• Structural Engineering and Mechanics
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• 제62권6호
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• pp.725-737
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• 2017

An analytical method considering axial equilibrium is proposed for the short- and long-term analyses of shear lag effect in reinforced concrete (RC) box girders. The axial equilibrium of box girders is taken into account by using an additional generalized displacement, referred to as the longitudinal displacement of the web. Three independent shear lag functions are introduced to describe different shear lag intensities of the top, bottom, and cantilever plates. The time-dependent material properties of the concrete are simulated by the age-adjusted effective modulus method (AEMM), while the reinforcement is assumed to behave in a linear-elastic fashion. The differential equations are derived based on the longitudinal displacement of the web, the vertical displacement of the cross section, and the shear lag functions of the flanges. The time-dependent expressions of the generalized displacements are then deduced for box girders subjected to uniformly distributed loads. The accuracy of the proposed method is validated against the finite element results regarding the short- and long-term responses of a simply-supported RC box girder. Furthermore, creep analyses considering and neglecting shrinkage are performed to quantify the time effects on the long-term behavior of a continuous RC box girder. The results show that the proposed method can well evaluate both the short- and long-term behavior of box girders, and that concrete shrinkage has a considerable impact on the concrete stresses and internal forces, while concrete creep can remarkably affect the long-term deflections.

• 재무관리연구
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• 제25권3호
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• pp.111-130
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• 2008

이 논문은 분수공적분 개념을 이용하여 KOSPI200지수와 지수선물가격간에 장기균형관계가 있는지를 살펴보고 있다. 이것을 위해 로그변환 현 선물가격 각각의 분수차분계수를 주파수영역 (frequency domain)의 GPH 추정량을 구한 다음, 현 선물 회귀식의 추정을 통해 도출한 균형오차의 차분계수와 비교하였다. 이 방법은 전통적인 공적분방법에서 규명하지 못한 금융시계열자료의 통계적인 특성을 분석할 수 있는 장점이 있다. 분석결과를 요약하면 다음과 같다. 첫째, 정수차원의 차분구조모형에서는 공적분검정을 통한 장기균형관계의 증거를 찾기가 어려웠다. ADF 단위근 검정과 KPSS 정상성 검정에서 상반된 결과가 제시되어 두 시계열을 I(1)으로 확정하기가 불가능하였다. 둘째, GPH 추정량를 이용하여 차분계수를 추정한 결과, 두 시계열 모두 불안정한 장기기억구조를 가지는 것으로 식별되었고 균형오차는 정상적인(stationary) 장기기억구조를 가져 현 선물가격간에 분수공적분관계가 있는 것으로 파악되었다. 이 논문은 선물시장과 현물시장이 장기균형관계를 국내 선행연구에서 이용하지 않았던 분수공적분을 이용하여 분석했다는 점에서 그 의의를 찾을 수 있다.

• 유통과학연구
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• 제13권11호
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• pp.39-46
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• 2015

Purpose - In Korea, there has been a recent trend that shows housing prices have risen rapidly following the International Monetary Fund crisis. The rapid rise in housing prices is spreading recognition of this as a factor in housing price volatility. In addition, this raises the expectations of housing prices in the future. These expectations are based on the assumption that a relationship exists between the current housing prices and expected housing prices in the real estate industry. By performing an empirical analysis on the validity of the claim that an increase in current housing prices can be correlated with expected housing prices, this study examines whether a long-term equilibrium relationship exists between expected housing prices and existing housing prices. If such a relationship exists, the recovery of equilibrium from disequilibrium is analyzed to derive related implications. Research design, data, and methodology - The relationship between current housing prices and expected housing prices was analyzed empirically using the Vector Error Correction Model. This model was applied to the co-integration test, the long-term equilibrium equation among variables, and the causality test. The housing prices used in the analysis were based on the National Housing Price Trend Survey released by Kookmin Bank. Additionally, the Index of Industrial Product and the Consumer Price Index were also used and were obtained from the Bank of Korea ECOS. The monthly data analyzed were from January 1987 to May 2015. Results - First, a long-term equilibrium relationship was established as one co-integration between current housing price distribution and expected housing prices. Second, the sign of the long-term equilibrium relationship variable was consistent with the theoretical sign, with the elasticity of housing price distribution to expected housing price, the industrial production, and the consumer price volatility revealed as 1.600, 0.104,and 0.092, respectively. This implies that the long-term effect of expected housing price volatility on housing price distribution is more significant than that of the industrial production and consumer price volatility. Third, the sign of the coefficient of the error correction term coincided with the theoretical sign. The absolute value of the coefficient of the correction term in the industrial production equation was 0.006, significantly larger than the coefficients for the expected housing price and the consumer price equation. In case of divergence from the long-term equilibrium relationship, the state of equilibrium will be restored through changes in the interest rate. Fourth, housing-price volatility was found to be causal to expected housing price, and was shown to be bi-directionally causal to industrial production. Conclusions - Based on the finding of this study, it is required to relieve the association between current housing price distribution and expected housing price by using property taxes and the loan-to-value policy to stabilize the housing market. Further, the relationship between housing price distribution and expected housing price can be examined and tested using a sophisticated methodology and policy variables.

