• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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• pp.45-50
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• 2021

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point. The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the 'process mean shift problem'. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.86-94
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• 1997

For the efficient operation and maintenance( 0 & M), irrigation facilities were graded on the basis of their indices related to the 0 & M condition and the characteristics of reservoirs managed by Farmland Improvement Association(FIA) were examined. The results obtained are summarized as follows : 1. Characteristics of reservoirs include effective storage capacity, irrigation area, basin area, height and length of bank. Each characteristic is scored by the principle component analysis method. Variables which compose one index are categorized on the basis of their unit and each variable is scored so that the score of each unit sums to 100 for each index. 2. The Optimum MAnagement System of Irrigation Facilities(OMASIF) for Pyoungtaek area was developed by connecting general data of the irrigation facilities to image data. The database system is divided into three tables; LookUp Table, Facility Table, and Image Table. Image Table is again divided into five sub-tables, Image Table, Construction Cost Table, Acreage Table, 0 & M Cost Table, and Specification Table. 3. The evaluating criteria for the 0 & M of irrigation facilities can be established using the OMASIF. Irrigation facilities evaluated as poor state by the criteria should be repaired.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.339-339
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• 2013

We study on the optical and electrical properties of indium-free ZTO(ZnSnO)/Ag/ZTO (ZAZ) multilayer electrodes for the low-cost transparent electrode. In the first step, each single layer was deposited using rf magnetron in-line sputter with various working pressure based on $O_2$/$Ar+O_2$ ratio (0~3%) and power at room temperature. Secondly, we studied the optical and electrical properties by analyzing the refractive index, extinction coefficient, transmittance and resistivity of each layer. Finally, we optimized the thickness of each layer using macleod simulation program based on the analyzed optical properties and fabricated the multilayer electrode. As a result, We achieved a low sheet resistance of $11{\Omega}$/sq and anaverage transmittance of 80% in the visible region of light (380~780 nm). This indicates that indium-free ZAZ multilayer electrode is a promising low-cost and low-temperature processing electrode scheme.

• The Journal of Korea Robotics Society
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• v.8 no.2
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• pp.92-103
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• 2013

Humanoid robot is the most intimate robot platform suitable for human interaction and services. Biped walking is its basic locomotion method, which is performed with combination of joint actuator's rotations in the lower extremity. The present work employs humanoid robot simulator and numerical optimization method to generate optimal joint trajectories for biped walking. The simulator is developed with Matlab based on the robot structure constructed with the Denavit-Hartenberg (DH) convention. Particle swarm optimization method minimizes the cost function for biped walking associated with performance index such as altitude trajectory of clearance foot and stability index concerning zero moment point (ZMP) trajectory. In this paper, instead of checking whether ZMP's position is inside the stable region or not, reference ZMP trajectory is approximately configured with feature points by which piece-wise linear trajectory can be drawn, and difference of reference ZMP and actual one at each sampling time is added to the cost function. The optimized joint trajectories realize three phases of stable gait including initial, periodic, and final steps. For validation of the proposed approach, a small-sized humanoid robot named DARwIn-OP is commanded to walk with the optimized joint trajectories, and the walking result is successful.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.24-34
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• 2009

DPF(Diesel Particulate Filter)s have been used to reduce the most of PM(particulate matters) from the exhaust emissions of diesel engine vehicles. Metal foam is one of promising materials for the DPFs due to its cost effectiveness, good thermal conductivity and high mechanical strength. It can be fabricated with various pore sizes and struct thickness and coated with catalytic wash-coats with low cost. In order to design metal foam filter and analyze the flow phenomena, pressure drop and filtration experiment are carried out. Partial DPF which has PM reduction efficiency of more than 50 % is designed in this paper. Also, CFD analysis are performed for different configurations of clean filters in terms of pressure drop, uniformity index, and velocity magnitude at face of filter. Filter thickness and the gap between front and rear filters are optimized and recommended for manufacturing purpose.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.68-77
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• 2018

Regarding demand response (DR) by residential users (R-users), the users try to reduce electricity costs by adjusting their power consumption in response to the time-varying price. However, their power consumption may be affected not only by the price, but also by user convenience for using appliances. This paper proposes a methodology for appliance scheduling (AS) that considers the user convenience based on historical data. The usage pattern for appliances is first modeled applying the copula function or clustering method to evaluate user convenience. As the modeling results, the comfort distribution or representative scenarios are obtained, and then used to formulate a discomfort index (DI) to assess the degree of the user convenience. An AS optimization problem is formulated in terms of cost and DI. In the case study, various AS tasks are performed depending on the weights for cost and DI. The results show that user convenience has significant impacts on AS. The proposed methodology can contribute to induce more DR participation from R-users by reflecting properly user convenience to AS problem.

