• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.2
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• pp.131-138
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• 2010

This technical report was developed to suggest the guideline to assess the safe use and handling metalworking fluids (MWFs) in machining operation. The basis of this method developed in this study was based on self assessment procedure recommended by Organization Resources Counselors (ORC) of the United States (US). In addition, various MWF management elements obtained from the review on various articles, reports and author's experience regarding MWF were newly added to the evaluation guideline. A total of four areas were finally selected in order to control exposure to MWF used in machining operations. They are all related to the presence and efficiency of the control measures, exposure assessment, management on tank and sump, and safe treatment of chips and metal fines generated during machining operations. Each area is consisted of several related elements. Several evaluation areas and elements used in this study could be revised, replaced, added and deleted according to the process environment, evaluation objectives and evaluator's (manager) criteria etc. This evaluation guide manual could be used for safe management of MWF in metalworking operation. In addition, industrial hygienists can use this evaluation method for auditing and evaluating the management status on MWF.

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.4
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• pp.155-189
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• 2003

In this research, the comprehensive evaluation model of IS(information systems) for public sectors is theoretically constructed through reviewing and integrating previous IS evaluation-related research. This model is hypothesized to consist of five sectors(System Sector, User Sector, Organization and Management Sector, Resource Management Sector and Strategic Contribution Sector), ten evaluation items belonging to these five evaluation sectors, and sixty two evaluation indices for these ten evaluation items. The results of empirical analyses to test the validity of the research model show that the evaluation sectors turn out to be the same ones as proposed in the hypothetical model. The evaluation items(System Quality, Information Quality, Service Quality) in System Sector proves to be consistent with the hypothetical model. However, in case of User Sector, two evaluation items(Perceived Usefulness and User Satisfaction) which are included in the hypothetical model are found to be merged into one item(User Satisfaction). And, it is shown that four evaluation items such as the Efficiency of Internal Process, Customer Satisfaction, Organizational Innovation, and the Degree of Informatization competence improvement are included in Organization and Management Sector, differently from the research model in which the items, Organizational innovation and the Degree of Informatization competence improvement, are not divided. As a final result, sixty two evaluation indices that comprise all the evaluation items belonging to five sectors are found to be reduced to fifty seven ones through factor analyses, criterion-related validity tests and reliability analyses.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.4
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• pp.87-96
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• 1998

Using the concept of cellular manufacturing systems(CMS) in job shop manufacturing system is one of the most innovative approaches to improving plant productivity. However. several constraints in machine duplication cost, machining capability, cell space capacity, intercell moves and exceptional elements(EEs) are main problems that prevent achieving the goal of maintaining an ideal CMS environment. Minimizing intercell part traffics and EEs are the main objective of the cell formation problem because it is a critical point that improving production efficiency. Because the intercell moves could be changed according to the sequence of operation, it should be considered in assigning parts and machines to machine ceil. This paper presents a method that eliminates EEs under the constraints of machine duplication cost and ceil space capacity attaining two goals of minimizing machine duplications and minimizing intercell moves simultaneously. Developing an algorithm that calculates the machine duplications by cell-machine incidence matrix and part-machine Incidence matrix, and calculates the exact intercell moves considering the sequence of operation. Based on the number of machine duplications and exact intercell moves, the goal programming model which satisfying minimum machine duplications and minimum intercell moves is developed. A linear programming model is suggested that could calculates more effectively without damaging optimal solution. A numerical example is provided to illustrate these methods.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.4
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• pp.1-13
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• 2016

In response to the government's recent attempts to introduce competition and efficiency criteria in the rural railway service provision, this study is to empirically estimate public service values on continuous operation of two rural railways-Young Dong Line (YDL) and Donghae Nambu Line (DNL)-that will be realized beyond the passengers' use values. Based on a contingent valuation survey conducted on 600 passengers and local residents, YDL respondents were willing to pay significantly higher amount compared to those of DNL respondents. Especially tourists traveling on YDL were willing to pay the highest amount, and local residents of DNL were willing to pay relatively high amount. The results will provide useful information in makings decisions on the selection of PSO railways, the amount of PSO compensation and which railways to close, so on.

• The Journal of the Acoustical Society of Korea
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• v.8 no.4
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• pp.74-82
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• 1989

In this paper, we have studied on the methodologies of implementation and the performance evaluations about the real-time packetized coding of multi-channel speech signals. Our suggested coding algorithm is very, simple and it has majorly the data handling operations rather than the numerical calculations. And it gives about $40\%$ of compression ratio with less than the conventional codings. Nevertheless, using this algorithm, we can save the memories for the speech signal and we can raise the efficiency of the channel transmission. Especially because of its simplicity of algorithm, we can easily obtain the merits of the multi-channel operations.

