• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2C
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• pp.71-79
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• 2009

This study is to develope the resilient modulus prediction model, which is the function of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered granite soil, and crushed-rock soil mixture. The model consists of the maximum Young's modulus and nonlinear values for higher strain, analogous to dynamic shear modulus. The maximum value is modeled by model parameters, $A_E$ and the power of mean effective principal stress, $n_E$. The nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, ${\varepsilon}_r$ and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea, was evaluated using a 3-D elastic multilayer computer program (GEOTRACK). The results were compared with measured elastic vertical displacement during the passages of freight and passenger trains at two locations, whose sub-ballasts were crushed stone and weathered granite soil, respectively. The calculated vertical displacements of the sub-ballasts are within the order of 0.6mm, and agree well with measured values. The prediction models are thus concluded to work properly in the preliminary investigation.

• Journal of Food Hygiene and Safety
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• v.38 no.6
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• pp.420-429
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• 2023

GC-MS/MS using liquid-liquid extraction (LLE) and C18 cartridges was used to identify and quantify levels of chlorpyrifos, chlorpyrifos-methyl, cypermethrin, deltamethrin and permethrin in bulk raw milk. A calibration curve spanning 10 ng/mL to 200 ng/mL was obtained with a satisfactory correlation coefficient of 0.99. The limits of detection (LOD) and limits of quantitation (LOQ) for chlorpyrifos, chlorpyrifos-methyl, cypermethrin, deltamethrin, and permethrin in the matrix ranged from 0.06 to 1.81 ng/mL and 0.19 to 6.04 ng/mL, respectively. The recoveries of 5 pesticides from spiked samples at 37.5-125 ng/mL ranged from 86.1 to 102.1%. The measurement of uncertainty of the GC-MS/MS method for these five pesticides was developed based on the analytical process and quantification. An analysis method that is easier and faster than the method specified in the Korean food standards codes for analyzing these five pesticides in raw material milk was developed. Moreover, the analytical method for chlorpyrifos, chlorpyrifos-methyl, cypermethrin, deltamethrin, and permethrin in bulk raw milk by GC-MS/MS was established.

• Information Systems Review
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• v.22 no.4
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• pp.21-39
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• 2020

Recently, deep learning has shown high performance in various applications such as pattern analysis and image classification. Especially known as a difficult task in the field of machine learning research, stock market forecasting is an area where the effectiveness of deep learning techniques is being verified by many researchers. This study proposed a deep learning Convolutional Neural Network (CNN) model to predict the direction of stock prices. We then used the feature selection method to improve the performance of the model. We compared the performance of machine learning classifiers against CNN. The classifiers used in this study are as follows: Logistic Regression, Decision Tree, Neural Network, Support Vector Machine, Adaboost, Bagging, and Random Forest. The results of this study confirmed that the CNN showed higher performancecompared with other classifiers in the case of feature selection. The results show that the CNN model effectively predicted the stock price direction by analyzing the embedded values of the financial data

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.5
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• pp.467-478
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• 2024

The International Maritime Organization has adopted a strategy for reducing greenhouse gas emissions from international shipping, with enhanced targets to address ship-induced emissions. The liquid-hydrogen proton-exchange membrane fuel cell is promising for complying with such regulations. In general, ship design must adhere to the prescriptive rules of classification societies. However, increasing environmental regulations are enforcing the introduction of new fuels and systems, with the prescriptive rules lagging. Hence, we devise a method to verify new technologies by combining the hazard and operability study (HAZOP) and layer of protection analysis (LOPA) for a hydrogen fuel gas-supply system. The HAZOP allows us to identify hazardous scenarios, whereas the LOPA enables us to quantitatively complement the qualitative HAZOP results. The existing initiating event frequency and failure-on-demand probability of independent protection layers (IPLs) are identified. To determine the adequacy of the existing IPLs, we compare the estimated current mitigation with a risk-acceptance criterion. Additional IPLs are recommended when required to satisfy the risk criteria. Results show that HAZOP-LOPA can be potentially used to assess novel systems not yet adopted in the maritime sector.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.27-35
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• 2015

The material properties of crack growth models at an elevated temperature were derived from the results of numerous crack growth tests for Mod.9Cr-1Mo (ASME Grade 91) steel specimens under fatigue loading and creep loading at an elevated temperature. These crack growth models were needed for defect assessment under creep-fatigue loading. The mathematical crack growth rate models for fatigue crack growth (FCG) and creep crack growth (CCG) were determined based on the test results, and the models were compared with those of the French design code RCC-MRx to investigate the conservatism of the code. The French design code RCC-MRx provides an FCG model and a CCG model for Grade 91 steel in Section III Tome 6. It was shown that the FCG model of RCC-MRx is conservative, while the CCG model is non-conservative compared with the present test data. Thus, it was shown that further validation of the property was required. Mechanical strength tests and creep tests were also conducted, and the test results were compared with those of RCC-MRx.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.99-99
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• 2017

