• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.199-202
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• 2005

In this paper, the six sigma scheme is employed together with the rigid-viscoplastic finite element method to obtain the optimal metal flow lines in hot press forging. In general, the six sigma process is consisted of following five steps : define, measure, analyze, improve and control. Each step Is investigated in detail to meet customer's requirements through improvement of product quality. A forging simulator, AFDEX-2D, is used for analysis of the metal flow lines of a multi-stage hot forging process under various conditions of major factors, determined at each step of the six sigma process. The analyzed results are examined in order to reveal the effects of major factors on the metal flow lines and the formed shapes. The effects are used to find an optimal process and the optimal process with die is devised and tested. The comparison between required metal flow lines and experiments shows that the approach is effective for optimal process in hot forging design considering metal flow lines.

• Journal of the Korean Dietetic Association
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• v.13 no.4
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• pp.331-344
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• 2007

This study was performed to improve the hospital food service in quality and customer satisfaction by using 6-sigma strategy which was processed by DMAIC methods. The research procedure was as follows; analyzing the main causes of customer dissatisfaction of food service by using numerical method, and then finding out the standardized problem solving methods, and finally reforming food service process. The effectiveness of 6-sigma activity was measured by ‘food service quality index’, ‘customer satisfaction index’ and ‘total food service satisfaction index’. Food service quality index was calculated by adding grade of soup temperature, food service, delivery time, and setting accuracy. Statistical data analyses were completed by using the Minitab Ver. 14. By performing 6 sigma activity, food service quality index was increased from 67 to 79 points (p<0.05) and customer satisfaction index also rise from 73 to 79points (p<0.05). Satisfaction of meals’ taste, diverse menu, food setting accuracy, remove of food service, overall food service were significantly improved(p<0.05). The results of capability analysis in food service quality index, customer satisfaction index, and total food service satisfaction index were improved 2.11$\sigma$ to 2.49$\sigma$, 1.88$\sigma$ to 2.43$\sigma$, and 2.04$\sigma$ to 2.47$\sigma$ respectively (p<0.05). Therefore this study showed that subjective food service improving process could be measured by objective numerical value which might be used for financial value in hospital management.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.74-80
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• 2021

This study investigated the process quality level of a K5 gas mask, which recently acquired its operational capability, through statistical process analysis for the mass production stages and their lots. The tensile adhesion strength was the only operating requirement in the manufacturing process of the K5 gas mask. For this purpose, the results of tensile adhesion strength between the lens and facial rubber during the initial and second mass production stages were analyzed using conventional statistical and statistical process analysis methods. The conventional statistical results indicated that the second mass production stage was better than the initial mass production stage. In cases of a control chart and process capability of tensile adhesion strength, the process quality level was also improved by following the mass production stages. The improvement was caused by process stabilization and work skill elevation. These results and methods are expected to be conducted and utilized in the third mass production stage. Moreover, quality improvement of K5 gas mask mass production can be achieved using the Lean 6 sigma procedure, MDAIC (Define, Measure, Analyze, Improve, Control).

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.777-780
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• 2005

모바일 오디오 적용을 위한 저전력 ${\Sigma}{\Delta}$ Modulator 에 대한 설계와 layout 을 보였다. 전체 구조는 3 차 단일 피드백 루프이며, 해상도는 16bit 을 갖는다. 샘플링 주파수에 따른 Over-sampling Ratio 는 128(46kHz) 또는 64(96kHz) 가 되도록 하였다. 차동 구조를 사용한 3 차 ${\Sigma}{\Delta}$ modulator 내의 적분기에 사용된 Op-Amp 는 DC-Gain 을 높이기 위해서 Gain-boosting 기법이 적용되었다. ${\Sigma}{\Delta}$ modulator 의 기준 전압은 전류 모드 Band-Gap Reference 회로에서 공급이 되며, PVT(Process, Voltage, Temperature) 변화에 따른 기준 전압의 편차를 보정하기 위하여, binary 3bit 으로 선택하도록 하였다. DAC 에서 사용되는 단위 커패시터의 mismatch 에 의한 성능 감소를 막기 위해, DAC 신호의 경로를 임의적으로 바꿔주는 scrambler 회로를 이용하였다. 4bit Quantizer 내부의 비교기 회로는 고해상도를 갖도록 설계하였고, 16bit thermometer code 에서 4bit binary code 변환시 발생하는 에러를 줄이기 위해 thermometer-to-gray, gray-to-binary 인코딩 방법을 적용하였다. 0.18um CMOS standard logic 공정 내 thick oxide transistor(3.3V supply) 공정을 이용하였다. 입력 전압 범위는 2.2Vp-p,diff. 이며, Typical process, 3.3V supply, 50' C 시뮬레이션 조건에서 2Vpp,diff. 20kHz sine wave 를 입력으로 할 때 SNR 110dB, THD 는 -95dB 이상의 성능을 보였고, 전류 소모는 6.67mA 이다. 또한 전체 layout 크기는 가로 1100um, 세로 840um 이다.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.343-347
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• 2008

There are two kind of system in hotel for evaluating management. the first is infra system, for example Front management system - reservation system, C/I, C/O system, POS system , web system, call center management -, Back office system, interface system, and so on which manage direct control for hotel, and next is strategic system, for example BSC , CS . which is supporting hotel management. The purpose of this study was to find using the Balanced Scorecard to evaluate hotel management perfomance. Management performance is based on productivity, quality, time, effect, and responsiveness. Hotel economic value is not equal visual asset which is measured financial value. It is include hotel brand, image, customers who have good loyalty, employees who give customers special service, and systems which was affected by internal process. In conclusion, innovation, growth, internal system process, empioyee and customer have effect hotel performance. Therefore hotel has to know non-financial performance which has positively relate to financial performance.