• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.57-67
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• 2007

Many researches have recently discussed about the film thickness as a good substitute or supplement for VMA or other volumetric criteria in the design procedure. Some researchers have not only proposed the specific number for the recommended film thickness, but also introduced the new calculation procedures or concepts. Each model (index model and the virtual model) has its own advantages and disadvantages in terms of the ability to account for the volumetric properties of the mixture. In this paper, the modified virtual model was proposed to combine advantages from both models. However, it cannot be disregarded the way to determine the appropriate particle shape factors for different sources and sizes of aggregates. In order to evaluate the different calculation methods, mixtures with two aggregate sources and eight gradations were designed based on the dominant aggregate size range (DASR) porosity concept. Superpave indirect tensile test (IDT) and asphalt pavement analyzer (AEA) test were used to describe the performance of mixtures. Test results indicated that the virtual model, which is the same to the modified virtual model for sphere 1:1 case, is better than the conventional standard model to define the range of the film thickness to have better performance of asphalt mixtures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.293-308
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• 2012

The shear behavior at the particle/surface interface such as rock joint can determine the mechanical behavior of whole structure. Therefore, a fundamental understanding of the mechanisms governing its behavior and accurately estimation of the interface strength is essential. In this paper, PFC, a numerical analysis program of discrete element method was used to investigate the effects of the surface roughness on interface strength. The surface roughness was characterized by smooth, intermediate, and rough surface, respectively. In order to investigate the effects of particle shape and crushing on particle/surface interface behavior, one ball, clump, and cluster models were created and their results were compared. The shape of particle was characterized by circle, triangle, square, and rectangle, respectively. The results showed that as the surface roughness increases, interface strength and friction angle increase and the void ratio increases. The one ball model with smooth surface shows lower interface strength and friction angle than the clump model with irregular surface. In addition, a cluster model has less interface strength and friction angle than the clump model. The failure envelope of the cluster model shows non-linear characteristic. From these findings, it is verified that the surface roughness and particle shape effect on the particle/surface interface shear behavior.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.45-51
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• 2012

The calcium hydroxide$(Ca(OH)_2)$ which is the cement hydrate flowed into the tunnel by groundwater is reacted with microorganism in the soil, carbon dioxide$(CO_2)$ and the vehicle's exhaust gas$(SO_3)$. So its by-products are precipitated at the drainage pipe and these cause the drainage clogging. By this phenomenon, Degradation of water flow at the drainage system of the tunnel occurred and also pore water pressure is increased. Hence the acceleration of seepage and degradation of lining is occurred. The purpose of this study is to evaluate the field applicability of the Quantum Stick and Magnetic treatment in prevention of scale deposits at the Namsan ${\bigcirc}{\bigcirc}$ tunnel and the Zone ${\bigcirc}{\bigcirc}{\bigcirc}$ of subway. These technologies were installed into drainpipes with their performance monitored through occasional site visits. SEM and XRD were also performed on scale collected from these drainpipes. As a result, in case which factor technology is applied, scale creation is remarkably decreased and especially Quantum Stick treatment performing better than Magnetic treatment. Therefore, additional application of Quantum Stick or Magnetic treatment to the existing drainage is expected to decrease the drainage clogging of the drainage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1027-1033
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• 2011

A VCM sheet is a metal sheet on which PET/PVC is coated for outer panels of home appliances. The purpose of this study is to obtain methods for suppressing PET tearing that occurs during the press forming of the VCM sheet. In order to identity the factors that minimize PET tearing, an FE analysis was performed. The occurrence of PET tearing cannot be predicted using the conventional forming limit diagram. PET is torn by friction between a die and sheet, which is caused by the thickening of material at a die corner. To reduce the thickening of material, the blank shape was re-designed and the thickened material at a flange was removed by a trimming process. The results of the FE-analysis involving modified process parameters showed that the thickness of the product at a die corner is distributed within the clearance of drawing and flangeforming process. A forming experiment was conducted to verify the proposed process parameters. A good final product was obtained without PET tearing of the VCM sheet.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1991.06a
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• pp.37-44
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• 1991

