• Ocean Systems Engineering
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• 제5권2호
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• pp.77-89
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• 2015

As the exploitation of oil and gas resources advances into deeper waters and harsher environments, the design and analysis of the flexible risers has become the research focus in the offshore engineering filed. Due to the complexity of the components and the sliding between the adjacent layers, the bending response of the flexible risers is highly non-linear. This paper presents the finite element analysis of the flexible risers under bending loads. The detailed finite element model of the flexible riser is established in ABAQUS software. This finite element model incorporates all the fine details of the riser to accurately predict its nonlinear structural behavior. Based on the finite element model, the bending moment-curvature relationships of a flexible riser under various axisymmetric loads have been investigated. The results have been compared with the analytical ones obtained from the literature and good agreements have been found. Moreover, the stress of the tendon armors has been studied. The non-linear relationship between the armor tendons' stress and the bending loads has been obtained.

• 한국수자원학회논문집
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• 제50권5호
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• pp.325-334
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• 2017

본 연구에서는 다공성 매질의 공극율과 투수능 그리고 유체의 동점성 계수와 같은 물리적 특성에 따른 유체흐름의 비선형 거동에 대한 수치적 분석을 수행하였다. 적용된 수치모형은 ANSYS CFX 3차원 유동해석 모형이며, 모형의 검증은 기존의 물리적 실험 결과 및 수치모의 결과의 적용을 통해 수행되었으며, 적용된 압력경사와 유속과의 관계 그리고 마찰계수와 레이놀즈 수와의 관계에 대해 비교적 잘 일치하였다. 다공성 매질의 공극율과 투수능 그리고 유체의 동점성 계수의 값을 변화시키면서 모의한 결과 유체의 동점성 계수가 다공성 매질의 유체흐름의 비선형 거동에 가장 큰 영향을 미치는 것으로 나타났다.

• Journal of the Korean Data and Information Science Society
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• 제27권3호
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• pp.629-638
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• 2016

최근에 많이 활용되고 있는 데이터 분석을 위한 연관성 규칙 마이닝은 대용량 데이터베이스에 많이 활용되고 있는 서 두 항목간의 관계를 측도화 함으로써 두 개 이상의 항목간의 관련성을 표시하여 주는 기법이다. 연관성 규칙의 여부를 판단하기 위한 연관성 평가 기준에는 지지도, 신뢰도, 그리고 향상도 등이 있으며, 이들 세 가지 기준을 이용하여 연관성 규칙 생성 여부를 판단하게 된다. 이에 대한 기존의 연구 결과는 결정함수를 이용하는 방법과 회귀모형을 이용하는 방법으로 분류할 수 있다. 회귀모형을 이용하여 수행한 연구에는 지지도와 신뢰도에 의한 모형, 세 가지 평가 기준의 쌍에 의한 모형, 표준화 향상도를 포함한 세 가지 평가 기준의 쌍에 의한 모형, 그리고 세 가지 평가 기준 전부를 고려한 모형 등이 있다. 본 논문에서는 기존의 연구를 확장하는 의미에서 표준화 향상도를 포함한 세가지 평가 기준 전부를 고려한 비선형 회귀모형을 이용하여 연관성 규칙의 수를 추정하는 방안에 대해 강구하고자 한다. 또한 분산분석에서의 F 통계량과 수정 결정계수를 이용하여 각 모형의 유의한 정도를 비교하는 동시에 분산팽창계수에 의한 공선성 문제를 진단함으로써 가장 유용한 회귀 모형을 탐색하고자 한다.

• Geomechanics and Engineering
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• 제24권4호
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• pp.307-321
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• 2021

In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.

• 한국병원경영학회지
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• 제28권1호
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• pp.37-51
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• 2023

Purposes: There exist many non-covered services that the National Health Insurance does not cover, and thus, their prices are set by individual health care providers. However, little study has been done to investigate how hospitals set prices for those services. The purpose of this study is to examine the relationship between ownership, profitability, and prices of those services for a sample of general hospitals. Methodology/Approach: Data regarding the prices of major non-covered services (e.g., upper-level hospital room fees, MRI, Da 7inci robot surgery, and LASIK) were obtained from the Health Insurance Review and Assessment Service and the financial information, as well as other characteristics, were derived from the financial reports from the Korea Health Industry Development Institute. Descriptive statistics, t-tests, and multiple linear regression analyses were used to test the relationship between the independent variables and the dependent variables. Findings: Hospitals owned by private universities appeared to have higher prices for non-covered services while regional public hospitals tend to have lower prices. Profitability, measured by operating margin, was not significantly related to the prices. Hospitals that charge higher prices were more likely to be located in the capital area (Seoul, Incheon, and Gyeonggi), and to employ larger number of personnel. Practical Implications: Public hospitals tend to charge lower prices for non-covered services. Relative market power appears to be related to pricing. Further research is needed to investigate whether such a relationship varies over time and its effects on the quality and access.

• The Journal of Asian Finance, Economics and Business
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• 제7권6호
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• pp.109-116
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• 2020

The study examines the nexus between financial development and economic growth in India during Q1: 1996 to Q3: 2018. This study employs time-series data of real GDP and ratio of broad money to GDP as a proxy for economic and financial development, respectively. The data are obtained from RBI database on the Indian economy. All variables are seasonally adjusted using X12-arima technique and expressed in natural logarithm form. Non-linear Autoregressive Distributed Lag (NARDL) bound test has been used to check for cointegrating relationship of these two variables. Empirical findings suggest that, unlike in the short run, in the long run financial development does impact economic growth positively. Further, a symmetric effect of positive and negative components of financial development is found for the Indian economy, whereas the effect of control variable like exchange rate and trade openness is in consonance with common economic intuition. Exchange rate is in consonance with intuitive economic logic that a fall in exchange rate makes exports cheaper and increases the quantity of export, which improves the balance of payment and leads to a rise in aggregate demand, hence improves economic growth. This paper contributes to the existing literature on India by breaking down financial indicator into positive and negative components to examine the finance-growth relationship.

