• 한국환경생태학회지
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• 제7권1호
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• pp.35-48
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• 1993

본 연구는 과중한 이용압력과 대기오염 및 산성우에 의한 만성적 피해로 날로 훼손되어 가는 북한산국립공원을 대상으로 기왕에 조사된 기초자료(박 등, 1987)와 비교하여 천이의 발달상태를 알아보고자 하였다. 북한산국립공원 26군데의 조사구를 선정하여 식물군집구조조사를 실시한 결과 다음과 같은 결론을 얻었다. 1. 식물군집구조분석을 위해 TWINSPAN에 의한classification 및 ordination기법중 RA, DCA, CCA를 적용하여 분석한 결과 북한산 국립공원은 해발고에 따라 4개의 군집으로 분리되었다. 분리된 각각의 군집은 아까시나무-참나무류군집, 혼효림군집, 졸참나무군집, 신갈나무군집이었다. 추정되는 천이계열은 해발고 500m이상의 교목상층에서 소나무$\longrightarrow$신갈나무, 해발고 500m이하 교목상층에서 아까시나무$\longrightarrow$상수리나무, 신갈나무, 산벚나무, 팥배나무$\longrightarrow$졸참나무 순이었으며, 교목하층과 관목층에서는 산초나무, 참싸리나무$\longrightarrow$개옻나무, 진달래, 철쭉$\longrightarrow$당단풍 순이었다. 2. 1987년도의 식물군집구조조사와 비교하여 천이가 진행된 자료는 얻을 수 없었고, 인간의 간섭과 대기오염 등에 의해 천이가 진행되지 못하는 것으로 추측되었다.

• 대한환경공학회지
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• 제30권10호
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• pp.1039-1046
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• 2008

수중에 존재할 수 있는 항생제물질 중 cefaclor를 제거하기 위하여 UV/H$_2$O$_2$ 공정을 적용하였다. 기존 회분식반응기의 경우 시료를 채취하면 시료가 감소하여 UV램프와 제거대상물질의 유효접촉면적이 감소하는 것을 보완하기 위해 외부에 혼합조를 설치하여 실험을 실시하였다. UV반응기 내부는 완전혼합을 위해 4개의 baffle을 설치하였으며 광자의 방출을 방지하기 위해 반응조 외부를 알루미늄 호일로 감쌌다. OH radical의 생성은 pCBA(p-Chlorobenzoic acid)를 이용하여 간접적으로 측정하였으며, 의사일차반응식(pseudo-frist order reaction)을 이용하여 반응속도상수를 구하였다. 본 연구의 최적 OH radical 생성조건은 pH 3, 과산화수소 주입량은 5 mmol/L 그리고 펌프순환유량은 400 mL/min로 나타났으며, 반응속도상수는 0.1051 min$^{-1}$이었다. 최적의 OH radical 생성조건에서 cefaclor는 40 min안에 완전히 제거되었으며 반응속도상수는 0.093 min$^{-1}$이었다. 초기 cefaclor의 농도가 낮을 수록 빠르게 제거되었으며, OH radical에 의해 분해되어 중간생성물질(intermediates)인 chloride(Cl$^-$), nitrate(NO$_3{^{2-}}$), sulfite(SO$_4{^{2-}}$) 그리고 acetic acid(CH$_3$COO$^-$) 등의 음이온과 phenylglycine을 생성하였다. 반응시간 6 hr 이후 TOC의 77% 감소, phenylglycine의 소멸 그리고 acetic acid가 감소하는 것으로 보아 cefaclor는 UV/H$_2$O$_2$ 공정에 의해 빠르게 분해될 뿐만 아니라 CO$_2$와 H$_2$O의 형태로 무해화(mineralization)되는 것으로 보인다.

• Steel and Composite Structures
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• 제4권5호
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• pp.385-402
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• 2004

Nearly 400 composite railway bridge decks of a new kind belonging to the trough type with U-shaped cross section have been constructed in Belgium over the last fifteen years. The construction of these bridge decks is rather complex with the preflexion of precambered steel girders, the prestressing of a concrete slab and the addition of a 2nd phase concrete. Until now, they have been designed with a classical computation method using a pseudo-elastic analysis with modular ratios. Globally, they perform according to the expectations but variability has been observed between the measured and the computed camber of these bridge decks just after the transfer of prestressing and also at long-term. A statistical analysis of the variability of the relative difference between the measured camber and the computed camber is made for a sample of 36 bridge decks using no less than 10 variables. The most significant variables to explain this variability at prestressing are the ratio between the maximum tensile stress reached in the steel girders during the preflexion and the yield strength and the type of steel girder. For the same sample, the long-term camber under permanent loading is computed by two methods and compared with measurements taken one or two years after the construction. The camber computed by the step-by-step method shows a better agreement with the measured camber than the camber computed by the classical method. The purpose of the paper is to report on the statistical analysis which was used to determine the most significant parameters to consider in the modeling in order to improve the prediction of the behaviour of these composite railway bridge decks.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.502-507
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• 2010

