• Title/Summary/Keyword: Free faces

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A new and simple HSDT for thermal stability analysis of FG sandwich plates

  • Menasria, Abderrahmane;Bouhadra, Abdelhakim;Tounsi, Abdelouahed;Bousahla, Abdelmoumen Anis;Mahmoud, S.R.
    • Steel and Composite Structures
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    • v.25 no.2
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    • pp.157-175
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    • 2017
  • The novelty of this work is the use of a new displacement field that includes undetermined integral terms for analyzing thermal buckling response of functionally graded (FG) sandwich plates. The proposed kinematic uses only four variables, which is even less than the first shear deformation theory (FSDT) and the conventional higher shear deformation theories (HSDTs). The theory considers a trigonometric variation of transverse shear stress and verifies the traction free boundary conditions without employing the shear correction factors. Material properties of the sandwich plate faces are considered to be graded in the thickness direction according to a simple power-law variation in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are assumed as uniform, linear and non-linear temperature rises within the thickness direction. An energy based variational principle is employed to derive the governing equations as an eigenvalue problem. The validation of the present work is checked by comparing the obtained results the available ones in the literature. The influences of aspect and thickness ratios, material index, loading type, and sandwich plate type on the critical buckling are all discussed.

Numerical and Experimental Study on Linear Behavior of Salter's Duck Wave Energy Converter (비대칭 형상 파력발전 로터의 선형 거동에 대한 수치적·실험적 연구)

  • Kim, Dongeun;Poguluri, Sunny Kumar;Ko, Haeng Sik;Lee, Hyebin;Bae, Yoon Hyeok
    • Journal of Ocean Engineering and Technology
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    • v.33 no.2
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    • pp.116-122
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    • 2019
  • Among the various wave power systems, Salter's duck (rotor) is one of the most effective wave absorbers for extracting wave energy. The rotor shape is designed such that the front part faces the direction of the incident wave, which forces it to bob up and down due to wave-induced water particle motion, whereas the rear part, which is mostly circular in shape, reflects no waves. The asymmetric geometric shape of the duck makes it absorb energy efficiently. In the present study, the rotor was investigated using WAMIT (a program based on the linear potential flow theory in three-dimensional diffraction/radiation analyses) in the frequency domain and verified using OrcaFlex (design and analysis program of marine system) in the time domain. Then, an experimental investigation was conducted to assess the performance of the rotor motion based on the model scale in a two-dimensional (2D) wave tank. Initially, a free decay test (FDT) was carried out to obtain the viscous damping coefficient. The pitch response was extracted from the experimental time series in a periodic regular wave for two different wave heights (1 cm and 3 cm). In addition, the viscous damping coefficient was calculated from the FDT result and fluid forces, obtained from WAMIT, are incorporated into the final response of the rotor. Finally, a comparative study based on experimental and numerical results (WAMIT & OrcaFlex) was performed to confirm the performance reliability of the designed rotor.

Halide Perovskite Single Crystals (할라이드 페로브스카이트 단결정)

  • Choi, Jin San;Jo, Jae Hun;Woo, Do Hyun;Hwang, Young-Hun;Kim, Ill Won;Kim, Tae Heon;Ahn, Chang Won
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.5
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    • pp.283-295
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    • 2021
  • For the last decades, a research hotspot for the halide perovskites (HPs) is now showing great progress in terms of improving efficiency for numerous photovoltaic devices (PVDs). However, it still faces challenges in the case of long-term stability in the air atmosphere. Defect-free high-quality HP single crystals show their promising properties for the remarkable development of highly efficient and stable PVDs. Here, we summarize the growth processing routes for the stable HP single crystals as well as briefly discuss the pros and cons of those well-established synthesis routes. Furthermore, we briefly include the comparison note between the HP single crystals and polycrystalline perovskite films regarding their device applications. Based on the future progress, the review concludes subjective perspectives and current challenges for the development of HPs high-quality PVDs.

