• Journal of Welding and Joining
• /
• 제22권6호
• /
• pp.19-24
• /
• 2004

The laser welding and its analysis of thin-sheet carbon steels were carried out with high power $CO_{2}$ laser. The main factor of weld quality of laser welding is gap and edge quality. This work was preformed to focus on the gap tolerance problem during laser welding. First, bead on plate welding of thin sheet was examined to investigate the effect of laser welding variables, and to obtain optimum welding condition. Butt welding was also carried out to show the effect of gap on the laser weldability of thin sheet. In order to investigate the effect of gap on formability of welded thin sheet, LDH test was caried out. At high welding speed, the partial penetration was obtained by low heat input. Otherwise, porosity was formed in the bead at low weld speed because of too much heat input. The optimum welding condition of welding was derived from bead width, penetration and hardness property. The maximum gap tolerance on laser welding was observed to be about 0.2mm. This gap size has good relationship with beam size of laser spot(about 0.3mm). The formability of welded sheet was about $80{\%}$ value of base metal and the gap size has not affected on the formability, although weld quality is dependent on the gap size.

• The Journal of Advanced Prosthodontics
• /
• 제6권3호
• /
• pp.177-184
• /
• 2014

PURPOSE. The aim of this study was to measure the changes on the marginal and internal adaptation of zirconia based anterior fixed partial dentures after the porcelain firing process. MATERIALS AND METHODS. A total of 34 anterior fixed partial dentures using LAVA CAD/CAM system (3M ESPE, Germany) were applied. Two silicone replicas were obtained: one is obtained before porcelain firing process (initial) and the other is obtained after porcelain firing process (final), followed by the examination under a binocular stereomicroscope. Kruskal Wallis and Wilcoxon Signed Ranks tests were used for the statistical analysis (P<.05). RESULTS. No statistically significant difference was found between initial and final marginal gap values (P>.05). At the internal gap measurements, final marginal area values ($59.54{\mu}m$) were significantly lower than the initial marginal area values ($68.68{\mu}m$)(P<.05). The highest and the lowest internal gap values were observed at the incisal/occlusal area and at the marginal area, respectively. In addition, lower internal gap values were obtained for canines than for central incisors, lateral incisors and premolars at the incisal area (P<.05). CONCLUSION. The firing cycles did not affect the marginal gap of Lava CAD/CAM system, but it is controversial for the internal gap.

• International Journal of Contents
• /
• 제13권4호
• /
• pp.47-62
• /
• 2017

This paper analyzes how much the gap existed between the public group and expert group using future issues and future core technologies that are announced in government institutions based on ontology. We calculated gap with two groups' point of view, one is expert groups' ideas that are based on future hopeful technologies documents, and another is public people ideas that are based on documents of contest that is hosted by 'Ministry of Science, ICT and Future Planning (MSIP)', and 'Institute for Information & communications Technology Promotion (IITP)'. For calculating these, we suggested SDGM model. In the case of ETRI Meta-trend ICT Field, there is a little gap between expert group and public group, and another case that is XT (ETRI determined future technologies excluding ICT field) Field, the gap is increasing annually. Moreover, in the case of all ETRI Meta trend, the gap is bigger than ICT and XT field. We analyzed, also, KEIT's future issues for generalizing this model. The gap existed between two groups. Utilizing SDGM model of this paper, people can interpret easily how much the gap exists between future technologies and issues that are announced in institutions.