• Journal of the military operations research society of Korea
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• v.30 no.2
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• pp.50-62
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• 2004

Every year, about 250,000 new recruits enter the military under the R.O.K military draft system. When the fresh soldier groups arrived at the Recruit Training Center, their supplies are distributed before they get basic military training. The supplies are divided by season, summer and winter. There are 14 class of summer items and 20 class of winter items, and the each class has about a few kinds of items. Totally, there are the hundreds kinds of supplies and the supplies distribution system is manually operated. However, in the current system, many problems such as spending a lot of time, manpower and high change rate due to the inaccurate distribution have been raised. This paper suggests the automated supplies distribution system to solve the above problems. We choose the appropriate facilities in the system by using the AHP(Analytic Hierarchy Process) and analyse the operating efficiency of the new system by simulation. The new suggested system shows about $39.25\%$ improvement in throughput and 3.75 times reduction of manpower compared to the current system.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1207-1214
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• 1995

We present an optimized integer cosine transform(OICT) as an alternative approach to the conventional discrete cosine transform(DCT), and its fast computational algorithm. In the actual implementation of the OICT, we have used the techniques similar to those of the orthogonal integer transform(OIT). The normalization factors are approximated to single one while keeping the reconstruction error at the best tolerable level. By obtaining a single normalization factor, both forward and inverse transform are performed using only the integers. However, there are so many sets of integers that are selected in the above manner, the best OICT matrix obtained through value minimizing the Hibert-Schmidt norm and achieving fast computational algorithm. Using matrix decomposing, a fast algorithm for efficient computation of the order-8 OICT is developed, which is minimized to 20 integer multiplications. This enables us to implement a high performance 2-D DCT processor by replacing the floating point operations by the integer number operations. We have also run the simulation to test the performance of the order-8 OICT with the transform efficiency, maximum reducible bits, and mean square error for the Wiener filter. When the results are compared to those of the DCT and OIT, the OICT has out-performed them all. Furthermore, when the conventional DCT coefficients are reduced to 7-bit as those of the OICT, the resulting reconstructed images were critically impaired losing the orthogonal property of the original DCT. However, the 7-bit OICT maintains a zero mean square reconstruction error.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.537-543
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• 2015

Air-source heat pumps are widely used in winter as heating units due to their higher efficiency compared to electronic heaters or gas fired equipment. However, the air-source heat pump can cause discomfort during periodic defrosting operations. In this study, a PCM unit for continuous heating was adopted to solve this problem. The PCM unit consisted of a PCM, a heat exchanger, and control valves. It was installed between the outdoor and indoor units. The performance of the proposed system was measured during both defrosting and heating operations. The indoor unit showed an average leaving temperature of $26^{\circ}C$ after adopting the PCM unit for continuous heating during the defrosting operation.

• Design & Manufacturing
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• v.18 no.2
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• pp.51-56
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• 2024

In this study, a tool was developed for analyzing production lead time in turning operations. It is expected to help to reduce machining time and to identify, for example, tool change intervals. The tool was developed using Visual Basic.Net and features a user-friendly graphical user interface (GUI) that allows users to easily input cutting conditions and calculate the usage time and feeding distance for each cutting tool based on a G-code program. Object-oriented programming techniques were also used to encapsulate and classify complex logic, thereby efficiently organizing and managing the functions and data structures of this analysis tool. The analysis tool provides various outputs. It calculates the use time of each detailed process of the turning operation, the use time of each tool, the use time of each type of feeding, and also generates the data needed for cutting time analysis, which can be visualized in charts. The analysis tool developed in this study is expected to significantly contribute to improving the efficiency of manufacturing processes and increasing productivity, particularly, in the manufacturing of components requiring massive material removal, such as aircraft parts.

• International Journal of Contents
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• v.10 no.1
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• pp.62-67
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• 2014

Usually, cloud storage systems are developed based on DFS (Distributed File System) for scalability and reliability reasons. DFSs are designed to improve throughput than IO response time, and therefore, they are appropriate for batch processing jobs. Recently, cloud storage systems have been used for update intensive applications such as OLTP and so on. However, in DFSs, in-place update operations are not carefully considered. Therefore, when updates are frequent, I/O performance of DFSs are degraded significantly. DFSs with RAID techniques have been proposed to improve their performance and reliability. Their performance degradation caused by frequent update operations can be more significant. In this paper, we propose an in-place update method for DFS RAID exploiting a differential logging technique. The proposed method reduces the I/O costs, network traffic and XOR operation costs for RAID. We demonstrate the efficiency of our proposed in-place update method through various experiments.