Cu<SUB>54</SUB>Ni<SUB>6</SUB>Zr<SUB>22</SUB>Ti<SUB>18</SUB> 벌크비정질 합금의 Nd:YAG 레이저 점용접 특성

김종현(J. H. Kim),이제훈(J. H. Lee),신승용(S. Y. Shin),배정찬(J.C. Bae),이창희(C. H. Lee) 한국레이저가공학회 2005 한국레이저가공학회지 Vol.8 No.2

  Weldability is largely dependent on the phase evolution and the microstructure of the weld. For the weld ability of the Cu<SUB>54</SUB>Ni<SUB>6</SUB>Zr<SUB>22</SUB>Ti<SUB>18</SUB> bulk metallic glass, the crystallization affects the sensitivity of the weld to the brittle failure.<BR>  In order to suppress the irreversible crystallization, Nd:YAG laser welding was chosen. The pulsed Nd:YAG laser was irradiated onto the BMG plate and the effects of the pulse shape [peak power intensity and pulse duration time] on the crystallinity were evaluated.

주택 실내ㆍ외에서의 PM<SUB>10</SUB>, PM<SUB>2.5</SUB> 농도와 호흡기계증상과의 관련성 조사

박지연(Ji Yeon Park),서혜경(Hye Kyung Seo) 한국실내환경학회 2005 한국실내환경학회지 Vol.1 No.2

This study, conducted from April to May 2004 in the metropolitan and surrounding areas of Seoul, Korea, was performed to show the relationship between indoor and outdoor levels of PM<SUB>10</SUB> and PM<SUB>2.5</SUB> concentrations in 14 residential houses. In addition, indoor/outdoor ratios of PM<SUB>10</SUB>, PM<SUB>2.5</SUB> concentrations were calculated. The relationship between the PM<SUB>10</SUB>, PM<SUB>2.5</SUB> concentrations and respiratory symptoms by self recording questionnaire of 14 houses was investigated. In conclusion, although the results of this study failed to establish the relationship between PM<SUB>10</SUB>, PM<SUB>2.5</SUB> concentrations and respiratory symptoms among residents, the levels of indoor PM<SUB>2.5</SUB> were significantly higher than those of outdoor levels. The indoor PM<SUB>10</SUB>, PM<SUB>2.5</SUB> concentrations were increased by the amount of time spent of residents. Further research should be directed to establish the relationship between PM<SUB>10</SUB>, PM<SUB>2.5</SUB> concentration and respiratory symptoms.

유아교육기관에서의 실내공기질 조사 및 실내활동에 따른 입자상오염물질의 농도특성

최영아(Young-A Choi),이태정(Tae-Jung Lee),김동술(Dong-Sool Kim) 한국실내환경학회 2006 한국실내환경학회지 Vol.3 No.3

This study was performed to investigate indoor air quality and to characterize the concentration of particulate matters followed by human activities in preschool classrooms. Concentrations of PM<SUB>10</SUB>, PM<SUB>2.5</SUB>, and PM₁ were measured every 5-minute intervals by means of a dust monitor adopting the principle of light scattering. Two mini-volume air samplers were used further to measure the I/O concentration ratio of PM₁? and to calibrate the dust monitor since the photometric method often exaggerates the mass of fine particles. The calibration factor in the study environment was determined as 0.64. In the preschool classrooms, the ranges of average indoor PM<SUB>10</SUB>, PM<SUB>2.5</SUB>, and PM₁ concentrations were 51.5~117.6, 21.5~98.4, and 16.2~84.5 ㎍/㎥, respectively, while that of I/O concentration ratio was 0.8~1.3. Based on correlation analysis among various environmental parameters, PM₁ was slightly correlated with humidity (r=0.416, p<0.01). However, outdoor PM<SUB>10</SUB> was strongly related with indoor PM<SUB>2.5</SUB> (r=0.95, p<0.01), with PM₁ (r=0.94, p<0.01), and with PM<SUB>10</SUB> (r=0.84, p<0.01). The trend of PM<SUB>2.5</SUB> and PM₁ concentrations appeared to be very similar unlike the case of PM<SUB>10</SUB>. Since the elevated coarse particle concentration (2.5㎛<dp<10㎛) and the average PM<SUB>2.5</SUB>/PM<SUB>10</SUB> ratio were highly dependent on classroom activities, the parameter of PM<SUB>2.5</SUB>/PM<SUB>10</SUB> ratio was intensively studied with 7 different indoor activities in the preschool classrooms.

