher the rate of increase, the lower were the resulting head rice recoveries.