• Journal of Korea Port Economic Association
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• v.28 no.3
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• pp.111-125
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• 2012

This study investigates the behavioral characteristic difference of the container volumes of three ports-Gwangyang, Incheon, and Pyeongtaek-Dangjin. All series span the period January 2003 to December 2011. I first test whether the series are stationary or not. I can reject the null hypothesis of a unit root in each of the level variables and of a unit root for the residuals from the cointegration at the 5 percent significance level. I hitherto make use of error-correction model and find that Gwangyang port is the slowest in adjusting the short-run disequilibrium, whereas the adjustment speed of Incheon is much faster than that of Gwangyang. The impulse response functions indicate that container volumes increase only a little to the negative shocks in exchange rate, while they respond positively to the shocks in the business activity in a great magnitude and decay very slowly to its pre-shock level. meaning that the shocks last very long. The accumulative response to the exchange rate increase of 20 won per dollar and the 5 point industrial production increase is the smallest in Gwangyang, no more than a half of that of two ports. The intervention-ARIMA models also forecast that Gwangyang port will have much lower growth rate than Incheon and Pyeongtaek-Dangjin port in trading volumes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.107-117
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• 2014

This study tests homogeneity and performs multiple comparison analysis among treatment levels of each factor group through t-test by materials and analysis of variance by structural type and service period. For that descriptive statistical analysis is performed for static and dynamic response characteristics and their ratios of calculated versus measured values based on a good many safety assessment reports for bridges. Homogeneity and post hoc test based on descriptive statistical analysis provide the measures for homogeneity identification among comparison groups in addition to the statistical reference values such as central tendency, variation and shape. This study is expected to be valuable for structural integrity assessment and design by comparing the measured and calculated values with the reference values for the homogeneous group identified, which can help the engineers review the adequacy of the values and put the group database to practical use.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.281-288
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• 2014

The objective of this study was to estimate the vibration reduction capacities of a floating track system using a resilient rubber mat, and to compare the results with the track support stiffness and track impact factor of a conventional slab track system by performing field tests using actual vehicles running along a service line. The theoretically designed track support stiffness and track impact factor were compared with the measured track support stiffness and track impact factor for each tested track. The calculated and measured track support stiffness of the floating track system were found to be similar, and the floating track system satisfied the design specifications of the track impact factor. The overall vibration level and track support stiffness of the floating track system were thereupon found to be significantly lower than those of the conventional slab track system. The experimental results thus showed that the vibration reduction effect of the floating track system is greater than that of the conventional slab track.

• The Korean Journal of Financial Management
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• v.18 no.2
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• pp.169-191
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• 2001

본 연구는 우리나라와 일본의 주가, 금리와 환율 등 주요 금융자산가격변수들이 상호간에 주고받는 영향을 3변량 MA-GARCH모형을 사용하여 분석하여 보았다. 우선 각 시장의 조건부 수익률을 기준으로 볼 때 우리나라에서는 외환위기 이후 주식시장과 채권시장의 상관관계는 낮아진 반면 외환시장과 주식시장, 외환시장과 채권시장의 상관관계는 10%p 이상씩 높아진 것으로 나타났다. 따라서 외환위기 이후 주식, 채권시장의 외환시장과의 연관성은 크게 높아져 환율 움직임의 영향력이 전반적으로 커졌다고 이해할 수 있다. 이에 비해 일본의 경우 각각의 금융시장간 상관계수는 10% 이하의 매우 낮은 수준에 불과하여 상호관련성이 낮은 수준을 보여 주었다. GARCH 추정이 도출한 각 시장의 조건부표준편차들간의 상관계수를 보면, 우리나라와 일본 모두 외환시장 변동성$\leftrightarrow$채권시장 변동성, 주식시장 변동성$\leftrightarrow$채권시장 변동성 사이의 상관관계는 28-29% 정도이며, 외환시장 변동성$\leftrightarrow$주식시장 변동성 사이의 관계는 21% 정도로 상대적으로 낮은 수치를 보여 주었다. 반면에 금융시장 변동성의 각 국간 상관관계는 90% 내외의 높은 상관관계를 가져, 국가내의 시장간 관계보다 더 높은 수치를 보여 주었다. 따라서 우리나라와 일본의 금융시장 변동성은 국내금융시장간의 요인보다는 모두 미국 주식시장에서의 충격이나 국제유가 급등락 등 외부적 요인에 대해 크게 영향을 받는 것으로 판단해 볼 수 있을 것이다.

