• KDI Journal of Economic Policy
• /
• 제24권2호
• /
• pp.53-82
• /
• 2002

Earlier papers, regarding this topic, have shown that the optimal environmental tax rate under the second best situation typically smaller than that under the first best world, the well known Pigouvian tax. This paper casts a doubt on the generality of this result, since the conclusion was derived from the models which employed rather strict assumptions on the utility function, which is homothetic and separable. This paper, with simple-static CGE model, shows that the result of earlier studies is sensitive to the assumption on the utility function. According to the simulation results, as previous studies pointed out, if the utility function is assumed to be homothetic, the optimal environmental tax rate is smaller than the Pigouvian tax. In contrast, if certain type of non-homotheticity is allowed, the optimal environmental tax rate could be greater than the Pigouvian tax. The results of this simulation also imply that the enlargement of environmental tax base could enhance the efficiency of overall tax system. Hence, there will be a less burden to share for the tax authority from the policy change.

• Journal of the Korean Data and Information Science Society
• /
• 제17권3호
• /
• pp.861-869
• /
• 2006

Burn-in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, the problem of determining optimal burn-in time for a system which performs given mission is considered. It is assumed that the given mission time is not a fixed constant but a random variable which follows an exponential distribution. Assuming that the underlying lifetime distribution of a system has an eventually increasing failure rate function, an upper bound for the optimal burn-in time which maximizes the probability of performing given mission is derived. The obtained result is also applied to an illustrative example.

• Journal of the Korean Data and Information Science Society
• /
• 제20권4호
• /
• pp.655-660
• /
• 2009

최근의 글로벌경제위기 상황에서 국내 금융외환시장이 높은 환율변동을 보이며 불안한 모습을 보이고 있다. 따라서 그 어느 때보다 금리, 환율 등 가격변수들의 움직임 및 이들 간의 관계에 대한 관심이 높다. 본 연구에서는 국내시장을 중심으로 환율, 금리의 추이 및 인과관계에 대하여 연구하였다. 글로벌경제위기 상황에서 원/달러환율, 콜금리의 움직임에서 나타나는 주요 특징을 알아보고, 교차상관분석 및 그랜저 인과관계검정 등을 이용하여 두 변수간의 상호연관관계에 대하여 선도/지연 관계를 중심으로 분석하였다.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 1998년도 학술발표회논문집
• /
• pp.131-133
• /
• 1998

Electron temperature, electron density and electron energy distribution function were measured in Radio-Frequency Inductively Coupled Plasma(RFICP) using a probe method. Measurements were conducted in argon discharge for pressure from 10 mTorr to 40 mTorr and input rF power from 100W to 600W and flow rate from 3 sccm to 12 sccm. Spatial distribution of electron temperature, electron density and electron energy distribution function were measured for discharge with same aspect ratio (R/L=2). Electron temperature was found to depend on pressure, but only weakly on power. Electron density and electron energy distribution function strongly depended on both pressure and power. Electron density and electron energy distribution function increased with increasing flow rate. Radial distribution of the electron density and electron energy distribution function were peaked in the plasma center. Normal distribution of the electron density, electron energy distribution function were peaked in the center between quartz plate and substrate. These results were compared to a simple model of ICP, finally, we found out the generation mechanism of Radio-Frequency Inductively Coupled Plasma.

• 대한통합의학회지
• /
• 제8권4호
• /
• pp.59-66
• /
• 2020

Purpose : This study aimed to present normative data for older Korean adults completing the Yonsei dual task cognitive screening test (Y-DuCog) and identify changes in cognitive function on the Montreal Cognitive Assessment - Korean (MoCA-K) with age. Methods : From May 2019 to August 2019, 195 healthy adults aged ≥60 years participated in this study. All participants completed the Y-DuCog to assess their dual-task performance and the MoCA-K to assess their cognitive function. Participants were divided into three groups based on their age: 60~69 years, 70~79 years, and ≥80 years. Results : The results of the Y-DuCog showed that dual-task performance time, effect, and correct response rate decreased significantly with age (p<.001). Scores from the three groups showed differences on all items (p<.001). Cognitive function on the MoCA-K also decreased significantly with age (mean score ± standard deviation [SD]; 27.33 ± 2.61 in subjects aged 60~69 years; 24.82 ± 3.20 in subjects aged 70~79 years; and 22.10 ± 4.91 in subjects aged ≥80 years; p<.001). Conclusions : Occupational therapists should be aware of the decline in cognitive function and dual-task performance time, effect, and correct response rate in older adults and consider interventions to treat this decline. Further studies are needed with larger groups of participants to examine factors, such as sex and education, that may impact dual-task performance and cognitive function.

