• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.288-293
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• 2023

To optimize the process parameters of laser powder bed fusion process to fabricate the high density STS316L alloy, the effect of laser power, scanning speed and hatching distance on the relative density was studied. Tensile properties of additively manufactured STS316L alloy using optimized parameters was also evaluated according to the build direction. As a result of additive manufacturing process under the energy density of 55.6 J/mm³, 83.3 J/mm³ and 111.1 J/mm³, high density STS316L specimens was suitably fabricated when the energy density, power and scan speed were 83.3 J/mm³, 225 W and 1000 mm/s, respectively. The yield strength, ultimate tensile strength, and elongation of STS316L specimens in direction perpendicular to the build direction, show the most competitive values. Anisotropic shape of the pores and the lack of fusion defects probably caused strain localization which result in deterioration of tensile properties.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.302-309
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• 2023

In general, castings often have complex shapes and significant variations in thickness within a single product, making grid generation for simulations challenging. Casting flows involve multiphase flows, requiring the tracking of the boundary between air and molten metal. Additionally, considerable time is spent calculating pressure fields due to density differences in a numerical analysis. For these reasons, the Cartesian grid system has traditionally been used in mold filling simulations. However, orthogonal grids fail to represent shapes accurately, leading to a momentum loss caused by the stair-like grid patterns on curved and sloped surfaces. This can alter the flow of molten metals and result in incorrect casting process designs. To address this issue, simulations in the Cartesian grid system involve creating a large number of grids to represent shapes more accurately. Alternatively, the Cut Cell method can be applied to address the problems arising from the Cartesian grid system. In this study, analysis results based on the number of grid in the Cartesian grid system for a casting flow analysis were compared with results obtained using the Cut Cell method. Casting flow simulations of actual products during various casting processes were also conducted, and these results were analyzed with and without applying the Cut Cell method.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.4
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• pp.145-160
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• 2023

The purpose of this study was to compare and analyze diurnal thermal environments using Unmanned Aerial Vehicles(UAV)-derived physical parameters(NDVI, SVF) and ENVI-met modeling. The research findings revealed significant correlations, with a significance level of 1%, between UAV-derived NDVI, SVF, and thermal environment elements such as S↑, S↓, L↓, L↑, Land Surface Temperature(LST), and Tmrt. In particular, NDVI showed a strong negative correlation with S↑, reaching a minimum of -0.52^** at 12:00, and exhibited a positive correlation of 0.53^** or higher with L↓ at all times. A significant negative correlation of -0.61^** with LST was observed at 13:00, suggesting the high relevance of NDVI to long-wavelength radiation. Regarding SVF, the results showed a strong relationship with long-wave radiative flux, depending on the SVF range. These research findings offer an integrated approach to evaluating thermal comfort and microclimates in urban areas. Furthermore, they can be applied to understand the impact of urban design and landscape characteristics on pedestrian thermal comfort.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.1
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• pp.63-77
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• 2022

The importance of start-ups and venture companies in the Korean economy is growing. However, the successful growth of startups and venture companies are still challenging as 70% of startups fail within 5 years. A new perspective on innovation is essential to overcome the liability of newness and the liability of smallness in the existing market and obtain the competitive advantage. Recent phenomenon in the Korean startups ecosystem is the remarkable growth of unicorns and future unicorns. Their business models, types of business, and success cases serve as a good example. Neverthless, the process of unicorn and future unicorn startups making new industries and innovative business has poorly understood. In this paper, we first define 175 unicorns and future unicorn startups participating in the K-unicorn project as a unicorn group and analyze current trends of the group. Then the in-depth analyses of industry sectors are conducted. Specifically, focusing on the unicorn forming the new market, we examine the unicorn making the processes of industry category innovation through the business innovation model. Lastly, broadening the scope of the analysis to the unicorn group, policy implications in startups and venture ecosystem are suggested.

