Earticle

Research was conducted to obtain a fire investigation database by observing the evolution of lithium ion batteries and debris according to each solvent. Hot water, room temperature water, water with ice, and water with dry ice are placed in each tank, a torch is used to activate a fully charged 18650 lithium-ion battery, then each tank is placed on fire. As a result of the study, the lower the temperature, the shorter the extinguishing time, the time taken for extinguishing, the temperature difference before and after the experiment, the percentage of residual value of lithium ion, the remaining battery after runaway, whether or not an explosion occurred during the fire, the duration of the explosion, and the residual value in the wreckage increased, and it was confirmed that the fire suppression time and the residual rate in ice water were high.

문화재의 훼손은 다양한 형태로 발생된다. 특히 옥외에 노출되어 있는 금속문화재의 표면 손상은 인위적인 훼손인 페인트나 유성물질 성분의 낙서 등과 같은 행위로 유물의 역사적, 미술사적 가치를 저하시킨다. 그러므로 본 연구에 서는 친환경적이고 인체에 무해한 dry-ice pellet cleaning을 페인트 및 유성물질을 제거하는데 적용하였으며 결과를 습포 법과 비교하였다. 실험 결과 습포법으로 제거할 경우 유성페인트는 제거는 되었으나 금속 표면에 얼룩이 남아 있었으며 락 카 스프레이는 제거가 잘 이루어지지 않고 수지가 들떠 있는 현상이 나타났다. Dry-ice pellet cleaning으로 유성페인트를 제거한 경우 표면관찰, 색도계, FT-IR, SEM 분석을 통해 유물 표면에 손상 없이 깨끗하게 제거되었으며 락카 스프레 이로 제거한 경우 육안 관찰로는 깨끗하였으나 SEM 관찰 결과 미세 입자가 표면에 남아있는 것이 관찰되었다. 그러므로 본 연구를 통해 dry-ice pellet cleaning의 대체 가능성과 한계성을 함께 확인할 수 있었다.

Damage of cultural properties happens variously. Particularly, the surface damage of metal cultural properties exposed outdoors lowers historical and art historical value of artifact by artificial damage such as paint, scribbling containing oily material and so on. Therefore, this study compared dry-ice pellet cleaning with poultice when clearing paint and oily material environment-friendly, harmlessly to humans and without damage of artifact. As the result of experiment, when clearing those (paint and oily material) by poultice, oily paint was cleared, but there were spots of metal surface. Also, Lacquer spray wasn’t well cleared, and resin came off the surface of artifact. When clearing those by dry-ice pellet cleaning, oil paint was cleanly cleared without surface damage of artifact according to Stereoscopic microscope observation, color-measurement, FT-IR, SEM analysis. Also, lacquer spray seemed to be cleared with the naked eye, but there were minute particles on surface according to the result of SEM observation. Consequently, we could confirm possibility of dry-ice pellet cleaning substitution.

This study was performed to compare the performance of Sanita-Kun dry medium culture plate with those of traditional culture medium and Petrifilm dry medium culture plate for the enumeration of the mesophilic aerobic bacteria in milk, ice cream, ham, and codfish fillet. Mesophilic aerobic bacteria were comparatively evaluated in milk, ice cream, ham, and codfish fillet using Sanita-Kun aerobic count (SAC), Petrifilm aerobic count (PAC), and traditional plate count agar (PCA) media. According to the results, all methods showed high correlations of 0.989~1.000 and no significant differences were observed for enumerating the mesophilic aerobic bacteria in the tested food products. SAC method was easier to perform and count colonies efficiently as compared to the PCA and PAC methods. Therefore, we concluded that the SAC method offers an acceptable alternative to the PCA and PAC methods for counting the mesophilic aerobic bacteria in milk, ice cream, ham, and codfish fillet products.

This study was performed to compare the efficiency and accuracy of Sanita-Kun dry medium with those of conventional culture and Petrifilm dry medium methods for enumerating coliforms and Escherichia coli in milk, ice cream, ham, and codfish fillet. All 3 methods showed high correlations each other and no significant differences in enumerating coliforms and E. coli. In addition, the Sanita-Kun method was easier to count microbial load than the Petrifilm method. Therefore, we concluded that the Sanita-Kun method can be used as an alternative to conventional culture and Petrifilm methods for the analysis of coliforms and E. coli in milk, ice cream, ham, and codfish fillet products.

The experiment was carried out to study the effect of dry ice expanded tobacco (DIET) blending ratio on the physical properties of cigarettes. Vnencapsulated pressure drop (UPD) of the cigarette decreased from 85 mmWG to 78 mWG when the DIET blending ratio increased from 0% to 60%, but it increased in the range of over 60% blending ratio. But the overall UPD/EPD ratio of these cigarettes showed a decreasing tendency. Cigarette ventilation rate increased from 55% to 66% with the increased blending ratio of expanded tobacco and loose ends also showed the same tendency. The higher the blending ratio of expanded tobacco, the faster became the static burning time from 7' 34" to 5' 02". However, the cigarette hardness was almost not affected by the blending ratio.ing ratio.