Exosomes: Nomenclature, Isolation, and Biological Roles in Liver Diseases

  • Seol Hee Park;Eun Kyeong Lee;Joowon Yim;Min Hoo Lee;Eojin Lee;Young-Sun Lee;Wonhyo Seo
    • Biomolecules & Therapeutics
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    • v.31 no.3
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    • pp.253-263
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    • 2023
  • The biogenesis and biological roles of extracellular vesicles (EVs) in the progression of liver diseases have attracted considerable attention in recent years. EVs are membrane-bound nanosized vesicles found in different types of body fluids and contain various bioactive materials, including proteins, lipids, nucleic acids, and mitochondrial DNA. Based on their origin and biogenesis, EVs can be classified as apoptotic bodies, microvesicles, and exosomes. Among these, exosomes are the smallest EVs (30-150 nm in diameter), which play a significant role in cell-to-cell communication and epigenetic regulation. Moreover, exosomal content analysis can reveal the functional state of the parental cell. Therefore, exosomes can be applied to various purposes, including disease diagnosis and treatment, drug delivery, cell-free vaccines, and regenerative medicine. However, exosome-related research faces two major limitations: isolation of exosomes with high yield and purity and distinction of exosomes from other EVs (especially microvesicles). No standardized exosome isolation method has been established to date; however, various exosome isolation strategies have been proposed to investigate their biological roles. Exosome-mediated intercellular communications are known to be involved in alcoholic liver disease and nonalcoholic fatty liver disease development. Damaged hepatocytes or nonparenchymal cells release large numbers of exosomes that promote the progression of inflammation and fibrogenesis through interactions with neighboring cells. Exosomes are expected to provide insight on the progression of liver disease. Here, we review the biogenesis of exosomes, exosome isolation techniques, and biological roles of exosomes in alcoholic liver disease and nonalcoholic fatty liver disease.

A Framework for Construction Research Program Valuation (건설기술 연구과제 종합 기술가치 분석)

  • Kim, Changyoon;Kim, Hyoungkwan;Park, Sang-hyuk;Han, Seung-heon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.6D
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    • pp.831-837
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    • 2008
  • Korean construction industry faces diverse social and economical changes. Labor shortage, Free Trade Agreements (FTA), high oil prices alert industry practitioners to the new challenges and opportunities. It is time to make novel approaches for significant improvement of industry performance. Korean government and companies have plans for interdisciplinary research and development efforts. To this end, technology evaluation and market needs analysis should be extensively carried out prior to research initiation. Research programs developed in this way are presented in term of budget estimate, research scope and timeline. A framework for construction technology valuation methodology is also suggested to evaluate the holistic technology value and return on investment of research, development and commercialization.

Korean Politics of 20 years after Democratic Transition: Delayed Reform and New Challenge (민주화 20년의 한국정치: 지체된 개혁과 전환기의 혼돈)

  • KIM, Man-Heum
    • Korean Journal of Legislative Studies
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    • v.15 no.2
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    • pp.131-158
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    • 2009
  • 20 years has passed since June democratization movement of 1987 that made the representative system worked democratically on the basis of free election politics. So far, democratic movement bloc has been elected to government power at least two times. Conservative bloc of old ruling forces made a peaceful re-turn-over and grasped the government power. It looks that electoral democracy has been working very well. But people's distrust in Korean politics is not decreasing. Recently, crisis of representation is discussed. Korean representative system faces the dual tasks. One originates from the delay of institutional reform, another from the change of political circumstances. This paper diagnose the Korean representative democracy of today, focusing on those dual tasks. Especially, it is proposed to reform the present Korean presidentialism of winner-takes-all power structure. It is also to resolve the problem of Korean parliamentary politics deeply depending on the presidency.

A Study on Social and Solidarity Economy in France:Challenge and Result (프랑스 사회연대경제의 도전과 성과)

  • Jong oh Lee
    • Global Cultural Contents
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    • no.32
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    • pp.219-235
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    • 2018
  • This study started with the two fundamental questions of the global economic crisis : whether the present economic, economic and social system can survive the present life, and whether the crisis can solve the crisis with economic logic. It was an attempt to explore alternative economic models of alternative economic models by examining the history, status, challenge, challenge and success tasks of the French social solidarity economie (ESS, Economie Sociale et Solidaire), an alternative to the new economic and social development. The roles and duties of the social solidarity economy (civic groups, corporations, and governments) were examined to have a successful outcome in order to re-evaluate the functions and roles of the French social solidarity economy. Though the le repport of Vercamer(2010) and the charter of Social Economy(1980), we analyzed four projects that move the social economics model of sharing: democratic operations, human centered economy, solidarity investments, free participation, free participation, etc. Subsequently, the activities of social solidarity, which account for more than 10 percent of the current French economy, have drawn hints on the social and social implications of the Korean society, and have focused on creating a new alternative to the economic and social crises facing the Korean society, and exploring the possibility of a socio-economic crisis in Korea today. These studies have introduced the ideological factors and the types of achievements in the French social solidarity economie, from the 19th century to the present, and at the same time, the rationale and justification for continued economic experiment in Korea, which faces depression and economic crises.

