• 한국전기전자재료학회논문지
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• 제28권5호
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• pp.320-325
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• 2015

This paper dealt with a defect identification algorithm which is based on single partial discharge (PD) pulse analysis in gas insulated structure. Four types of electrode systems such as a needle-plane, a plane-needle, a free particle and a crack inside spacer were fabricated to simulate defects in gas insulated switchgear (GIS). We measured single PD pulse by an oscilloscope with a sampling rate of 5 GS/s and a frequency bandwidth of 1 GHz. Data aquisition and signal processing were controlled by a LabVIEW program. Physical shapes of PD pulses were compared with kurtosis, skewness and time-based parameters as rising time, falling time and pulse-width. These parameters were analysed by an algorithm with a back propagation algorithm (BPA). By applying the algorithm, the identification rate was 97% for the needle-plane electrode, 96% for the plane-needle electrode, 91% for the free particle and 93% for the crack inside spacer. The results verified that the algorithm could identify the type of defects in GIS.

• International Journal of Korean Welding Society
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• 제1권2호
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• pp.36-44
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• 2001

To get the appropriate welding process variables, mathematical modeling in conjunction with many experiments is necessary to predict the magnitude of weld bead shape. Even though the experimental results are reliable, it has a difficulty in accurately predicting welding process variables for the desired weld bead shape because of nonlinear and complex characteristics of welding processes. The welding condition determined for the desired weld bead shape may cause the weld defect if the welding current/voltage/speed combination is improperly selected. In this study, the $2^{n-1}$ fractional factorial design method and correlation parameter were used to investigate the effect of the welding process variables on the fillet joint shape, and the multiple non-linear regression analysis was used for modeling the gas metal arc welding(GMAW）parameters of the fillet joint. Finally, a fuzzy rule-based method and a neural network method were proposed so that the complexity and non-linearity of arc welding phenomena could be effectively overcome. The performance of the proposed neuro-fuzzy system was evaluated through various experiments. The experimental results showed that the proposed neuro-fuzzy system could effectively check the welding conditions as to whether or not weld defects would occur, and also adjust the welding conditions to avoid these weld defects.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.133-138
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• 2005

Automotive pulleys play a key role in driving the cooling pump, oil pump, air-conditioner and so on by using an engine power. Researches on design processes and technologies of the pulleys can be found in many literatures. On the other hand, the areas related to manufacturing processes of the pulleys have been treated negligently. Vast data extracted from various information systems are transformed, integrated, and summarized to become a special database for helping users make a decision. The database, namely the data warehouse has been popularly used in the marketing and customer management of enterprises and recently applied to improve the design and manufacturing processes. In this study the manufacturing process of pulleys were analyzed through the intensive investigation of shop-floors and the interviews with workers and managers. The defects generated during a manufacturing process were categorized in a few types and the causes of defects examined for extracting the dominant parameters in the setup process for producing pulleys. As the first step to construct the data warehouse for the manufacturing processes of pulleys, authors proposed its architecture focused on the reduction of defect rate during the setup process.

• Journal of Periodontal and Implant Science
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• 제38권4호
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• pp.717-722
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• 2008

Purpose: The subepithelial connective tissue graft(SCTG) has been proven to be a highly predictable treatment modality for coverage of gingival recession. This case report was performed to evaluate the effect of various root coverage procedures using SCTG on gingival recession. Materials and Methods: Three patients presents with Miller's class I recession defect on the maxillary canine. Each other SCTG(coronally advanced flap, Bruno's Tech., envelope Tech.) were performed for root coverage. Clinical parameters assessed included recession depth, recession width, and keratinized gingival width. Measurements were taken at baseline and 2 months and follow up end. Results: The average of root coverage was 4 mm(100% of the pre-operative recession depth) at the 2, 5 months examination. The average increase of keratinized tissue between the baseline and the 2 months amounted to 3.2mm. Conclusion: Within the above results, various root coverage using SCTG is an effective procedure to Miller's class I recession defect and patient could be satisfied aesthetic requirement.

• 한국물환경학회지
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• 제28권2호
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• pp.292-299
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• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• 핵의학기술
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• 제16권2호
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• pp.49-56
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• 2012

