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Multi-Level Inverter Circuit Analysis and Weight Reduction Analysis to Stratospheric Drones (성층권 드론에 적용할 멀티레벨 인버터 회로 분석 및 경량화 분석)

  • Kwang-Bok Hwang;Hee-Mun Park;Hyang-Sig Jun;Jung-Hwan Lee;Jin-Hyun Park
    • Journal of the Korean Society of Industry Convergence
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    • v.26 no.5
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    • pp.953-965
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    • 2023
  • The stratospheric drones are developed to perform missions such as weather observation, communication relay, surveillance, and reconnaissance at 18km to 20km, where climate change is minimal and there is no worry about a collision with aircraft. It uses solar panels for daytime flights and energy stored in batteries for night flights, providing many advantages over existing satellites. The electrical and power systems essential for stratospheric drone flight must ensure reliability, efficiency, and lightness by selecting the optimal circuit topology. Therefore, it is necessary to analyze the circuit topology of various types of multi-level inverters with high redundancy that can ensure the reliability and efficiency of the motor driving power required for stable long-term flight of stratospheric drones. By quantifying the switch element voltage drop and the number and weight of inverter components for each topology, we evaluate efficiency and lightness and propose the most suitable circuit topology for stratospheric drones.

Moving and Differentiating the Center Area of Busan Using Space Syntax Theory (공간구문론을 활용한 부산의 중심지 이동과 분화)

  • Sung-Yeol KIM;Ji-Hyun KIM
    • Journal of the Korean Association of Geographic Information Studies
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    • v.26 no.4
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    • pp.200-217
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    • 2023
  • The purpose of this study is to analyze the urban spatial network of Busan in a time-series manner to examine the planning role of centeral area change and spatial management. The analysis method used the ASA(Angular Segment Analysis) technique of the space syntax theory, and the analysis period was divided into three periods from 1937 to 2022, when the Busan urban planning was established. As the result, the center area formed in Nampo-dong and Gwangbok-dong were differentiated and moved to Seomyeon, and then the process of redifferentiated into Yeonsan was confirmed in Seomyeon. It is also room for the center area to move to the western region in the future, and it was possible to identify the center area formed by the policy-set and amenity elements. In addition, we examined the system of urban spatial structure through the intelligibility analysis of space syntax theory, and found that the qualitative interpretation of existing studies and the interpretation from the perspective of space syntax theory were consistent with each other. Through this, it was possible to confirm that the role of the plan for space management.

Performance Evaluation for Repair of Composite Maintenance Robot Using Carbon Fiber Spray Method (탄소섬유 분사형 복합재 유지보수 로봇의 보수성능평가)

  • Geun-Su Song;Dae-Ham Cheon;Jae-Youl Lee;Kwang-Bok Shin
    • Composites Research
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    • v.37 no.2
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    • pp.76-85
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    • 2024
  • In this paper, a composite maintenance robot using carbon fiber spray method was developed that automatically sprays mixture was created for repair to damaged areas to repair them. To develop a robot, a repair process was developed in which a mixture of milled carbon fiber, epoxy resin, and hardener is sprayed and consolidated on the damaged area. To automate the repair process, an EOAT based on a collaborative robot was developed that can automatically suction and spray the mixture onto the damaged area. To evaluate the repair performance of the robot, 0° and 90° unidirectional specimens were manufactured and tested in accordance with ASTM D3039. Tests were performed on undamaged specimen, damaged specimen, and repaired specimen by a robot after damaged. As a result of the specimen test, the tensile strength of the 0° and 90° specimens was recovered by 10% and 90% after repair. Based on the test results, the repair performance of the developed composite maintenance robot was verified.

History of Biology Education in Korea During the Periord of 1880-1945 (1880-1945 년간의 한국 생물교육의 역사)

