PURPOSES : The number of snowfall and the amount of snowfall are gradually increasing, and due to the characteristics of Seoul, which has a lot of traffic, it is difficult to respond quickly with a snow removal method that relies on snow removal vehicles. Therefore, it is necessary to develop an IoT based eco-friendly snow removal system that can respond to unexpected heavy snow in winter. In this study, the low temperature operation and snow removal performance of the IoT road condition snow removal detector and the snow removal system using CNT and PCM are evaluated in the climatic environment chamber. METHODS : To make artificial snow, it consists of an climatic environment chamber that can simulate a low temperature environment and equipment that can supply compressed air and cold water. Depending on the usage characteristics of the climatic environment chamber, use an air-water type snow maker. In order to make artificial snow, wet temperature, which takes into account the actual air temperature and the amount of moisture in the air, acts as the most important variable and is suitable for making snow, below –1.5 ℃. The lower the water temperature, the easier it is to freeze, so the water source was continuously supplied at 0 ℃ to 4 ℃. One of the two different pipes is connected to the water tank to supply water, and the other pipe is connected to the compressor to supply high-pressure air. Water is dispersed by compressed air in the form of many small droplets. The sprayed microscopic water particles freeze quickly in the low temperature environmental climatic chamber air and naturally fall to the floor, forming snow. Based on the KS C IEC 60068-2-1 cold resistance test standard, an integrated environmental test procedure was prepared to apply to IoT-based snow removal systems and performance evaluation was performed accordingly. The IoT based eco-friendly snow removal system is needed to in winter, so visual check and inspect the operation at the climatic chamber before setting up it to the actual site. In addition, grid type equipment was manufactured for consistent and reliable snow removal performance evaluation under controlled environmental conditions. RESULTS : The IoT-based eco-friendly snow removal system normally carried out the task of acquiring data and images without damaging the appearance or freezing in a low temperature environment. It showed clear snow removal performance in areas where PCM and CNT heating technology were applied to the concrete slab. This experiment shows that normal snow removal tasks can be carried out in low temperature environments in winter. CONCLUSIONS : The integrated environmental test procedures and grid type evaluation equipment are applied to low temperature operation and snow removal performance evaluation of snow removal systems. In the climatic environment chamber, where low temperature environments can be simulated, artificial snow is created regardless of the season to derive quantitative experimental results on snow removal performance. PCM and CNT heating technology showed high snow removal performance. The system is expected to be applied to road site situations to preemptively respond to unexpected heavy snow in winter.

With the development of drone technology, drones are being used in various industries. In general, drones use lithium-based battery pack, which is sensitive to external impact and temperature characteristics. Therefore, in order to prevent this problem, a battery case for protecting the battery from the outside is used. Usually, carbon fiber is used as case material, carbon fiber is expensive and has disadvantages of being difficult to manufacture. In this study, a battery case was fabricated to minimize the influence of external impact and temperature by using expanded polypropylene material, and also the battery efficiency test was performed using fabricated case. After basic design for battery case was conducted, a system capable of maintaining temperature was constructed by attaching a surface heating element inside the case, and the effect of maintaining temperature according to the presence or absence of the case was confirmed. Using manufactured prototype case, flight tests were carried out to check the battery voltage level according to the presence or absence of the case and to analyze the effect of improving the battery efficiency for the flight time of the drone.

In this paper, cycle performance analysis of two-stage compression two-stage expansion refrigeration system using eco-friendly refrigerants is presented to offer the basic design data for the operating parameters of the system. Eco-friendly refrigerant R600a(Isobutane) for freon refrigerant R22 were used working fluids in this study. The coefficient of performance(COP) of R600a is about 5% greater than that of R22 two-stage compression refrigeration system in the range of evaporation temperature –30℃∼-60℃. The coefficient of performance of two-stage compression and two-stage expansion refrigeration system decreases with the increasing condensation temperature and superheating degree but increases with the increasing evaporation temperature, subcooling degree and mass flow rate ration of intercooler.

Natural gas is the most realistic fuel among eco-friendly fuels. Natural gas production is limited, and in Korea, it is supplied and utilized in the form of liquefied natural gas (LNG). In the case of LNG, the vaporization point is 163 degrees below zero, so ordinary metal cannot be used due to its brittleness. The International Maritime Organization (IMO) defines metals that can be used in the IGC Code, and is used for storage containers, transportation containers, etc. based on the metals. Welding is essential in the manufacture of large structures such as LNG storage tanks. In this study, weldability studies related to cryogenic materials were conducted. In Part I of this study, high-manganese steel and part II were studied for two types of stainless steel (STS304L, STS316L), and in Part III, aluminum (AL5083). During laser welding, the shape of the Bead on Plate (BOP) was analyzed, and a total of nine cases were analyzed using laser power and welding speed as variables. It was confirmed that the penetration and the width of the welding width were linearly proportional to the amount of heat input. Based on this study, it is possible to conduct a follow-up study to find the optimal welding conditions for butt welding and fillet welding.

