• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.161-167
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• 2020

In the process of cutting large aircraft parts, the tool may be abnormally worn or damaged due to various factors such as mechanical vibration, disturbances such as chips, and physical properties of the workpiece, which may result in deterioration of the surface quality of the workpiece. Because workpieces used for large aircrafts parts are expensive and require strict processing quality, a maintenance plan is required to minimize the deterioration of the workpiece quality that can be caused by unexpected abnormalities of the tool and take maintenance measures at an earlier stage that does not adversely affect the machining. In this paper, we propose a method to indirectly monitor the tool condition that can affect the machining quality of large aircraft parts through real-time monitoring of the current signal applied to the spindle motor during machining by comparing whether the monitored current shows an abnormal pattern during actual machining by using this as a reference pattern. First, 30 types of tools are used for machining large aircraft parts, and three tools with relatively frequent breakages among these tools were selected as monitoring targets by reflecting the opinions of processing experts in the field. Second, when creating the CNC machining program, the M code, which is a CNC auxiliary function, is inserted at the starting and ending positions of the tool to be monitored using the editing tool, so that monitoring start and end times can be notified. Third, the monitoring program was run with the M code signal notified from the CNC controller by using the DAQ (Data Acquisition) device, and the machine learning algorithms for detecting abnormality of the current signal received in real time could be used to determine whether there was an abnormality. Fourth, through the implementation of the prototype system, the feasibility of the method proposed in this paper was shown and verified through an actual example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.4
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• pp.133-141
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• 2023

Approximately 40,000 elevators are installed every year in Korea, and they are used as a convenient means of transportation in daily life. However, the continuous increase in elevators has a social problem of increased safety accidents behind the functional aspect of convenience. There is an emerging need to induce preemptive and active elevator safety management by elevator management entities by strengthening the management of poorly managed elevators. Therefore, this study examines domestic research cases related to the evaluation items of the elevator safety quality rating system conducted in previous studies, and develops a statistical model that can examine the effect of elevator maintenance quality as a result of the safety management of the elevator management entity. We review two types: odds ratio analysis and logistic regression analysis models.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.5 s.112
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• pp.83-93
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• 2005

Research was initiated to investigate turf performance under USGA soil system. USGA system 45 centimeters deep was built with rootzone layer, intermediate layer, and drainage layer. Six turfgrass entries were comprised of 3 blends and 3 mixtures from cool-season grasses (CSG). Turfgrass color and quality ratings were best in spring and fall, especially early May to early July and late August to early November. Kentucky bluegrass (KB) consistently produced the greatest performance, while perennial ryegrass (PR) the poorest. Intermediate turf performance between KB and PR was observed with tall fescue (TF). Among CSG mixtures it increased with KB but decreased with PR. There were considerable variations in summer turf Performance. No summer drought injury was found in KB and TF. However, PR showed poor performance through summer as compared with others. Among mixtures, it decreased with PR. It was suggested that PR mix in less than $20\%$ in the mixtures to have an acceptable quality in summer. Cultural intensity also affected it. With lowering mowing height, KB of rhizomatous-type in growth habit kept good quality, while PR and TF with bunch-type in growth habit poor quality. Mowing quality was greatly different among CSG. KB produced clean-cut surface, but PR unclean one. If had an intermediate mowing quality between KB and PR. A great difference in green color retention was observed among CSG. The longest CSG was PR that kept green for 339 days, while the shortest one TF for 267 days. KB continued to keep green for 290 days. The mixtures kept green in color for 292 to 315 days, depending on turfgrass mixing intensity. The greater the PR in content, the longer the green color duration. These results demonstrate that KB was the best and PR the worst among CSG grown in USGA system under a domestic climate, in regards of turf quality, color, mowing quality, summer turf performance and green color duration. KB and TF are most adequate for high-maintenance and low-maintenance area, respectively. In case of mixtures for high-quality turf, it was desirable to use KB-based mixture with PR of below $20\%$ in seeding rate.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.999-1007
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• 2009

This paper considers the optimal periodic preventive maintenance (PM) policy following the expiration of free-repair warranty. We assume that two periodic PM models with random maintenance quality which were proposed by Wu and Clements-Croome (2005) and Jung (2006b), respectively. Given the cost structure to the user during the cycle of the product, we derive the expressions for the expected cost rate per unit time. Also, we obtain the optimal PM number and the optimal PM period by minimizing the expected cost rate per unit time. The numerical examples are presented for illustrative purpose.

