• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.234-243
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• 2002

When a vehicle is operated over sort terrain, torque(or soil thrust) applied to driving wheel brings about shear displacement far soil due to compression and shear failure of soil under tire. This shear displacement give rise to slip and a additional sinkage due to slip. This additional sinkage is usually referred to as slip-sinkage. The slip-sinkage is affected by soil conditions and inflation pressure of tire. This slip-sinkage influence tractive performance on driving wheel . We conducted the experimental study far investigating the effect of slip on sinkage and tractive performance of driving wheel, such as motion resistance, thrust and drawbar pull. The experiment was carried out over three different soil conditions(soft, hard and very hard soil) far a tire with three levels of inflation pressure(120kPa, 240kPa and 360kPa). The results of this study show qualitatively slipsinkage characteristics and slip-tractive performance relationships of driving wheel with soil conditions and inflation pressure of tire.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.583-592
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• 2015

Zero-inflation has recently attracted much attention in integer-valued time series. This article deals with conditional variance (volatility) modeling for the zero-inflated count time series. We incorporate zero-inflation property into integer-valued GARCH (INGARCH) via conditional Poisson and negative binomial marginals. The Cholera frequency time series is analyzed as a data application. Estimation is carried out using EM-algorithm as suggested by Zhu (2012).

• Communications for Statistical Applications and Methods
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• v.27 no.1
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• pp.37-46
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• 2020

Recurrent event data frequently occur in clinical studies, demography, engineering reliability and so on (Cook and Lawless, The Statistical Analysis of Recurrent Events, Springer, 2007). Sometimes, two or more different but related type of recurrent events may occur simultaneously. In this study, our interest is to estimate the covariate effect on bivariate recurrent event times with zero inflations. Such zero inflation can be related with susceptibility. In the context of bivariate recurrent event data, furthermore, such susceptibilities may be different according to the type of event. We propose a joint model including both two intensity functions and two cure rate functions. Bivariate frailty effects are adopted to model the correlation between recurrent events. Parameter estimates are obtained by maximizing the likelihood derived under a piecewise constant hazard assumption. According to simulation results, the proposed method brings unbiased estimates while the model ignoring cure rate models gives underestimated covariate effects and overestimated variance estimates. We apply the proposed method to a set of bivariate recurrent infection data in a study of child patients with leukemia.

• Journal of the military operations research society of Korea
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• v.30 no.1
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• pp.135-152
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• 2004

Ever since Benoit's(1973, 1978) study, the relationship between defense spending and economic growth has been the subject of extensive empirical works. While a number of studies have reported that higher defense expenditure stimulate economic growth, many other studies have reported that an increase in military burden may hinder economic growth. To the extent that countries differ substantially in socioeconomic structures, the effects of defense spending cannot be generalized across countries. In this paper, Granger causality tests are performed between Korean defense expenditure and economic growth, consumption, investment, inflation and unemployment rate during the period from 1970 to 2002. The results show that Korean defense expenditure did not affect economic growth and unemployment rate. However, Korean defense expenditure caused consumption and inflation to decrease and investment to increase. On the other hand Korean defense expenditure was not Granger-caused by economic growth, consumption, investment, inflation and unemployment rate. In conclusion, the opportunity cost of Korean defense expenditure seemed to be relatively moderate considering Korean security environment. Even if it was not statistically significant, Korean defense burden at least did not bother economic growth.

• East Asian Economic Review
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• v.22 no.3
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• pp.337-370
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• 2018

This paper discusses the design of monetary policy in a New Keynesian small open economy framework by introducing nominal wage rigidities and incomplete exchange rate pass-through on import prices. Three main findings are summarized. First, with the existence of an incomplete exchange rate pass-through and nominal wage rigidities, the optimal policy is to seek to minimize the output gap, the variance of domestic price and wage inflation, as well as deviations from the law of one price. Second, the CPI inflation targeting Taylor rule is welfare enhancing when there is a technological shock to the economy. The exception occurs when there is a foreign income shock, which minimizes welfare losses under the domestic inflation targeting Taylor rule. Last, two stylized Taylor rules turn out to be a bad approximation, but the modified Taylor rules that respond to the unemployment gap rather than the output gap are a closer approximation to the optimal policy.

• East Asian Economic Review
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• v.23 no.4
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• pp.409-427
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• 2019

This paper sets up a new Keynesian model with external habit to explore the role of each shock over business cycles in Korea. The estimated model via maximum likelihood shows that the productivity shock plays a pivotal role in explaining the output variations before and after the financial crisis since mid-1970s. It also shows that the model with external habit is more successful in explaining the business cycles in Korea after the Asian financial crisis than the model without habit. The monetary policy shock which dominates by accounting for more than 70 percent of the unconditional variance of the inflation rate before the financial crisis is less important in the inflation rate fluctuations after the financial crisis. This partly reflects the regime change of the monetary policy to the inflation targeting rule after the financial crisis.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.174-181
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• 1999

in order to elucidate the characteristic of velocity distribution of the cavity air. Exploratory tests were conducted on an unloaded rolling radial tire operated at various speeds and inflation pressure. A hot-wire anemometer, rotating with the tire, was used to measure the flow velocity inside the tire cavity. Tow different types of experiments were performed ; one for the effects of rolling speed with constant inflation pressure, the other for the various cavity pressures with constant rolling speed. Experimental results are given as plots of the mean velocity distributions versus the distance from the rim. It is observed that the magnitude of mean velocity in the cavity air shows increasing natures with the increasing of the inflation pressures and rolling speeds.

• Journal of the Korean Operations Research and Management Science Society
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• v.11 no.1
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• pp.12-23
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• 1986

The minimum attractive rate of return (MARR) has been used for many years as a decision criterion in engineering economic analysis. Typically, inflation has been either ignored in such studies or considered by adjusting each of the individual cash flows associated with a project for inflation, frequently a lengthy process. This research investigates a new decision criterion for economic analysis, the comparative rate of return (CRR). The CRR is defined to be the minimum rate of return earned on uninflated cash flows of proposed expenditures is simplified, since the analysis can be performed on the uninflated cash flows. The research presents a derivation of the CRR and investigates its relationships to the MARR, inflation rate project cash flows and project life.

• Communications for Statistical Applications and Methods
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• v.8 no.3
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• pp.805-814
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• 2001

The problem of 'outliers', observations which look suspicious in some way, has long been one of the most concern in the statistical structure to experimenters and data analysts. We propose a model for outliers problem and also analyze it in linear regression model using a Bayesian approach with the variance-inflation model. We will use Geweke's(1996) ideas which is based on the data augmentation method for detecting outliers in linear regression model. The advantage of the proposed method is to find a subset of data which is most suspicious in the given model by the posterior probability The sampling based approach can be used to allow the complicated Bayesian computation. Finally, our proposed methodology is applied to a simulated and a real data.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.2
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• pp.15-23
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• 1992

This paper dvelops an inventory model with partial backorders considering both inflation rate and discount rate under the situation of deterministic demand and lead time and then make an economic analysis. Especially, the inventory model with partial backorders provided here is the inventory model minimizing annual total cash outflows, which is extended by the addition of inflation rate and discount rate into "Inventory Model with Partial Bakorders" of Park [6]. An iterative solution procedure is developed to find an optimal inventory policy. To provide guidelines for economic analysis of inventory model with partial backorders, sensitivity analysis for selected values of parameters is performed.performed.