As the part of efforts to respond to the environmental pollution, the demand for clean energy is increasing. Natural gas is one of the most realistic alternatives, and interest in the storage and transportation containers to utilize the natural gas is growing. The production area of ​​natural gas is limited, and in Korea, it is imported in the form of liquefied natural gas. LNG is a cryogenic state with a vaporization point of -163°C, so the ordinary metal cannot be used due to its brittleness. The international maritime organization (IMO) defines the metals that can handle LNG in the IGC Code, and the research is ongoing. This study was a preliminary study to check the weldability of related metals and confirmed the shape of bead on plate (BOP) during the laser welding for each material. In part I, a study was conducted on the high manganese steel, and in part II, a study was conducted on the materials of STS304L and STS316L among the stainless steel. Based on this study, it can be used as an optimal welding condition for the butt and fillet welding.

As demand for eco-friendly energy increases, demand for natural gas and Liquefied natural gas (LNG) storage technologies continues to increase. LNG is a cryogenic environment with a temperature of -163°C, so ordinary metals cannot be used due to brittleness. Accordingly, IGC Code designates the cryogenic materials such as Invar, STS304L, Al5083-0, and High Manganese Steel. For fabricating those materials, research on welding possibility is the most important. Thus this study focused on the possibility of laser welding of the cryogenic materials. The weldability of High Manganese Steel was researched in this paper, the shape and the dimensions of the beads after bead on plate (BOP) welding were observed. The experiment was conducted on a total of 25 cases with laser power and welding speed of 5 cases each, and the width, height, and penetration of the beads were confirmed. It was confirmed that the paramenter of bead increased linearly with the laser power, and the paramenters of bead increased linearly with decreasing welding speed. Based on this study, high manganese steel can be applied in various industries by applying it to butt welding.

PURPOSES: This study investigates the effect on concrete pavement accordance with the curing methods in cool weather and supports the best method in the field. METHODS: Two field tests evaluated the curing methods of concrete pavement in cool weather. Firstly, five curing methods were tested, including normal curing compound, black curing compound, bubble sheet, curing mat, and curing mat covered with vinyl. Concrete maturity was compared from temperature data. Secondly, normal curing compound and curing mat with vinyl, which showed the best performance, were compared in terms of maturity and join condition index. RESULTS: From the field tests, it is an evident that curing mat with vinyl accelerated the concrete strength. Therefore, it is possible to conduct saw-cut works in cool weather, which minimizes damage on concrete at joint. CONCLUSIONS: For concrete pavement in cool weather, using curing mat with vinyl as the curing method could overcome the strength delay. Therefore, strength and durability problems on concrete at joint due to cool weather would be fewer in the future.

PURPOSES : This paper focuses on strength development according to the mix design with cement type and mineral admixture from laboratory and field tests in cool weather. METHODS : Two methods evaluated the mix design of concrete pavement in cool weather. Firstly, laboratory tests including slump, air contents, setting time, strength, maturity, and freezing-thawing test were conducted. Three alternatives were selected based on the tests. Secondly, a field test was conducted and the optimum mix design in cool weather was suggested . RESULTS : It is an evident from the laboratory test that a mix with type Ⅲ cement showed better performance than the one with type Ⅰ cement. There was a delay in strength development of a mix with mineral admixture compared to mix design without any mineral admixture. In the field test, type Ⅲ cement+flyash 20% mix design proved the best performance. CONCLUSIONS : For concrete pavement in cool weather, mix design using type Ⅲ cement could overcome the strength delay due to mineral admixture. Moreover, it is possible to make sure of durability of pavement. Therefore, strength and durability problems due to cool weather would decrease.