In order to design nano structured materials with enhanced thermoelectric properties, the alloys in the pseudo-binary $Bi_2Te_3$-PbTe system are investigated for their micro structure properties. For this synthesis, the liquid alloys are cooled by the water quenching method. Micro structure images are obtained by using an electron probe micro analyzer(EPMA). Dendritic and lamellar structures are clearly observed with the variation in the composition ratio between $Bi_2Te_3$ and PbTe. The increase in the $Bi_2Te_3$ composition ratio causes to change of the structure from dendritic to lamellar. The Seebeck coefficient of sample 5, in which the mixture rate of $Bi_2Te_3$ is 83%, is measured as the highest value. In contrast, the others decrease with the increase of the $Bi_2Te_3$ composition ratio. Meanwhile, p-type characteristics are observed in sample 6, at 91%-$Bi_2Te_3$ mixture rate. The power factors of the all samples are calculated with the Seebeck coefficient and resistivity.

• 한국대기환경학회지
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• 제22권6호
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• pp.808-820
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• 2006

In regard to indoor air quality patterns, the government introduced various polices that were about managing and monitoring quality of indoor air as a major assignment, and also executed 'Indoor Air Quality Management Act' which was presented in the May, 2004. However, among the multi-usage facilities controlled by the Act, the school was not included yet. This study goal was to investigate PM 10 pollution patterns of the high school classrooms using a pattern recognition method based on cluster analysis and disjoint principal component analysis, and further to survey levels of inorganic elements in May, June, and September, 2004. A hierarchical clustering method was examined to obtain possible objects in pseudo homogeneous sample classes by transformation raw data and by applying various distance. Following the analysis, the disjoint principal component analysis was used to define homogeneous sample class after deleting outliers. Then three homogeneous Patterns were obtained as follows: the first class had been separated and objects in the class were considered to be sampled under semi-open condition. This class had high concentration of Ca, Fe, Mg, K, Al, and Na which are related with a soil and a chalk compounds. The second class was obtained in which objects were sampled while working air-conditioners and was identified low concentration of PM 10 and elements. Objects in the last class were assigned during rainy day. A chalk, soil element and various types of anthropogenic sources including combustions and industrial influenced the third class. This methodology was thought to be helpful enough to classify indoor air quality patterns and indoor environmental categories when controlling an indoor air quality.

• 약학회지
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• 제4권1호
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• pp.53-55
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• 1959

본 실험에 있어서는 우리가 일상 제일 많이 먹고 있는 발효식품의 1종이고 본보 제8보에 보고한 바와 같이 Vitamin $B_{12}$의 중요한 자원이 되고 있는 침채류가 그 발효기간중 Vitamin $B_{12}$의 함량에 대하여 어떠한 변화를 하고있으며 침채류발효에 있어서 발효에 관여하는 미생물에 의하여 Vitamin $B_{12}$가 새로 생성되는가 혹은 되지않는가를 알기 위하여 본 실험에 착수한 것이다. 그럼으로 본보고에 있어서는 보통방법으로 김치를 담그고 또한 김치를 멸균한 재료로서 무균조작으로 담그므로서 발효를 억제하면 Vitamin $B_{12}$ 함량은 별로 변화하지 않을 것이라고 추상하며 멸균김치를 따로 담거서 이 두 김치의 액부에 대하여 그 발효기간중 Vitamin $B_{12}$의 량적 변화를 조사하여 그 성적을 비교검토하고 이에 보고하는 바이다.

• Membrane and Water Treatment
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• 제10권6호
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• pp.471-484
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• 2019

The complex combination of organic contaminants in the wastewater made water treatment challenging; hence, organic matter in water bodies is usually measured in terms of organic carbon. Since it is important to identify the types of compounds when deciding suitable treatment methods, this study implemented a quantitative and qualitative analysis of the organic matter content in an actual graywater sample from Ulsan, Republic of Korea using mass spectroscopy (MS). The graywater was treated using adsorption to remove the organic contaminants. Using orbitrap MS, the organic matter content between an untreated graywater and the treated effluent were compared which yielded a significant formula count difference for the samples. It was revealed that CHON formula has the highest removal count. Isotherm studies found that the Freundlich equation was the best fit with a coefficient of determination ($R^2$) of 0.9705 indicating a heterogenous GAC surface with a multilayer characteristic. Kinetics experiments fit the pseudo-second order equation with an $R^2$ of 0.9998 implying that chemisorption is the rate-determining step between the organic compounds and GAC at rate constant of $52.53g/mg{\cdot}h$. At low temperatures, the reaction between GAC and organic compounds were found to be spontaneous and exothermic. The conditions for optimization were set to achieve a maximum DOC and TN removal which yielded removal percentages of 94.59% and 80.75% for the DOC and TN, respectively. The optimum parameter values are the following: pH 6.3, 2.46 g of GAC for every 30 mL of graywater sample, 23.39 hrs contact time and $38.6^{\circ}C$.

