• Title/Summary/Keyword: critical phenomena

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A Delphi Study on Competencies of Future Green Architectural Engineer (근미래 친환경 건축분야 엔지니어에게 필요한 역량에 대한 델파이 연구)

  • Kang, So Yeon;Kim, Taeyeon;Lee, Jungwoo
    • Journal of Engineering Education Research
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    • v.21 no.3
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    • pp.56-65
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    • 2018
  • With rapid advance of technologies including information and communication technologies, jobs are evolving faster than ever. Architectural engineering is no exception in this regard, and the green architectural engineering is emerging fast as a promising new field. In this study, a Delphi study of expert architectural engineers are conducted to find out (1) near future prospects of the field, (2) near future emerging jobs, (3) competencies needed for these jobs, and (4) educational content necessary to build these competencies with regards to the green architectural engineering. Initial Delphi survey consisting of open-ended questions in the above four areas were conducted and came out with 65 items after duplicate removal and semantic refinements. Further refinements via second and third wave of Delphi results into 40 items that the 13 architectural engineering experts may largely agree upon as future prospects with regards to the green architectural engineering. Findings indicate that it is expected that the demand for green architectural engineering and needs for automatic energy control system increase. Also, collaborations with other fields is becoming more and more important in green architectural engineering. The professional work management skills such as knowledge convergence, problem solving, collaboration skills, and creativity linking components from various related areas seem to also be on the increasing need. Near future ready critical skills are found to be the building environment control techniques (thermal, light, sound, and air), the data processing techniques like data mining, energy monitoring, and the control and utilization of environmental analysis software. Experts also agree on new curriculum for green building architecture to be developed with more of converging subjects across disciplines for future ready professional skills and experiences. Major topics to be covered in the near future includes building environment studies, building energy management, energy reduction systems, indoor air quality, global environment and natural phenomena, and machinery and electrical facility. Architectural engineering community should be concerned with building up the competencies identified in this Delphi preparing for fast advancing future.

Design Reliability Estimation of Low Energy Exploding Foil Initiator (LEEFI형 착화장치의 설계 신뢰도 추정)

  • Lee, Minwoo;Back, Seungjun;Son, Youngkap;Jang, Seung-gyo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.5
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    • pp.40-48
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    • 2018
  • This paper presents a simulation-based design reliability estimation method of a low-energy exploding foil initiator (LEEFI) using a meta-model and describes the design reliability estimation results. The flyer velocity of the LEEFI is critical to initiate the explosive. Evaluation of the flyer velocity from mechanistic models in open literature requires a long computation time due to the multi-physical phenomena that generate the velocity. Moreover, the higher levels of confidence required for an initiator with high reliability incur higher computation costs. Thus, a meta-model of the flyer velocity over time was constructed in order to increase the computational efficiency for a reliable estimation. For different distributions and sigma levels of the design variables, the design reliability estimation results using the meta-model are provided. Additionally, the computational efficiency and accuracy of the estimation method are analyzed.

Sampled-Data Modeling and Dynamic Behavior Analysis of Peak Current-Mode Controlled Flyback Converter with Ramp Compensation

  • Zhou, Shuhan;Zhou, Guohua;Zeng, Shaohuan;Xu, Shungang;Cao, Taiqiang
    • Journal of Power Electronics
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    • v.19 no.1
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    • pp.190-200
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    • 2019
  • The flyback converter, which can be regarded as a nonlinear time-varying system, has complex dynamics and nonlinear behaviors. These phenomena can affect the stability of the converter. To simplify the modeling process and retain the information of the output capacitor branch, a special sampled-data model of a peak current-mode (PCM) controlled flyback converter is established in this paper. Based on this, its dynamic behaviors are analyzed, which provides guidance for designing the circuit parameters of the converter. With the critical stability boundary equation derived by a Jacobian matrix, the stable operation range with a varied output capacitor, proportional coefficient of error the amplifier, input voltage, reference voltage and slope of the compensation ramp of a PCM controlled flyback converter are investigated in detail. Research results show that the duty ratio should be less than 0.5 for a PCM controlled flyback converter without ramp compensation to operate in a stable state. The stability regions in the parameter space between the output capacitor and the proportional coefficient of the error amplifier are enlarged by increasing the input voltage or by decreasing the reference voltage. Furthermore, the ramp compensation also can extend to the stable region. Finally, time-domain simulations and experimental results are presented to verify the theoretical analysis results.

