• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.413-420
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• 2003

A gas chromatography/mass spectrometric assay method was developed for the simultaneous determination of neutral and bacis twenty-five disruptors $(ED_S)$ in frog and fish. Afther homogenization and sonication of 5 g of sample, purification was achieves in one step with a solid phase extraction procedure using silica gelflorisl. Eluton was performed with 50mL of acetone : n-hexane (1 : 9) solution. The eluate was concentrated to approximately 10uL and dissolves with 100 uL of hexane and analyzed by GC-MS (SIM). The peaks had good chromatographic properties and the extraction of these compounds from sample also gave relatively high recoveries with small variatoins. Detection limits were 0.1 ng/g for 4-nitrotoluene, benzophenone, hexachlorobenzene, atrazine, malathion, o,p-DDT, o,p-DDT and permethrin, and 0.2 ng/g for heptachlor epoxide, γ-chlordane, α-chlordane, p,p'-DDE, p,p'-DDD, cypermethrin and fenvalerate, and 0.3 ng/g for trifluralin, metribuzin, alachlor, dieldrin and p,p'-DDT, and 0.5 ng/g for heptachlor, aldrin and parathion, and 0.7 ng/g for endrin, and 0.8 ng/g for nitrofen. The recoveries were between 33 and 109%. The method was used to analyze twenty-five frogs and forty-six fishes fishes samples caught from various regions in Korea. Benzophenone was detected at concentration of up to 17.2 ng/g in frog or fish. Heptachlor, aldrin, γ-chlordane, p,p'-DDE, p,p'-DDD, endrin and o,p-DDD were detected at concentrations of 0.7-12.5 ng/g in frog or fish. Also significant leveles of dieldrin (up to 22.5 ng/g) were observed. The developed method may be valuable to be used to the national monitoring project of EDS in biota samples.

• Geomechanics and Engineering
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• v.12 no.5
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• pp.831-847
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• 2017

Conventional geotechnical engineering soil binders such as ordinary cement or lime have environmental issues in terms of sustainable development. Thus, environmentally friendly materials have attracted considerable interest in modern geotechnical engineering. Microbial biopolymers are being actively developed in order to improve geotechnical engineering properties such as aggregate stability, strength, and hydraulic conductivity of various soil types. This study evaluates the geotechnical engineering shear behavior of sand treated with xanthan gum biopolymer through laboratory direct shear testing. Xanthan gum-sand mixtures with various xanthan gum content (percent to the mass of sand) and gel phases (initial, dried, and re-submerged) were considered. Xanthan gum content of 1.0% sufficiently improves the inter-particle cohesion of cohesionless sands 3.8 times and more (up to 14 times for dried state) than in the untreated (natural) condition, regardless of the xanthan gum gel condition. In general, the strength of xanthan gum-treated sand shows dependency with the rheology and phase of xanthan gum gels in inter-granular pores, which decreases in order as dried (biofilm state), initial (uniform hydrogel), and re-submerged (swollen hydrogel after drying) states. As xanthan gum hydrogels are pseudo-plastic, both inter-particle friction angle and cohesion of xanthan gum-treated sand decrease with water adsorbed swelling at large strain levels. However, for 2% xanthan gum-treated sands, the re-submerged state shows a higher strength than the initial state due to the gradual and non-uniform swelling behavior of highly concentrated biofilms.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.560-564
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• 2011

The objective of this study is to propose a mathematical model for a pervaporation process for concentrating hydrogen peroxide. The process was developed by NASA, which consists of a shell and membrane tubes, where a liquid hydrogen peroxide solution flows in the shell, and a sweep gas flows in the tubes countercurrent to each other. The liquid retentate is concentrated as more water molecules permeate and evaporate through the membrane than hydrogen peroxide. For this process, a mathematical model has been developed in the form of a system of nonlinear partial differential algebraic equations based on a sorption-diffusion mechanism for permeation, an Arrhenius relationship for the temperature dependency of the permeate flux, and mass and momentum balances for the liquid concentrations and flows in the membrane module. The dynamic behavior of the concentration of hydrogen peroxide in the retentate side has been simulated by solving a simplified version of the proposed model, and the result is compared with the experimental data reported in the NASA patent.

