This study examined the effect of ultraviolet (UV) application on bacterial disinfection in a commercialized humidifier using ultrasonic wave (UW). To accurately examine disinfection kinetics in tap-water condition, tap-water was sterilized using a filter, and then inoculated with pure cultures of E. coli and P. putida with known viable counts. The disinfection kinetic characteristics were experimentally compared when UV alone, UW alone, and UW+UV together were applied in disinfecting the added bacteria in the commercialized humidifier. When UV alone was applied, bacterial disinfection kinetics followed a first-order decay reaction, and showed an approximately 10-time weaker disinfection compared to the typical UV disinfection in water treatment or wastewater treatment. When UW alone was applied, bacterial disinfection kinetics followed a second-order decay reaction with a low disinfection rate constant of 0.0002 min-1(CFU/mL)-1. When UV and UW were applied together, however and interestingly, the disinfection rate constant (0.0211 min-1(CFU/mL)-1) was approximately 100 times increased than that for the UW alone case. These results revealed that the co-use of UV and UW can provide synergistic effect on bacterial disinfection in a tap-water condition in household humidifiers.

To check the linguistic features of the interviews from the humidifier disinfectant victims, the research compared the interviews with the modern spoken corpus and analyzed them in respect of vocabulary and grammar. The results are as follows. First, a common point was deduced by the lexical metaphor that the relationship between the informants and their companion animals, the victims of the case, is as close as a family member. The result is very meaningful, in that it is very rare that the materials of the lexical metaphor provide and predict the relationship between humans and companion animals. Second, the actuality of the semi-formal talk was well revealed by the grammatical feature, in terms of many fragmentary sentences and frequent uses of the ‘-haeyo’ style. However, certain types of conclusive endings such as ‘-keodeunyo’, ‘-jyo’, or ‘-jahnayo’, which are used by the speaker's assumption on the state of hearer's knowledge, were frequently used compared to the modern spoken corpus. The features of these conclusive endings assuming hearer's knowledge and ignorance show that the linguistic materials of informants implicate their intent to inform the society of the case and to get recognition from the society.

Toxicities to many organs caused by humidifier disinfectants have been reported. Recently, humidifier disinfectants have been reported to cause cardiovascular, embryonic, and hepatic toxicities. This study was designed to investigate the toxic mechanism of humidifier disinfectants and compare toxicity in a cellular model and a zebrafish animal model. Because brain toxicity and skin toxicity have been less studied than other organs, we evaluated toxicity in a human dermal cell line and zebrafish under various concentrations of humidifier disinfectants that included polyhexamethyleneguanidine phosphate (PHMG), oligo-[2-(2-ethoxy)-ethoxyethylguanidinium- chloride] (PGH) and methylchloroisothiazolinone/methylisothiazolinone (CMIT/MIT). A human dermal fibroblast cell line was treated with disinfectants (0, 2, 4, 6, 8, and 16 mg L-1) to compare their cytotoxicity. The fewest PHMG-treated cells survived (up to 33%), while 49% and 40% of the PGH- and CMIT/MIT-treated cells, respectively, survived. The quantification of oxidized species in the media revealed that the PHMGtreated cells had the highest MDA content of around 28 nM, while the PGH- and CMIT/ MIT-treated cells had 13 and 21 nM MDA, respectively. As for brain toxicity, treatment of the zebrafish tank water with CMIT/MIT (final 40 mg L-1) for 30 min resulted in a 17- fold higher production of reactive oxygen species (ROS) than in the control. Treatment with PGH or PHMG (final 40 mg L-1) resulted in 15- and 11-fold higher production, respectively. The humidifier disinfectants (PHMG, PGH, and CMIT/MIT) showed severe dermal cell toxicity and brain toxicity. These toxicities may be relevant factors in understanding why some children have language disorders, motor delays, and developmental delays from exposure to humidifier disinfectants.

목적: 가습기의 살균제 성분으로 사용된 PHMG(polyhexamethylene guanidine)와 PGH Oligo[2-(2-ethoxy) ethoxyethyl guanidine chloride]는 주로 살균제나 부패방지제 등으로 사용되는 구아니딘(guanidine) 계열의 화학물질이다. 본 연구는 가습기 살균제로 인한 소프트 콘택트렌즈의 물리적 특성의 변화를 비교 분석하였다. 방법: 살균제의 재료인PHMG와 PGH의 성분이 포함된 가습기 살균제를 물 2L 기준 0.25%를 첨가하여 희석하였으며 시간경과 별로 각각 수화시킨 후 Disposable soft contact lens와 Daily-wear soft contact lens에 대한 기본적인 물리적 특성의 변화량을 water content, refractive index, spectral transmittance, pH 등을 측정하여 분석하였다. 결과: Disposable soft contact lens의 굴절률은 1.406에서 1.331로 Daily-wear soft contact lens은 1.450에서 1.441으로 감소하였으며 함수율은 55.62%에서 69.47%, 34.49%에서 37.50%로 각각 증가하였다. 가시광선 투과율 측정 결과, UV-B 영역의 투과율은 시간의 경과에 따라 약 3% 정도의 증가량을 보였다. 실험 후 pH 변화는 8.0에서 8.4로 증가하였다. 또한 두 종류의 소프트 콘택트렌즈 모두 1일 경과 후 가장 많은 변화량을 보였다. 결론: 가습기 살균작용을 위해 사용하는 물질인PHMG, PGH는 소프트 콘택트렌즈의 물리, 화학적 특성 변화를 가져오는 것으로 나타났다.