• 국제지역연구
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• 제21권4호
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• pp.159-172
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• 2017

비관측요인(unobserved-component)모형을 이용한 GDP의 추세-순환요인 분해에서, 통상적으로 추세는 확률보행 과정을 갖는 것으로 가정된다. 본 연구는 추세를 ARIMA 과정으로 표현하는 경우, GDP 변동에서 갖는 추세요인의 의미가 어떻게 달라지는가를 살펴보고, GDP에 대한 예측력이 개선될 수 있는가의 여부를 미국의 데이터를 이용하여 실증적으로 분석하였다. 모형은 GDP만의 단일변수모형과 물가를 포함하는 2변수모형의 두 가지를 고려하여 설정하였으며, 모형 추정은 비관측요인모형을 상태-공간모형으로 전환한 후 칼만 필터(Kalman filter)를 이용한 최대우도추정법을 사용하였다. GDP에 대한 예측은 축차적 추정(recursive estimation)을 이용한 동적 표본외예측(dynamic out-of-sample) 방식을 사용하였으며, 예측력 비교결과에 대한 검정은 Diebold-Mariano 검정을 이용하였다. 분석 결과는 첫째, 모형의 추정결과에서 ARIMA 추세의 계수가 통계적으로 유의적인 값을 가지며, 둘째, ARIMA 추세 모형이 확률보행 추세 모형보다 GDP 변동의 분산 및 자기 상관성(autocorrelation)을 보다 잘 설명하며, 셋째, 예측력에서 단일변수보다는 2변수모형의 예측력이 그리고 확률보행 추세보다는 ARIMA 추세를 갖는 모형의 예측력이 통계적으로 유의하게 높은 것으로 나타났다. 이러한 결과들은 GDP 추세-순환 요인 분해에서 추세를 ARIMA 과정으로 표현하는 것이 보다 타당하다는 것을 시사하고 있다.

• Advances in environmental research
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• 제4권2호
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• pp.69-81
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• 2015

A new magnetite-silica core/shell nanocomposite ($Fe_3O4@nSiO_2@mSiO_2$) was synthesized and functionalized with trimethylchlorosilane (TMCS). The prepared nanocomposite was used for the removal of diesel oil from aqueous media. The characterization of magnetite-silica nanocomposite was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), surface area measurement, and vibrating sample magnetization (VSM). Results have shown that the desired structure was obtained and surface modification was successfully carried out. FTIR analysis has confirmed the presence of TMCS on the surface of magnetite silica nanocomposites. The low- angle XRD pattern of nanocomposites indicated the mesoscopic structure of silica shell. Furthermore, TEM results have shown the core/shell structure with porous silica shell. Adsorption kinetic studies indicated that the nanocomposite was able to remove 80% of the oil contaminant during 2 h and fit well with the pseudo-second order model. Equilibrium studies at room temperature showed that the experimental data fitted well with Freundlich isotherm. The magnetic property of nanocomposite facilitated the separation of solid phase from aqueous solution.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
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• pp.123-127
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• 2003

This experiment was performed to investigate the characteristics of sonolytic reaction as the basic data for development of the ultrasonic AOP(Advanced Oxidation Process) process from which the refractory organic compounds in aqueous solution which are not readily removed by the existing conventional wastewater treatment processes can be destructed and removed. Trichloroethylene (TCE), benzene, and 2,4-dichlorophenol(DCP) were used as the samples, and their destruction efficiency were measured in terms of experimental parameters of the initial solution concentration, initial solution pH, reaction temperature, acoustic frequencies and intensities. Results showed that the destruction efficiencies of all of the sample materials were above 80% within 120 minutes of sonolytic reaction in all reaction condition. The reaction order of these three compounds was verified as Pseudo first order. From the fore-mentioned results, it can be concluded that the refractory organic compounds could be removed by the ultrasonic irradiation with radicals, such as H$.$and OH$.$causing the high increase of pressure and temperature. Finally, it appears that the new AOP technology using ultrasonic irradiation can be applied to the treatment of refractory substances which are difficult to be decomposed by the conventional methods.