• 한국토양비료학회지
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• 제42권5호
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• pp.336-340
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• 2009

최근 급속한 산업화가 진행되고 있는 중국의 편서풍 영향 하에 위치한 우리나라의 경우에는 장거리 이동에 따른 강우의 산성도 변화 및 예상되는 피해에 대한 대책 마련을 위하여 강우의 화학성에 대한 지속적인 모니터링이 필요하다. 태안지역 강우의 화학적 특성을 알아보기 위하여 2007년 4월부터 10월까지 19점의 빗물을 채수하여 pH 및 화학적 성분조성을 조사하였다. 강우량을 고려한 가중평균(volume-weighted mean) 이온농도 변화와 알카리성 물질들에 의한 빗물의 산성도 중화를 평가한 결과는 다음과 같다. 조사기간 중 평균 pH값은 4.9를 보였다. 빗물의 EC는 조사기간 평균 $32.9{\mu}S\;cm^{-1}$을 나타냈으며, 월별로는 9월에 $9.7{\mu}S\;cm^{-1}$로 조사기간 중 가장 낮은 값을 보였으며, 강우량이 가장 적었던 4월에 $91.4{\mu}S\;cm^{-1}$의 높은 수치를 나타내어 강우량 분포에 따른 EC의 계절적 특성을 보였다. 빗물의 조성에서 양이온 구성은 $Na^+$> $NH_4{^+}$ > $Ca^{2+}$ > $H^+$ > $Mg^{2+}$ > $K^+$의 순이었으며, $Na^+$와 $NH_4{^+}$가 전체 양이온 함량의 70% 이상을 차지하였다. 음이온은 $SO_4{^{2-}}$ > $NO_3{^-}$ > $Cl^{-}$ 순으로 $SO_4{^{2-}}$가 약 56%를 차지하였다. Sulfate의 조사기간 중 평균 함량은 $152.1{\mu}eq\;L^{-1}$ 이었다. 총 sulfate 함량 중 비해염 sulfate $(nss-SO_4)^-$ 함량은 평균 90%로 빗물 중에 함유된 sulfate의 대부분이 인위적인 발생원에서 기인되었다. 또한, 강우 산성도의 중화 정도를 알아보기 위하여 평가한 fractional acidity (pAi) 및 theoretical acidity ($pH_{the}$.) pH를 비교한 결과 1:1 직선의 오른쪽으로 분포되어 있음에 따라 본 조사기간 강우의 산성도가 빗물에 포함된 각종 알카리 물질들에 의해 중화되었음을 보였다.

• 한국축산식품학회지
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• 제30권3호
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• pp.495-503
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• 2010

육질등급별 도체등급요인에 대한 분석 결과는 육질등급이 3등급에서 $1^{++}$등급으로 높아지면서 도체중, 등지방두께, 근내지방도는 증가하였으며(p<0.05) 육색, 지방색, 조직감 및 성숙도는 낮아지는 경향이었다(p<0.05). 한우고기의 이화학적 특성에서, 육질등급이 3등급에서 $1^{++}$등급으로 증가될수록 전단력은 8.29 kg에서 2.83 kg으로 감소하였고, 보수력은 52.41%에서 58.03%로, 조지방 함량은 3.57%에서 25.68%로 증가하였다(p<0.05). 기계적으로 측정한 육색에서 명도는 $1^{++}$등급 쇠고기가 41.53으로 가장 높았고 가열감량은 3등급쇠고기가 22.11%로 가장 높았다(p<0.05). 도축 후 24시간에 측정한 pH는 5.53-5.66범위로 정상적인 pH 값을 나타내었다. 6점 만점으로 평가된 관능특성에서, 육질등급이 3등급에서 $1^{++}$등급으로 높아질수록 연도, 다즙성, 향미 및 전체평점은 증가하였다(p<0.05). 조지방 함량은 다즙성(0.59), 연도(0.71), 향미(0.55) 및 전체평점(0.6)과 상관관계가 있었으며. 전단력은 다즙성, 연도, 향미 및 전체평점과 각각 -0.47, -0.64, -0.52 및 -0.61의 상관관계가 있었다. 이상의 연구결과에서 $1^{++}$ 등급 쇠고기에 비하여 $1^+$등급이하 등급은 전단력이 높고, 조지방 함량이 낮은(p<0.05) 것은 한우고기의 연도증진과 근내지방함량에 대한 연구가 필요하다고 생각된다.