영산강 하구언 방조제의 건설로 인한 항만 및 이의 인접해역 해면의 변화는 예상한 바 있으며 실제 여러개소에서 월 2회정도의 주기로 목포 구항부근 상업지역에서 해면상승에 따라 주기적으로 침수되는 현상이 나타나고 있다 목포항의 영산강 하구언 방조제 조성으로 인한 조류성분중 최고기록을 가진 수로에서는 6kts 정도로 감소된 것으로 보고되고 있으나 주위자연환경 변화에 따른 수면 상승 및 해수면의 주기적인 변화 등에 대한 상세한 언급 및 깊이 있는 분석은 회피되어왔다. 수자원의 효율적관리를 위해 하구언 방조제는 이미 건설되었고 앞으로 대규모의 항만개발과 대불산업단지조성을 위해 추가 3개의 만입해안해역에 댐으로 해역을 막아 매립공사를 추진하고 있다 그러나 이 지역에 대한 분석은 타당성의 여부만을 강조한 상업적 용역이 이루어지고 있고 장래 개발에 대해 학술적이고 실질적인 문제점 추출과 해결방아네 대해서는 무시하거나 경시한 바가 많다 더구나 태풍 저기압 등과 같은 자연재해를 고려한 분석은 시도되지 못하고 있다 따라서 개발전후의 현상에 대한 상세한 자료 및 현장 조사와 극한 상태를 고려하여 개발에 따른 수위상승 부진동, 조류 수질등 이해역의 변화요소를 수집하고 분석하며 과학적 접근방법에 기초를 둔 수치모델의 실험을 포함하여 현장관측 및 측정자료를 검증하는 것이 필수적이라고 사료되어 종합분석의 한단계로 여기서는 하구언 및 하구간척(Land Reclamatic of Estuary barren)으로 해역축소에 따른 해면변화의 실제현상을 조사하여 정리하고 이를 수치모델을 통해 시뮬레이션하여 보았다 이는 종합개발의 좋은 기초자료로 이용됨은 물론이로 이지역의 개발에 기여할 것으로본다.적절하게 가정된 지반의 응력-변형률 관계와 간극수압특성에 의하여 고려되었다. 그 결과 응력 및 변위가 심하게 발생하는 지역은 황색 점토층이었으며 이로부터 황색 점토층에서 부터 파괴면이 생성되어 다른 지역으로 전파되었음을 유추할 수 있었다.form trap with 2.88[eV] deep of injected space charge from the chathode in the crystaline regions. The origin of ${\alpha}$$_2$ peak was regarded as the detrapping process of ions trapped with 0.9[eV] deep originated from impurity-ion remained in the specimen during production process of the material, in the crystalline regions. The origin of ${\beta}$ peak was concluded to be due to the depolarization process of "C=0"dipole with the activation energy of 0.75[eV] in the amorphous regions. The origin of ${\gamma}$ peak was responsible to the process combined with the depolarization of "CH$_3$", chain segment, with the activation energy of ca

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.593-601
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• 2021

The axial fan is an element of a blower used for ventilation in various industrial fields. Many studies on aerodynamic performance have been conducted to assess axial fans using fluid dynamics. The subject was a large axial fan size, 1800 mm in diameter with 100 horsepower. The blower's axial fan consisted of blades, hubs, hub caps, and bosses are important components. The blade design has a great influence on the aerodynamic performance. 3D point data is extracted using an aerodynamic performance prediction program, and a 3D modeling shape is generated. The blades and hubs, which are important components, can be easily modified if processed by cutting owing to the environment in which blades and hubs are manufactured through die casting or gravity casting. In this study, the structural safety of components and the analysis results of weak areas at the rated operating speed of the axial fan were verified using the maximum stress and safety factor. The tip clearance reflected in the design was the rotation of the blade. To check whether there is interference with other components, the displacement result was derived to verify the structural safety of the axial fan.

• Trans-
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• v.13
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• pp.35-58
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• 2022

This study predicts the paradigm shift that the development of artificial intelligence technology will bring to the production of music content, and suggests that works created through collaboration between artificial intelligence and humans can have artistic value as finished products. Anyone can easily produce music content using artificial intelligence composition programs, and it has become an opportunity to inspire artists with various attempts and creative ideas. Although artificial intelligence technology provides convenience in human life and benefits a lot in the efficient aspect of work, it is difficult to escape the perception of data-based pattern music in the art field so far. Pattern music with many quantitative elements is not recognized as a complete creation due to the absence of abstract symbolism or meaning pursued by art. However, it predicts that if qualitative elements such as emotions and creativity are given to artificial intelligence music through human collaboration, it can be recognized as a complete work of art. The development of artificial intelligence technology increases access to culture and art from the public, and it can be expected that anyone can enjoy it as well as aesthetic experiences. In addition, various contents can be produced by improving individual digital literacy, and it is an opportunity to share and communicate with others. As such, artificial intelligence technology serves as a medium connecting the public with culture and art, and is narrowing the gap between humans and technology through art activities. Along with this cultural phenomenon, we predict the possibility of research on the production of artificial intelligence music contents with artistic value and the development of various convergence and complex art contents using artificial intelligence technology in the future.

• Analyses & Alternatives
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• v.7 no.3
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• pp.85-114
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• 2023