좌심실 용적 및 구혈률은 관상동맥질환 환자의 치료에 있어 예후예측 및 경과 관찰에 매우 중요한 지표이며, 현재 게이트 심근관류 SPECT (Myocardial perfusion SPECT)를 이용하여 심근관류 이상을 진단하는 동시에 좌심실 용적 및 구혈률(Ejection fraction, EF)을 측정하는 방법이 널리 사용되고 있다. 게이트 심근관류 SPECT와 심초음파(Echocardiography)로 산출한 좌심실 용적 및 구혈률이 높은 상관성을 가진다는 많은 보고들이 있으나 심근관류결손의 유무와 정도에 상관없이 비교되었으며, 제한된 환자들에서 비교 분석이 시행되었다. 이에 본 연구에서는 $^{201}Tl$ 게이트 심근 관류 SPECT에서 부하기(G-Stress) 및 휴식기(G-Rest) 좌심실 구혈률을 관류 결손 여부와 성별, 심실 용적에 따라 심초음파와 비교하여 그 상관성을 알아보고자 하였다. 2011년 4월부터 2012년 5월까지 본원에서 $^{201}Tl$ 게이트 심근관류 SPECT 검사와 심초음파를 일주일 내 시행한 환자 중 성인 291명(남:여=165:126, 평균나이 $64.6{\pm}10.8$세)을 대상으로 하였다. 이 중 정상으로 진단받은 환자 190명과 가역성 관류결손, 고정 관류결손으로 판정 받은 환자 58명, 43명을 대상으로 연구 분석하였다. 데이터 분석에는 QGS (Quantitative gated SPECT) 소프트웨어를 이용하였고, 자동화된 방식으로 EF, 확장기말 용적(End-diastolic volume, EDV), 수축기말 용적(End-systolic volume, ESV)을 산출하였다. 본 연구에서는 심근관류결손의 가역성 여부와 성별을 기준으로 게이트 심근 관류 SPECT에서의 부하기/휴식기와 심초음파에서의 EF, EDV, ESV를 반복측정 분산분석(repeated-measures anova)과 Bland-Altman 분석을 이용하여 차이를 비교하고, pearson 상관계수를 구하여 각각의 상관관계를 분석 하였다. 전체 환자 중 부하기와 휴식기, 심초음파에서의 EF는 높은 상관관계(G-Stress와 G-Rest r=0.909, G-Stress와 EC r=0.833, G-Rest와 EC r=0.825)를 나타냈으나, 전체 환자 중 EF, EDV, ESV는 통계적으로 유의한 차이를 보였다(p<0.01). 관류 결손 여부에 따른 EF값의 차이는 정상 군에서 통계적으로 유의한 차이를 보였고(p<0.01), 관류 결손이 있는 환자 군에서 통계적으로 유의한 차이를 보였다(가역성 관류결손, 고정 관류결손 p<0.01). 성별에 따라 차이를 분석한 결과, 정상 군 중 남성에서의 EF는 통계적으로 유의한 차이를 보이지 않았고(p>0.05), 여성에서의 EF는 통계적으로 유의한 차이를 보였다(p<0.01). 여성환자 중, 좌심실용적으로 분류하였을 때 평균 확장기말 용적보다 적은 군에서 유의한 차이를 보였고, 평균 보다 큰 군에서는 통계적으로 유의한 차이를 보이지 않았다. $^{201}Tl$ 게이트 심근 관류 SPECT 중 부하기 및 휴식기에서의 좌심실 구혈률과 심초음파와의 상관관계는 전체적으로 높은 것으로 나타났다. 하지만 EF, EDV, ESV는 통계적으로 유의한 차이를 보였다. 관류 결손의 정도, 성별, 좌심실 용적은 LVEF의 정확성에 영향을 미칠 수 있을 거라 사료되며, 이에 대한 추가적인 연구가 필요할 것이다.

• 소성∙가공
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• 제24권4호
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• pp.280-286
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• 2015

Hemming is used to connect two sheet metal components by folding the edge of an outer panel around an inner panel to create a smooth edge. The minimization of hemming defects is critical to the final quality of automobile products because hemming is one of the last operations during fabrication. Designing the hemmed part is not easy and is influenced by the geometry of the bent part. Therefore, the main problem for automotive parts is dimensional accuracy since formed products often deviate geometrically due to large springback. Few numerical approaches using 3-dimensional finite element model have been applied to hemming due to the small element size which is needed to properly capture the bending behavior of the sheet around small die corner and the comparatively big size of automotive opening parts, such as doors, hoods and deck lids. The current study concentrates on the 3-dimensional numerical simulation of hemming for an automotive door. The relationship between the design parameters of the hemming operation and the height difference defect is shown. Quality improvement of the automotive door can be increased through the study of model parameters.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.985-988
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• 2004

The carrier lifetime of boron doped Cz silicon samples after light induced degradation could be improved by optimized rapid thermal processing (RTP). The important five different parameters varied in order to investigate which parameter is important for the stable lifetime after light induced degradation, $\tau_d$. The Plateau temperature and the Plateau time influenced on the lifetime after light induced degradation. Especially, the Plateau temperature showed a strong influence on the stable lifetime. The optimal plateau temperature is approximately $900^{\circ}C$ t for a plateau time of 120 s. The stable lifetime increased from $15\mu}s$ to $25.5{\mu}s$. The normalized defect concentration, $N_t^*$, decreased from $0.06{\mu}s^{-1}$ to $0.037{\mu}s^{-1}$ by RTP-process.

• 한국전기전자재료학회논문지
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• 제27권12호
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• pp.877-882
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• 2014

It has been confirmed that the inner defect of transformer and the perfect diagnosis for aging are closely related to safe electric power transmission system and that the detection of accident and diagnosis technique turn out to be very important issues. Since electric power machinery consists of various kinds of components, however, it is very difficult to make a diagnosis for aging by one parameter. Thus, diagnosis for aging is feasible only through the combination of various parameters. Recently, various expert systems have been developed and applied to diagnosis for aging, but they are not yet reliable enough to apply to the real system. In this paper, XLPE which is ultra high voltage cable insulator material were chosen to investigate the influence of void on insulator material using partial discharge. Obtained data have been processed by PRPD (phased resolved partial discharge) distribution function and K-means. And statistical and cluster distribution of partial discharge have been analysed and investigated.

• Journal of Welding and Joining
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• 제10권3호
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• pp.1-12
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• 1992

A literature review was conducted to survey informations available on the welding metallurgy of aluminum alloys and its effect on fusion weldability, especially on solidification cracking and pore formation. Solidification cracking behavior of Al weld is a complicate matter as compared to other high alloys, where a relatively simple Fe-X(most detrimental elements S, P, B, Si, etc) binary diagram can be successfully applicable. Both additive and synergistic effects of elements should be considered together. A same element play a different role from system to system. Porosity, caused by hydrogen contamination of the weld is one of the most troublesome welding problems. The primary sources of hydrogen are believed to be an absorbed moisture on the filler metal or base metal and in the shielding gas. It is extremely important that reliable quality-control procedures be employed to eliminate all possible sources of hydrogen contamination. Selection of proper process and parameters is sometimes more important than controlling of alloying elements in order to make a defect-free weld.