• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.15-22
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• 2007

As we detect defects and eliminate them in early stages, we can make better quality software. For doing this task, we need to use a defect tracking system which con effectively track and manage defects that give severe effects on software quality. Those existing defect tracking systems have some weaknesses as we apply them to organizations that use CMMI for process improvements. Major problems of those systems are that they require the organizations to collect many types of defect data at a time without providing the proper explanation and even without the support of defect management process. The organizations at CMMI maturity level 2 and 3 have problems for analyzing those defects because there is no specific process area at CMMI maturity level 2 and 3 which directly handles defect managing activites. This paper resolves those problems by developing a defect tracking system which offers methods of managing defects. And the system provides guidelines of which defects should be gathered for each CMMI mathurity levels. The system also has functions to generate various status and statistic information on defects, and to assign defect data to the person in charge so that he or she track the defect to the closure

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.223-228
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• 2005

In oprical disk drives, surface defects on a disk distort tracking error signal and disturb a precision tracking control.. A conventional method against disk defect is held the tracking control signal when a defective portion is detected. However, if the defective portion is getting longer, objective lens will get away from following track. In order to keep the postion of spot from following track, the servo system must predict tracking error and control the object lens in the defective portion. A tracking control system for optical disk drives was proposed recently based on both Coprime Factorization(CF) and Zero Phase Erro. Tracking(ZPET) control. The system was proposed for overcome the limit of previously tracking error. But there were no research about the method against the defective portion. This paper proposes a new and simple ZPET construct. as a new method against the defective portion. From experimental results, we have proved that proposed method improves the performance against the defective portion, decreases the uncertainty of a model, and requires less memory than the previously proposed method.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.137-139
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• 2007

In optical disk drives, a conventional control method in the presence of surface defect is holding the previous tracking control command. It is known that the method has a long settling time. This paper proposes a new control method which reduces the settling time. An optical head generally has coupled dynamics between focusing and tracking servo system. We present how to compensate the coupled dynamics so that reduced settling time is achieved. It is verified by experiments that the proposed method brings an improved performance in the presence of surface defect as well as in the normal operating condition.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.56-64
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• 2006

This paper proposes a new and simple input prediction method for robust servo system. A robust tracking control system for optical disk drives to reject disk runout was recently proposed based on both Coprime Factorization(CF) and Zero Phase Error Tracking(ZPET) control. The CF control system can be designed simply and systematically. Moreover, this system has not only stability but also robustness to parameter uncertainties and disturbance rejection capability. Since optical disk tracking servo systems can detect only racking error, it was proposed that the reference input signal for ZPET could be estimated from tracking errors. In this paper, we propose a new control structure for the ZPET controller. It requires less memory than the previously proposed method for the reference signal generation. Therefore, it is very effective in runout control. Furthermore, this method can be applied to defective optical disk like surface defects on disk. Numerical simulation and experimental result show the proposed method effective.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.67-73
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• 2007

An optical pick up generally has coupled dynamics between focusing and tracking servos. The coupled dynamics reduces tracking performance of optical disk drives. A conventional control method is holding the previous tracking control command in the presence of surface defect. The method has a long settling time. If the defective area is getting larger, objective lens will get away from the following track. In order to overcome this problem, this paper proposed a new control method for optical disk drives based on a prediction of tracking error and focusing error. We present how to compensate the coupled dynamics so that reduced setting time is achieved. It is verified by experiments that the proposed method brings an improved performance in the presence of surface defect as well as in the normal operating condition.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.185-185
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• 2011

CNCO-W 케이블의 절연결함 형태의 추정을 위해 곡률반경은 10 ${\mu}m$의 침(needle) 및 트래킹(tracking) 결함을 모의하고 부분방전 펄스의 위상분포를 분석하였다. 트래킹 결함에서는 $40^{\circ}{\sim}120^{\circ}$ 및 $200^{\circ}{\sim}285^{\circ}$에 분포하였으며, 침 결함과 비교하여 트래킹 결함에서는 펄스수가 증가하였으며, 정극성에서 넓게 분포하였다.

• The KIPS Transactions:PartD
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• v.15D no.3
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• pp.321-326
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• 2008

The software defects that are not found in the course of a project frequently appear during the conduct of the maintenance procedure after the complete development of the software. As the frequency of surfacing of defects during the maintenance procedure increases, the cost likewise increases, and the quality and customer reliability decreases. The defect rate will go down only if cause analysis and process improvement are constantly performed. This study embodies the defect tracking system (DTS) by considering the Pareto principle: that most defects are repetitions of defects that have previously occurred. Based on the records of previously occurring defects found during the conduct of a maintenance procedure, DTS tracks the causes of the software defects and provides the developer, operator, and maintenance engineer with the basic data for the improvement of the software concerned so that the defect will no longer be manifested or repeated. The basic function of DTS is to analyze the defect type, provide the measurement index for it, and aggregate the program defect type. Doing these will pave the way for the full correction of all the defects of a software as it will enable the defect correction team to check the measured defect type. When DTS was applied in the software configuration management system of the W company, around 65% of all its software defects were corrected.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.293-298
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• 2013

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1725-1727
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• 1998

In this paper the patterns of partial discharges(PD) occurred from some defects at the interface of cable joints as the function of the phase of the applied voltage were investigated in order to discern the kind of a defect. The results obtained in this study show that it is possible to distinguish the PD patterns between the void discharges and the treeing or tracking discharges which were occured at the cable joint interface. While the state of defect transfers from a void discharge into a tree or tracking discharge with a aging time, the skewness for both half of the applied voltage cycle is observed to go to the negative value.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.3
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• pp.19-23
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• 2005

To minimize the weld defect in manufacturing of the welded tube by using $CO_2$ laser, the monitoring of the welding quality and the seam tracking along the butt-joint lengthwise to the tube axis are studied. The longitudinal butt-joint is shaped from $60kgf/mm^2$ grade steel sheet by 2 roll bending method, and welded by the $CO_2$ laser welding system equipped with the seam tracker and plasma sensor. The laser welded tube has the thickness of 1.5mm, diameter of 105.4mm and length of 2000mm. The precise positioning of the laser beam on the butt-joint to be assembled is obtained within $200{\mu}m$ by the laser vision sensor. The artificial defects in the butt-joint are well observed by the signal of plasma intensity measured from the plasma sensor of UV wavelength range within 400nm. The developed $CO_2$ laser tube welding system has the function of the precision seam tracking and the real-time monitoring of the welding quality. In conclusion, the laser welded tube can be used for manufacturing of automobile chassis and components after hydro-forming.