• Applied Microscopy
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• 제47권3호
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• pp.131-147
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• 2017

In this work further optical and electrical investigations of pure and Zr doped $Mn_3O_4$ (from 0 up to 20 at.%) thin films as a function of frequency. First, the refractive index, the extinction coefficient and the dielectric constants in terms of Zr content are reached from transmittance and reflectance data. The dispersion of the refractive index is discussed by means of Cauchy model and Wemple and DiDomenico single oscillator models. By exploiting these results, it was possible to estimate the plasma pulse ${\omega}_p$, the relaxation time ${\tau}$ and the dielectric constant ${\varepsilon}_{\infty}$. Second, we have performed original ac and dc conductivity studies inspired from Jonscher model and Arrhenius law. These studies helped establishing significant correlation between temperature, activation energy and Zr content. From the spectroscopy impedance analysis, we investigated the frequency relaxation phenomenon and hopping mechanisms of such thin films. Moreover, a special emphasis has been putted on the effect of the oxidation in air of hausmannite thin films to form $Mn_2O_3$ ones at $350^{\circ}C$. This intrigue phenomenon which occurred at such temperature is discussed along with this electrical study. Finally, all results have been discussed in terms of the thermal activation energies which were determined with two methods for both undoped and Zr doped $Mn_3O_4$ thin films in two temperature ranges.

• Environmental Analysis Health and Toxicology
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• 제18권2호
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• pp.137-143
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• 2003

합성화학물질들이 환경중에 유입되어 인체에는 물론 환경생태계에 많은 영향을 미치고 있어 이들의 유해성 검증은 매우 중요한 일이라 할 수 있다. 실제 산업체에서 사용되는 수많은 화학물질들의 유전적 손상 유발유무는 더욱이 중요한 일이라 할 수 있다. 이에 산업체 공정과정에서 널리 사용되는 것으로 알려진 8종의 합성화학물질에 대해 마우스의 골수세포를 이용한 in vivo 소핵시험을 수행하여, 소핵형성 유발유무를 관찰하였다. 양성대조군으로 사용된 mitomycin는 음성대조군과 비교시 유의하게 소핵을 유발하는 반면, 비교적 마우스에서 높은 50% 치사량을 보이는 phenylisocyanate, m-aminochlorobenzene 및 2-chloro-4-nitroaniline 등의 합성물질들을 비롯한 나머지 5종의 물질들은 본 실험결과 통계적으로 유의하게 소핵을 유발하지 않는 것을 관찰 할 수 있었다.

• 한국과학교육학회지
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• 제17권3호
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• pp.301-311
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• 1997

The purpose of this study is to construct a structural equation model and to analyze causal relationships among variables related to attitudes to science using structural equation modeling(SEM) with LISREL VII. The sample consisted of 483 10th grade boys from a general high school in Pusan, Korea. The questionnaires (ABC-attitude scale: affection, behavioral intention, cognition scale of attitude towards science) were developed by the researcher through a pilot study. And other instruments have modified previous ones. Five instruments were used in this study: GALT(group assessment of logical thinking), MTSlS(modified test of science inquiry skill), ABC-attitude scale, MSAS(modified scientific attitude scale), CSAT(common science achievement test). Structural equation modeling with LISREL VII($J\ddot{o}reskog$ & $S\ddot{o}rbom,$ 1993) was employed to estimate the causal inferences about hypothesized relationships among observed data sets. Three competing models consisted of five latent variable(scientific thinking ability, science inquiry skill, attitude towards science, scientific attitude, science achievement) - lP(inquiry preceding) model, AP(attitude preceding) model and AM(attitude mediating) model - were developed. Among these competing models, IP model satisfied the observed data sets. The causal relationships among "attitudes to science" and other latent variables were reliably identified. According to the results of the present study, science inquiry skill was the most significant variable that can predict science achievement. But scientific thinking ability has not directly influenced science achievement. This study suggests that inquiry based teaching-learning processes should be offered to students for improvement of science achievement. At the same time, it seems to be important to develop positive attitude towards science. Understanding of relationships among variables related to attitudes to science will be helpful to the development of science curriculum and to the design of science teaching and learning process. LISREL has been recognized as a useful approach in testing a SEM. However, in this study, LISREL approach was estimated as much more useful method for research design.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(환경)
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• pp.585-595
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• 1994

