• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.5
• /
• pp.850-856
• /
• 2001

Even though the hydraulic servo system has been widely used in industrial and military equipments since it has a lot of advantages, it is not easy to design controller due to the high nonlinearities and the parametric uncertainties. The dynamic behavior of the real process in the hydraulic servo system differs from that described by its model because the model is linearized. Another reason of the difference is caused by the variety of parameters, since the system parameters of the dynamic equation are affected by the operating conditions such as temperature and pressure. In this study, the designing process of the MRNC with a PID compensator is introduced and applied to the load sensing hydraulic servo system. The results show that the designed controller guarantees the robust control performance despite of both the nonlinearities and the parametric uncertainties.

• Analytical Science and Technology
• /
• v.23 no.4
• /
• pp.363-370
• /
• 2010

This study was performed to validate reference materials (RMs) for proficiency testing (PT) in waste inter-laboratories. Dioxin RMs were prepared from fly ash in industrial incinerators. The relative standard deviations (RSDs) of analytical results were 2.6~15.7% for the dioxin RMs in 10 replicates (between and withinbottles). Data were collected and statistical analysis was performed by the One-way ANOVA test. The combined uncertainties of target isomers in dioxin analysis were 0.114~7.091.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.12a
• /
• pp.63-72
• /
• 2007

Current estimates of the ice-mass balance over the Greenland and the Antarctica using retrievals of time-varying gravity from GRACE are presented. Two different GRACE gravity data, UTCSR RL01 and UTCSR RL04, are used for the estimates to examine the impact of the relative accuracy of background models in the GRACE data processing for inter-annual variations of GRACE gravity data. In addition, the ice-mass balance is appraised from the conventional GRACE data, which represents global gravity, and the filtered GRACE data, which isolates the terrestrial gravity effect from GRACE gravity data. The former estimate shows that there exists similar negative trends of ice-mass balance over the Greenland from UTCSR RL01 and UTCSR RL04 while the time series from the both GRACE data over the Antarctica differ significantly from each other, and no apparent trends are observed. The result for the Greenland from the latter calculation is similar to the former estimate. However, the latter calculation presents positive trends of ice-mass balance for the Antarctica from both GRACE data. These results imply that residual oceanic geophysical signals, particularly for ocean tides, significantly corrupt the ice-mass estimate over the Antarctica as leakage error. In addition, the spatial alias of GRACE is likely to affect the ice-mass balance because the spatial spectrum of ocean tides is not conserved via GRACE sampling, and thus ocean tides contaminate terrestrial gravity signal. To minimize the alias effect, I suggest to use the combined gravity models from GRACE, SLR and polar motion.

• Environmental and Resource Economics Review
• /
• v.14 no.3
• /
• pp.753-773
• /
• 2005

This paper is a study of the investment dynamics focusing on crude oil supply by OPEC and non-OPEC. Oil supply capacity is first determined by a leader, OPEC, and by an aggregate that represents non-OPEC producers. OPEC wants to increase a gain from oil price increase while keeping its market share relative to non-OPEC's share. An investment rule model is developed for OPEC crude oil supply capacity in response to non-OPEC's decision. In presence of oil price uncertainty, oil price threshold is derived above which it is optimal for OPEC to expand oil supply capacity since otherwise the increased supply of non-OPEC results in weakening of OPEC market share in the world oil market. In addition, a lower threshold price is derived below which OPEC triggers a capacity reduction to regain its otherwise forgone profits. A simulation is provided for calculating the capacity expansion and reduction thresholds.

• Journal of Distribution Science
• /
• v.14 no.9
• /
• pp.5-13
• /
• 2016

Purpose - This study proposes a framework for service innovation strategy to cope with the emergence of electric vehicles. Research design, data, and methodology - This study designs an electric-vehicle lease program and collects the resulting data to analyze. By analyzing the previous studies on the electric-vehicle market with cases, a theoretical framework based on existing theories is to be set. Results - This study proposes a strategy for the rapid diffusion of electric vehicles. First, a partitioned-pricing system is proposed to create an advantage for electric vehicles in terms of initial purchasing cost relative to traditional internal combustion vehicles. Second, focusing on reducing switching costs is important because electric vehicles have relatively low resale values due to the uncertainty of battery life. Third, a battery-leasing strategy is supposed to reduce the cost of switching from a traditional internal combustion vehicle to an electric vehicle. Conclusions - This paper can provide strategic guidance for decision makers in firms that have already entered the electric-vehicle leasing market by making a recommendation such as a service innovation strategy. The proposed strategy can be considered as an electric vehicle market in the future and can contribute to the wider diffusion of electric vehicles.