Inconel 718 alloy has excellent mechanical properties at room temperature, high temperature and cryogenic conditions. UTS of base metal is about 900MPa at room temperature; this is increased up to 1300MPa after heat treatment & aging-hardening. Mechanical properties of Inconel 718 Alloy were similar to those shown in the the results for tensile test; mechanical properties of Inconel 718 alloy's GTAW were similar to those of base metal's properties at room temperature. Mechanical properties at cryogenic conditions were better than those at room temperature. Heat-treated Inconel 718, non- filler metal GTAW on Inconel 718 and GTAW used filler metal on Inconel 718's UTS was 1400MPa at cryogenic condition. As a result, the excellent mechanical properties of Inconel 718 alloy under cryogenic conditions was proved through tensile tests under cryogenic conditions. In addition, weldability of Inconel 718 alloy under cryogenic conditions was superior to that of its base-metal. In this case, UTS of hybrid joint (IS-G) at -100˚C was 900MPa. Consequently, UTS of Inconel 718 alloy is estimated to increase from -100˚C to a specific temperature below -100˚C. Therefore, Inconel 718 alloy is considered a pertinent material for the production of Lox Pipe under cryogenic conditions.

In this study, we attempt to analyze for 4 compounds (MEK, MIBK, n-Butyl acetate, i-Butyl alcohol) in ambient air using on-line thermal desorber (on-line TD) with gas chromatograph/flame ionization detector (GC/FID). These compounds will be regulated by KMOE (Korean ministry of environment) within 2010. We tested two different experimentation. First, we try to find the influence of Nafion dryer for the 4 compounds. Second, we want to know basic analytical characteristic of target compounds through the linearity, reproducibility, and minimum detection limit. According to this study, target compounds are removed in Nafion dryer more than 80 percent, respectively. So, we progressed next experimentation progressed without Nafion dryer using hydrophobic cold trap. Results for each compounds showed good linearity (r²＝0.99 upper) and good precision (RSD＝1 % below). In additional, we analyzed the ozone precusors standard gas (56 compounds) using the same method to see if there are any peaks to be overlapped in ambient air. These results showed that there is no peak overlapped. This means that analytical system of this study could be used on-line analytical system. Minimum detection limit (MDL) value for this system are less than minimum malodor threshold concentration.

저온기 플라스틱 하우스내의 기상에 따른 수박의 저온장애 방지를 목적으로 하우스내의 위치별 온도분포와 냉해 발생률을 측정하였으며, 저온장해시 수박의 가시적인 증상을 조사하였다. 남북동 2중 하우스(남쪽 창)에서 온도분포 (12월 중순)는 중앙을 기준으로 동편(93.8%)이 서편(85.3%)보다 높고, 북쪽이 남쪽보다 1일 평균온도가 약 1~2℃ 높게 나타났다. 또한 부엽토(황토+퇴비: 2.5ton/200m2)가 사토나 황토 또는 점토에 비하여 남.북의 양방향에서 높게 발생되었다. 잎에서 냉해의 형태적 증상으로는 잎이 수침상으로 되었다가 잎이 점점 위로 말기며, 황화되는 경향을 보였으며, 냉해가 심할수록 줄기의 도관이 점점 막히는 경향을 보였다. 뿌리의 신장은 줄기나 잎의 생육보다 저온에 대하여 더욱 민감하게 작용하였다. 30℃에서 주근과 측근의 생장이 왕성하였으나 22℃에서는 측근의 발생이 억제되는 경향을 보였으며, 14℃와 6℃에서는 뿌리의 신장이 거의 정지되는 현상을 보였다. 이상의 결과에서 저온기에서는 온도가 높은 중앙부위에 수박을 정식하여 양쪽 가장자리로 줄기를 유인하여 재배양식이 온도관리 측면에서 휠씬 효율적인 것으로 나타났으며, 하우스내의 온도는 최저 22℃이상으로 하는 것이 뿌리 생장에 유리할 것으로 사료된다.

냉축열 잠열재로 Na2SO4.10H2O를 선정하여 냉축열을 위한 잠열축열 온도 수준을 NH4Cl과 KCI을 잠열온도 조절제로 활용하여 16℃에서 -0.3℃까지 조절하였으며, 상변화 사이클에 의한 열특성 변화 추이와 물성의 안정성을 실험 분석하여 다음과 같은 결과를 얻을 수 있었다. 1. 냉축열재로 선택한 Na2SO4.10H2O는 물성이 불안정한 상변화 잠열 재였으나, 조핵제로 BRX를, 증점제로 CBP를 첨가하여 물성을 안정시켰으며, NH4Cl과 KCl을 상변화 온도조절제로 선택하여 상변화 온도를 조절할 수 있다. 2. SSD＋NH4Cl서 NH4Cl을 g~21wt%로 증가시킴에 따라 상변화 온도는 16~-0.3℃로 조절할 수 있었으며, 잠열축열량은 30kca1/kg에서 23.4kca1/kg으로 감소하였고, 상변화 온도조절제, KCl을 l7wt%에서 25wt%로 증가시킴에 따라 상변화 온도를 14℃에서 4℃까지 조절할 수 있었다.