교내 신축건물의 실내공기오염물질에 관한 연구

이건주(Keon Joo Lee) 상지대학교 환경과학기술연구소 2007 환경과학연구 Vol.13 No.1

  신축건물에서 발생되는 실내공기 오염물질 중 포름알데히드(HCHO)와 PM₁?, PM<SUB>2.5</SUB>의 농도분포특성을 파악하고자 교내 신축건물중 자연과학관, 한의학관, 믿음관을 대상으로 실내공기 오염도 실태조사를 실시한 결과 평균값은 PM₁?의 경우 한의대는 87.96 ㎍/㎥, 기숙사는74.07 ㎍/㎥, 자연과학관은 64.84 ㎍/㎥이고 PM<SUB>2.5</SUB>의 경우 한의대는 46.29 ㎍/㎥, 기숙사는27.77 ㎍/㎥, 자연과학관은 37.03 ㎍/㎥으로 조사되었다. 그중 인체에 직접 적인 영향을 미치는 포름알데히드와 PM₁?, PM<SUB>2.5</SUB>의 교내 측정을 통하여 학생에게 미치는 영향을 예측, 평가하였다.   The study for evaluation the concentration distribution characteristics of M₁?, PM<SUB>2.5</SUB> and Formaldehyde(HCHO), indoor-air pollutants from new buildings, (that was) conducted as an investigation into the actual condition of indoor-air pollution in Natural Science hall, Oriental Medicine hall, and Miteum Hall. In the case of M₁?, Oriental Medicine hall, Miteum Hall and Natural Science hall of average density are 87.96 ㎍/㎥, 74.07 ㎍/㎥, 64.84 ㎍/㎥ respectively. In the case of PM<SUB>2.5</SUB>, Oriental Medicine hall, Miteum Hall and Natural Science hall of average density are 46.29 ㎍/㎥, 27.77 ㎍/㎥, 37.03 ㎍/㎥ respectively. Then we predicted and estimated about the influence on students through measurement of M₁?, PM<SUB>2.5</SUB> and Formaldehyde(HCHO) affecting the human body directly.

Photoreflectance 측정에 의한 InxGal-xP의 특성 연구

김동렬(D. L. Kim),유재인(J. I. Yu) 한국레이저가공학회 2005 한국레이저가공학회지 Vol.8 No.3

  InxGa<SUB>1-X</SUB>P/GaAs structures were grown by chemical beam epitaxy(CBE). Pure phosphine (PH₃) gases were used as group V sources. For the group Ⅲ sources, TEGa, TmIn were used. InxGa<SUB>1-X</SUB>P epilayer was grown on SI­GaAs substrate and has a 1­㎛ thick. We have investigated the characteristics of InxGa<SUB>1-X</SUB>P by the photoreflectance(PR) spectroscopy. The PR spectrum of InxGa<SUB>1-X</SUB>P shows third derivative feature whose peaks provide energy gap. The energy gap of InxGa<SUB>1-X</SUB>P has deduced composition x. From temperature dependance of PR spectra, temperature coefficient is dEg/dT=-3.773×10?⁴ eV/K, and Varshni coefficients a and β values obtained 4×10?⁴ eV/K and 267 K respectively. Also, interaction αB was 19.4 meV using the Bose­Einstein temperature relation, and Θ value related the average phonon frequency were 101.4 K. In particular, shoulder peak related to defects observed in PR signal that measured in temperature 82 K.