  • 김훈수
    • Animal Systematics, Evolution and Diversity
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    • v.10 no.1
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    • pp.97-123
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    • 1994
  • The author devided th period of 1876-1945 into three epochs ; the Opening of Ports in 1876 -before the Political Reform in 1894 , the Political Reform- the Japanese annexation of Korea in 1910 , and the Epoch of Japanese Colony during 1910-1945. As civilization through including educational reform rised. The modern school system began to be introduced nongovernmentally and governmentally to Korea in the 1880's without any school laws. Were chronologycally established school regulation by Korea Government in 1895-1893, school laws by Korean Government under the supervision of the Japanese Residency-General of Korea in 1906-1910, and the educational laws of Korea by the Japanese Government-General of Korea in 1911-1943. In these epochs, the numbers of elementary , secondary and higher educational institutions and the numbers of pupils and students had increased slowly. Japanese had developed sonwhat primary education and secondary technical education, but it had checked extremely the Korean peoples to receive secondary liberal education and higher education, On the epoch of Japanese colony, Japanese occupied nearly half of elementary school teachers, almost of public secondary school teachers educated in Japan, and nearly all of professor educated in Japan in public and national colleges which were technical, and in one imperial university . Forty or more Korean teachers taught natural history chief at private secondary schools for Koreans , more than half of them being graduates of colleges of agriculture and forestry in Korea and Japan. The author mentioned curricula , and subjects and textbooks connected with biology of elementary, secondary and higher educational institutions. The pup8ls and students received biological knowledge through learning sciences at primary schools ; natural history (plants, animals and minerals ) at secondary schools including normal schools ; botany, zoology, genetics and major subjects related with biology such as anatomy, physiology, bacteriology, pland breeding at medical colleges and colleges of agriculture and forestry. There were no departments of biology , botany or zoology in Korea. Only seven Koreas graduated from departments of biology, botany or zoology at imperial universities in Japan. Some of them played the leading parts to develop education and researches of biology in the universities after 1945 Liberation.

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Korean Art from the view of foreigners in Korea from the period of independence to 1950s (광복 후부터 1950년대까지 한국에서 활동한 외국인이 본 한국미술)

  • Cho, Eun-Jung
    • The Journal of Art Theory & Practice
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    • no.4
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    • pp.123-144
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    • 2006
  • Foreigners who arrived in Korea after the age of enlightenment were Japanese, Chinese and 'Westerners' who were Europeans and Americans. The westerners were diplomats who visited Korea for colonization or for increasing their economical profits by trading after the spread of imperialism, and tourists curious of back countries, artists, explores and missionaries to perform their roles for their religious beliefs. They contacted with Korean cultural and educational people as missionaries and instructors during Japanese colonial period. In 1945, the allied forces occupied Korea under the name of takeover of Japanese colony after Japan's surrender and the relation between foreigners and Korean cultured men enter upon a new phase. For 3 years, American soldiers enforced lots of systems in Korea and many pro-American people were educated. This relationship lasted even after the establishment of the government of Korean Republic and especially, diplomats called as pro-Korean group came again after Korean War. Among them, there were lots of foreigners interested in cultures and arts. In particular, government officials under American Forces who were influential on political circles or diplomats widened their insights toward Korean cultural assets and collected them a lot. Those who were in Korea from the period of independence to 1950s wrote their impressions about Korean cultural assets on newspapers or journals after visiting contemporary Korean exhibitions. Among them, A. J. McTaggart, Richard Hertz and the Hendersons were dominant. They thought the artists had great interests in compromising and uniting the Orient and the West based on their knowledge of Korean cultural assets and they advised. However, it was different from Korean artist's point of view that the foreigners thought Korean art adhered oriental features and contained western contents. From foreigners' point of view, it is hard to understand the attitude Korean artists chose to keep their self-respect through experiencing the Korean war. It is difficult to distinguish their thought about Korean art based on their exotic taste from the Korean artists' local and peninsular features under Japanese imperialism. We can see their thought about Korean art and their viewpoint toward the third world, after staying in Korea for a short period and being a member of the first world. The basic thing was that they could see the potentialities through the worldwide, beautiful Korean cultural assets and they thought it was important to start with traditions. It is an evidence showing Korean artists' pride in regard to the art culture through experiencing the infringement of their country. By writing about illuminating Korean art from the third party's view, foreigners represented their thoughts through it that their economical, military superiority goes with their cultural superiority. The Korean artist's thought of emphasizing Korean history and traditions, reexamining and using it as an original creation may have been inspired by westerners' writings. 'The establishment of national art' that Korean artists gave emphasis then, didn't only affect one of the reactions toward external impact, 'the adhesion of tradition'. In the process of introducing Korean contemporary art and national treasure in America, different view caused by role differences-foreigner as selector and Korean as assistant-showed the fact evidently that the standard of beauty differed between them. By emphasizing that the basis to classify Korean cultural assets is different from the neighborhood China and Japan, they tried to reflect their understanding that the feature of Korean art is on speciality other than universality. And this make us understand that even when Korean artists profess modernism, they stress that the roots are on Korean and oriental tradition. It was obviously a different thought from foreigners' view on Korean art that Korean artists' conception of modernism and traditional roots are inherent in Korean history. In 1950s, after the independence, Korea had different ideas from foreigners that abstract was to be learned from the west. Korea was enduring tough times with their artists' self-respect which made them think that they can learn the method, but the spirit of abstract is in the orient.