Analysis and Improvement Specific Frequency Reception Noise Phenomena Due to RF Radiation Signal (RF 방사 신호로 인한 특정 주파수 수신 잡음 현상의 원인분석 및 개선)

  • Kwon, Jung-Hyuk;Kim, Jong-Min;Lee, Wang-Sang
    • Journal of Aerospace System Engineering
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    • v.16 no.3
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    • pp.73-83
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    • 2022
  • The purpose of this paper was to identify a method to improve received noise in a specific frequency band, caused by RF radiation signals during aircraft operation. The communication equipment of the aircraft is critical to the performance and safety of the flight mission, as it is responsible for the function of internal and external communications. Noise-free, clean communication quality, as well as transmission and receiving functions have to be implemented. Thus, the cause analysis of the reception noise in a specific frequency band, was analyzed through trouble shooting. The receiving noise due to the RF radiation signal emitted from the subsystem unit inside the aircraft, was improved by shielding with a CAP with electroless nickel plating applied. Additionally, the measurement and verification results of the improvement method are also described.

Conceptual design of small modular reactor driven by natural circulation and study of design characteristics using CFD & RELAP5 code

  • Kim, Mun Soo;Jeong, Yong Hoon
    • Nuclear Engineering and Technology
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    • v.52 no.12
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    • pp.2743-2759
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    • 2020
  • A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the Thot and Tcold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.

Transcriptional Regulatory Role of NELL2 in Preproenkephalin Gene Expression

  • Ha, Chang Man;Kim, Dong Hee;Lee, Tae Hwan;Kim, Han Rae;Choi, Jungil;Kim, Yoonju;Kang, Dasol;Park, Jeong Woo;Ojeda, Sergio R.;Jeong, Jin Kwon;Lee, Byung Ju
    • Molecules and Cells
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    • v.45 no.8
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    • pp.537-549
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    • 2022
  • Preproenkephalin (PPE) is a precursor molecule for multiple endogenous opioid peptides Leu-enkephalin (ENK) and Met-ENK, which are involved in a wide variety of modulatory functions in the nervous system. Despite the functional importance of ENK in the brain, the effect of brain-derived factor(s) on PPE expression is unknown. We report the dual effect of neural epidermal growth factor (EGF)-like-like 2 (NELL2) on PPE gene expression. In cultured NIH3T3 cells, transfection of NELL2 expression vectors induced an inhibition of PPE transcription intracellularly, in parallel with downregulation of protein kinase C signaling pathways and extracellular signal-regulated kinase. Interestingly, these phenomena were reversed when synthetic NELL2 was administered extracellularly. The in vivo disruption of NELL2 synthesis resulted in an increase in PPE mRNA level in the rat brain, suggesting that the inhibitory action of intracellular NELL2 predominates the activation effect of extracellular NELL2 on PPE gene expression in the brain. Biochemical and molecular studies with mutant NELL2 structures further demonstrated the critical role of EGF-like repeat domains in NELL2 for regulation of PPE transcription. These are the first results to reveal the spatio-specific role of NELL2 in the homeostatic regulation of PPE gene expression.

Empirical Study of Cross-Border E-commerce Brand Formation

  • Jing Zhang;Ziyang Liu
    • Journal of the Korea Society of Computer and Information
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    • v.28 no.11
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    • pp.209-226
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    • 2023
  • Cross-border e-commerce has emerged as a crucial force in stabilizing China's foreign trade, driving the transformation and upgrade of China's foreign trade, and contributing to global economic development and stability. As a result, promoting the high-quality development of cross-border e-commerce has become a common challenge within the Chinese industry. However, with the rapid growth of cross-border e-commerce, it faces new phenomena and challenges, such as a mix of quality, fierce competition, and price competition. Brands serve as distinguishing markers for identifying entities, and brand building is a prudent choice for achieving high-quality development in cross-border e-commerce. This article utilizes brand theory, employing a combined qualitative and quantitative approach, with a specific focus on key elements within the operations of cross-border e-commerce enterprises. Through an analysis of the key elements influencing the formation and development of brands within the internal operations of Chinese cross-border e-commerce enterprises, it investigates their internal formation mechanisms and assesses the significance of these critical factors in influencing brand formation. The research process is based on data from overseas consumers, conducting empirical analysis, ultimately providing certain guidance for brand development in cross-border e-commerce enterprises.