• 소성∙가공
• /
• 제29권3호
• /
• pp.157-162
• /
• 2020

Blind rivet nuts are increasingly used in automotive for the joining of sheets. Their application, however, requires appropriate design guides to prevent catastrophic events arising from the failure of joints. In this study, the shaft shape of a frequently used M8 blind rivet nut is optimized based on 3D numerical analysis of the blind rivet nut considering the characteristics of thread. The thread needs to be modeled to suitably consider the fastening of the M8 bolt after the crimping process. FE analysis showed that while the friction in the contact between crimp flange and plate has no significant effect on the crimp geometry, shaft thickness (t) and shaft height (h) are the most significant design variables. The parameter study including various combinations of t and h reveals that they affect the gap (the distance between the crimped flange and the plate that develops through riveting) and the load acting on the plate. The gap is an indicator of the tightening force. It is found that t is inversely proportional to the gap, and proportional to the load, whereas h is proportional to the gap and inversely proportional to the load. Based on our FE analysis results, we propose the range 0.062 < t/h < 0.1 to ensure sufficient fastening (high clamping load, small gap) of the M8 blind rivet nut. The design guide for determining the t/h ratio proposed in this study can be used for general quantitative analysis of the size and the t/h ratio of blind rivet nuts.

• 한국정보통신학회논문지
• /
• 제21권5호
• /
• pp.984-990
• /
• 2017

국내 문화 콘텐츠 산업은 2000년대부터 급속한 성장을 보이고 있다. 이에 정부는 차세대 국내 성장 산업으로 문화콘텐츠 산업을 지정하고 이를 육성하기 위해 다양한 법규를 만드는 등 예산의 지원도 아끼지 않고 있으며, 각 지자체에서도 문화콘텐츠산업의 다양한 정책들을 마련하고 있다. 하지만 이러한 문화 콘텐츠산업의 중요성이 강조되고 있음에도 불구하고 문화콘텐츠의 경쟁력을 분석한 연구가 거의 이루어지고 있지 않고 있다. 본 연구에서는 LQ분석과 GAP분석을 토대로 권역별 문화콘텐츠산업의 현황수준과 역량분석을 하여 경제적 파급효과를 제시하였다. 이를 통해 부산의 고 부가가치 문화 콘텐츠 산업의 경쟁력을 검토하고 문화 콘텐츠 활성화를 위한 계획을 수립 할 예정이다. 또한 본 연구는 부산과 다른 지역의 경쟁력을 비교하고 부산시의 경제적 기여도를 보여줄 것이다.

• 대한원격탐사학회지
• /
• 제37권5_1호
• /
• pp.885-901
• /
• 2021

천리안위성 2A호의 2분 주기 고속 관측(rapid-scan) 자료를 이용하여, 가시·수증기·적외 채널의 시간 해상도와 표적의 크기가 해당 채널의 중규모 대기운동벡터 생산에 미치는 영향을 분석하였다. 중규모 대기운동벡터 산출을 위하여 2-10분의 영상 시간 간격 변화 하에서 표적의 크기를 8×8에서 40×40 화소 크기로 변환시키며, 시·공간적인 조건 변화에 따른 벡터 생산량과 평균 속력, 오차 특성의 변화 양상을 비교하였다. 그 결과, 표적의 크기가 작을수록 위성의 시간 간격 변화에 따른 벡터 개수의 변화와, 표준화된 평균 제곱근 편차(Normalized Root Mean Squared Vector Difference; NRMSVD) 값의 변화가 더욱 뚜렷해졌다. 또한 고도별 오차 특성 분석 결과에서는 평균 속력이 낮고 대기 현상의 시·공간 규모가 작은 하층(700-1000 hPa)의 경우, 짧은 시간 간격의 영상 자료와 작은 표적을 이용하는 것이 벡터 산출에 더욱 유리하게 작용하는 것을 확인할 수 있었다. 위성의 시간 간격과 표적의 크기는 대기 순환의 시·공간 규모와 밀접한 연관이 있는 요소이다. 따라서, 대기운동벡터 활용 목적에 맞게 표적 크기와 위성 시간 간격을 최적화하는 과정이 필요하며, 중규모 기상현상의 실황 분석을 위한 대기운동벡터 산출 알고리즘에서는 표적 크기와 영상 시간 간격을 각각 16×16, 4분으로 설정해주는 것이 가장 적합하다고 판단된다.