• 대한물리의학회지
• /
• 제18권1호
• /
• pp.51-57
• /
• 2023

PURPOSE: Recently, the proportion of respiratory diseases has been increasing worldwide, and deaths from respiratory diseases in Korea are increasing. Maintaining a healthy respiratory function is a crucial factor in preventing respiratory diseases. There are various ways to improve respiratory function, such as respiratory muscle and aerobic exercises. In other countries, respiratory muscle exercise is performed using a respiratory resistance mask, but such research is insufficient in Korea. Therefore, this paper proposes a respiratory exercise program using a respiratory resistance mask. METHODS: This study was conducted by dividing healthy adults in their 20s into a treadmill exercise + respiratory resistance mask group and a treadmill exercise group into an experimental group and a control group. The changes in the subject's physical function before and after exercise were confirmed by cardiopulmonary exercise and pulmonary function tests. RESULTS: As a result of the study, the experimental and control groups increased their physical function significantly (p < .05). On the other hand, when the increase rate according to the group was confirmed, the increase rate of the experimental group was higher. CONCLUSION: Based on this study, it is necessary to develop a respiratory exercise program using respiratory exercise tools such as a respiratory resistance mask and provide it easily to various subjects.

• 대한기계학회논문집A
• /
• 제21권12호
• /
• pp.2165-2171
• /
• 1997

The analysis model is the infinite power law creep material containing the rigid inclusion with crack shape. The present analysis is performed using the complex pseudo-stress function method. The strain rate intensity factor is developed as new fracture mechanics parameter which represents the stress and strain rate distribution near a crack tip in power law creep material. The strain rate intensity factor is developed in terms of Kolosoff stress functions.

• 소성∙가공
• /
• 제20권8호
• /
• pp.595-600
• /
• 2011

This paper investigates the effect of strain rate on the anisotropic deformation behavior of advanced high strength steel sheets. Uniaxial tensile tests were carried out on TRIP590 and DP780 steel sheets at strain rates ranging from 0.001/sec to 100/sec to determine yield stresses and r-values at various loading angles from the reference rolling direction. R-values were determined by the digital image correlation technique. Hill48 and Yld2000-2d yield functions were tested for their capability to describe the plastic deformation anisotropy of the materials. Initial yield loci were constructed using the Yld2000-2d yield function, which adequately described the anisotropic behavior of the materials. The shape of the initial yield loci was found to change with different strain rate, and the anisotropic behavior decreased with increasing strain rate.

• 산업기술연구
• /
• 제27권B호
• /
• pp.245-253
• /
• 2007

Failure rate serves as a pivotal role in reliability study. Of all, the constant failure rate is the most popularly used in field exercises. In reality, however, the electrical and electronic parts' life is represented by not only the constant failure rate but the decreasing and/or increasing failure rates. Explicit consideration and incorporation of them into the model development may yield more desirable results. In this study, we built a reliability model for failure rates varying over time intervals and derived well known measures such as probability density function, reliability function, mean life, moments, and mission time. We then evaluated mean life with consideration of the first-year multiplier and compared the results those with constant failure rate. The results given in the study may provide a reference applying for practical decision making.

• International Journal of Reliability and Applications
• /
• 제13권2호
• /
• pp.91-104
• /
• 2012

Sarhan and Kundu (2009) introduced a new distribution named as the generalized linear failure rate distribution. This distribution generalizes several well known distributions. The probability density function of the generalized linear failure rate distribution can be right skewed or unimodal and its hazard function can be increasing, decreasing or bathtub shaped. This distribution can be used quite effectively to analyze lifetime data in place of linear failure rate, generalized exponential and generalized Rayleigh distributions. In this paper, we apply the simulated annealing algorithm to obtain the maximum likelihood point estimates of the parameters of the generalized linear failure rate distribution. Simulated annealing algorithm can not only find the global optimum; it is also less likely to fail because it is a very robust algorithm. The estimators obtained using simulated annealing algorithm have been compared with the corresponding traditional maximum likelihood estimators for their risks.