Dynamical Study on the Blasting with One-Free-Face to Utilize AN-FO Explosives (초유폭약류(硝油爆藥類)를 활용(活用)한 단일자유면발파(單一自由面發破)의 역학적(力學的) 연구(硏究))

  • Huh, Ginn
    • Economic and Environmental Geology
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    • v.5 no.4
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    • pp.187-209
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    • 1972
  • Drilling position is one of the most important factors affecting on the blasting effects. There has been many reports on several blasting factors of burn-cut by Messrs. Brown and Cook, but in this study the author tried to compare drilling positions of burn-cut to pyramid-cut, and also to correlate burn-cut effects of drilling patterns, not being dealt by Prof. Ito in his theory, which emphasized on dynamical stress analysis between explosion and free face. According to former theories, there break out additional tensile stress reflected at the free face supplemented to primary compressive stress on the blasting with one-free-face. But with these experimented new drilling patterns of burn-cut, more free faces and nearer distance of each drilling holes make blasting effects greater than any other methods. To promote the above explosive effect rationary, it has to be considered two important categories under-mentioned. First, unloaded hole in the key holes should be drilled in wider diameter possibly so that it breaks out greater stress relief. Second, key holes possibly should have closer distances each other to result clean blasting. These two important factors derived from experiments with, theories of that the larger the dia of the unloaded hole, it can be allowed wider secondary free faces and closes distances of each holes make more developed stress relief, between loaded and unloaded holes. It was suggested that most ideal distance between holes is about 4 clearance in U. S. A., but the author, according to the experiments, it results that the less distance allow, the more effective blasting with increased broken rock volume and longer drifted length can be accomplished. Developed large hole burn-cut method aimed to increase drifting length technically under the above considerations, and progressive success resulted to achieve maximum 7 blasting cycles per day with 3.1m drifting length per cycle. This achievement originated high-speed-drifting works, and it was also proven that application of Metallic AN-FO on large hole burn-cut method overcomes resistance of one-free-face. AN-FO which was favored with low price and safety handling is the mixture of the fertilizer or industrial Ammonium-Nitrate and fuel oil, and it is also experienced that it shows insensible property before the initiation, but once it is initiated by the booster, it has equal explosive power of Ammonium Nitrate Explosives (ANE). There was many reports about AN-FO. On AN-FO mixing ratio, according to these experiments, prowdered AN-FO, 93.5 : 6.5 and prilled AN-FO 94 : 6, are the best ratios. Detonation, shock, and friction sensities are all more insensitive than any other explosives. Residual gas is not toxic, too. On initation and propagation of the detonation test, prilled AN-FO is more effective than powered AN-FO. AN-FO has the best explosion power at 7 days elapsed after it has mixed. While AN-FO was used at open pit in past years prior to other conditions, the author developed new improved explosives, Metallic AN-FO and Underwater explosive, based on the experiments of these fundmental characteristics by study on its usage utilizing AN-FO. Metallic AN-FO is the mixture of AN-FO and Al, Fe-Si powder, and Underwater explosive is made from usual explosive and AN-FO. The explanations about them are described in the other paper. In this study, it is confirmed that the blasting effects of utilizing AN-FO explosives are very good.