• Journal of Korea Port Economic Association
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• v.27 no.1
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• pp.263-280
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• 2011

The global financial crisis, triggered by the subprime mortgage crisis in 2007, has put the world economy into the recession with financial market turmoil. I tested whether variables were cointegrated or whether there was an equilibrium relationship. Also, Generalized impulse-response function (GIRF) and accumulation impulse-response function (AIRF) may be used to understand and characterize the time series dynamics inherent in economical systems comprised of variables that may be highly interdependent. Moreover, the IRFs enables us to simulate the response in freight to a shock in the USD/JPY exchange rate, Dow Jones industrial average index, Dow Jones volatility, Chinese Import volatility. The result on the cointegration test show that the hypothesis of no cointergrating vector could be rejected at the 5 percent level. Also, the empirical analysis of cointegrating vector reveals that the increases of USD/JPY exchange rate have negative relations with freight. The result on the impulse-response analysis indicate that freight respond negatively to volatility, and then decay very quickly. Consequently, the results highlight the potential usefulness of the multivariate time series techniques accounting to behavior of Freight.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.261-275
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• 2011

To maintain the traffic flow during tunnel expansion, cars must be protected from falling rocks during excavation and to do so, a protector has to be installed inside the tunnel before beginning the excavation. In Korea, tunnel expansion by blasting rather than by mechanical excavation has been widely achieved. For this reason, a series of numerical analysis were performed to analyze the characteristics of impact load according to material behaviour of blasted rock by using Explicit FEA program. From the numerical results, it is found that the impact loads when rock is assumed as an elastic-plastic material appear to be only 7~12% compared with that when it is elastic.

• Computational Structural Engineering
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• v.10 no.3
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• pp.145-155
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• 1997

In this study, static and dynamic transient analysis of tracked vehicle structure with recoil impact load is performed for transient impact and traveling load using ANSYS and ABAQUS FEM codes. When transient impact loads are applied at tracked vehicle, the maximum dynamic Von Mises stress occurs between beam stiffener of upper plate and race ring and stress level is about 390-450 MPa. The results of transient analysis shows similar level and tendency with static stress with dynamic force effect of 1.6. The excessive stresses occur around the race ring for the both cases. When the traveling loads are applied on the tracked vehicle, the maximum Tresca stress occurs around suspension #1 and is about 450 MPa and results of static and nonlinear transient analysis are quite similar.

• International Area Studies Review
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• v.16 no.3
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• pp.77-97
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• 2012

Estimated coefficients has serious problems including inconsistency, biasness, etc. because many researches about the effect of fiscal decentralization on a country's economic growth use the traditional OLS method. Researches use the data intactly so that so called "spurious regression" phenomenon exists. This causes fundamental fallacy. This research tries unit root test, cointegration test, and then estimates the United States' economic time series by using VECM. The analysis of the effect of the state level-fiscal decentralization on economic growth shows two long term-equilibriums. During short term-dynamic adjustment, fiscal decentralization and economic growth move the same or different directions. In case of prediction GDP increases steeply and then from 2015 gently; and fiscal decentralization index shows a general reduction trend and then decreases slowly. At local level it shows two long term-equilibriums. During short term-dynamic adjustment, fiscal decentralization and economic growth also move the same or different directions. Impulse response analysis shows the very negative effect of fiscal decentralization on economic growth.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.106-111
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• 2018

Hydrodynamic ram phenomenon could be generated by external threats such as impact and blast in the aircraft. High strain rate deformation caused by the hydrodynamic ram phenomenon is one of the main factors to influence structural survivability. Mechanical properties of composite structure change rapidly under conditions of high strain rate. Therefore, it is necessary to experimentally investigate the influence of strain rates for aircraft structural survivability. In this paper, tensile tests of composite material were conducted for low and high strain rates to investigate the influence of the various strain rates. Tensile modulus increases more compared to tensile strength at high strain rate under hydrodynamic ram condition. Regression analysis was conducted to predict tensile modulus at various strain rates because it is one of the main damaging factors for composite structures under high strain rate conditions. Also, the mechanical properties of composite materials were acquired and analyzed under high strain rate conditions. It is hypothesized that the results from this study would be used for designing aircraft composite structures and evaluation considering structural survivability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.235-244
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• 2021

This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.