• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.163-166
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• 2005

A hole expansion process is an important process in producing a hub-hole in a wheel disc of a vehicle. In this process, the main parameter is the formability of a material that is expressed as the hole expansion ratio. The hub-hole expansion process is different from conventional forming processes or hole flanging processes from the view-point of its deformation mode and forming of a thick plate. In the process, a crack is occurred in the upper edge of a hole as the hole is expanded. Since prediction of the forming limit by hole expansion experiment needs tremendous time and effort, an appropriate fracture criterion has to be developed fur finite element analysis to define forming limit of the material. In this paper, the hole expansion process of a hub-hole is studied by finite element analysis with ABAQUS/standard considering several ductile fracture criteria. The fracture mode and hole expansion ratio is compared with respect to the various fracture criteria. These criteria do not predict its fracture mode or hole expansion ratio adequately and show deviation from experimental results of hole expansion. A modified ductile fracture criterion is newly proposed to consider the deformation characteristics of a material accurately in a hole expansion process. A fracture propagation analysis at the hub-hole edge is also performed for high accuracy of prediction using the new fracture criterion proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.903-913
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• 2011

A numerical study is carried out to analyze the steady three-dimensional turbulent flow through cylindrical and fan-shaped holes and the film cooling of these holes at low and high blowing ratios. Compressible Reynoldsaveraged Navier-Stokes equations and the energy equation are solved using a finite-volume-based solver, and a shearstress transport model is used as the turbulence closure. The effects of the compound angle, pitch to diameter ratio, and lateral expansion angle of the hole on the film-cooling effectiveness are evaluated by the film-cooling effectiveness. It is observed that the compound angle of the hole enhances the film performance for the cylindrical hole, and a small hole pitch induces interactions between the coolants from the adjacent holes, thus reducing the film-cooling performance.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.321-325
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• 2008

Void areas(holes) as an inevitable phenomenon exist in geographic routing of wireless sensor networks, because the unpredictable and harsh nature application environment or uneven energy consumption. Most of the existing schemes for the issue tend to construct a static detour path to bypass a hole. The static detour path may lead to uneven energy consumption of the nodes on the perimeter of the hole; thus it may enlarge the hole. At the same time, traffic would concentrate on the peripheral node of the hole; thus the nodes on the perimeter of the hole tend to be depleted quietly. In previous work, we have proposed a hole geometric model to reduce the energy consumption and packet collisions of the nodes on the hole boundary. This scheme, however, still has the static detour path problem. Therefore, we extend the previous work by constructing a dynamic detour path hole geometric model for wireless sensor networks in this paper. The location of hole detour anchors is dynamically shifted according to Gaussian function, just generating dynamic hole detour paths.

• Smart Media Journal
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• v.3 no.4
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• pp.28-34
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• 2014

Recently the depth-image-based rendering (DIBR) method is usually used in 3D image application filed. Virtual view image is created by using a known view with associated depth map to make a virtual view point which did not taken by the camera. But, disocclusion area occur because the virtual view point is created using a depth image based image 3D warping. To remove those kind of disocclusion region, many hole filling methods are proposed until now. Constant color region searching, horizontal interpolation, horizontal extrapolation, and variational inpainting techniques are proposed as a hole filling methods. But when using those hole filling method some problem occurred. The different types of annoying artifacts are appear in texture region hole filling procedure. In this paper to solve those problem, the multi-directional extrapolation method is newly proposed for efficiency of expanded hole filling performance. The proposed method is efficient when performing hole filling which complex texture background region. Consideration of directionality for hole filling method use the hole neighbor texture pixel value when estimate the hole pixel value. We can check the proposed hole filling method can more efficiently fill the hole region which generated by virtual view synthesis result.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.71-77
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• 2021

Several cooling techinques have been studied for protecting gas turbine blades from hot gas. In terms of film-cooling techniques, various shapes of film cooling holes have been studied including fan shaped holes, which are used on gas turbine blades. However, owing to increasing demands on smaller gas turbines, a research on film-cooling holes on thin walls is required. This study was conducted at blowing ratios of 1 and 2, using numerical analysis. Through the numerical analysis, the effect of geometrical parameters on the effectiveness of fan-shaped hole film cooling was studied. Moreover, optimization was performed on three geometrical parameters: metering length, lateral expansion angle and forward expansion angle. As a result, we realized that the optimal fan-shaped holes on each blowing ratio were found to have very similar geometry and cooling performance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.131-134
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• 2004

The hub hole is usually formed with a stretch flanging process followed by a blanking process of a hole. Since the hole is made by blanking, the blanked surface is so rough that the formability in the region is rather poor. The emerging task is to identify the formability of the blanked region in the forming simulation and to relate the criterion to the real forming process by experiments. In this paper, the blanked region of a hole surface is modeled by a defected-edge finite element for stretch flanging simulation. The analysis deals with the level of defect in the blanked region in order to identify the formability in the real process. The analysis provides the formability depending on the level of defect and seeks the way to match the level of defect to that of the real surface. The approach makes the analysis possible to deal with the formability of the high strength steel and predict the fracture at the hole surface during the stretch flanging simulation.