• 품질경영학회지
• /
• 제43권2호
• /
• pp.127-140
• /
• 2015

Purpose: To obtain the area for improvement, the Importance-Performance analysis(IPA) uses relatively simple questions, that is, satisfaction and importance at attribute level. However, no attempt has been made to consider the gap between own company's performance and those of competitors in IPA, in the field of quality management. This study is aimed to suggest a new prioritizing method for improvement and to test for validity of the proposed technique. Methods: This study used data collected from Song and Lim(2015), which is satisfaction of employees, customers and competitors as well as importance data for 7 quality attributes of K animal hospital. A correlation comparison with other priority methods such as Bacon(2003)'s model and Matzler and Hinterhuber(1998)'s QI index is conducted. Results: The priority results by the proposed method shows better in correlation coefficient with customer perceived priority for improvement than other methods. Conclusion: From the result of the current study, it can be concluded that the result of the proposed method is valid, while it is relatively easy to understand and analyze, and therefore no additional survey is necessary for improvement priority.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
• /
• pp.153-156
• /
• 2006

A turbine stage consists of a stator and rotor. A stator provides the required inlet flow conditions so that a rotor can produce the necessary power. Passing wakes generated at the trailing edge of a stator make an interaction with a rotor. In the present study, this interaction flow mechanism is investigated using the numerical analysis. In case of the large gap distance between the stator and rotor, the stator and rotor flow analysis can be separated. First, only the stator flow field is solved. Second, the rotor flow field is solved including the passing wake information from the stator analysis. The passing wake experiences the shearing as it approaches to the rotor leading edge. And it is chopped when it strikes the rotor body. After that, the chopped wakes becomes the prolongation as it goes downstream. Also, the aerodynamic characteristics with the variation of the gap distance between a stator and rotor was investigated. Pressure jumps due to the passing wakes result in the pressure and lift loss and it gets stronger with the closer gap distance. This unsteady effect proves to be directly related to the fatigue and noise in turbomachinery and this study would be helpful to investigate such fields.

• 품질경영학회지
• /
• 제43권3호
• /
• pp.397-408
• /
• 2015

Purpose: Express mail service(EMS) supplied by 'Korea POST'is an international postal service which brings letters, documents and parcels to a destination abroad in the fastest and safest way. This service is in a tough competition with global companies such as TNT, FedEx, DHL or UPS. To build an effective strategy for being competitive, an intensive study on EMS service quality should be accomplished from a customer's perspective. Methods: Kano model and improvement gap analysis are used to categorize and prioritize EMS service quality attributes. A 5-point Lickert scale is employed to apply the Kano model and improvement gap analysis. Each quality attribute can be classified as weak in comparison with competitors, critical for improvement, or potentially competitive. Results: Price, on-time delivery and delivery quality are to be kept as is; fast delivery, parking convenience and staff expertise can be potentially competitive; and the other attributes are considered to be critical for improvement. Conclusions: Fast reimbursement and proper compensation when shipping items are lost or damaged are to be improved with high priority. Efforts to secure fast delivery, parking convenience and staff expertise are needed to be competitive in the future.

• 한국정밀공학회지
• /
• 제18권12호
• /
• pp.73-81
• /
• 2001

The MIAB welding uses a rotating arc as its heat source and is known as an efficient method fur pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. The electro-magnetic force is affected by magnetic flux density, arc current, and arc length. Especially, the magnetic flux density is an important factor on arc rotation and weld quality. This paper presents a 2D finite element model for the analysis of magnetic flux density in the actual welding conditions. The magnetic flux density is mainly dependent on gap between two pipes, the position of coil from gap center, exciting current, and relative permeability. Thus, the relations between magnetic flux density and main factors were investigated through experiment and analysis. Experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The analysis results of magnetic flux density reveal that it increases with increasing exciting current, increasing relative permeability, decreasing distance from gap center to coil, and decreasing gap size. It is considered that the results of this study can be used as important data on the design of coil system and MIAB welding system.