An exploratory study on fashion criticism in social media using text mining - Focusing on panel discussion of fashion show in YouTube - (텍스트 마이닝을 이용한 소셜 미디어의 패션 비평에 관한 탐색적 연구 - 유튜브의 패션쇼 Panel discussion을 중심으로 -)

  • Dawool Jung;Se Jin Kim
    • The Research Journal of the Costume Culture
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    • v.32 no.2
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    • pp.215-231
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    • 2024
  • The changing media landscape has diversified how and what is discussed about fashion. This study aims to examine expert discussions about fashion shows on social media from the perspective of fashion criticism. To achieve this goal objectively, a text mining program, Leximancer, was used. In total, 58 videos were collected from the panel discussion section of Showstudio from S/S 21 to S/S 24, and the results of text mining on 24,080 collected texts after refinement are detailed here. First, the researchers examined the frequency of keywords by season. This revealed that in 2021-2022, digital transformation, diversity, and fashion films are now commonly used to promote fashion collections, often replacing traditional catwalk shows. From 2023, sustainability and virtuality appeared more frequently, and fashion brands focused on storytelling to communicate seasonal concepts. In S/S 2024, the rise of luxury brand keywords and an increased focus on consumption has been evident. This suggests that it is influenced by social and cultural phenomena. Second, the overall keywords were analyzed and categorized into five concepts: formal descriptions and explanations of the collection's outfits, sociocultural evaluations of fashion shows and designers, assessments of the commerciality and sustainability of the current fashion industry, interpretations of fashion presentations, and discussions of the role of fashion shows in the future. The significance of this study lies in its identification of the specificity of contemporary fashion criticism and its objective approach to critical research.

New horizon of geographical method (인문지리학 방법론의 새로운 지평)

  • ;Choi, Byung-Doo
    • Journal of the Korean Geographical Society
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    • v.38
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    • pp.15-36
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    • 1988
  • In this paper, I consider the development of methods in contemporary human geography in terms of a dialectical relation of action and structure, and try to draw a new horizon of method toward which geographical research and spatial theory would develop. The positivist geography which was dominent during 1960s has been faced both with serious internal reflections and strong external criticisms in the 1970s. The internal reflections that pointed out its ignorance of spatial behavior of decision-makers and its simplication of complex spatial relations have developed behavioural geography and systems-theoretical approach. Yet this kinds of alternatives have still standed on the positivist, geography, even though they have seemed to be more real and complicate than the previous one, The external criticisms that have argued against the positivist method as phenomenalism and instrumentalism suggest some alternatives: humanistic geography which emphasizes intention and action of human subject and meaning-understanding, and structuralist geography which stresses on social structure as a totality which would produce spatial phenomena, and a theoretical formulation. Human geography today can be characterized by a strain and conflict between these methods, and hence rezuires a synthetic integration between them. Philosophy and social theory in general are in the same in which theories of action and structural analysis have been complementary or conflict with each other. Human geography has fallen into a further problematic with the introduction of a method based on so-called political ecnomy. This method has been suggested not merely as analternative to the positivist geography, but also as a theoretical foundation for critical analysis of space. The political economy of space with has analyzed the capitalist space and tried to theorize its transformation may be seen either as following humanistic(or Hegelian) Marxism, such as represented in Lefebvre's work, or as following structuralist Marxism, such as developed in Castelles's or Harvey's work. The spatial theory following humanistic Marxism has argued for a dialectic relation between 'the spatial' and 'the social', and given more attention to practicing human agents than to explaining social structures. on the contray, that based on structuralist Marxism has argued for social structures producing spatial phenomena, and focused on theorising the totality of structures, Even though these two perspectives tend more recently to be convergent in a way that structuralist-Marxist. geographers relate the domain of economic and political structures with that of action in their studies of urban culture and experience under capitalism, the political ecnomy of space needs an integrated method with which one can overcome difficulties of orthhodox Marxism. Some novel works in philosophy and social theory have been developed since the end of 1970s which have oriented towards an integrated method relating a series of concepts of action and structure, and reconstructing historical materialism. They include Giddens's theory of structuration, foucault's geneological analysis of power-knowledge, and Habermas's theory of communicative action. Ther are, of course, some fundamental differences between these works. Giddens develops a theory which relates explicitly the domain of action and that of structure in terms of what he calls the 'duality of structure', and wants to bring time-space relations into the core of social theory. Foucault writes a history in which strategically intentional but nonsubjective power relations have emerged and operated by virtue of multiple forms of constrainst wihthin specific spaces, while refusing to elaborate any theory which would underlie a political rationalization. Habermas analyzes how the Western rationalization of ecnomic and political systems has colonized the lifeworld in which we communicate each other, and wants to formulate a new normative foundation for critical theory of society which highlights communicatie reason (without any consideration of spatial concepts). On the basis of the above consideration, this paper draws a new norizon of method in human geography and spatial theory, some essential ideas of which can be summarized as follows: (1) the concept of space especially in terms of its relation to sociery. Space is not an ontological entity whch is independent of society and has its own laws of constitution and transformation, but it can be produced and reproduced only by virtue of its relation to society. Yet space is not merlely a material product of society, but also a place and medium in and through which socety can be maintained or transformed.(2) the constitution of space in terms of the relation between action and structure. Spatial actors who are always knowledgeable under conditions of socio-spatial structure produce and reproduce their context of action, that is, structure; and spatial structures as results of human action enable as well as constrain it. Spatial actions can be distinguished between instrumental-strategicaction oriented to success and communicative action oriented to understanding, which (re)produce respectively two different spheres of spatial structure in different ways: the material structure of economic and political systems-space in an unknowledged and unitended way, and the symbolic structure of social and cultural life-space in an acknowledged and intended way. (3) the capitalist space in terms of its rationalization. The ideal development of space would balance the rationalizations of system space and life-space in a way that system space providers material conditions for the maintainance of the life-space, and the life-space for its further development. But the development of capitalist space in reality is paradoxical and hence crisis-ridden. The economic and poltical system-space, propelled with the steering media like money, and power, has outstriped the significance of communicative action, and colonized the life-space. That is, we no longer live in a space mediated communicative action, but one created for and by money and power. But no matter how seriously our everyday life-space has been monetalrized and bureaucratised, here lies nevertheless the practical potential which would rehabilitate the meaning of space, the meaning of our life on the Earth.