The region of the respiratory tract where inhaled particles deposit can have important implications for the causation of local or systemic toxic effects. For most aerosols of occupational importance, respiratory tract deposition can be predicted from the aerodynamic diameter of the particles. With the advent of cascade impactors, particularly those of personal sampler size, the determination of the aerodynamic diameters of aerosols has become more common. Some limitations of cascade impactor use are well recognized (e.g., particle bounce and substrate overloading) and are generally correctable. However, two important limitations of the instruments may not be receiving adequate attention: relative humidity effects on potentially hygroscopic aerosols and the collection characteristics of fibrous aerosols as compared to their actual deposition site potential. The results of this study, when compared to results of previous controlled laboratory trials, suggest that, while potentially hygroscopic lead aerosols from lead acid battery plant operations do not appear to be affected by changes in plant environmental humidity levels, the potential - exists for significant size changes upon inhalation. Secondly, fibers were detected in aerodynamic size ranges that would be associated with deep lung deposition; however, upon microscopic examination, these same fibers would actually be predicted to deposit in the upper airways. This study suggests that the physicalchemical properties and morphological features of an aerosol should be carefully considered by industrial hygienists before cascade impactors are used in attempts to predict the effects of inhaled aerosols.

• 한국항해학회지
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• 제9권1호
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• pp.1-40
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• 1985

The transport of cargoes carried by coastal and ocean-going vessels has increased with the rapid growth of the Korean economy these days. This increase of the sea-borne cargoes has made the Korean coastal traffic so congested that this can be a cause of large pollution as well as great marine casualties such as loss of human lives and properties. Marine casualties generally result from the complicated interaction of natural and human factors; the former being the topographic, marine traffic volume and meteorological conditions, and the latter being the quality of seafares. In this paper, the authors analyse the trend of marine casualties in the Korean coastal and clear up the cause of accidents and examine closely the mutual relations among sea accidents, weather conditions, and marine traffic volume. These accidents are classified into several patterns on hte point of view of ship's size, ship's type and ship's age and its characteristics of each pattern are described in detail. Also, the authors estimate the amount of economical losses resulting from marine casualties which are classified into the accident patterns, and clarify the effects of those losses on B/B(Balance Sheet) and P/L(Profit & Loss) of Korean shipping companies and Korean national economy. The analyzed results of marine casualties are summarized as follows: 1) The average number of sea accidents is 248 cases per year with the loss of 107 persons during last 13 years. 2) Collision is the top of causes of sea accidents (approx. 36.4%), shipwreck the second (approx. 20.3%), agroung the third rank (approx. 18.2%). 3) The ship's number under 1, 000G/T is approx. 74% of total ship's number of accidents. 4) 80% of total number of marine accidents is taken plact at the coastal waters. (involved ports & narrow channels) 5) Marine casualties are occur likely to in the night, the winter and the summer. 6) The average amount of economical losses is approx. 18.5 billion won. (approx. 0.14% of GNP) 7) Shipwreck is the top of the amount of economical losses (approx. 60.4%), collision the second (aprox. 24.5%), aground the third (approx. 9.9%). 8) The amount of economical losses is approx. 5.24% of gross capital of shipping co., 1.24% of shipping revenue, 1.38% of shipping total income in 1983.