• Journal of Korean Society of Rural Planning
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• v.30 no.1
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• pp.33-42
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• 2024

The purpose of this study is to investigate the possible relationship between population migration and population inequality in rural areas. This study conducted a case study on the eup·myeon(rural)areas in Chungcheongbuk-do. First, the population migration was divided into four patterns, and the characteristics of population migration in rural areas were analyzed based on the net migration. The analysis results showed that there was serious migration between rural areas, and the population in rural areas mainly moved out to urban areas within the province, but the urban population outside the province moved out to rural areas. The main areas of population inflows included areas such as Deoksan-eup, Jincheon-gun, Osong-eup and Ochang-eup, Cheongju-si. Second, the Theil index was used to quantitatively analyze the level of population inequality between rural areas. The Theil index of the population aged 0~14 increased from 0.38 to 0.53, that of population aged 15-64 increased from 0.22 to 0.30, and that of population aged over 65 increased from 0.07 to 0.09, indicating an increase in population inequality. Finally, due to the continued large-scale inflows of population into Osong-eup and Ochang-eup, the Theil index of total population in Cheongju-si increased from 0.13 in 2009 to 0.23 in 2020, which meant that the level of population inequality had increased. Similarly, due to the continued large population inflows into Deoksan-eup, the Theil index of total population in Jincheon-gun increased from 0.14 in 2009 to 0.18 in 2020, which meant that the level of population inequality had increased. In conclusion, large-scale population inflows into specific areas will lead to an increase in the level of population inequality.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.1-9
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• 2024

This study proposes a multi-scale template matching technique with image pyramids (TMI) to measure structural dynamic displacement using a vision sensor under atmospheric turbulence conditions and evaluates its displacement measurement performance. To evaluate displacement measurement performance according to distance, the three-story shear structure was designed, and an FHD camera was prepared to measure structural response. The initial measurement distance was set at 10m, and increased with an increment of 10m up to 40m. The atmospheric disturbance was generated using a heating plate under indoor illuminance condition, and the image was distorted by the optical turbulence. Through preliminary experiments, the feasibility of displacement measurement of the feature point-based displacement measurement method and the proposed method during atmospheric disturbances were compared and verified, and the verification results showed a low measurement error rate of the proposed method. As a result of evaluating displacement measurement performance in an atmospheric disturbance environment, there was no significant difference in displacement measurement performance for TMI using an artificial target depending on the presence or absence of atmospheric disturbance. However, when natural targets were used, RMSE increased significantly at shooting distances of 20 m or more, showing the operating limitations of the proposed technique. This indicates that the resolution of the natural target decreases as the shooting distance increases, and image distortion due to atmospheric disturbance causes errors in template image estimation, resulting in a high displacement measurement error.

• Journal of Korean Society of Forest Science
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• v.113 no.2
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• pp.259-270
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• 2024

Since 2013, Korea has allocated significant budgets and manpower nationwide to prevent the spread of pine wilt disease and to reduce damage. As a result, the number of damaged trees decreased from 2.18 million in 2014 to 310,000 in 2021. However, the damage has increased again since then. Despite the overall decrease in the number of damaged trees, the scope of the damage continues to expand every year. Previous studies have develope In order to judge the control performance, a quantitative control performance analysis method to objectively evaluate control performance. This method takes into consideration two factors-quantity change and the change in the damage area, which is an area factor. This approach provides a more comprehensive assessment than the control guidelines that only suggest changes in damage grade based on the volume of damaged trees. The expansion of the damage range is also an important factor in analyzing control performance, but previous studies have not reflected this. Therefore, this study calculates the change in the distance of the pine wilt disease boundary area for Gyeongsangbuk-do, where changes in the damage range can easily be observed from year to year. The study then creates application criteria and coefficients and uses them to improves control performance index calculation formula. As a result, it was possible to calculate a quantitative analysis of the control performance, taking into account the changes in the damage range. When the improved formula was applied to 26 cities, counties, and districts in Gyeongsangbuk-do, it slightly decreased or increased compared to the existing calculation formula. This confirmed that the control performance index can change from a positive value (+), indicating increased damage, to a negative value (-), indicating reduced damage.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.74-82
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• 2024