대학도서관 내 실내공기질 조사 및 입자상물질의 특성에 관한 연구

김지현(Ji-Hyun Kim),이태정(Tae-Jung Lee),황인조(InJo Hwang),김동술(Dong-Sool Kim) 한국실내환경학회 2008 한국실내환경학회지 Vol.5 No.1

Recently Korean government introduced and strengthened the environmental polices to manage and enhance indoor air quality as a major assignment. As a result, “Indoor Air Quality Management Act”has been activated since May 2004. However, among many multi-usage facilities, the school environment has been excluded from such regulations. Thus, the purpose of this study is to survey indoor aerosol and CO₂ concentrations in a university library which is one of major school facilities. Concentrations of PM<SUB>10</SUB>, PM<SUB>2.5</SUB>, and PM₁ were intensively measured every 5 minute interval by means of a dust monitor with light-scattering principle. The mini-volume air samplers were used further to analyze inorganic elemental compositions of PM₁? and to inter-compare with the dust monitor. Carbon dioxide was simultaneously monitored by a multi-gas monitor equipped with a non-dispersive infrared system. PM<SUB>10</SUB> concentrations did not exceed the indoor air quality standard(150㎍/㎥) for all the sampling places. However, quick and steep increases of aerosol concentration were observed during the Asian Dust storm period. In addition, the concentration of PM<SUB>10</SUB>(74.1㎍/㎥) in the main university office was the highest among the entire sampling places. Although there was no specific pollution source in the library, the levels of aerosol and CO₂ increased quickly due to various outdoor sources and human activities. The average CO₂ concentration measured in three reading rooms, where ventilation was not fully operated, exceeded the indoor air quality standard of 1,000 ppm. Based on these case studies, effective management and reduction plans for indoor aerosol and CO₂ were suggested for the large scale public buildings including university libraries.

심폐지구력 검사로서 YMCA 스텝테스트와 최대산소섭취량 (VO<SUB>2max</SUB>)간의 상관성

이온(On Lee),김성수(Sung-soo Kim),김연수(Yeon-soo Kim),손현진(Hyun Jin Son),김유미(Kim Yu-Mi),최보율(Bo Youl Choi) 한국역학회 2008 Epidemiology and Health Vol.30 No.1

  The purpose of this study is to determine that YMCA step-test is useful method of cardiovascular fitness field-test for large scale study of epidemiology. 57 adults participated in this study. They are recruited considering subject"s clinic status and gender proportion. Cardiorespiratory fitness of each participant was determined by grade exercise testing(GXT) with gas analysis and YMCA step-test. There are at least more two days an interval between the tests. Data were analyzed with a statistics program, SPSS version 14.0, by applying Spearman correlation coefficient and independent t-test and Fisher"s exact test with a statistical significant level of α<.05. The results of this study were as followed. VO<SUB>2max</SUB> value exhibited significant correlation with YMCA step test scale(male : r=-.611, p=.001 ; female: r=-.656, p>.001). Our result is that validity of YMCA step-test is acceptable. YMCA step test is vary efficient as dimension of investigator"s and subject"s effort then the other field-test for assessment of cardiorespiratory. Therefore, Step test is useful for large scale study of epidemiology.