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A Legislative Study on Cultural HeritageBetween 1945 and 1960 - Focused on the Cultural Heritage Protection Act Legislated in 1962 - (1945~1960년 문화재 관련 입법 과정 고찰 - 1962년 문화재보호법 전사(前史) 관련 -)

  • Kim, Jongsoo
    • Korean Journal of Heritage: History & Science
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    • v.52 no.4
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    • pp.78-103
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    • 2019
  • The Conservation Decree of the Chosun Treasures Historic and Natural Monuments (hereinafter referred to as the Conservation Decree), which was enacted during the Japanese colonial period, was preserved in accordance with the provisions of article No. 100 of the constitutional law. However, legislative attempts were made to replace the Conservation Decree during the US military administration and early Korean Government. The first attempt was about the National Treasures Historic and Natural Monuments which were brought in by the Legislative Assembly of South Chosun (1947) during the US military administration. The second was a bill by the government for preservation of historical interests (1950), which was submitted to the National Assembly on March 15, 1950 (the so-called Preservation Act (1950)). These two bills were amended and supplemented on the basis of the existing contents of the Conservation Decree. Afterwards, from 1952 to 1960, the legislation of the Cultural Heritage Protection Act (1959) and the Cultural Heritage Bill (1960) were subsequently introduced and enacted. The government's attempt to enact such a cultural property bill was aimed at the legislature to replace the preservation order system that had been in effect since the Japanese colonial period. However, due to the political situation at the time, these laws did not reach final legislation. In October 1960, the government enacted the Regulations for the Preservation of Cultural Property, which was an administrative edict that was promulgated and enacted in November. This was the first official cultural property decree introduced by the Korean government. With the enactment and promulgation of the Cultural Heritage Protection Act in January 1962, Korea's judicial cultural property legislation was established, based on the Korean government's unremitting efforts and experience in legislation of cultural property. In that context, the Cultural Heritage Protection Act is a historical product. The Cultural Heritage Protection Act, which was enacted in 1962, is known to emulate or transplant Japan's Cultural Heritage Protection Act (1950). It was not fully recognized that it was an extension of the Korean government's legislative process of cultural property during the period of 1945-1960. Therefore, it is important to examine the legislative process of cultural property from 1945 to 1960 to understand the background of enacting the Cultural Heritage Protection Act in 1962 along with the establishment of the Korean Cultural Property Law.

Effect of Solid Matrix Priming on Peppers(Capsicum annuum L.) Germinability III. Germination Temperature and Duration of Dehydration (Solid Matrix Priming 처리가 고추종자의 발아에 미치는 영향 III. 발아온도와 건조기간)

  • Kim, Do-Hahn
    • Journal of agriculture & life science
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    • v.43 no.5
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    • pp.17-25
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    • 2009
  • The purpose of this study was to find out the optimum germination temperature and dehydration period at SMP processing, and applies 3 kind of seed treatment and compares yield with stand establishment of seeds of 12 pepper cultivars. It was showed that all 12 cultivars of nontreated seed does not entirely germinated in $15^{\circ}C$. It was that SMP seed germination rate 77(Yeomyeong)~100% (Deawang) high, and seeds 12 cultivars was tendency high by more than 93% at all temperatures excepting Bugang($35^{\circ}C$, 85%) and Yeomyeong($15^{\circ}C$, 77%). Dehydration condition of result were Gumsure, Dongbang Jonggagip, Hyangchon, Yeomyeong, Kwangbok, Wang by which 3 hours in $45^{\circ}C$ were proper, which 6 hours in $35^{\circ}C$ were proper Manitta, Joyang, and judged that 12 hours in $25^{\circ}C$ were proper in Bugang, Dabotap, Deawang. It was reported that water percentage of moisture content change of pepper seed by dehydration was difference a little in species, but was judged by 3-6 hours in $45^{\circ}C$. There was compared to SMP, Osmopriming, pH control by stand establishment were shown pH control of Hyangchon, Dabotap species was nontreated, osmopriming treatment. Also, Kwangbok species was tendency that stand establishment was low, and Deawang was good than other species. Yield of nontreated of yield day was tendency, and miss planted rate also appeared high for 90 day. There was difference in species, and processing of pH control and osmopriming was not shown stand establishment that is stabilized in all species. SMP processing condition could bring security of stable stand establishment in all species, and was considered that research that was under various environment condition should be proceeded conclusively.

