• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.201-208
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• 2005

This study presents the experimental study on improvement of frost/defrost performance in an heat pump system with newly developed fin and multiple compressors. As multiple compressors system, the variable and single speed compressor combinations has been introduced and compared with single speed 1-compressor system in a view point of improvement of frost/defrost performance. Also, newly developed corrugate shaped fin has been compared with conventional louver shaped fin. The frost/defrost performance is defined and some parameters are compared to discuss the effect of each combination. From this experimental study, it is known that if the variable and single speed compressor combination system equipped with corrugate shaped fin, the system performance has greatly improved not only for heating capacity, but also for frost performance.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.49-53
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• 2013

This paper describes the assessment of seismic performance of the concrete gravity dam seismically reinforced by post-tensioned anchors. In order to evaluate the seismic performance, the response spectrum analyses have been carried out for 7 different configurations of the post-tensioned anchors, and then their performance improvement in the maximum tensile and compressive stresses is compared to each other. The comparative results demonstrate that the layout of the post-tensioned anchors strongly influences the seismic performance of the concrete gravity dam. In this study, the slightly-inclined vertical anchorage system shows the largest improvement on the overall performance of the seismically-excited concrete gravity dam.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.177-187
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• 1994

In the design of modern computer systems, the speed gap between the CPUs and DRAMs has been a major concern. To relieve this problem at a low cost, several new DRAM architectures have been proposed. This study is aimed at evaluating quantitatively the impact of the new DRAM architectures (synchronous DRAM. dual-RAS synchronous DRAM, and enhanced DRAM) on the memory system performance. We developed a cache and memory simulator and performed various experiments using the traces generated from four benchmark programs. The simulation results show that the new DRAM architectures offer a better performance than a conventional one by 5~30% in a low cost system and their improvement in a high performance system is less than 1%. However, for resonable multiprogramming workoads, additional performance improvement of about 10~28% is expected in a high performance system while 1~3% in a low cost system.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.584-587
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• 2003

Iterative learning control is an approach to improve the transient response of systems that operate repetitively over a fixed time interval. It is useful for the system where the system output follows the different type input, in case of design or modeling uncertainty In this paper, we introduce the concept of iterative learning control and then apply the learning control algorithm for multi-motor system for performance Improvement.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.4
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• pp.100-113
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• 2010

Manufacturing companies' cost competitiveness with respect to equipment management can be achieved by satisfying additional market demands by their own capacity without purchasing additional equipments. In essence, it can be accomplished by making continuous investigation into bottlenecks and improvement on them. Therefore, equipment performance measure systems should be designed so that they can support manufacturing companies' such endeavors. With the purpose of establishing an effective equipment performance measurement system for detecting and improving bottlenecks, this study (1) suggests some desirable features that such a system should have, (2) evaluates conventional equipment performance measurement systems in terms of their usefulness for the detection and improvement of bottlenecks, and (3) proposes an improved system. We also perform a simulation experiment to demonstrate the limitations of the conventional systems and show how the proposed system can resolve the problems.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.5
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• pp.462-466
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• 2007

This paper proposes an automatic bandwidth control method for the performance improvement of Binary Amplitude Shift Keying (BASK) system for Giga-Bit Modem in millimeter band. In order to improve the performance of the BASK system with a fixed bandwidth, the proposed method is to adjust a bandwidth of low pass filter in receiver using the fuzzy system. The BASK system consists of a high speed shutter of the transmitter and a counter and a repeater of receiver. The repeater consists of four stage converters, and a converter is constructed with a low pass filter and a limiter. The inputs to the fuzzy system are the reminder and integral of remainder of counter, and output is a bandwidth. We used a Viterbi algorithm to find the optimum detection from the output of the counter. Simulation results showed that the proposed system improves the performance compared to the fixed bandwidth.

• Journal of Korean Society for Quality Management
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• v.47 no.4
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• pp.911-926
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• 2019

Purpose: In an infinite market competition, companies are adopting management systems to gain a competitive advantage. The expectancy effect of the management system is management performance improvement and accurate measurements. These can be made through quality records with integrity and maintainability. This paper examines the operation of records management standards, which are records, storage and management standards for quality records to understand the needs of records management standards and empathize with their needs. Methods: This paper examines PEC's (Pields Engineering Co., Ltd.) specific processes and standards for integrating individual management systems and establishing records management standards. We also look at the specific features of the Search Tool and Document Storage Management Standards that support records management standards. Results: The integration process of PEC's individual management system consists of five steps. A PDCA-based process was established to erode the confusion and inefficiencies caused by overlap between individual management systems. Also, by accurately grasping corporate competence, PEC established a record management standard suitable for the characteristics of the company. PEC's records management standards are used as a useful standard for organizing quality records, and have an impact on management performance improvement. Conclusion: PEC's records management standards enable the verification of quality performance rates and performance measures. Companies can implement appropriate quality improvement strategies based on the numbers identified by introducing records management standards. Companies can succeed in improving management performance when operating quality management that combines performance measurement techniques and records management standards.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.485-491
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• 2015

This paper shows the design improvement and test model of FAU (Frequency Analysis Unit) in PDD (Partial Discharge Diagnosis system) for 800kV GIS (Gas Insulated Switchgear). We found some problems during operation of previous FAU, such as the aging of fiber-optic converter that can cause communication error, the malfunction of signal analysis circuit etc. And then we solved those problems by design improvement and verified the performance through type test. To monitor partial discharge, the performance of UHF sensor is important but the performance of frequency analysis unit is also very important. So we solved communication error, the malfunction of signal analysis circuit and then increased the operation reliability of FAU by improving fiber-optic converter and signal analysis circuit. Accredited testing laboratory carried out the performance verification test according to performance test criteria and procedure of reliability test standards, IEC-60225, 61000 and 60068 etc. We confirmed the test results which correspond with the performance test criteria.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.2
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• pp.43-55
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• 1988

The control system of a drum boiler is very complex since the evaporization process in the boiler is a multivariable system which is affected one another. This study is concerned with the dynamic characteristics of the boiler process and improving methods of performance of a drum boiler control system. The PID control with feedforward of disturbances and the optimal regulator are compared, and the effects of control parameters on the performance of a boiler control system are investigated. From simulation, it is found that profer adjustment of control parameters significant improvement of response and that performance of a optimal regulated control system is better than that of a conventional PID control system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.41-44
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• 2005

This paper described improvement and operation of a 'Tail-Fan' anti-torque performance test system KARI (Korea Aerospace Research Institute) developed a 'Tail-Fan' anti-torque system of a helicopter and a performance test-rig to test the performance of the Tail-Fan. The test-rig was improved for full rotating test in 4300rpm(100%). Machinery and hydraulic parts ware changed to reduce vibration and to increase safety. To find the operation rotating speed for the performance test, vibration test were carried out rising accelerometers on tail gear box. The performance test conditions of the Tail-Fan to avoid a resonance were found from vibration test results. The Tail-Fan operation tests were performed safely frier to carry out performance test.