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Critical Analysis of Cultural Imperialism - From Simplistic Imperialism to Dynamic Cultural Fluid (문화제국주의의 비판적 고찰 - 단선적 문화제국주의에서 역동적인 국제적 문화 유동으로)

  • Yim, Dong-Uk
    • Korean journal of communication and information
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    • v.45
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    • pp.151-186
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    • 2009
  • This article focuses on analysing and interpreting cultural imperialism issues that have long been debated. One of issues among them is related to the characteristics of international cultural fluid. What had been debated is that cultural imperialism has been ended or not and the debates were connected to the so called 'reverse cultural imperialism'. The other issue is about this fluid is the continuation of globalization or a part of localization and this is related to the phenomena of cultural homogenization or hybrid. General trend was that simplistic cultural imperialism which had been occurred during the 1970s and 1980s was no longer effective but global dominance by transnational global media is still strong and worldwide. Therefore my research interest is centered on how they look international cultural exchanges with regard to cultural imperialism. And is the framework of cultural imperialism thesis still effective tool in researching and analysing international cultural flows? How do we look globalization relating to international exchanges? Is globalization an another aspect of imperialism? In conclusion, international cultural fluid is not so simple. Like natural phenomena or human progress, a phenomenon is not consisted of a single factor or relation. Cultural fluid is a complex one mixed with various phenomena and relations. This is related to internal and external contradictions, internal and external dynamics of a society and nation, and social and cultural life of human beings. Recent research results show that globalization and localization are closely related to many country's programming schedule, and particular cultural interpretation of specific programmes and culture are adopted to the country's culture and patterns. Cultural fluid has both-sides. One the hand it has useful and positive sides and on the other hand it has harmful and negative aspects. Imperialistic factor, globalization, cultural homogenization or hybrid are all operated and functioned together in cultual fluid. It is difficult to say that cultural imperialism thesis has been ended because American and global media's dominance is still effective. What needed at this time for us is a complex and dynamic analysis of international cultural fluid instead of simplistic cultural imperialism.

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