• 한국의류산업학회지
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• 제25권2호
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• pp.139-152
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• 2023

Despite efforts to apply 3D print (3DP) technology in the field of fashion and endless discussions about the possibility of future development, in reality, it is difficult to utilize 3DP technology in fashion for reasons related to material, technology, and cost constraints. The purpose of this study was to supplement the limitations of 3DP technology in order to promote its utilization in fashion and simultaneously find a solution to achieve aesthetic satisfaction in the design method. Specifically, through the development of fashion products with a 3DP polymer-fabric structure to which the parametric design methodology has been applied, this study explored the possibility of practical application and proposes a new 3DP fashion design method. The 3DP polymer-fabric developed as a result of the research was stably adhered to the fabric. Additionally, the study confirmed the possibility of making 3DP clothes that are amenable to the wearer's activities, as it was verified that cutting and sewing tailored to the human body's curvature and structure can be performed. The design process using the 3DP polymer-fabric presented in this study is meaningful in that it suggests a solution to complement the limitations of modern technology in connection with designers' creativity. Moreover, the design process presented in this study is expected to contribute to the commercialization and generalization of 3DP by providing practical help to allow fashion experts to utilize 3DP technology.

• Composites Research
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• 제22권6호
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• pp.39-44
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• 2009

가속노화장치를 이용하여 노출시간에 따른 탄소섬유/에폭시 복합재 링 시편의 노화 특성을 평가하였다. 온도, 수분, 자외선 등의 복합적인 노출조건은 최대 3000시간까지 적용하였다. 노출시간에 따른 링 시편의 인장특성과 곡률의 영향이 고려된 굽힘특성은 하중시험장치를 이용하여 평가하였으며 노화표면은 전자현미경을 통해 관찰하였다. 연구결과에 따르면 인장강성은 환경인자의 노출시간에 큰 영향을 받지 않지만 인장강도는 노출 초기에 물리시효 현상과 경화 반응으로 다소 증가하지만 노출시간이 길어지면 열화 영향으로 감소하였다. 굽힘탄성계수와 굽힘강도는 노출초기에 다소 증가하지만 노출시간이 길어지면 감소하는 양상을 나타내었다. 또한 전자현미경을 통해 관찰된 노화표면은 환경인자의 노출시간에 따라 달라지기 때문에 환경인자의 노출시간에 따른 기계적 특성의 변화를 규명하기 위한 정보를 제공해 준다.

• 한국재료학회지
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• 제33권5호
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• pp.205-213
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• 2023

This paper reports the results of an experimental examination using X-rays to test annealing materials for lapped bearing steel (STB2), to confirm the validity of the weighted averaging analysis method. The distribution behavior for the α_𝜓-sin²𝜓 diagram and the presence or absence of differences in the peak method, half-value breadth method, and centroid method were investigated. When lapping the annealed bearing steel (STB2) material, a residual stress state with a non-directional steep gradient appeared in the surface layer, and it was found that the weighted averaging analysis method was effective. If there is a steep stress gradient, the sin²𝜓 diagram is curved and the diffraction intensity distribution curve becomes asymmetric, resulting in a difference between the peak method, half-value breadth method, and centroid method. This phenomenon was evident when the stress gradient was more than 2~3 kg/mm²/㎛. In this case, if the position of the diffraction line is determined using the centroid method and the weighted averaging analysis method is applied, the stress value on the surface and the stress gradient under the surface can be obtained more accurately. When the stress gradient becomes a problem, since the curvature of the sin²𝜓 diagram appears clearly in the region of sin²𝜓 > 0.5, it is necessary to increase the inclination angle 𝜓 as much as possible. In the case of a lapping layer, a more accurate value can be obtained by considering 𝜎₃ in the weighted averaging analysis method. In an isotropic biaxial residual stress state, the presence or absence of 𝜎₃ can be determined as the presence or absence of strain for sin²𝜓≈0.4.

• 대한토목학회논문집
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• 제29권2A호
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• pp.145-153
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• 2009

본 연구에서는 포물선 아치의 횡-비틂 좌굴 강도에 관한 연구를 수행하였다. 포물선 아치는 아치의 중립축을 따라 곡률이 변하므로 일정한 곡률을 갖는 원형 아치의 경우보다 횡-비틂 좌굴 강도식을 유도하는 것이 복잡하며, 이에 대한 연구가 미흡한 실정이다. 본 연구에서는 ?의 효과를 고려하여 변곡률을 갖는 아치의 횡-비틂 좌굴식을 유도하고 포물선 아치의 좌굴강도를 계산하기 위하여 유한차분법을 이용한 수치해법을 제안하였다. 이러한 수치해법은 기존 연구자 및 유한요소해석 결과와 비교하였으며, 그 타당성을 검증하였다. 마지막으로, 변수해석을 수행하여 라이즈비의 영향에 따른 원형과 포물선 아치의 횡-비틂 좌굴 강도를 비교 분석하였다.