Canola(Brassica napus) 엽에서 추출한 미세막으로부터 PEG-dextran 2상분획법을 이용하여 세포막과 세포내막을 분리하였다. U2 상에 있는 원형질막의 K+-ATPase의 특이활성도가 미세막에 비하여 25℃에서 자란 canola는 6.6배, 10℃에서 4.6배 각각 증가되었다. 원형질막(U2)은 미세막이나 세포내막(L2) 보다 cytochrome-c-oxidase 활성이 적게 나타난 반면, 세포내막에서는 K+-ATPase의 특이활성도가 가장 적게 나타났다. 10℃에서 생장한 canola의 18:3/18:2 률은 25℃보다 29.2% 더 높게 나타났다. 원형질막의 2중결합지수는 10℃에서 생장한 canola가 25℃에서 생장한 것보다 8.9% 더 증가되었으며 세포내막에서도 같은 경향으로써 10℃에서 19.7% 더 증가되는 현상을 보였다. 또한 엽록소 함량은 10℃에서 생장한 것이 25℃에 비하여 17.3% 낮았다. Canola가 저온에서 생장시 주로 C18 지방산들이 변화되어, 세포막 내에 불포화 지방산이 많았으며, 그 중에서도 리롤렌산(18:3)이 크게 변화되는 현상을 보였다. 이러한 변화는 생리적으로 canola의 세포막이 저온에 살아가기 위한 하나의 수단으로 추정된다.

글로우 고압 방전 방식에 의한 저온 플라즈마(Non-thermal Plasma, NTP) 공정은 액상에서 광전자, 전자, OH-라디칼, 전자기 에너지 등 반응성이 높은 화학물질의 형성할 수 있다. 이 NTP는 공기를 carrier 가스로 활용하여 반응성이 높은 화학종을 생성하는데, 유기물을 효과적으로 산화시키는 고도산화공법의 일종이다. NTP의 강력한 산화력에도 불구하고, NTP 공정에서 발현되는 오염물질의 분해 메커니즘과 그 중간부산물 및 최종 생성물의 경로는 명확하게 밝혀지지 않아 연구가 필요한 실정이다. 본 연구는 폐수 내 다양한 오염물질이 어떠한 메커니즘으로 분해되는가를 실험적으로 규명하고, 2종(sulfamethazine sodium salt와 sulfathiazole sodium salt)의 sulfonamide 계열 항생제에 NTP 공정을 적용하여 제거성능과 분해경로를 검증한다. 또한, 대상 항생제의 분해가 폐수처리 과정에서의 분해 동역학 및 생태 독성과 어떻게 관련되는지를 확인하기 위해 주요 중간부산물 및 신규생성물의 fate를 확인한다. NTP 공정의 진보된 효과를 증명하기 위해 반응성 화학종인 과산화수소 (H2O2)의 순간 생성량을 정량하였으며, OH-라디칼 생성의 간접지표인 N-Dimethyl-4-Nitrosoaniline (RNO) 물질의 분해동역학적 성질을 바탕으로 분해속도계수를 산출하였다. H2O2의 농도는 초기 NTP 공정 적용 시 300 mg/L 까지 증가하였고, 1440 min 적용 시 약 12 mg/L로 감소하며 OH-라디칼 생성과 오염물질 분해에 관여하는 것을 확인하였다. 또한 RNO 물질은 일차함수 형태로 감소하며, 0.91/hr의 속도로 제거되었다. LC-MS/MS (6410 LC-ESI/MS/MS (QQQ), Agilent, USA) 분석을 통해 검출된 중간부산물과 신규생성물을 통해 분해경로를 확인하였다. 문헌과 실험결과의 비교는 NTP 공정이 OH-라디칼 발생 및 산화 환원제와 반응종의 상호 작용으로 인한 산화력 측면에서 다른 산화 공정보다 우수함을 보여준다. Daphnia magna를 이용한 생태독성(Toxicity Unit, TU) 결과는 폐수처리에 대한 NTP 공정 적용이 반응성 화학종의 생성촉진을 통해 독성의 저감에 기여함을 보여주며, 실험결과 TU 값은 초기 2.2 대비 24 hr 적용 후 0.8로 크게 감소하였고, 충분한 체류 시간이 핵심 설계요소임을 밝혔다. 궁극적으로 본 연구는 항생제의 효과적인 제어 및 부산물 관리방안에 대한 유용한 정보를 제공한다.