국내 콩의 소비량은 계속적으로 증가하고 있다. 재배 면적은 1995년 10,000ha에서 2013년 8,000ha까지 계속적으로 감소하였으며, 수입은 2009년 644.9백만 달러에서 2013년 883.3백만 달러까지 계속적인 증가 추세에 있다. 건조는 품질 손상을 최소화 및 수분을 제거하는 공정이다. 모든 곡물에는 건조 조건에 따라서 품질이 크게 변화하며, 건조 과정을 해석하여 해당 곡물의 적정 건조 조건을 구명하여 품질을 유지하는 위해서는 중요하다(Keum, 등 1977). 얇은 두께의 곡물층을 단층으로 하여 건조속도 및 건조공기의 조건을 나타내는 것을 박층(Thin layer)건조모델이라 한다. 박층건조모델을 계속적으로 쌓은 모델을 후층(Deep layer)모델이라 하며, 건조기 개발 및 건조조건 구명에 가장 기본이 된다(Basunia and Abe, 1998). 그러나 해외에서 만들어진 콩 박층건조 모델은 국내의 검은콩과 물성이 상이하여 건조조건이 다르게 설정 되어야 한다. 따라서, 본 연구목적은 건조온도 2수준, 상대습도 3수준에 대하여 검은 콩의 건조속도 측정하고, 곡물건조방정식으로 많이 이용되고 있는 4개의 건조방정식에 대하여 모델 적합성을 검정하여 검은콩 건조에 적합한 박층건조모델 결정하는데 있다. 공시재료는 2015년 강원도지역에서 생산된 검은콩을 실험에 사용하였으며, 초기 함수율은 14.7%,w.b.였다. 박층 건조공기 조성은 공기조화장치(MTH4100, SANYO, UK)를 사용하여 조성하였으며, 송풍기에 의해 공기충만실을 통과하여 건조 층을 통과하도록 구성하였다. 목표 평형함수율에 도달하면 실험을 종료하였다. 건조 층의 초기중량 및 경시적 변화는 전자저울(GF-4000, AND, Japan)을 이용하여 10분 간격 측정하여 저장하였다. 적정 박층건조모델을 결정하기 위하여 기존의 곡물건조방정식 중 널리 사용되고 있는 4개(Lewis, 1921; Page, 1949; Thompson, 1967; Moisture diffusion, 1975)의 건조모델을 이용하여 비교 검증하였다. 건조 초기 2시간 까지는 급격히 감소하다가 건조속도에 영향을 미치는 반건조시간(MR=0.5) 이후에는 완만하게 건조되는 것으로 나타났고 건조조건으로 건조온도 및 상대습도 모두의 영향이 미치는 것으로 나타났다. 4가지 건조 모델과 비교한 결과 Thompson 모델이 전체 건조 영역에서 비교적 잘 일치하였다.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.263-272
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• 1999

Slice method is commonly used in solving slope stability problems since it is easy to use and its computation time is rather short. But depending upon the assumptions on the inter-slice forces, different methods are available. Quite often the difference between methods are so big that it is very difficult to make engineering decisions. This paper describes a method to calculate the factor of safety of a slope using FLAC, a finite difference based program. A FISH routine is developed to calculate the factor of safety, and verified by comparing with Chen's limit equilibrium solution. An example problem was selected from Fredlund and Krhan's paper, and results were compared for different soil and water conditions. The difference was less than 0.01 when the soil is homogeneous, and less than 5 % when a weak layer is embedded. Since most geotechnical application programs are capable of considering complicated ground conditions as well as the effect of ground supports, numerical methods are believed to be very useful in making engineering decisions. The developed routine can be applied to the calculation of the factor of safety of jointed rock slopes or weathered rock slopes where the use of slice method is limited.

• The Korean Journal of Financial Management
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• v.24 no.1
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• pp.109-147
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• 2007

According to the perspective of capital structure theory, we analyzed the dynamism of the capital structure determinants by using panel data of 244 KOSDAQ firms based on two-step GMM system methodology suggested by Blundell Bond(1998). This dynamic methodology had not been used to analyse capital structure determinants in Korea. In the dynamic model of capital structure, profit had negative effect on the book leverage and market leverage, which meant supporting pecking order theory. Growth opportunity (MBR) affected negatively to the market leverage. For the determinants of leverage, earnings volatility had significantly positive effect on KOSDAQ 50 firms. KOSDAQ and KOSDAQ 50 firms had the target leverage. The adjustment speed in KOSDAQ firms was 0.4958 on the book leverage, it was faster than in KOSDAQ 50 firm's 0.2863 on the book leverage and the adjustment speeds for the market leverage were 0.7651 for KOSDAQ firms and 0.5643 for KOSDAQ 50 firms. There was difference in adjustment cost between KOSDAQ firms and KOSDAQ 50 firms.

