• Design & Manufacturing
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• v.17 no.3
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• pp.15-20
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• 2023

In the fine blanking process, which is a press operation known for producing parts with narrow clearances and high precision through the application of high pressure, die roll often occurs during the shearing process when the punch penetrates the material. This die roll phenomenon can significantly reduce the functional surface of the parts, leading to decreased product performance, strength, and fatigue life. In this research, we conducted an in-depth analysis of the factors influencing die roll in the curvature area of the fine blanking process and identified its root causes. Subsequently, we designed and experimentally verified a die roll reduction process specifically tailored for the door latch manufacturing process. Our findings indicate that die roll tends to increase as the curvature radius decreases, primarily due to the heightened bending moment resulting from reduced shape width-length. Additionally, die roll is triggered by the absorption of initial punch energy by scrap material during the early shearing phase, resulting in lower speed compared to the product area. To mitigate the occurrence of die roll, we strategically selected the Shaving process and carefully determined the shaving direction and clearance area length. Our experiments demonstrated a promising trend of up to 75% reduction in die roll when applying the Shaving process in the opposite direction of pre-cutting, with the minimum die roll observed at a clearance area length of 0.2 mm. Furthermore, we successfully implemented this approach in the production of door latch products, confirming a significant reduction in die roll. This research contributes valuable insights and practical solutions for addressing die roll issues in fine blanking processes.

• Journal of Korean Association for Spatial Structures
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• v.24 no.1
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• pp.47-55
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• 2024

The aim of this study is to evaluate the possibility of damage to cultural assets resulting from vibrations generated by construction vehicle traffic. The cultural heritage's natural vibration frequency was determined to be 150Hz by measurement. The damping ratios were calculated as 4.7% using the logarithmic decrement approach and 4.3% using the half-power method. The vibration measurements obtained during vehicle operation indicated that, despite an increase in vehicle velocity of up to 15 km/h, the vibrations remained below the detectable level of 0.13 mm/sec. When the road is curved and the terrain is sloped, a suitable speed for vehicle operation was found to be around 17 km/h, at which point vibrations were seen. The highest recorded vibration amplitude at this velocity was 0.217 mm/sec, which remains below the stringent regulation limit of 2 mm/sec. Thus, it can be concluded that there is no actual harm caused by vibrations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.245-256
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• 2000

A moment-curvature relationship to simulate the behavior of reinforced concrete beam under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the proposed model takes into consideration the bond-slip effect by using monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. The modification of the moment-curvature relation to reflect the fixed-end rotation and pinching effect is also introduced. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.497-504
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• 2012

Finite element analysis is to approximate a geometry model developed in computer-aided design(CAD) to a finite element model, thus the conventional shape design sensitivity analysis and optimization using the finite element method have some difficulties in the parameterization of geometry. However, isogeometric analysis is to build a geometry model and directly use the functions describing the geometry in analysis. Therefore, the geometric properties can be embedded in the NURBS basis functions and control points so that it has potential capability to overcome the aforementioned difficulties. In this study, the isogeometric structural analysis and shape design sensitivity analysis in the generalized curvilinear coordinate(GCC) systems are discussed for the curved geometry. Representing the higher order geometric information, such as normal, tangent and curvature, yields the isogeometric approach to be the best way for generating exact GCC systems from a given CAD geometry. The developed GCC isogeometric structural analysis and shape design sensitivity analysis are verified to show better accuracy and faster convergency by comparing with the results obtained from the conventional isogeometric method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.655-666
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• 2014

Recently, as the appearance and exterior design of the construction structure are highlighted, the irregularly shaped structures are increasing in a construction facility. Many softwares provide a quantity take-off function of 3D object under BIM environment, however, they are focused on the limited function based on the solid modeling method. Because the vast geometric information of the curved surface is difficult to extract in the 3D objects that consist of major changes in vertical section shape as the irregularly shaped structures, it is difficult to express a 3D object as a solid model. On the other hand, the irregularly shaped structures can be expressed in relatively free in the surface model because the surface model consists of points, lines and surfaces. Accordingly, the surface modeling method is suitable for the modeling of large irregularly shaped structures. This study suggests a quantity take-off algorithm for the irregularly shaped structures using the surface modeling approach that is beneficial in the design work of structures. Some case projects are used for verifying the accuracy of the proposed method.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.615-621
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• 2014

This study suggests the design and assembly drawing of the prefabricated precast concrete arch ammo magazines using the numerical analysis as well as the explosion verification test. The protective capacity of the proposed magazines is identified with the maximum support rotation angles measured by explosion verification tests according to the U.S. Unified Facility Criteria 3-340-02. Using numerical analysis, it is examined that oval-type members are better than the semi-circle ones in terms of protective capacity. Based on this numerical results, the design and assemble drawing for the prefabricated precast concrete arch ammo magazine are developed. It is identified that the structure constructed by invented design and assembly drawing has enough protective capacity against blast pressure caused by 133.75kg TNT explosion. The detonation point cannot be open due to the military security. In sum, it could be concluded that the ammo magazine proposed in this study has reliable protective capacity with enough redundancy. The redundancy means that there are more economic design approach with reducing the curved wall thickness.