• 프린팅코리아
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• v.13 no.9
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• pp.51-60
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• 2014

변화하는 인쇄산업의 비전을 제시해 준 국내 최대 인쇄인의 축제 K-PRINT Week가 지난 8월 27일(수)부터 30일(토)까지 'K-PRINT Week! 새로운 미래를 인쇄하다'라는 주제로 일산 킨텍스 제2전시장 7, 8홀에서 열렸다. 대한인쇄문화협회와 한국이 앤엑스가 공동으로 주최한 이번 전시회는 일산 킨텍스 제2전시장 7, 8홀에서 1만$6935m^2$ 규모로 27개국 275개사가 참가한 가운데 진행됐다. K-Print Week 2014는 최근 인쇄산업이 다양한 산업 분야로 확장되고 있는 인쇄시장의 트렌드에 맞춰 기존의 국제인쇄기자재전(KIPES)과 함께 한국레이블전, 한국인쇄패키지전, 한국디지털인쇄 솔루션전 등 4개 인쇄 관련 전시회가 통합 개최된 것으로, 지난 전시회보다 많은 바이어가 방문해 내수상담과 수출상담이 이뤄졌다. 또한 대한인쇄문화협회가 주최한 '친환경 무습수 인쇄기술의 현황과 전망' 국제컨퍼런스를 비롯한 다양한 세미나가 개최돼 방문객들에게 큰 관심을 불러 일으켰다.

• The Journal of the Korea Contents Association
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• v.15 no.2
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• pp.21-30
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• 2015

Image coding based on mixed raster content model generates don't care regions (DCR) in foreground and background layers, and its overall coding performance is greatly affected by region filling methods for DCRs. Most conventional methods for DCR filling fail in utilizing the local signal properties in hole regions and thus the high frequency components in non-DCR regions are reflected into DCR after signal filling. In addition, further high frequency components are induced to the filled signal because of signal discontinuities in the boundary of DCR. To solve this problem, a new DCR filling algorithm using the priority-based adaptive region growing is proposed in this paper. The proposed method uses the watershed algorithm and the flooding priority of each pixel for region filling is determined from the degree of smoothness in the neighborhood area. By growing the filled region into DCR based on the computed priority, the expansion of high-textured area can be minimized which can improve the overall coding performance. Experimental results show that the proposed method outperforms conventional algorithms.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.367-373
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• 2008

Recently, the NAT middlebox widely deployed in the home network environment prohibits DM operations from reaching user devices behind NAT. In this article, we focus on NAT issues to manage home network devices. Particularly, we discuss standardization efforts, and present our proposal to deploy DM services for VoIP and IPTV devices under NAT. By slightly changing behaviors of Simple Network Management Protocol (SNMP) Manager and Agent, and defining additional Management Objects (MOs) to gather NAT binding information, we could solve the NAT traversal problem under symmetric NAT. Moreover, we propose an enhanced method to search the UDP hole binding time of the NAT box. We applied our method to randomly selected 22 VoIP devices out of 194 NATed hosts in the real broadband network and have achieved 99% of the success ratio for exchanging SNMP request messages and 26% of enhancement for searching the UDP hole binding time.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.558-567
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• 2019

When used for broadcasting, multipurpose halls need to accommodate various types of programs such as speeches, Korean traditional music, musicals, pop music, and concerts. Therefore, multipurpose halls must meet a wide range of electric and architectural acoustic demands. However, there are few ways to alter acoustic environments for multipurpose halls, given these different demands. The current study investigates the effects of banners on acoustic environments in the presence of an acoustic shell or electric acoustic system. The results indicate that the installation of a 15% banner of wall area could vary the range of reverberation time ($T_{30}$) by 0.12 s, EDT (Early Decay Time) by 0.15 s, clarity of music ($C_{80}$) by 0.76 dB, and clarity of speech ($D_{50}$) by 6.43 % under different measurement circumstances. A computer simulation that enlarges the banner size to 40 % of the wall area varies the reverberation time from 0.11 s to 0.55 s depending on the room environment.