A Study on the Relationship between the Heritagization Process and Local Community in Gyeongju, a World Heritage City (세계유산도시 경주의 유산화 과정과 지역공동체의 관계에 관한 연구)

  • HAM Yerim;KIM Euiyeon
    • Korean Journal of Heritage: History & Science
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    • v.56 no.1
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    • pp.226-256
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    • 2023
  • Gyeongju has been the capital of Silla Kingdom for about 1,000 years, and many cultural heritages of the Silla period, such as the Wolseong Palace Site, Daereungwon Ancient Tomb Complex and Donggung Palace and Wolji Pond, are located in the city. Due to these characteristics, the process of heritagization has been carried out in Gyeongju from the Japanese colonial era to after liberation. Heritagization means selecting things from the past due to the needs of the present and making them heritages. In the case of South Korea, national government-led heritagization was achieved during the Japanese colonial period, and after liberation because of the restoration of national culture and the construction of a national identity. Gyeongju is a representative example. On the other hand, Gyeongju's heritagization process was carried out with little consideration of the local community, and thus the local community and Gyeongju's heritage have been distancing. In 2002, Gyeongju's heritage sites were nominated as World Heritage Sites. With the nomination, the perception of the role of local communities in heritage has been changed, and institutional mechanisms to promote the participation of local communities have been continuously reorganized. However, Gyeongju's heritagization process, which was thoroughly conducted through the central government and expert groups, was the reason why Gyeongju residents actually thought Gyeongju's heritage and the locality of Gyeongju were formed through the central government and expert groups. This has been the result of Gyeongju residents' passive participation in heritagization or heritage management to date. This study analyzed the heritagization process of Gyeongju through literature research and conducted an interview survey of residents who have lived in Gyeongju for a long time to understand the impact of the institutional heritagization process on residents and the relationship with heritage. Based on the analysis results, it was suggested that local residents and communities could take the initiative in managing the heritage of Gyeongju.

A Development of Automated Design and Structural Analysis Aided-Program based on GUI environment for Aluminum Extrusion Carbody Structures of Railway Vehicle for Design Engineers (설계자를 위한 GUI 환경기반 알루미늄 압출재 철도차량 차체구조물의 자동화 설계 및 구조해석 지원 프로그램 개발)

  • Kim, Jun-Hwan;Kang, Seung-Gu;Shin, Kwang-Bok;Lee, Young-Ju
    • Journal of the Korean Society for Railway
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    • v.15 no.4
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    • pp.323-328
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    • 2012
  • The purpose of this study is to develop automated structural design and analysis aided-program of aluminum extrusion carbody structures for railway vehicle. This developed program is called "AUTO-RAP" and could perform simultaneously structural design and verification for railway carbody structures made of aluminum extrusion independent of expertise and experience of design engineers. Design engineers are able to conduct the knowledge-based design by providing database of existing aluminum extrusion or user-defined function. The design verification is automatically programmed to evaluate its structural integrity according to Korean Railway Safety Law or Urban Transit Safety Law. In addition, this program could automatically generate an executable file of various commercial finite element programs such as ANSYS and ABAQUS and CAD files such as .stp and .iges by GUI environment applications using MFC(Microsoft Foundation Classes). In conclusion, it is expected to contribute to reduce product design cost and time of carbody structures aluminum extrusions in railway industry.

Removal of Heavy Metals from Acid Mine Drainage using AFMR Process (AFMR 공정을 이용한 광산폐수의 중금속 제거)

  • Paik, Byeong Cheon;Kim, Gwangbok
    • Journal of Korean Society of Environmental Engineers
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    • v.22 no.2
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    • pp.313-321
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    • 2000
  • This research is to remove heavy metals from AMD(Acid Mine Drainage) using AFMR(Anaerobic Floating Media Reactor) process. Two AFMR were operated at HRT(hydraulic retention time) of 3 days. COD/sulfate ratio from 0.3 to 0.8, temperature from $30^{\circ}C$ to $35^{\circ}C$, and alkalinity of 1.000mg/l(as $CaCO_3$). At COD/sulfate($SO{_4}^{2-}$) ratio of 0.5 and temperature of $35^{\circ}C$, the ratio of reduced sulfate($SO{_4}^{2-}$)/removed COD(mg/mg) kept about 1 and the reactor achieved 99.99% of Cr, Pb anee Fe, 98% of Cd, and 90% of Mn removal efficiencies, respectively. Decreasing temperature to $30^{\circ}C$ increased the ratio of reduced sulfate($SO{_4}^{2-}$)/removed COD(mg/mg) to 1.37. Amount of sulfate reduction maximized at the temperature of $30^{\circ}C$ and the COD/sulfate ratio of 0.4 in the influent and then removal efficiencies of heavy metals were 99.99% of Fe, 99.99% of Pb, 99,99% of Cr, 97.3% of Mn, 99.9% of Zn, 99.9% of Cd and 99.9% of Cu.

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