• 대한수학회보
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• 제60권4호
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• pp.905-913
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• 2023

Suppose that M is a strictly convex hypersurface in the (n + 1)-dimensional Euclidean space 𝔼ⁿ⁺¹ with the origin o in its convex side and with the outward unit normal N. For a fixed point p ∈ M and a positive constant t, we put 𝚽_t the hyperplane parallel to the tangent hyperplane 𝚽 at p and passing through the point q = p - tN(p). We consider the region cut from M by the parallel hyperplane 𝚽_t, and denote by I_p(t) the (n + 1)-dimensional volume of the convex hull of the region and the origin o. Then Schneider's characterization theorem for ellipsoids states that among centrally symmetric, strictly convex and closed surfaces in the 3-dimensional Euclidean space 𝔼³, the ellipsoids are the only ones satisfying I_p(t) = 𝜙(p)t, where 𝜙 is a function defined on M. Recently, the characterization theorem was extended to centrally symmetric, strictly convex and closed hypersurfaces in 𝔼ⁿ⁺¹ satisfying for a constant 𝛽, I_p(t) = 𝜙(p)t^𝛽. In this paper, we study the volume I_p(t) of a strictly convex and complete hypersurface in 𝔼ⁿ⁺¹ with the origin o in its convex side. As a result, first of all we extend the characterization theorem to strictly convex and closed (not necessarily centrally symmetric) hypersurfaces in 𝔼ⁿ⁺¹ satisfying I_p(t) = 𝜙(p)t^𝛽. After that we generalize the characterization theorem to strictly convex and complete (not necessarily closed) hypersurfaces in 𝔼ⁿ⁺¹ satisfying I_p(t) = 𝜙(p)t^𝛽.

• 소성∙가공
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• 제31권3호
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• pp.129-135
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• 2022

The purpose of this study was to quantitatively evaluate the influence of hardness of tool materials on wear resistance in the sheet metal forming process. Punches used in the wear test were made of STD-11 and K340 tool material, and the tempering temperature was set to 530℃ and 500℃, respectively, to control the hardness of the tool materials. The punches mimic the shape of stamping tool of automotive body component to reflect its plastic deformation, and are designed to concentrate wear on the curvature region of punches. Progressive die and coil sheet were used to save time, cost, and raw sheet materials. By quantitatively measuring the wear depth of the punches, the wear behavior and mechanism of the punches were investigated, and characteristics of hardness and wear resistance according to tool materials and tempering temperatures were evaluated. Testing results indicate that the punch made of K340 tool steel with higher hardness had better wear resistance than that of STD-11 tool steel, and the hardness and wear resistance of tool steel were significantly impacted by the tempering temperature.

• 대한토목학회논문집
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• 제26권1A호
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• pp.155-162
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• 2006

본 연구에서는 납면진받침(LRB)이 설치된 중경간 엑스트라도즈드교에서 교각의 파손, 상부구조의 이동변위, 그리고 케이블의 항복에 대한 지진위험도를 평가하였다. 지진위험도는 다수의 지진자료를 이용하여 지진에 대한 구조적 취약성을 평가한 지진취약도와 지진재해지도를 이용하여 해당지역에서의 지진재해도를 산정하여, 이들을 조합함으로써 평가할 수 있었다. 지진시 교각에서 소성힌지의 발생을 고려하기 위해 SAP2000을 사용하여 비선형 지진해석을 수행하였다. 지진자료는 암반노두에서 설계응답스펙트럼을 만족하는 인공지진을 작성한 후, SHAKE91을 사용하여 해당지역의 지반증폭효과를 고려하여 지진 가속도 시간이력을 구하여 사용하였다. 교각의 비선형 응답은 연성도를 사용하여 나타내었고, 2선형 직선의 모멘트-곡률 곡선으로 작성하였다. 본 연구에서는 대수정규분포함수로 지진취약도를 표현하였으며, 한반도를 대상으로 작성된 지진재해지도를 이용하여 지진재해도를 산정하였다. 해석결과 엑스트라도즈드교에서는 케이블과 거더보다는 교각하단에서 면진장치가 더 효과적인 것을 알 수 있었다.