본 연구에서는 고분자전해질 연료전지의 연료가습을 위하여 막 증발법을 적용한 막가습기를 제작하여 특징과 성능을 알아보았다. 막가습기 내부 물의 온도를 30~60℃, 연료기체의 유속을 300~3,000 mL/min, 막 가닥수를 10, 50, 100 가닥으로 변화 하였을 때 결과를 dew point로 나타내었다. 그 결과 60℃일 때 51.19℃, 900 mL/min일 때 54.22℃, 100 가닥일 때 60.03℃로 연료 가습성능이 가장 좋았다. 특히, 막 가습기 물질 전달식의 모델링을 통해 연료전지에 적용할 때 막 가습기 공경 크기에 따른 반응기체의 가습량을 예측하는 것이 가능하였다. 100 W급 스택에 적용하였을 때, 전압과 출력값이 변화되지 않고 안정적으로 작동하였으며 제작한 막 가습기는 기존 기포가습기보다 부피는 훨씬 작으면서도 가습 성능은 우수한 것을 알 수 있었다.

접목묘의 활착촉진을 위해서 활착촉진 시스템 내의 상대습도가 90% 이상으로 균일하게 조절되어야 하는바, 본 연구에서는 초음파 가습기와 전극봉식 가습기를 이용하여 상대습도를 조절할 때 가습방식에 따른 가습입자의 평균 입경과 활착촉진 시스템 내의 상대습도 분포를 분석하였다. 초음파 가습기와 전극봉식 가습기로부터 발생된 가습 입자의 평균 입경은 각각 7.58±0.14, 9.01±0.06 μm로 나타났다. 한편 가습기 토출구로부터의 거리가 증가할수록 가습 입자의 크기가 조금씩 증가하였는데, 이것은 가습기에서 발생된 입자가 토출구로부터 멀어질수록 입자가 서로 결합되어 가습입자의 크기가 조금씩 증가한 것으로 판단된다. 활착촉진 시스템 내의 상대습도를 90%로 설정한 조건에서 초음파 가습기와 전극봉식 가습기를 사용하였을 때 0.4, 1.1, 1.8 m 높이에서의 상대습도는 초음파식의 경우 각각 92.1±5.3, 90.9±5.6, 89.7±6.8%, 전극봉식의 경우 각각 93.4±5.4, 90.7±5.9, 89.3±7.0%로 나타났다. 초음파 가습기에서 발생된 가습 입자가 전극봉식에 비해서 다소 작기 때문에 부유가 쉽게 이루어져 시스템 내에서 상대습도의 공간 분포가 균일하게 나타난 것으로 판단된다.

It has been reported that students hold various intuitive ideas about classroom experiences as well as natural phenomena. In addition, students may hold intuitive ideas about some means of science instruction. Two everyday devices, such as a humidifier and an electric heater, were investigated in terms of students' intuitive ideas. A total of 36 students (nine students from each of the following level; fifth-, eighth-, eleventh-grades, and college) were selected from the Central Texas Area. The researcher interviewed each subject. Less than 30 percent of the subjects believed that prolonged use of an electric heater in a closed small room will lead to the decreament of humidity in the room. However, only two students were aware that increased temperature lowers the humidity. Students held two major intuitive ideas about humidifier: human-centered and air-centered. The subjects who held human-centered views about humidifier believed that a humidifier clears human throats and lungs, or helps people to breathe easier. The subjects whose ideas were categorized as air-centered responded that a humidifier generates oxygen, cleans air, or provides moisture into the air. Higher grade students held more sophisticated ideas about electric heater and humidifier. Students' intuitive ideas about electric heater and humidifier were qualitatively different from those expected. Therefore, everyday devices which may be frequently used for science instruction should be investigated in terms of students' intuitive ideas. At the same time intuitive ideas about such devices should be incorporated into the planning of science instruction, curriculum design, and teacher education.