Carbon dioxide is the fourth most abundant gas in the earth's atmosphere, and it is widely used in the chemical industry. Solid carbon dioxide is commonly known as dry ice. At low concentration, carbon dioxide appears to have little toxicological effect. At higher concentrations, however, it can produce an increased respiratory rate, tachycardia, cardiac arrhythmia, loss of consciousness, convulsion, and even death. Management of carbon dioxide poisoning requires the immediate removal of an individual from the toxic environment and administration of oxygen. It is important to know the concentration of carbon dioxide to which a patient has been exposed. We report a case of acute poisoning from solid carbon dioxide in a patient presenting with drowsiness and diminished mental capacity when she arrived in the emergency department. She recovered completely after administration of oxygen with conservative treatment.

액체 탄산의 단열팽창하여 얻은 드라이아이스 snow로부터의 펠렛제조기와 이들 펠렛을 이용한 표면 세정용 블래스팅 장치를 설계 제작하였다. 본 블래스팅 장치는 적은 압력과 적은 량의 공기로도 다양한 오염물질 녹, 기름때, 라커막, 페인트 제거에 강한 세정력을 얻을 수 있었다. 이 때 호퍼 용량은 12 kg이고, 펠렛 분사량은 0-1.2 kg/min 까지 조절이 가능하였다. 드라이아이스 펠렛의 impact는 한계 거리 안에서는 거리에 무관하며, 드라이아이스 분사의 impact stress, 각도 및 질량 속도에 의존하였다. 또한 블래스팅의 세정력은 impact와 대상 물질의 열적 성질 및 표면 조도에 의존하였으며, 유리, 구리, 황동, 강철, 아크릴 기판의 순서로 감소하였다. 그리고 세정 속도는 같은 기판에 붙은 오염물의 경도, 부착력에 의존하였으며 그리스, 에폭시, 페인트 순으로 감소하였다. 사용 중 소음도는 대략 85-100 dBA이었다.

Pelletizer of dry ice snow produced by adiabatic expansion of liquid carbon dioxide and their blaster were designed and manufactured. The blaster had a high cleaning power against various contaminants on the surface such as stain, oily dirt, lacquer film and paints with low blasting pressure and low consumption of blasting air. The capacity of hopper for dry ice pellet supply was 12 kg and the mass rate of pellet blasting was controlled in 0 to 1.2 kg/min. The impact of the pellets was independent of standoff distance within a certain limiting distance, and dependent on the impact stress, angle and mass rate of dry ice pellet blasting. On the other hand the cleaning power was influenced by thermal properties and surface roughness of the substrates and decreased in the order of glass, copper, brass, steel and acryl. The power was also affected by hardness and adhesion of the contaminant on the substrate, and decreased in the order of grease, epoxy and paint. The noise was detected during blasting in the range of 85 to 100dBA.

드라이아이스 스노우 젯(dry ice snow jet)을 액체 이산화탄소의 고압팽창에 의해 만들고 운반기체에 의해 더욱 가속시킬 수 있었다. 코팅의 제거기구는 표면 오염입자의 그것과 크게 다르지 않았다. 코팅의 제거를 Hutchings 식으로 정량적으로 표현할 수 있었다. 이들 식에 의한 plot에서 얻은 두개의 매개변수로 코팅의 제거 속도와 단위 이산화탄소의 질량에 의해 제거된 비 코팅면적을 예측할 수 있었으며 아울러 실험데이터의 신뢰도와 실험 에러의 보정도 가능하게 되었다. 노즐 기판 거리와 노즐길이를 바꾸었을 때 얻어진 이들 plot이 한점에서 만날 수 있음을 알 수 있었으며 이점이 jet plume을 모음에서 얻어진 scar 반경의 증대효과와 jet를 확산시킴에서 얻어진 scar 반경 증대효과가 균형을 맞추는 데서 얻어진 것으로 판단된다.

Dry ice snow jet was produced by high-pressure expansion of liquid carbon dioxide and subsequent acceleration by carrier gas flow. Removal mechanism for coating was not so different from that for contaminating particles on the surface. The removal of coating was quantitatively described by Hutchings' equation. The two parameters obtained from the plot, were used to predict the removal rate or the specific coating area removed by a unit mass of carbon dioxide. Their values also enhanced the reliability of the experimental data and enabled the experimental errors corrected. Hutchings' plots obtained with various values of either stand-off distance or nozzle length tends to meet apparently at a single unique point at which the scar-size enlargement by focusing jet plume was balanced with that by spreading it.