• Journal of Applied Biological Chemistry
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• v.57 no.4
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• pp.295-299
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• 2014

The mulberry (Morus alba L.) root barks were extracted with 80% aqueous methanol at room temperature. The concentrated extract was partitioned as ethyl acetate (EtOAc), n-BuOH, and $H_2O$ fractions. From the EtOAc fraction, five triterpenoids were isolated through the repeated silica gel and octadecyl $SiO_2$ column chromatographies. According to the results of physico-chemical and spectroscopic data including nuclear magnetic resonance, mass spectrometry, and infrared, the chemical structures of the triterpenoids were respectively determined as ${\alpha}$-amyrin (1), ${\alpha}$-acetyl amyrin (2), lupeol (3), betulinic acid (4), and glutinol (5). Compounds 1, 3, and 5 were isolated for the first time from the mulberry root bark.

• Applied Biological Chemistry
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• v.50 no.3
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• pp.233-237
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• 2007

The roots of Brassica campestris ssp rapa were extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH and $H_{2}O$. From the EtOAc and n-BuOH fractions, five compounds were isolated through the repeated silica gel column chromatographies. From the result of spectroscopic data including NMR and MS, the chemical structures of the compounds were determined as palmitic acid methyl ester (1), linolenic acid methyl ester (2), linoleic acid methyl ester (3), ${\beta}-sitosterol$ (4) and daucosterol (5).

• Korean Journal of Food Science and Technology
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• v.26 no.1
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• pp.68-73
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• 1994

An attempt was made to derermine the volatile flavor components of Dioscorea japonica. Essential oils from roots of the samples were isolated by simultaneous steam distillation-extraction(SDE) method using diethyl ether as solvent. Concentrated samples were analyzed by gas chromatography(GC) and combined gas chromatography-mass spectrometry(GC-MS). Fifty nine volatile flavor components, including 35 hydrocarbons, 5 aldehydes, 1 ketone, 9 alcohols, 2 esters, 3 acids and 4 miscellaneous ones were confirmed in the young roots of Dioscorea japonica. Forty two components, including 23 hydrocarbons, 2 aldehydes, 7 alcohols, 1 ester and 8 acids and 1 miscellaneous one were confirmed in the roots of mature stage. ${\sigma}-3-Carene$ and dodecanoic acid were regarded as the most abundant components in young and mature roots repectively. The profile of volatile flavor components was markedly different in young and mature roots of Dioscorea japonica.

• Journal of the korean Society of Automotive Engineers
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• v.18 no.6
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• pp.23-32
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• 1996

차량에서 엔진은 가장 큰 질량 집중체(concentrated mass)이다. 만약 엔진이 적절하게 구속되지 않거나 절연되어 있지 않으면, 차체에 진동을 일으키는 원인이 된다. 엔진은 다양한 진동 교란을 받는데 엔진 마운트는 이러한 모든 것들을 고립시키는 역할을 해야 하며, 엔진은 정적인 장착 하중에 대한 지지와 전후, 좌우 및 수직 방향의 운동에 대해 적절한 강성을 가져야 한다. 또한 정숙성을 향상시키기 위해서는 엔진 마운트의 재료인 고무의 강성계수를 낮추는 것이 필요한데 이는 일반적으로 내구성의 저하를 가져온다. 따라서 개발과정에서 강성계수를 낮추는 변경을 하면 부품의 내구성을 보정함에 따르는 재평가 또한 필요하게 된다. 엔진 마운트에 쓰이는 고무부품의 해석은 엔진 마운트 시스템에 대한 진동 해석 및 내구수명의 예측과 병행해야 하며, 진동해석으로부터 얻은 하중 지지 능력 등의 모든 요구 특성을 만족하기 위해서는 고무 재료의 특성에 대한 지식, 엔진 마운트의 장착 위치에 대한 결정 능력과 함께 주어진 조건에 대한 형상의 최적 설계 능력 등이 요구된다. 본 연구에서는 기본적인 형상을 파라미터화하여 엔진 마운트의 형상을 최적화 하는 절차를 제안하였다. 현재 승용차에 널리 사용되고 있는 부시형(bush type) 엔진마운트를 적용 모델로 선택하였으며, 엔진 마운트의 기본적인 형상을 몇개의 파라미터를 사용하여 정의하고 설계 사양으로 주어지는 강성값과 각 파라미터들의 조합으로 구성되는 형상이 갖는 강성값의 차이가 최소가 되도록 파라미터 값들을 최적화하였다. 최적화된 파라미터 값들로 구성되는 형상을 내구 성능, 성형성등을 고려하여 최종 형상으로 결정한다. 내구성능의 예측은 금속부품의 내구수명 예측에 널리 이용되고 있는 방법이 방진 고무부품의 경우에도 적용 가능한지를 검토하고, 방진 고무부품에도 일반적으로 적용될수 있는 내구수명 예측방안의 개발 가능성을 타진해 보았다. 본 연구의 목표는 시제품을 제작하기 이전에 설계된 부품에 대한 스프링 상수 및 내구특성을 체계적으로 규명하여 제품 시험의 횟수를 줄이고, 보다 정밀한 제품을 제작할 수 있도록 하기 위한 것이다.