• 한국터널지하공간학회 논문집
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• 제12권6호
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• pp.451-461
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• 2010

장기 부식 등 일반적인 건설재료의 문제점을 보완할 수 있는 대체재료로서, 섬유강화 복합재료의 활용이 증대되고 있다. 하지만 일반적으로 선형의 섬유강화 복합재료를 아치형인 터널구조물의 부재로서 활용하는 데는 많은 문제점이 대두된다. 따라서, 본 연구에서는 섬유강화 복합부재를 일정곡률로 인발성형 할 수 있는 신개념의 곡면 FRP 부재 성형장비를 개발하고 시제품을 생산하였으며, 시제품에 대한 물리적 특성 시험을 수행하였다. 이어, 곡면 FRP 시제품과 합체되어 제작된 콘크리트 복합부재에 대한 수치해석 검토 및 분석을 통하여 시제품의 터널 구조체로써의 적용성을 평가하였다. 수치해석적 적용성 검토 결과, 곡면 FRP 부재를 터널 구조물로 적용함에 있어서 터널 안정성을 충분히 확보할 수 있는 것으로 파악되었다.

• 한국지형학회지
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• 제27권3호
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• pp.87-103
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• 2020

The purpose of this study is to evaluate the risk of cropland and man-made infrastructures in a landslide-prone area using a GIS-based method. To achieve this goal, a landslide inventory map was prepared based on aerial photograph analysis as well as field observations. A total of 550 landslides have been counted in the entire study area. For model analysis and validation, extracted landslides were randomly selected and divided into two groups. The landslide causative factors such as slope, aspect, curvature, topographic wetness index, elevation, forest type, forest crown density, geology, land-use, soil drainage, and soil texture were used in the analysis. Moreover, to identify the correlation between landslides and causative factors, pixels were divided into several classes and frequency ratio was also extracted. A landslide susceptibility map was constructed using a bayesian predictive model (BPM) based on the entire events. In the cross validation process, the landslide susceptibility map as well as observation data were plotted with a receiver operating characteristic (ROC) curve then the area under the curve (AUC) was calculated and tried to extract a success rate curve. The results showed that, the BPM produced 85.8% accuracy. We believed that the model was acceptable for the landslide susceptibility analysis of the study area. In addition, for risk assessment, monetary value (local) and vulnerability scale were added for each social thematic data layers, which were then converted into US dollar considering landslide occurrence time. Moreover, the total number of the study area pixels and predictive landslide affected pixels were considered for making a probability table. Matching with the affected number, 5,000 landslide pixels were assumed to run for final calculation. Based on the result, cropland showed the estimated total risk as US $ 35.4 million and man-made infrastructure risk amounted to US $ 39.3 million.

• 한국지형학회지
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• 제26권3호
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• pp.53-67
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• 2019

The purpose of this study is to identify the quality of landslide susceptibility in a landslide-prone area (Jinbu-myeon, Gangwon-do, South Korea) by spatial prediction modeling approach and compare the results obtained. For this goal, a landslide inventory map was prepared mainly based on past historical information and aerial photographs analysis (Daum Map, 2008), as well as some field observation. Altogether, 550 landslides were counted at the whole study area. Among them, 182 landslides are debris flow and each group of landslides was constructed in the inventory map separately. Then, the landslide inventory was randomly selected through Excel; 50% landslide was used for model analysis and the remaining 50% was used for validation purpose. Total 12 contributing factors, such as slope, aspect, curvature, topographic wetness index (TWI), elevation, forest type, forest timber diameter, forest crown density, geology, landuse, soil depth, and soil drainage were used in the analysis. Moreover, to find out the co-relation between landslide causative factors and incidents landslide, pixels were divided into several classes and frequency ratio for individual class was extracted. Eventually, six landslide susceptibility maps were constructed using the Bayesian Predictive Discriminant (BPD), Empirical Likelihood Ratio (ELR), and Linear Regression Method (LRM) models based on different category dada. Finally, in the cross validation process, landslide susceptibility map was plotted with a receiver operating characteristic (ROC) curve and calculated the area under the curve (AUC) and tried to extract success rate curve. The result showed that Bayesian, likelihood and linear models were of 85.52%, 85.23%, and 83.49% accuracy respectively for total data. Subsequently, in the category of debris flow landslide, results are little better compare with total data and its contained 86.33%, 85.53% and 84.17% accuracy. It means all three models were reasonable methods for landslide susceptibility analysis. The models have proved to produce reliable predictions for regional spatial planning or land-use planning.