• Journal of the Ergonomics Society of Korea
• /
• v.25 no.4
• /
• pp.41-49
• /
• 2006

In a decision making process, the ambiguity of qualitative probabilistic expressions may result in a wrong conclusion. For this reason there had been many studies of quantifying qualitative probabilistic expressions in English-speaking countries. In this research, quantification of Korean qualitative probabilistic expressions is conducted through 4-step questionnaires. The numerical data of 78 verbal phrases were collected in the first questionnaire and classified in two categories (i.e., uncertainty and frequency). In each category, qualitative probabilistic expressions were divided into eleven groups according to the similarity of the numerical values. In the second questionnaire, subjects selected a representative expression for each group, which totaled 11. In the third questionnaire each subject was asked to rank eleven expressions from 1 to 11 with 1 indicating the highest probability. At last, subjects conducted pairwise comparisons to obtain relative weights, which are used to convert into the numerical probability scale.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.5
• /
• pp.30-35
• /
• 2008

As the quality of a weld feint is strongly influenced by process parameters during the welding process, an intelligent algorithms that can predict the bead geometry and shape to accomplish the desired mechanical properties of the weldment should be developed. This paper focuses on the development of mathematical models fur the selection of process parameters and the prediction of bead geometry(bead width, bead height and penetration) in robotic GMA(Gas Metal Arc) welding. Factorial design can be employed as a guide for optimization of process parameters. Three factors were incorporated into the factorial model: arc current, welding voltage and welding speed. A sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.5
• /
• pp.485-497
• /
• 2014

This paper presents the robot vision control schemes based on the Newton-Raphson (N-R) and the Extended Kalman Filter (EKF) methods for the tracking of moving targets. The vision system model used in this study involves the six camera parameters. The difference is that refers to the uncertainty of the camera's orientation and focal length, and refers to the unknown relative position between the camera and the robot. Both N-R and EKF methods are employed towards the estimation of the six camera parameters. Based on the these six parameters estimated using three cameras, the robot's joint angles are computed with respect to the moving targets, using both N-R and EKF methods. The two robot vision control schemes are tested by tracking the moving target experimentally. Given the experimental results, the two robot control schemes are compared in order to evaluate their strengths and weaknesses.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.4
• /
• pp.657-661
• /
• 2011

The chlorinated dioxins and furans have attracted considerable scientific and public concern because of their environmental persistence and super-toxicity through the foodchain. Recent dioxin scandals in several military bases have also contributed to a higher awareness on the side of food consumers as well as foodwaste combustion. However, there is continuing uncertainty over the relative importance of different sources of dioxins and furans to the soil environment. In difference to those awareness there is a main influence of potential soil contamination on the dioxin contents in groundwater. It is, therefore, important to provide a sound scientific framework and basis by which to evaluate the significance of the presence of dioxin in soils. Consequently, we have to identify the characteristics and nature of dioxin released into the soil environment, especially in agricultural aspect.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.23 no.6
• /
• pp.329-339
• /
• 2019

The strategy for the management of earthquakes is shifting from post recovery to prevention; therefore, seismic performance management requires quantitative predictions of damage and the establishment of strategies for initial responses to earthquakes. Currently, seismic performance evaluation for seismic management in Korea consists of two stages: preliminary evaluation and detailed evaluation. Also, the priority of seismic performance management is determined in accordance with the preliminary evaluation. As a deterministic method, preliminary evaluation quantifies the physical condition and socio-economic importance of a facility by various predetermined indices, and the priority is decided by the relative value of the indices; however, with the deterministic method it is difficult to consider any uncertainty related to the return-year, epicenter, and propagation of seismic energy. Also this method cannot support tasks such as quantitative socio-economic damage and the provision of data for initial responses to earthquakes. Moreover, indirect damage is often greater than direct damage; therefore, a method to quantify damage is needed to enhance accuracy. In this paper, a Seismic Risk Assessment is used to quantify the cost of damage of road facilities in Pohang city and to support decision making.