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Dual Faces of Nationalism reflected in Contemporary Korean Art and Society (현대 한국미술과 민족주의란 두 개의 얼굴)

  • Choi, Tae-Man
    • The Journal of Art Theory & Practice
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    • no.4
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    • pp.145-180
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    • 2006
  • In Korea, nation and nationalism are undeniable justice, absolute virtue and moreover system of desire. From the late Chosun Dynasty when the Korean Peninsula had to survive from the critical situation of being the arena of competition, and through the colonial period under Japanese imperialism, nationalism became stronger as a logic of survival. The policy of seclusion under closed and exclusive nationalism that didn't recognize the world situation well enough, eventually gave more pain to the nation. Nationalism in colonial Korea which was as reformed nationalism and on the other hand, as intransigent, resisting nationalism. Since the purpose of this writing is not for clarifying the argument raised on Korean nationalism, there is no use mentioning how it went with the change of time. But we have to focus on the fact that the word 'nation' which appeared under the influence of popular revolution and capitalism meaning 'a group of people', was translated and understood as a racial concept for strengthening the unity of 'single-race nation with five thousand years' history. First of all, there is nationalism used to fortify the system. 'The Charter of National Education' and 'The Pledge of Allegiance' were ornaments to intensify the ruling ideology and dictatorship to militarize entire South Korea for 'settling Korean democracy' professed nationalism. Also, another ruling ideology armed with 'self-reliance' put North Korea into the state of hypnosis called nationalism. Nationalism, claiming 'nation' outwardly, but in reality, being an illuminating, instructing ideology isolating each other was indeed a body with two faces. This made 'nation' in Korea mysterious and objective through work such as. The statue commemorating patriotic forefathers' and picture of national records' in South Korea art. Nationalism used to strengthening the system encountered the magical 'single-race' and made 'ghost' being an extreme exclusion to other nations. We can find pedigreed pureness not allowing any mixed breeds from the attitude accepting western art -via Japan or directly- and making it vague by using the word Korean and Asia. There's nationalism as a resistant ideology to solidify the system on the other side. It came out as a way of survival among the Great Power and grew with the task of national liberation to became as a powerful force facing against the dictatorship dominating South Korea after the liberation. This discussion of nationalism as a resistance ideology was active in 1980s. In 1980, democracy movement against the dictatorship of 5th Republic originated from military power which came out suppressing the democratic movement in Gwangju, spread out from the intellects and the students to the labors, farmers and the civilians. It is well known that the 'Nation-People(Minjoong)'s Art Movement could come out under this social condition. Our attitude toward nationalism is still dual in this opening part of 21st century. On one hand, they are opposing to the ultra-nationalism but are not able to separate it from nationalism, and on the other, they have much confusion using it. In fact, in a single-race nation like Korea, the situation of being nationalism and jus sanguinis together can cause dual nationalism. Though nationalism is included in the globalization order, it is evidence that it's effective in Korea where there are still modern fetters like division and separation. In particular, in the world where Japan makes East Asia Coalition but exposed in front of nationalism, and China not being free from Sinocentrism, and American nationalism taking the world order, and Russia fortifying nationalism suppressing the minority race after the dissolution of socialism, Korean nationalism is at the point to find an alternative plan superior to the ruling and resisting ideology.

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Development of a Theme-Selection Activity in 'Clothing Life' in Relation to SDGs for the Free Semester Program (지속가능발전목표(SDGs) 성취를 위한 의생활 자유학기제 주제선택활동 프로그램 개발)

  • Choi, Ye Ji;Park, Mi-Jeong;Shim, Huen-Sup
    • Journal of Korean Home Economics Education Association
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    • v.32 no.3
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    • pp.27-48
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    • 2020
  • The purpose of this study is to develop a theme-selection activity in 'clothing life' in relation to SDGs(Sustainable Development Goals) for the free semester program. After analyzing the contents of the 'clothing life' area of middle school home economics textbooks based on the SDGs, the content system and learning goals were set. Then a program was developed and the validity and the feasibility of the program were verified. As a result of the analysis of textbooks, the contents of 'clothing life' included all the three basic dimensions of social development, economic growth, and environment protection, yet focus only on 1 or 2 goals of each area. Based on the results of the analysis, a 'Righteous(義) Clothing(衣) Life' program was developed. The developed program consists of teaching-learning process plans and teaching-learning materials in eight class periods, including 'The future everyone dreams of' based on SDG12, 'Two faces of fast fashion' based on SDG1, SDG5, SDG8, SDG10, 'Living as Homoclimatus' based on SDG13, and 'The future we create' based on SDG9 and SDG12. Through the expert evaluation process for the developed program, the program's teaching and learning adequacy and feasibility were reviewed and feedback was actively reflected to correct and supplement the program. Through this study, it is expected that it will contribute to laying the foundation for establishing home economics as a subject that educates citizens who practice sustainable life, and a pivotal subject in education for sustainable development.