• Journal of Welding and Joining
• /
• v.22 no.6
• /
• 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
• /
• v.6 no.3
• /
• 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
• /
• v.13 no.4
• /
• 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.

• Transactions of Materials Processing
• /
• v.29 no.3
• /
• 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.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.5
• /
• pp.984-990
• /
• 2017

The domestic cultural contents industry has been growing rapidly since the 2000s. The government has designated the cultural content industry as the next generation domestic growth industry. In order to cultivate this, various regulations are made and the budget is supported. Local governments are preparing various policies of cultural contents industry. This study presents the economic ripple effect by analyzing the status level and competence of the cultural contents industry in region based on LQ(location quotient) analysis and GAP analysis. Through this, this study will examine the competitiveness of the cultural content industry with high added value in Busan and draw out the plan for activation of cultural contents. Also, this study will compare competitiveness of Busan with other regions and show the economic contribution of Busan City.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.885-901
• /
• 2021

This paper illustratesthe impact of the temporal gap between satellite images and targetsize in mesoscale atmospheric motion vector (AMV) algorithm. A test has been performed using GEO-KOMPSAT-2A (GK2A) rapid-scan data sets with a temporal gap varying between 2 and 10 minutes and a targetsize between 8×8 and 40×40. Resultsshow the variation of the number of AMVs produced, mean AMV speed, and validation scores as a function of temporal gap and target size. As a results, it was confirmed that the change in the number of vectors and the normalized root-mean squared vector difference (NRMSVD) became more pronounced when smaller targets are used. In addition, it was advantageous to use shorter temporal gap and smaller target size for the AMV calculation in the lower layer, where the average speed is low and the spatio-temporal scale of atmospheric phenomena is small. The temporal gap and the targetsize are closely related to the spatial and temporalscale of the atmospheric circulation to be observed with AMVs. Thus, selecting the target size and temporal gap for an optimum calculation of AMVsrequires considering them. This paper recommendsthat the optimized configuration to be used operationally for the near-real time analysis of mesoscale meteorological phenomena is 4-min temporal gap and 16×16 pixel target size, respectively.

• Journal of Korean Society for Quality Management
• /
• v.43 no.2
• /
• 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
• /
• 2006.08a
• /
• 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.

• Journal of Korean Society for Quality Management
• /
• v.43 no.3
• /
• 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.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.12
• /
• 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.