도로시설은 교통을 위한 가장 기본적인 인프라 시설로, 원활한 교통흐름을 위해 다양한 정보가 노면에 표시되어 있다. 이러한 정보는 도로를 유지 관리하는 과정에서 지속적으로 제거되고 다시 표시하게 된다. 노면표시를 제거하는데 있어서 기존의 방법은 토치와 그라인더를 이용한 반복 작업으로 위험성과 함께 작업자가 운행 중인 차량에 직접 노출되는 문제점을 갖고 있었다. 또한 노면표시 중 일부인 차선을 효과적으로 제거하기 위한 개선방안으로 자동화 장비의 도입과 워터젯을 이용한 차선제거 장비가 개발되어 활용되고 있으나 몇 가지 문제점을 갖고 있다. 이에 본 연구는 친환경 세척기술의 하나인 드라이아이스 블래스터 장비 도입을 통하여 자동화 차선제거 장비개발의 가능성을 검토하고자 하였다. 기본 연구 수행 결과 드라이아이스 블래스터를 차선제거에 적용하는 것은 가능할 것으로 판단되며, 향후 구체적인 장비 개발을 위한 경제성 및 타당성 분석하는데 추가적인 연구가 요구될 것으로 판단된다.

Road is one of the infrastructure facilities, on which lines include various information for guiding a smooth traffic flow. This line marking work is continually removed and re-marked during maintenance. However, some problems exist when the line marking work is conducted. Traditional methods of using grinders and torches have risk of repetitive skill, and workers are exposed directly to the hazardous situations. Moreover, even though the equipment has developed, the line removing work induces environmental contamination and pollution line on the road. Therefore, this study can become one of the eco-friendly cleaning technologies using dry ice blaster equipment, and the new development of equipment will improve method of pavement marking removal. Also, it can introduce innovative automation in construction.

이 연구는 과학 활동의 인식론적 논제에 초점을 둔 탐구 실험을 설계 및 시범 적용하고, 실험 활동과 반성적 논의를 분석하여 교육적 함의를 도출하고자 하였다. 사범대학 과학교육과에 소속된 대학원생 3명이 자발적으로 연구에 참여하였다. 연구참여자들은 실험 1에서 안정적 탐구의 특징을 보여주었지만, 실험 2의 작지만 지속적인 변화는 실험을 새로운 설명체계를 찾는 유동적 탐구의 국면으로 이끌었다. 연구참여자들은 여러 가지 밑천을 동원해서 새로운 가설과 모형을 제안하고, 이를 검증할 추가 실험을 요청하였다. 반성적 논의과정에서 연구참여자들은 다음과 같은 세 가지 인식론적 논제를 이끌어 냈다. 첫째, 실험 초기에 자신의 관찰이 이론 의존적이었다. 둘째, 관찰사항이 더 이상 이론에 의존할 수 없는 위기 국면에 봉착하면 관찰과 이론의 조정이 진행된다. 셋째로 관찰과 이론의 관계에 따라 안정적 탐구나 유동적 탐구가 수행된다. 이상의 연구 과정과 결과를 토대로 도출된 예비교사 교육의 함의는 다음과 같다. 첫째, 이 연구에서는 안정적 탐구에 뒤이어 유동적 탐구가 자발적으로 진행 될 수 있음을 보였으며 그 활동의 예시를 함께 제시하였다. 둘째, 이 연구에서는 탐구에 뒤따른 반성적 논의를 통해 연구참여자들이 자신의 경험에 기반하여 인식론적 논제를 이끌어 낼 수 있음을 확인하였다.

The purpose of this study is to design and apply a pilot inquiry experiment focusing on the epistemological issues of scientific activities, and derive educational implications by analyzing experimental activities and reflective discussions. Three graduate students who major in science education participated in the study voluntarily. Participants showed the characteristics of stable enquiry in Experiment 1. However, the small but continuous changes in Experiment 2 led the experiment to a phase of fluid enquiry seeking new theories. Participants mobilized various resources, proposed new hypotheses, and models and requested additional experiments to verify them. In the process of reflective discussions, the participants led to the following three epistemological issues. First, at the beginning of the experiment, their observations were theoretically dependent. Second, when the observations were no longer coherent with theory, they face a crisis, and the adjustment of observation and theory proceeds. Third, stable enquiry and fluid enquiry are performed according to the relationship between observation and theory. The educational implications of school science inquiry based on the above process and results are as follows: First, this study shows that fluid enquiry can follow stable enquiry naturally, and examples of the activities are presented together. Second, in this study, it was confirmed that participants could draw up epistemological issues based on their experiences through reflective discussions following inquiry.