The purpose of this study is to analyze Russia-Central Asia relations since the launch of the EAEU in 2015 and forecast the future from a structural realism perspective. Bilateral relations have both elements of close cooperation and elements of conflict. Russia and Central Asia, which have the characteristics of an authoritarian alliance, also have a symbiotic relationship in which they have no choice but to cooperate with each other to maintain the regime. Based on this, Russia has made various efforts to reunify Central Asia. Central Asia also has no choice but to cooperate with Russia for its survival, but at the same time, it has expanded its scope of cooperation in the international community to avoid being subjugated to Russia again. However, as China's power expands, Russia's relative weakness, and wariness toward Russia increases after the Ukraine War, the gap in bilateral relations is widening. In particular, as China's influence grows, Russia's nervousness also increases. This is why Putin visits Central Asia and holds active summit talks even during the war in Ukraine. If competition between Russia and China surfaces, there is a high possibility that the international order in Central Asia will become unstable. However, it is still unlikely that the power of Russia and China will reverse in Central Asia. Above all, the security, historical, and cultural connections between Russia and Central Asia are areas that are difficult for China to catch up with. Therefore, a weakening of Russia's influence compared to the past is inevitable, but its superiority is expected to continue. If Russia breaks away from belligerence and transforms into an attractive cooperative partner, there is a possibility that bilateral relations will take an upward turn again. However, it seems unlikely that such changes and innovations will occur under the Putin regime. Therefore, the biggest obstacle to realizing Putin's goal of reunifying Central Asia is Putin himself.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.31-43
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• 2022

Startups are recognized as the vitality of the economy, and countries are competing to attract competitive overseas entrepreneurs and startups to their own startup ecosystem. In this global trend, entrepreneurs cross the border without hesitation, expecting abundant available resources and a startup friendly environment. Despite the increasing frequency of start-up migration between countries, studies related to this are very rare. Therefore, this study has chosen the cross-border migration of startups between countries as a research topic, and those who have been involved in the cross-border entrepreneurial migration to South Korea as a research sample. This study consists of two stages. The first research stage hires a Delphi method to collect expert opinions and find major factors related to the global startup migration. Drawing on the prior literature on the regional startup ecosystem at the national level, this stage is to conduct expert interviews in order to discover underlying factors and subfactors important for global migration of startups. The second stage measures the importance of the factors and subfactors using the AHP model. The priorities of factors and factors were identified hiring the overseas entrepreneurs who moved to Korea as the AHP survey samples. The results of this study suggest some interesting implications. First, a group of entrepreneurs with nomadic tendencies was found in the trend of global migration of entrepreneurs. They had already started their own businesses with the same business ideas in multiple countries before settling down in Korea. Second, important unique factors and subfactors in the context of global start-up migration were identified. A good example is the government's support package, including start-up visas. Third, it was possible to know the priority of the factors and subfactors that influence the global migration of startups This study is meaningful in that it preemptively conducted exploratory research focusing on a relatively new phenomenon of global startup migration, which recently catches attention in the global startup ecosystem. At the same time, it has a limitation in that it is difficult to generalize the meanings found in this study because the research was conducted based on the case of South Korea

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.2
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• pp.55-64
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• 1988

Stow nets have widely been used in the western sea of Korea from the olden age. The original structure of a stow net is a large square-sectional bag net made of 4 netting panels, and the front fringes of top and bottom panels are connected to the top and bottom beams respectively. Wire ropes, which is originated from the holding anchor are gradually forked and biforked, and finally 4 pieces of wire rope (biforked pendants) are jointed to each beam. Much convenience caused by long and heavy beams were problemed, then some studies have been carried out to improve the net since 1930's. The most effective improvement were achieved in 1980 by Mr. Han and his colleagues. The key point of improvement was that the beams were removed and the belt shaped shearing device made by canvas was attached to the side panels, the head rope and ground rope to the front fringe of top and bottom panel, and biforked pendants are joined to the shearing device. Even though this is the epoch-making improvement of a stow net, the further study should be required to find out more effective method. The authors carried out a model experiment on the stow net to determine the vertical and horizontal opening of a net mouth, and also examine the front, top and side-view configuration of the net. The model net was constructed depending on the Similarity Law of Fishing Gear in 1/10 and 1/20 scale and set against to the current at shallow and speedy flowing channel. The vertical and horizontal openings were determined by using scaled bamboo poles, and the configuration was observed by using specially prepared observation platform and underwater observation glass, and also photographed by using specially prepared underwater photographic equipment. The results obtained can be summarized as follows: 1. The opening height and width of the shearing device varied in accordance with the relative length of the biforked pendants. Considering the height and width of shearing device in 6 cases of the arrangement system of biforked pendants, the best result was obtained in the case that the 2nd, 3rd and 4th pendents from the bottom-most was 5%, 9% and 4% longer than that. 2. On the top-view configuration the excessive deformation of head rope and ground rope were observed. In the actual net, 54m long head rope and ground rope were attached to the front fringe of top and bottom panels so that the head rope may be lifted to make the net mouth open highly. But actually the head rope and the ground rope are streamed backward without any lift, and also the netting followed the ropes were deformed until the 2/5 in the whole length of the net. This deformation may be guessed to disturb the entrance of fish school into the net and also caused the net to get caught by obstacles in the sea bed and to be broken largely. 3. Hydrodynamic resistance R of the actual net may be deduced as R(kg)=29.2$\times$103 v1.65. It is also expressed as R(kg)=5.9$\times$d/l$\times$ab v1.65. depending on the formula deduced by Koyama to estimate the resistance of trawl nets, where d/l denote the ratio between diameter of netting twine and length of mesh leg in every part of side panel, a and b, the stretched circumference of the mouth and the stretched length of the net, respectively.