• The Korean Journal of Elementary Counseling
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• v.7 no.2
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• pp.181-196
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• 2008

The purposes of this study were to develop vocational cards for elementary school children as a useful means to be applicable to elementary career counseling, to carry out a career counseling program by using vocational cards, and ultimately to determine the effect of the program on the career maturity of elementary schoolers. After job selection criteria were prepared in light of the characteristics of different occupations, changing business world and school children, how many number of vocational cards would be suitable for elementary schoolers was decided, and leading occupations were selected according to Holland classification in consideration of promising job list for the future, analysis of schoolbook and dream job among school children. And then what should be described on vocational card was determined, and their size was selected. Students who participated in the career counseling program based on vocational cards were significantly different in career maturity from others who didn't. To improve the reliability of quantitative approach, the students were asked to describe how they felt, and they made a positive assessment of the program as they found it to be interesting and of use for their understanding of themselves and business world. In conclusion, the vocational card for elementary middle-year students developed in this study catered to the career development stage of elementary schoolers, and the career counseling program using the vocational cards had a positive effect on enhancing the career maturity of children.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.09a
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• pp.16-42
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• 1995

변환기에 있는 국내 외주위탁 시장의 특징은 대기업을 중심으로 시장이 형 성되어 있다는 것이다. 즉, 전체 시장규모의 약 절반 가량을 대기업들의 그 룹내 정보시스템 관리 비용이 차지하고 있으며, 자본금 10억 이상의 대형 외 주업체가 전체 70%정도를 점유하고 있다. 대부분의 그룹들은 계열사들의 정 보 시스템 부문을 통합하여 시스템 통합 회사를 설립하고, 이를 통해 내부 정보 시스템의 관리 및 운영을 실시하고 있다. 따라서, 계열사들은 기업의 환경과 요구 사항에 관계없이 무조건적으로 그룹내 시스템 통합 업체에 정 보 시스템을 외주 위탁하여 왔다. 하지만, 기업의 미래는 정보 시스템이 제 공하는 정보의 질에 의해 좌우된다고 해도 과언이 아니므로, 계열사들은 외 주위탁을 위해 그룹내 시스템 통합 업체 뿐 아니라 전문 기술과 경험을 가 지고 있는 외부 회사들을 고려하여야 한다. 즉, 기업의 환경과 필요한 정보 기술에 적합한 외주 위탁 회사를 선정하도록 하여야 한다. 계열사들이 기업 내부의 상황과 그룹의 환경에 따라 최적의 외주위탁 전략을 결정하도록 하 기 위해 본 연구에서는 두 가지 요소 -조직의 정보강도, 그룹의 영향지수-를 도입하였다. 이 요소들을 사용하여 계열사들의 독특한 업무의 환경에 적합한 외주위탁 상황 모형을 제시하고, 제시된 모델의 적합성 여부를 검증하기 위 해 시스템 통합 업체를 가진 국내 대기업의 사례들을 분석, 평가해 보았다. 6개의 그룹에서 11개의 계열사들을 선정하여 각 계열사들의 현재의 외주위 탁 전략, 조직의 정보강도, 그룹의 영향요소 및 정보 시스템에 대한 사용자 만족도를 상위 관리자들과의 인터뷰를 통해 조사하였다. 이 사례 연구들의 결과는 각 계열사들의 상황에 따라 제시된 외주위탁 전략과 현재의 외주위 탁 전략이 일치할 때 정보 시스템에 대한 사용자 만족도가 보다 높은 것으 로 나타났다. 할 수 있는 효율적인 distributed system를 개발하는 것을 제시하였다. 본 논문은 데이타베이스론의 입장에서 아직 정립되어 있지 않은 분산 환경하에서의 관계형 데이타베이스의 데이타관리의 분류체계를 나름대로 정립하였다는데 그 의의가 있다. 또한 이것의 응용은 현재 분산데이타베이스 구축에 있어 나타나는 기술적인 문제점들을 어느정도 보완할 수 있다는 점에서 그 중요성이 있다.ence of a small(IxEpc),hot(Tex> SOK) core which contains two tempegatlue peaks at -15" east and north of MDS. The column density of HCaN is (1-3):n1014cm-2. Column density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.업순서들의 상관관계를 고려하여 보다 개선된 해를 구하기 위한 연구가 요구된다. 또한, 준비작업비용을 발생시키는 작업장의 작업순서결정에 대해서도 연구를 행하여, 보완작업비용과 준비비용을 고려한 GMMAL 작업순서문제를 해결하기 위한 연구가 수행되어야 할 것이다.로 이루어 져야 할 것이다.태를 보다 효율적으로 증진시킬 수 있는 대안이 마련되어져야 한다고 사료된다.$\ulcorner$순응$\lrcorner$의 범위를 벗어나지 않는다. 그렇기 때문에도 $\ulcorner$순응$\lrcorner$