기후변화를 고려한 포장 보조기층의 적정입도분포에 관한 실험연구

최재순(Jaesoon Choi),한누리(Nuri Han) 한국지반환경공학회 2013 한국지반환경공학회논문집 Vol.14 No.7

최근, 시강우량의 최대치의 기록이 매년 바뀌고 있으며 이로 인해 도로의 침수피해 사례가 증가하고 있다. 이러한 이유로 새로운 배수포장체가 개발되고 있으나 보조기층에 대해서는 별도의 고려가 없다. 본 연구에서는 보조기층의 강도와 투수성을 함께 고려한 적정입도분포 기준을 제안하며, 이때 실내실험을 통해 각각의 강도특성 및 투수성을 비교하고자 한다. 실험에 앞서 국내외 보조기층 기준에 대한 시방기준을 토대로 4가지의 대표적인 입도분포를 산정하고 이를 실험하였다. 실험에 있어서 강도특성은 회복 탄성계수 산정을 비교하고, 투수특성은 수직방향의 상향 및 하향 투수계수를 비교하였다. 회복탄성계수 산정은 MR 시험을 통하였으며, 이때 본 연구에서는 진동삼축시험기기를 보완하여 이를 구현하도록 하였다. 투수시험의 경우에는 2가지 투수시험이 수행되었으며, 하향의 흐름에 대한 투수시험으로는 기존의 변수위 투수시험이 적용되었고, 상향의 경우 직경 150mm의 중형 Rowe Cell 투수시험기를 이용하여 시험을 수행하였다. 연구결과, 회복탄성계수와 투수계수의 결과들을 종합하여 포장체 보조기층의 강도특성과 투수 특성을 모두 만족할 수 있는 적정입도분포를 선정하고, 이를 통해 적정입도기준 마련이 가능할 것으로 판단된다. Recently, a top record of hourly-based rainfall has been changed annually and flood damages of road have increased. To solve this problem, pavements for drainage were developed and practically constructed but there was no considerations on sub-base. In this research, we proposed standard for distribution of particle size of sub-base to consider strength characteristic and drainage property. We focused to compare coefficients strength and permeability by laboratory tests. Prior to tests, 4 samples were selected under the consideration on the international or domestic design guideline. In the tests, strength characteristics were compared with resilient modulus. Also, permeability characteristics were compared with coefficient of upward and downward permeability. Resilient modulus was determined with MR test using cyclic triaxial testing system. Two permeability tests were carried out. One is variable head permeability test for downward drainage and the other is Rowe Cell test for upward drainage. In the case of Rowe Cell test, middle-sized sampler with 150mm diameter was used for this study. Consequentially, we tried to find the optimum distribution of particle size to satisfy both of strength and permeability characteristics for sub-base.

아파트 오수정화시설의 처리현황과 주변인자에 대한 연구

선용호(Yong-Ho Seon) 상지대학교 환경과학기술연구소 1999 환경과학연구 Vol.5 No.1

  본 연구는 생활하수 배출시설 중 인구밀집시설인 원주 단계 택지내 아파트를 임의로 3곳을 지정하여 아파트 오수정화시설의 처리효율을 알아보고, 전년도 처리효율과의 비교를 통하여 주변인자에 의한 영향에 대해 알아보고자 하였다. 실험은 Standard Method와 수질오염공정시험법에 준하여 10개항목을 실시하였다. 실험결과를 보면 전년에 비하여 BOD, COD<SUB>Cr</SUB> 제거율이 약 10~13%정도 낮아졌으며, 이는 IMF이후 경제적인 요인으로 인해 아파트 관리소 측의 폐슬러지 수거나, 오수정화시설의 정비 불량 등 관리 소홀과 각 가정의 식생활 패턴이 경제적인 식단으로 바뀌어가기 때문인 것으로 판단된다. 전년과 마찬가지로 각 아파트 오수정화시설은 방류수 수질기준에 크게 미치지 못하는 수치를 나타냈으며, 이에 대한 해결 방안으로 오수정화시설의 전문환경관리인에 의한 관리와 계절적인 요인이나, 입주자들의 식생활 패턴 등 주변인자에 대한 철저한 분석과 대응이 필요할 것으로 사료된다.   It was carried out a performance test for sewage treatment systems in three highly populated apartments located in dangae building site in Wonju, and comparing the last year"s results investigated the environmental effects about the study site on the performance. EPA Standard Method and Korea Standard Method were used for analyses of 10 items in our experiments. Because of the weak maintenance of sewage treatment systems with the change of life style due to the change of economic menu pattern after IMF, it was found that the removal efficiency of BOD and COD<SUB>Cr</SUB> was decreased in 10~13%. As same as last year"s results, it was found that the effluent concentration of BOD and SS was higher than the standard limits. We suggest that the solution of above problems is the improvement of the management of environmental engineer and the analysis of the envionmental effects.

80 kW<SUB>th</SUB>급 미분탄 연소 시스템에서 하수슬러지 혼소시 연소 특성 연구

채태영(Taeyoung Chae),이재욱(Jaewook Lee),이영재(Youngjae Lee),양원(Won Yang) 한국청정기술학회 2019 청정기술 Vol.25 No.1