• Journal of Korean Society for Quality Management
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• v.40 no.4
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• pp.599-614
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• 2012

Purpose: We measure service quality based on service process, and examine relationships among product quality, product and service loyalty. Methods: We develop a construct to evaluate process based service quality. We collect data from customers of auto maintenance centers to measure perceived product quality, service and product quality. We test relationships between constructs using structural equation model and regression analysis. Results: Relationships among perceived-product quality, service quality, service loyalty, and product loyalty are all significant. Conclusion: Perceived-product quality has a indirect impact through service quality and loyalty in addition to a direct impact on product loyalty.

• The Journal of Internal Korean Medicine
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• v.26 no.1
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• pp.1-11
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• 2005

Backgrounds : Gamichungsangboha-tang extract has been known to improve pulmonary functions and quality of life within four weeks of treatment. Cessation of treatment causes recurrence of symptoms and regression of pulmonary function and poorer quality of life. Long-term herbal therapy is difficult to maintain due to economic burden and other reasons. AF-365 is made with reduced dosage of Gamichungsangboha-tang extract. This study was designed to evaluate the effectiveness of AF-365 for maintenance therapy. Materials and Methods : The subjects consisted of 27 patients with asthma who had beed treated with AF-365 for four weeks. First, patients were treated with Gamichungsangboha-tang extract for four weeks. Second patients stopped herbal medicine for four weeks and after that they took AF-365. Pulmonary function test(PFT) was checked before and after four weeks of treatment. Quality of Life Questionnaire for Adult Korean Asthmatics(QLQAKA) was checked every two weeks from the beginning. The effects of AF-365 were analysed throughout the last four weeks. Results : Treatment of AF-365 for four weeks resulted in significant increase in PEFR%, QLQAKA. The QLQAKA of the step3, step4 group classified by Global initiative for asthma(GINA) showed significant improvement, and the QLQAKA of the step2 group showed no significant difference. In step3 group, PEFR% increased significantly. Conclusions : This study supports a role for AF-365 in maintenance of pulmonary function and quality of life, especially in persistent symptomatic asthmatics.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.2
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• pp.46-49
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• 2010

This paper has proposedfor wireless Ad-hoc networks with robust route maintenance schemes. The device feature Bluetooth and/or IEEE 802.11 network interfaces and communicate in a decentralized manner. The nodes have the responsibility of self-organizing so that the network is robust to the variations in network topology due to node mobility as well as the fluctuations of the signal quality in the wireless environment.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.150.3-150
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• 2001

Requirements for Distributed Monitoring and Control Networks (DMCN) differ greatly from those of typical data networks. Specifically, any DMCN technology which employs a fieldbus protocol is different from If network protocol TCP/IP. In general, one needs to integrate fieldbus protocol and TCP/IP to realize DMCN over IP network or internet Interoperability between devices and equipments is essential to enhance the quality and the performance of predictive maintenance (PM). This paper suggests a basic framework for LonWorks-based DMCN over IP network and a method to guarantee interoperability between devices and equipments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.171-180
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• 2007

The quality of ready-mixed concrete(henceforth abbreviated remicon) is influenced by various factors such as ingredient of material, difference of property, mixing ratio, mixing time, mixing error, conditioning of construction, method of curing and temperature, humidity time in transportation. These factors make it hard to confirm the quality of remicon till placing in site. As the quality control in field is very important to ensure the quality of building. Moreover in modern building production, the more important the inquiry of performance improvement, the more important the manufacture and the quality control of remicon. In this study, to examine and analyze the quality of remicon we used slump, air content and compressive strength in 7, 28 days as to remicon which placed during on year. As a result, we found that the slump and air content were satisfied with reference code and the compressive strength was more than the design standard strength so we concluded that the quality control of remicon was to be agreeable.

• Journal of Korean Society for Quality Management
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• v.28 no.3
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• pp.145-154
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• 2000

Effective management of knowledge is essential to keep up with demands of this challenging information age. The first step for this kind of management would be to define indicators to evaluate the quality of knowledge. In this paper, we use five latent variables (intrinsic quality, representational quality, ease of use of quality, maintainable quality, usage of quality) as basis for a preliminary path analysis for knowledge management. Preliminary study results showed that high intrinsic quality does not necessarily guarantee high frequency of use. A modified questionnaire is made and is used for SERVQUAL. The result of SERVQUAL shows that customers are not relatively happy about both intrinsic quality and its ease of use. Additional path analyses are done for both expected and observed quality indicators. The path model based on the expectation indicated that the presentation method of knowledge would induce its easy maintenance while that based on observation did not back up the same phenomenon.