• Journal of Microbiology and Biotechnology
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• 제17권7호
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• pp.1221-1225
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• 2007

A ${\beta}$-ionone-resistant mutant strain isolated from the red yeast Xanthophyllomyces dendrorhous KCTC 7704 was used for batch and continuous fermentation kinetic studies with glucose media in a 2.5-1 jar fermentor at $22^{\circ}C$ and pH 4.5. The kinetic pattern of growth and carotenoid concentration in the batch fermentations exhibited a so-called mixed-growth-associated product formation, possibly due to the fact that the content of intracellular carotenoids depends on the degree of physical maturation toward adulthood. To determine the maximum specific growth rate constant (${\mu}_m$) and Monod constant ($K_s$) for the mutant, glucose-limited continuous culture studies were performed at different dilution rates within a range of $0.02-0.10\;h^{-1}$. A reciprocal plot of the steady-state data (viz., reciprocal of glucose concentration versus residence time) obtained from continuous culture experiments was used to estimate a ${\mu}_m$ of $0.15\;h^{-1}$ and $k_s$ of 1.19 g/l. The carotenoid content related to the residence time appeared to assume a typical form of saturation kinetics. The maximum carotenoid content ($X_m$) for the mutant was estimated to be $1.04\;{\mu}g/mg$ dry cell weight, and the Lee constant ($k_m$), which was tentatively defined in this work, was found to be 3.0 h.

• Smart Structures and Systems
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• 제21권5호
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• pp.591-600
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• 2018

The probabilistic characterization of wind field characteristics is a significant task for fatigue reliability assessment of long-span railway bridges in wind-prone regions. In consideration of the effect of wind direction, the stochastic properties of wind field should be represented by a bivariate statistical model of wind speed and direction. This paper presents the construction of the bivariate model of wind speed and direction at the site of a railway arch bridge by use of the long-term structural health monitoring (SHM) data. The wind characteristics are derived by analyzing the real-time wind monitoring data, such as the mean wind speed and direction, turbulence intensity, turbulence integral scale, and power spectral density. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method is proposed to formulate the joint distribution model of wind speed and direction. For the probability density function (PDF) of wind speed, a double-parameter Weibull distribution function is utilized, and a von Mises distribution function is applied to represent the PDF of wind direction. The SQP algorithm with multi-start points is used to estimate the parameters in the bivariate model, namely Weibull-von Mises mixture model. One-year wind monitoring data are selected to validate the effectiveness of the proposed modeling method. The optimal model is jointly evaluated by the Bayesian information criterion (BIC) and coefficient of determination, $R^2$. The obtained results indicate that the proposed SQP algorithm-based finite mixture modeling method can effectively establish the bivariate model of wind speed and direction. The established bivariate model of wind speed and direction will facilitate the wind-induced fatigue reliability assessment of long-span bridges.

• Asian-Australasian Journal of Animal Sciences
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• 제5권2호
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• pp.357-363
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• 1992

The experiment was carried out to estimate the energy and protein requirements of Khaki Campbell $\times$ Thai Native growing ducks. The growing stage was divided into 2: the first was a starting stage from 0 to 4 weeks of age and the second was a growing stage from 4 to 18 weeks of age. In the starting stage, the birds were given diets containing 2.70, 2.75, 2.80, 2.85 and 2.90 Mcal ME/kg and ME/protein ratio of 150/l for the energy requirement trial, and diets containing 17.0%, 18.5%, 20.0% and 21.5% protein and 2.8 Mcal ME/kg for the protein requirement trial. It was found that there were no significant differences in body weight gain of feed efficiency among the energy or protein levels. In the growing stage, no significant differences in body weight gain or feed efficiency were found among the energy levels from 2.70 to 2.90 Mcal ME, or protein levels from 15.5% to 20.0%. The age at first lay was 105-117 days and this is earlier than that observed in purebred Khaki Campbell ducks. The feed cost for raising ducks was lower in the low energy and low protein diets. In conclusion, Khaki Campbell $\times$ Thai native ducks can be raised with a diet low in ME as 2.7 Mcal/kg during the whole growing period. As for the protein. 7.0% in the starting stage and 15.5% in the growing stage is practical.