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 2002년도 제20회 동계학술발표회 논문집
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• pp.59-89
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• 2002

The rapid diffusion of information and telecommunication (IT) technologies during the recent decennia produced fundamental changes in the economic activity at a global level, resulting in what became coined as the "new economy". However, empirical evidence on the contribution of IT equipment to growth and productivity is at best mixed, with the more or less consistent results on the positive link between the two relating to the United States in the 1990-s. Although the empirical literature on the link between IT investment and economic performance employs a wide variety of methodologies, the overwhelming majority of the studies appears to be employing the assumption of linearity of the IT-performance relationship and predominantly explores the direct nature thereof. In this study we relax both these assumptions and find that the indirect, or aggregate productive efficiency, effects of IT investment are as important as are the direct ones The estimated non-linear nature of the indirect relationship between IT investment intensity and productive efficiency accommodates the concepts of critical mass and complementary (infrastructure) capital offered in the literature. Our key finding is that the world economy′s average level of IT investment intensity remained below the estimated critical mass. Since in this study we developed a methodology that allows one to explicitly measure the critical mass of IT investment intensity, its individual estimation at a country or industrialsector level may help evaluate the extent to which IT investment activity has to be encouraged or discouraged.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.833-840
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• 2021

This paper examines the effect of the interest rate set by Bank Indonesia on financial system stability as measured by the credit gap in Indonesia for quarterly data for the period 1976 Q1 to 2019 Q4. We suppose that the relationship between the Central Bank rate and the credit gap is non-linear. Hence, this study applies a smooth transition regression (STR) model to investigate the relationship between these variables. Our results are: first, by performing STR estimation we obtained a threshold level of Central Bank rate of 2.01. Second, a decrease in the Central Bank rate results in a reduction in the credit gap when the Central Bank rate is above or below the threshold level. The effect of the Central Bank rate is five times greater for the high regime than for the low regime. Third, we find evidence that the effect of the exchange rate, economic growth, inflation, and GDP per capita on the credit gap for the high regime is the opposite of the low regime. We suggest that policymakers need to keep the Central Bank interest rate low and stable so that the role of the bank as a financial intermediary remains stable and conducive to strengthening financial stability.

• Environmental Analysis Health and Toxicology
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• 제31권
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• pp.1.1-1.13
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• 2016

Objectives To investigate the accuracy and scientific validity of the current very low risk factor for hereditary diseases in humans following exposures to ionizing radiation adopted by the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection. The value is based on experiments on mice due to reportedly absent effects in the Japanese atomic bomb (A-bomb) survivors. Methods To review the published evidence for heritable effects after ionising radiation exposures particularly, but not restricted to, populations exposed to contamination from the Chernobyl accident and from atmospheric nuclear test fallout. To make a compilation of findings about early deaths, congenital malformations, Down's syndrome, cancer and other genetic effects observed in humans after the exposure of the parents. To also examine more closely the evidence from the Japanese A-bomb epidemiology and discuss its scientific validity. Results Nearly all types of hereditary defects were found at doses as low as one to 10 mSv. We discuss the clash between the current risk model and these observations on the basis of biological mechanism and assumptions about linear relationships between dose and effect in neonatal and foetal epidemiology. The evidence supports a dose response relationship which is non-linear and is either biphasic or supralinear (hogs-back) and largely either saturates or falls above 10 mSv. Conclusions We conclude that the current risk model for heritable effects of radiation is unsafe. The dose response relationship is non-linear with the greatest effects at the lowest doses. Using Chernobyl data we derive an excess relative risk for all malformations of 1.0 per 10 mSv cumulative dose. The safety of the Japanese A-bomb epidemiology is argued to be both scientifically and philosophically questionable owing to errors in the choice of control groups, omission of internal exposure effects and assumptions about linear dose response.

• Steel and Composite Structures
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• 제35권4호
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• pp.579-598
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• 2020

Consideration of the panel zone (PZ) deformations in the analysis of steel moment frames (SMFs) has a substantial effect on structural response. One way to include the PZ effect on the structural response is Krawinkler's PZ model, which is one of the best and conventional models. However, modeling of Krawinkler's PZ model has its complexity, and finding an alternative procedure for PZ modeling is of interest. In this study, an efficient model is proposed to simplify Krawinkler's PZ model into an Adjusted Rigid-End Zone (AREZ). In this way, the rigid-end-zone dimensions of the beam and column elements are defined through an appropriate rigid-end-zone factor. The dimensions of this region depend on the PZ stiffness, beam(s) and columns' specifications, and connection joint configuration. Thus, to obtain a relationship for the AREZ model, which yields the dimensions of the rigid-end zone, the story drift of an SMF with Krawinkler's PZ model is equalized with the story drift of the same structure with the AREZ model. Then, the degree of accuracy of the resulting relationship is examined in several connections of generic SMFs. Also, in order to demonstrate the applicability of the proposed model in SMFs, several SMFs ranging from 3- to 30-story representing low- to high-rise buildings are examined through linear static and dynamic time history analysis. Furthermore, non-linear dynamic analyses of three SMFs conducted to validate the degree of accuracy of the proposed model in the non-linear analysis of SMFs. Analytical results show that there is considerable conformity between inter-story drift ratio (IDR) results of the SMFs with Krawinkler's PZ model and those of the centerline SMFs with AREZ.