본 연구에서는 저온환경에서 콘크리트 동해를 방지하기 위해 생석회의 화학반응을 활용한 발열시트 및 단열재를 사용하여 제작한 거푸집 특성을 실험을 통해 평가하였다. -10°C 정온조건에서 거푸집 실험 결과, 발열시트가 부착된 거푸집의 경우 발열시트 내부 생석회의 발 열로 인해 타설 초기에 일반거푸집에 비해 10°C이상 높은 온도이력을 보여주었고 단열재를 부착한 거푸집의 경우 콘크리트 수화열을 보존하 여 지속적으로 높은 온도를 유지하는 특징을 나타냈다. 아이소핑크와 발열시트를 부착한 거푸집과 진공단열재를 붙인 거푸집이 압축강도나 적산온도에서 가장 높은 값을 가졌다. 압축강도 측정시 진공단열재 및 아이소핑크와 발열시트를 부착한 거푸집이 재령 3일에서 약 5 MPa로 가 장 높게 측정되었다. 몽골 현지 외기온도에서도 실험을 하였는데 앞선 결과와 마찬가지로 발열시트, 단열재를 함께 붙인 거푸집이 48시간 동안 25°C 이상으로 가장 높은 온도이력를 나타내었다. 따라서 거푸집에 발열시트 및 단열재 부착을 함으로써 발열 및 단열효과로 인해 저온환경에 서 콘크리트 강도발현에 도움을 주는 것을 확인할 수 있었다.

본 연구는 저온환경에서 경화가 가능한 알루미나시멘트 및 아질산염을 사용한 보수용 시멘트 모르타르의 기초성능을 평가하고자 하였다. 이를 위해 국내 건설현장에서 사용되고 있는 보수용 모르타르를 조사 및 선정하였으며, 이를 대상으로 알루미나시멘트, 아질산염을 치 환하여 혼입량 조절에 따른 실험평가를 실시하였다. 그 결과, 알루미나시멘트, 아질산염을 보수용 모르타르에 치환하여 사용할 경우 초기 강도 발현이 증진되었다. 또한 내화학성이 개선되었고 수축거동이 감소하였으며 동결융해에 대한 저항성이 증대되었다. 알루미나시멘트와 아질산 염을 2:1의 비율로 7.5% 치환하여 외부구조물에 시공한 결과 표면상태가 5개월 이상 양호하게 유지되었으며, 실제 외부구조물에 사용성이 우 수한 것으로 판단된다.

무스카리는 백합과의 단자엽식물로서 전세계에 약 50여종이 자생하고 있으며, 내한성이 강한 추식구근으로 지중해 연안과 중앙아시아 지역에 걸쳐 자생하고 있다. 주로 분화용이나 화단용으로 이용되며, 화색은 청색, 백색, 자주색이 있다. 우리나라에서는 번식은 주로 모구 의 기부에서 형성되는 자구를 분리하여 사용되고 있으나, 바이러스 감염, 모구의 비싼 가격, 대량번식의 어려움 등의 문제점이 있다. 따라 서 본 실험은 무스카리의 종자번식의 가능성을 알아보기 위해, 종자발아에 미치는 저온처리 및 발아에 필요한 온도와 광 조건에 대해 알아 보고자 실시하였다. 파종전 0과 15℃에서 15~90일까지 저온처리 후 20℃에서 파종한 결과 발아율이 0~6.7%로 매우 낮았다. 5와 10℃에 서는 저온 처리일수가 경과할수록 발아율이 높아졌는데, 5℃에서 75일과 90일처리는 파종전에 이미 각각 54%, 71%가 발아한 상태였고, 최종 발아율은 66.7%와 84.0%로 가장 높은 발아율을 보여 주었다. 5℃에서 70일간 저온처리 한 후 5, 10, 15, 20, 25, 30℃에서 파종하였는 데, 파종 전 발아율은 34%였고, 최종 발아율은 10℃에서 82.7%로 가장 높았고, 5와 15℃에서 각각 75.3%와 76.7%, 20~30℃에서는 48.0~58.0%로 나타났다. 그러나 50% 발아율까지의 일수는 15℃에서 4.7일로 가장 짧았으며, 10과 5℃에서 각각 18.7일, 28.3일로 길었 다. 따라서 무스카리 종자는 파종 전 5℃에서 75~90일간 저온처리한 후 10~15℃에서 파종하는 것이 발아율 향상에 효과적일 것으로 판단 되었다.

To the goal of improving the early compressive strength of the mortar including Ground granulated blast furnace slag under low-temperature environment, Industrial byproducts including SiO2 and Al2O3 was fired and than 7% of it was added into Ground granulated blast furnace slag. By checking compressive strength and activity index from different mixing rate, in spite of low strength development than OPC 100%, when using firing powder, the expectation of increasing strength by curing time was affirmative