• The Korean Journal of Applied Statistics
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• v.22 no.4
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• pp.819-827
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• 2009

Kim et al. (2006) analyzed the donation data surveyed by Voluneteer 21 in year 2002 at South Korea using a Poisson regression based on the mixture of two Poissons and detected significant variables for affecting the number of donations. However, noting the large deviation between the predicted and the actual frequencies of zero, we developed in this note a Poisson regression model based on a distribution in which zero inflated Poisson was added to the mixture of two Poissons. Thus the population distribution is now a mixture of three Poissons in which one component is concentrated on zero mass. We used the EM algorithm for estimating the regression parameters and detected the same variables with Kim et al's for significantly affecting the response. However, we could estimate the proportion of the fixed zero group to be 0.201, which was the characteristic of this model. We also noted that among two significant variables, the income and the volunteer experience(yes, no), the second variable could be utilized as a strategric variable for promoting the donation.

• Tribology and Lubricants
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• v.32 no.2
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• pp.61-66
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• 2016

Total thickness variation (TTV), BOW, and surface roughness are essential characteristics for high quality sapphire substrates. Many researchers have attempted to increase removal rate by controlling the key process parameters like pressure and velocity owing to the high cost of consumables in sapphire chemical mechanical polishing (CMP). In case of the pressure approach, increased pressure owing to higher deviation of pressure over the wafer leads to significant degradation of the TTV. In this study, the authors focused on reducing TTV under the high-pressure conditions. When the production equipment polishes multiple wafers attached on a carrier, higher loads seem to be concentrated around the leading edge of the head; this occurs because of frictional force generated by the combination of table rotation and the height of the gimbal of the polishing head. We believe the skewed pressure distribution during polishing to be the main reason of within-wafer non-uniformity (WIWNU). The insertion of a hub ring between the polishing head and substrate carrier helped reduce the pressure deviation. Adjusting the location of the hub ring enables tuning of the pressure distribution. The results indicated that the position of the hub ring strongly affected the removal profile, which confirmed that the position of the hub ring changes the pressure distribution. Furthermore, we analyzed the deformation of the head via finite element method (FEM) to verify the pressure non-uniformity over the contact area Based on experiment and FEM results, we determined the optimal position of hub ring for achieving uniform polishing of the substrate.

• Journal of the Korean association of regional geographers
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• v.16 no.5
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• pp.610-622
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• 2010

The proportion of overweight and obese individuals in the United States has been continuously increasing up to recently. Many studies related to obesity have concentrated on jurisdictional levels of aggregation, making it very difficult to dearly illustrate at risk regions. In other words, little research has been conducted in relation to spatial patterns considering spatial dependency and heterogeneity by spatial autocorrelation models over space. In response, this research analyzes spatial patterns between overweight/obesity and risk factors, such as high blood pressure and diabetes, over space. Specifically, the Moran''s I and Geary''s C will be conducted for global and local measures. What is more, the Ordinary Least Square (OLS) linear regression and Geographically Weighted Regression methods will be applied to identify spatial dependency and spatial heterogeneity. Data provided by the Behavioral Risk Factor Surveillance System (BRFSS) have Body-Mass Index (BMI) rates, containing 4 rates of under, healthy, overweight, and obesity. In addition, high blood pressure and diabetes rates in the United States will be used as independent variables. Lastly, we are confident that this research will be beneficial for a decision maker to make a prevention plan for obesity.