• Korean Journal of Heritage: History & Science
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• v.45 no.4
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• pp.92-103
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• 2012

The Cheomsungdae was built in the Silla dynasty during the reign of queen Seondeok. It has a round cylindrical structure with a flowing curved fa ade. The identity of the Cheomsungdae has not been revealed since there is not much historical evidence or documents about the building. This study is trying to investigate the building technique and method from the technical point of view of the past when it was constructed. There have been much work and studies done for the Cheomsungdae, but not much were focusing on the technical aspects of the building. In addition there are many questions and doubts about the hypothesis of the building technique of Cheomsungdae since there aren't any remaining documents or historical evidence supporting it. Among many questions, we think that the discussion on falsework technique is not considering traditional construction method of the Dujabee (a traditional construction technique using various tools and equipment for the stability of the building) technique. Therefore, it is hard to identify them as reliable historical facts. As the result of the study, we want to provide the basic data on the construction techniques of Korean traditional architecture and broaden the study scope of technical history by narrowing the errors. The study could be summarized into three points. 1. The historical architecture Cheomseongdae was constructed by using traditional crane techniques such as a Noklo (pulley ladder). Cheomseongdae was re-evaluated as a high level technology for the history of architecture. 2. The benchmark method on Cheomseongdae construction has been applied with a precise scientific method based on the geometrical principals using the central axis. 3. In terms of the history of Korean traditional architecture technology, as there aren't many studies done we proposed various basic data for the traditional crane techniques and criteria of Korean traditional architecture technology. We could expect various and active studies for the technical approach of the history of architecture.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.345-352
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• 2024

K-Pop Square Media, located at COEX in Samseong-dong, has gained public attention and mass media focus by showcasing various three-dimensional videos on a large LED display. The video content on the distinctive large curved LED display utilizes a form of media façade technique, establishing itself as a new landmark and attraction within the spatial characteristics of the COEX Plaza. This study aims to examine the characteristics of media facades used in outdoor advertising in urban spaces, focusing on K-Pop Square Media. The approach for this research involves three aspects: Firstly, examining the 'spatial characteristics' of urban public spaces by referencing Kevin Lynch's five elements constituting urban space and William J. Mitchell's exploration of smart spaces and changes in spatial paradigms. Secondly, analyzing the 'digital nature' of outdoor advertising through an examination of three types of Digital Out-Of-Home (DOOH) Media. Thirdly, exploring the 'technological advancements and content composition of media facades' by investigating types of display media (projection, LED screens), the inception of media facades, and the latest display technology like Anamorphic displays. Through this research, it becomes evident that K-Pop Square Media exhibits characteristics of publicness, communicativeness, artistry, and placemaking through the spatial characteristics of smart spaces, the media-specific aspects of Digital Out-Of-Home advertising, and the content composition of media facades.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.371-383
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• 2012

Shaping the root canal system to maintain original canal curvature is essential to clinical success in endodontic treatment. Opposed to most root canals that are curved, endodontic instruments are made from straight metal blanks. They have a tendency of straightening the root canal during preparation and frequently result in procedural errors. A new treatment method to maintain original canal curvature during shaping has been introduced for preventing procedural errors. The aim of this study was to compare the ability of instruments to maintain original canal curvature of continuous rotary system and single file system. Thirty ISO 15, 0.02 taper, Endo Training Blocks(Dentsplay Maillefer) were used. Specimens were assigned to 1 of 3 groups for shaping: specimens in group 1 were shaped with ProFile #20/.06 at the WL. Specimens in group 2 were shaped with Mtwo #35/.04 at the WL. Specimens in group 3 were shaped with WaveOne Primary reciprocating files at the WL after the glide path was achieved with PathFile. Pre- and postinstrumentation digital images were superimposed and processed with Matlab r2010b(The MathWorks Inc, Natick, MA) software to analyze the curvature-radius ratio(CRr), representing canal curvature modification. Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file were analyzed with 1-way ANOVA(P<.05). Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file system were analyzed with independent t-test(P<.05). A statistically significant difference(P<0.05) was noted on each Ni-Ti file. ProFile and WaveOne instrumentations maintained the original canal curvature significantly better(P<0.05) than Mtwo file. There were no significant difference(P>0.05) between continuous rotary system and single file system. Under the conditions of this study, ProFile and WaveOne instruments maintained the original curvature significantly better than Mtwo file and were less modification of the canal curvature compared. There was no significant difference between continuous rotary system and single file system in shaping of simulated canals. As clinical practitioners, it may be advantages to use hybrid approach when root canal shapes depending on the design and usage of Ni-Ti files.