• 해운물류연구
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• 제34권4호
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• pp.545-563
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• 2018

본 연구의 목적은 VLCC(Very Large Crude Oil Carrier) 운임에 영향을 미치는 주요 결정요인의 장기적 탄성치를 추정하는 것이다. 이를 위해 본 연구는 영국 해운 전문 기업인 클락슨이 공표하는 연간 VLCC 운임을 종속변수로, 원유(Crude oil) 물동량, VLCC 선복량, 벙커유 가격, Libor 금리를 설명변수로 사용하였다. 본 연구는 벡터오차수정모형(Vector Error Correction Model; VECM)을 사용하여 운임 결정 장기균형함수를 추정하였으며, 추정결과 물동량 1.0% 증가 시 운임 6.4% 증가, 선복량 1.0% 증가 시 운임 1.9% 감소, 벙커유 가격 1.0% 증가 시 운임 0.3% 감소, 금리 1.0% 증가 시 운임은 0.18% 증가하는 것으로 나타났다. 벙커유 가격의 경우 일반적인 직관과 반대되는 마이너스(-) 부호로 계수가 추정되었는데, 이는 설명변수 중 벙커유 가격이나 금리 등의 2차 변수가 운임에 미치는 영향력은 적은 반면 직접적인 수급 변수가 운임을 결정하는 주요 요인이기 때문인 것으로 이해된다. 후속연구에서 컨테이너선, 건화물선 등 다른 선종들을 대상으로 연구를 수행하고 다양한 선종별 운임의 결정요인을 비교 분석하는 것이 필요하다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2233-2235
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• 2004

This paper presents a therapy that uses a constant drug dosage for leading a HIV patient to a LTNP (Long-Tenn Non-Progressor). From analysis of CTLp (Cytotoxic T Lymphocyte precursor) concentration at equilibrium point and bifurcation of equilibrium points, we found the therapy with a drug whose efficacy is less than one brings higher CTLp concentration at the equilibrium point. From this fact, we propose a treatment with constant drug dosage. which can induce LTNP.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권4호
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• pp.259-266
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• 2005

This paper presents a therapy that uses a constant drug dosage for leading HIV-infected patient to LTNP (Long-Term Non-Progressor). Based on analysis of CTLp (Cytotoxic T Lymphocyte precursor) concentration at equilibrium point and its bifurcation, we found the therapy with a drug whose efficacy is less than a certain level brings higher CTLp concentration at the equilibrium point. We observed a treatment with constant drug dosage whose efficacy is less than full treatment may lead HIV-infected patient to LTNP. It turns out that the treatment whose efficacy is less than full treatment is better in the point of performance on controllability.

• 자원ㆍ환경경제연구
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• 제26권3호
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• pp.287-317
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• 2017

경제성장과정에서 석면을 활용해왔지만, 석면이 치명적인 환경성질환을 유발하는 1급 발암물질로 지정되면서 전 세계적으로 엄격한 석면사용규제 조치를 실시하고 있다. 석면노출과 환경성질환의 발현 간에 수십 년에 걸친 장기 잠복기가 존재한다는 특성을 고려하여, 한국의 석면 소비량과 악성중피종 발병 간의 시차를 분석하고 장기관계를 추정한다. 이와 함께, 한국에 비해 상대적으로 석면규제가 오랜 기간 이루어지고 장기시계열 자료를 갖춘 영국과 미국을 대상으로 한 비교분석도 병행한다. 시차분석에서는, 3개 국가 모두에서 30년 이상의 장기시차가 존재할 때, 석면 소비와 악성중피종 발병 간의 교차상관성이 높은 것으로 나타난다. 또한 변수간 장기시차가 존재할 경우 석면 소비량과 악성중피종 발병 간에 장기균형관계가 존재한다. 그리고 시차분포모형을 활용한 결과, 석면 소비량이 장기시차를 두고 악성중피종에 유의한 정의 영향을 미치고 있다.

• Journal of the Korean Statistical Society
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• 제4권2호
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• pp.113-125
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• 1975

The money market has been existing in various forms for a long time. Until 1972, however, the market had supplied mainly short-term loans of commercial banks and loans of informal money lenders to business corporations. There was no market for notes and commercial papers of business corporations. Consequently, business corporations had to rely primarily upon commercial banks for short-term credit loans to supplement their working capital. The interest rate on loans of commercial banks had been set below a free market equilibrium rate and thereby, generated excess demands for the loans. Unsatisfied potential borrowers thus had to turn to informal money lenders for short-term cerdit loans of prohibitively high interest rate. Since 1972 investment and finance companies have been operating in the money market and their role in mobilizing short-term loans is increasing. This paper aims at estimating the equilibrium size of the money market.

• 무역학회지
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• 제44권1호
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• pp.75-86
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• 2019

This study performs a factor analysis that affects the bunker oil price using the Co-integration model and Vector Error Correction Model (VECM). For this purpose, we use data from Clarkson and the analysis results show 17.6% decrease in bunker oil price when the amount of crude oil production increases at 1.0%, 10.3% increase in bunker oil price when the seaborne trade volume increases at 1.0%, 1.0% decrease in bunker oil price when total volume of vessels increases at 1.0%, and 0.003% increase in bunker oil price when 1.0% increase in world GDP, respectively. This study is meaningful in that this study estimates the speed of convergence to long-term equilibrium and identifies the price adjust mechanism which naturally exists in bunker oil market. And it is expected that the future study can provide statistically more meaningful econometric results if it can obtain data during more long-periods and use more various kinds of explanatory variables.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.462-467
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• 1998

A rational method for prediction of long-term deflections of reinforced concrete beams under sustained loads was proposed. Strain and stress distributions of uncracked and fully cracked sections after creep and shrinkage were determined from the requirements of strain compatibility and force equilibrium of a section, and then long-term deflections were calculated from the section analysis results. In fully cracked section analysis, noncoincidence of the neutral axis of strain and the neutral axis of stress after creep and shrinkage was taken into account. The accuracy of the proposed method was verified by comparison with several experimental measurements of beam deflections. The proposed approximate procedure gave the better predictions than the existing approximate methods. At the same time, the proposed method also retained simplicity of the calculation, since maximum long-term deflection could be obtained without tedious integration of the curvatures.