• Health Policy and Management
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• v.32 no.1
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• pp.113-121
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• 2022

This study aims to compare the healthcare status of South Korea and other member of the Organization for Economic Cooperation and Development (OECD) using the OECD health statistics 2021. We used the position value for relative comparison (PARC) index to measure the five elements of the healthcare system, demand, supply, accessibility, quality, and cost. For the statistical analysis, Mann-Kendall test was performed to examine the trend of the PARC values from 2000 to the most recent year. The results showed that supply, demand, accessibility, and quality were above median than the OECD median and the cost was below median. In sectors such as primary care, health employment and mental health care were below median average. With these result, necessary steps for a sustainable healthcare should be taken into effort by policy makers.

• Korea Trade Review
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• v.47 no.1
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• pp.13-24
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• 2022

This study was conducted because the global economic downturn caused by COVID-19 caused a surge in logistics costs and it was no longer possible to predict logistics costs using existing methods. For this study, we made the assumption that economic indicators affect logistics cost. Chapter 2 examines the current status of the liner market and factors affecting logistics costs. Based on this, Chapter 3 collects independent and dependent variables to determine the analysis model. As the independent variable, economic indicators of major countries constituting the SCFI were selected, and the dependent variables were the SCFI Europe Index and the SCFI USA Index. In Chapter 4, a panel analysis was conducted based on this, and it was confirmed that major economic indicators had a negative (-) effect on SCFI. This is contrary to the existing research results, which can be attributed to the special situation caused by COVID-19 and the imbalance of demand and supply by region. The results of this study are meaningful in that they can predict long-term logistics cost volatility without analyzing supply and demand, and can be applied to other studies as well.

• Journal of Korea Multimedia Society
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• v.9 no.11
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• pp.1421-1434
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• 2006

Spatial data warehouses provide analytical information for decision supports using SOLAP (Spatial On-Line Analytical Processing) operations. Many researches have been studied to reduce analysis cost of SOLAP operations using pre-aggregation methods. These methods use the index composed of fixed size nodes for supporting the concept hierarchy. Therefore, these methods have many unused entries in sparse data area. Also, it is impossible to support the concept hierarchy in dense data area. In this paper, we propose a dynamic pre-aggregation index method based on the spatial hierarchy. The proposed method uses the level of the index for supporting the concept hierarchy. In sparse data area, if sibling nodes have a few used entries, those entries are integrated in a node and the parent entries share the node. In dense data area, if a node has many objects, the node is connected with linked list of several nodes and data is stored in linked nodes. Therefore, the proposed method saves the space of unused entries by integrating nodes. Moreover it can support the concept hierarchy because a node is not divided by linked nodes. Experimental result shows that the proposed method saves both space and aggregation search cost with the similar building cost of other methods.

• Korea Journal of Hospital Management
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• v.21 no.4
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• pp.1-12
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• 2016

The purpose of this study are suggest to performance measurement model of Electronic Medical Record(EMR) and Key Performance Index(KPI). For data collection, 665 questionnaires were distributed to medical record administrators and insurance reviewers at 31 hospitals, and 580 questionnaires were collected(collection rate: 87.2%). Regarding methodology, Critical Success Factor(CSF) and index of the information system were derived based on previous studies, and these were set as performance measurement factors of EMR system. The performance measurement factors were constructed by perspective using BSC, and analysis on causal relationship between factors was conducted. A model of causal relationship was established, and performance measurement model of EMR system was proposed through model validation. Analysis on causal relationship between performance management factors revealed that utility cognition of the learning & growth perspective factor had causal relationship with job efficiency(${\beta}=0.20$) and decision support(${\beta}=0.66$) of the internal process perspective factors, and security had causal relationship with system satisfaction(${\beta}=0.31$) of the customer perspective factor. System quality had causal relationship with job efficiency(${\beta}=0.66$) and decision support(${\beta}=0.76$) of the internal process perspective factors, all of which were statistically significant(P<0.01). Job efficiency of the internal process perspective had causal relationship with system satisfaction(${\beta}=0.43$), and decision support had causal relationship with decision support satisfaction(${\beta}=0.91$) and job satisfaction (${\beta}=0.74$), all of which were statistically significant(P<0.01). System satisfaction of the customer perspective had causal relationship with job satisfaction(${\beta}=0.12$), job satisfaction had causal relationship with cost reduction(${\beta}=0.53$) of the financial perspective, and decision support satisfaction had causal relationship with productivity improvement(${\beta}=0.40$)of the financial perspective(P<0.01). Also, cost reduction of the financial perspective had causal relationship with productivity improvement(${\beta}=0.37$), all which were statistically significant(P<0.05). Suitability index verification of the performance measurement model whose causal relationship was found to be statistically significant revealed that $X^2/df=2.875$, RMR=0.036, GFI=0.831, AGFI=0.810, CFI=0.887, NFI=0.838, IFI=0.888, RMSEA=0.057, PNFI=0.781, and PCFI=0.827, all of which were in suitable levels. In conclusion, the performance measurement indices of EMR system include utility cognition, security, and system quality of the learning & growth perspective, decision support and job efficiency of the internal process perspective, system satisfaction, decision support satisfaction, and job satisfaction of the customer perspective, and productivity improvement and cost reduction of the financial perspective. In this study, it is expected that the performance measurement indices and model of EMR system which are suggested by the author, will be a measurement tool available for system performance measurement of EMR system in medical institutions.