In this study, feature point detection and displacement measurement performance depending on feature extraction algorithms were compared and analyzed according to environmental changes and target types in the feature point-based displacement measurement algorithm. A three-story frame structure was designed for performance evaluation, and the displacement response of the structure was digitized into FHD (1920×1080) resolution. For performance analysis, the initial measurement distance was set to 10m, and increased up to 40m with an increment of 10m. During the experiments, illuminance was fixed to 450lux or 120lux. The artificial and natural targets mounted on the structure were set as regions of interest and used for feature point detection. Various feature detection algorithms were implemented for performance comparisons. As a result of the feature point detection performance analysis, the Shi-Tomasi corner and KAZE algorithm were found that they were robust to the target type, illuminance change, and increase in measurement distance. The displacement measurement accuracy using those two algorithms was also the highest. However, when using natural targets, the displacement measurement accuracy is lower than that of artificial targets. This indicated the limitation in extracting feature points as the resolution of the natural target decreased as the measurement distance increased.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.90-101
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• 2009

Analysis of multi-channel seismic reflection data from the Southern Ulleung Basin reveals that Plio-Quaternary section in the area consists of nine stacked sedimentary units separated by erosional unconformities. On the southern slope, these sedimentary units are acoustically characterized by chaotic seismic facies without distinct internal reflections, interpreted as debris-flow bodies. Toward the basin floor, the sedimentary units are defined by well-stratified facies with good continuity and strong amplitude, interpreted as turbidite/hemipelagic sediments. The seismic facies distribution suggests that deposition of Plio-Quaternary section in the area was controlled mainly by tectonic movement and sea-level fluctuations. During the Pliocene, sedimentation was mainly controlled by tectonic movements related to the back-arc closure of the East Sea. The back-arc closure that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted crustal blocks, were supplied to the basin, depositing Unit 1 which consists of debris-flow deposits. During the Quaternary, sea-level fluctuations resulted in stacked sedimentary units (2-9) consisting of debris-flow deposits, formed during sea-level fall and lowstands, and thin hemipelagic/turbidite sediments, deposited during sea-level rise and highstands.

• Sim-seong Yeon-gu
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• v.30 no.1
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• pp.1-30
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• 2015

The Red Book contains C.G. Jung's insightful comment on life suggesting the thoughts of the Eastern philosophers, particularly that of Lao Zi. The author reviewed Jung's commentaries in the Red Book in comparison with Lao Zi Dao De Jing. Jung's comments on the image of despised Surpreme Being, on the Simplicity, the attitudes of 'the Spirit of the Depth' toward intellectual knowledges and speech, toward the small and the mockered one resemble to what Lao Zi spoke on Dao in his Dao De Jing. The 'good and evil' are regarded by both C.G. Jung and Lao Zi as two poles in one total psyche. The favorite words of Lao Zi : 'emptiness' or 'empty' are frequently mentioned in the Red Book. The investigation in this concern revealed that C.G. Jung, contrary to Lao Zi has applied the word 'emptiness' mostly as the opposite to the fullness. C.G. Jung's way of encountering with the darkest side of soul in the Hell and his bold confrontation to the authoritative person such as Philemon, above all, the intensity of his experiences in the state of the utmost tension between the opposites are extraordinarily impressive and somehow strange when regarded from traditional eastern way of behavior such as I-You relationship and the patterns of emotional life based on Confucian tradition. Confucius never talked about the prodigies, feasts of strength and disorders or spirits. Lao Zi never mentioned infernal cruelty. Noteworthy is however, both have enough experienced the cruelty of life and conflicts in the reality and what they spoke was not a process in search for solution but the final proposals for the solution of human agony. C.G. Jung was, like great shaman in central and East-Asia forced to go through inferno in his unique way and from these experiences obtained the insight which resembles not only to Lao Zi but also to wisdoms from the western philosophies and also from the Christianity.