• Title/Summary/Keyword: MULTI-LAYERED STRUCTURE

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Vibrational characteristics of sandwich annular plates with damaged core and FG face sheets

  • Xi, Fei
    • Steel and Composite Structures
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    • v.44 no.1
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    • pp.65-79
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    • 2022
  • The main goal of this paper is to study the vibration of damaged core laminated annular plates with FG face sheets based on a three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. In this study the effect of microcracks on the vibrational characteristic of the sandwich plate is considered. In particular, the structures are made by an isotropic core that undergoes a progressive uniform damage, which is modeled as a decay of the mechanical properties expressed in terms of engineering constants. These defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as "isotropic damage" and it is fully described by a scalar parameter. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular plate is assumed to have any arbitrary boundary conditions at the circular edges including simply supported, clamped and, free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution, and boundary conditions.

Seismic Design of Vertical Shaft using Response Displacement Method (응답변위법을 적용한 수직구의 내진설계)

  • Kim, Yong-Min;Jeong, Sang-Seom;Lee, Yong-Hee;Jang, Jung-Bum
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.6C
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    • pp.241-253
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    • 2010
  • For seismic design of a vertical shaft, three-dimensional Finite Element (FE) analyses were performed to evaluate the accurate response of a vertical shaft and to apply a Response Displacement Method (RDM). Special attention is given to the evaluation of seismic base and response displacement of surrounding soil, estimation of load and loading method. Based on the result, it was found that shear wave velocity of seismic base greater than 1500m/s was appropriate for the seismic design. It was also found that double cosine method which evaluates a response displacement of surrounding soil was most appropriate to consider the characteristic of multi-layered soil. Finally, shape effect of the structure was considered to clarify the dynamic behavior of vertical shaft and it would be more economical vertical shaft design when a vertical shaft was analyzed by using RDM.

Using three-dimensional theory of elasticity for vibration analysis of laminated sectorial plates

  • Liyuan Zhao;Man Wang;Rui Yang;Meng Zhao;Zenghao Song;N. Bohlooli
    • Steel and Composite Structures
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    • v.48 no.1
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    • pp.1-17
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    • 2023
  • The main goal of this paper is to study vibration of damaged core laminated sectorial plates with Functionally graded (FG) face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular sector plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions.

Study on the Testing Method for Moisture Permeability of Packaging Containers according to the Amount of Desiccant (흡습제 투입량에 따른 포장용기의 투습도 시험 방법 고찰)

  • Doyoung Kim;Yeeun Noh;Kyoungmin Kim;Jimin Jang
    • Journal of Korea Society of Industrial Information Systems
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    • v.28 no.6
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    • pp.107-113
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    • 2023
  • In the field of ammunition, storage performance is recognized as important, and the moisture-proof performance of packaging containers is very important. In the ammunition field, paper cans with a multi-layered structure are mainly used as packaging containers. It is made by layering materials that play various roles. These packaging containers are mainly evaluated for moisture-proof performance according to the Korean Industrial Standard KS T 1314. The moisture permeability is determined through linear regression analysis of the change in weight of the moisture absorbent added inside. In this study, the effect of the amount of desiccant added on the moisture permeability test results of packaging containers was confirmed. It is considered appropriate that the amount of desiccant used in testing ammunition packaging containers be approximately 70% or more of the internal volume.

An Longitudinal Analysis of Changing Beliefs on the Use in IT Educatee by Elaboration Likelihood Model (정교화 가능성 모형에 의한 IT 피교육자 신용 믿음 변화의 종단분석)

  • Lee, Woong-Kyu
    • Asia pacific journal of information systems
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    • v.18 no.3
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    • pp.147-165
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    • 2008
  • IT education can be summarized as persuading the educatee to accept IT. The persuasion is made by delivering the messages for how-to-use and where-to-use to the educatee, which leads formulation of a belief structure for using IT. Therefore, message based persuasion theory, as well as IT acceptance theories such as technology acceptance model(TAM), would play a very important role for explaining IT education. According to elaboration likelihood model(ELM) that has been considered as one of the most influential persuasion theories, people change attitude or perception by two routes, central route and peripheral route. In central route, people would think critically about issue-related arguments in an informational message. In peripheral route, subjects rely on cues regarding the target behavior with less cognitive efforts. Moreover, such persuasion process is not a one-shot program but continuous repetition with feedbacks, which leads to changing a belief structure for using IT. An educatee would get more knowledge and experiences of using IT as following an education program, and be more dependent on a central route than a peripheral route. Such change would reformulate a belief structure which is different from the intial one. The objectives of this study are the following two: First, an identification of the relationship between ELM and belief structures for using IT. Especially, we analyze the effects of message interpretation through both of central and peripheral routes on perceived usefulness which is an important explaining variable in TAM and perceived use control which have perceived ease of use and perceived controllability as sub-dimensions. Second, a longitudinal analysis of the above effects. In other words, change of the relationship between interpretation of message delivered by IT education and beliefs of IT using is analyzed longitudinally. For achievement of our objectives, we suggest a research model, which is constructed as three-layered. While first layer has a dependent variable, use intention, second one has perceived usefulness and perceived use control that has two sub-concepts, perceived ease of use and perceived controllability. Finally, third one is related with two routes in ELM, source credibility and argument quality which are operationalization of peripheral route and central route respectively. By these variables, we suggest five hypotheses. In addition to relationship among variables, we suggest two additional hypotheses, moderation effects of time in the relationships between perceived usefulness and two routes. That is, source credibility's influence on perceived usefulness is decreased as time flows, and argument quality's influence is increased. For validation of it, our research model is tested empirically. With measurements which have been validated in the other studies, we survey students in an Excel class two times for longitudinal analysis. Data Analysis is done by partial least square(PLS), which is known as an appropriate approach for multi-group comparison analysis with a small sized sample as like this study. In result. all hypotheses are statistically supported. One of theoretical contributions in this study is an analysis of IT education based on ELM and TAM which are considered as important theories in psychology and IS theories respectively. A longitudinal analysis by comparison between two surveys based on PLS is also considered as a methodological contribution. In practice, finding the importance of peripheral route in early stage of IT education should be notable.

Analysis of Grounding Resistance and Soil Resistivity Using Mock-up System in Jeju Soil (제주토양 목업시스템을 사용한 접지저항 및 대지저항률 분석)

  • Boo, Chang-Jin;Ko, Bong-Woon;Kim, Jeong-Hyuk;Oh, Seong-Bo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.8
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    • pp.536-543
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    • 2016
  • The installation of grounding systems is important for the safe operation of power systems, and the soil resistivity is an important design consideration for such systems. It varies markedly with the soil type, moisture content and temperature. The Jeju geological structure is formed in a multi-layered structure characteristic of volcanic areas and, and the geological ground resistance values can appear even constructed the same areas ground system different from the soil structure. In this study, a mock-up system using representative soil from Jeju was constructed to analyze the variation of the grounding resistance. The mock-up system was configured using the Gauss-Newton algorithm inversion method to analyze the model numerically using the Wenner method through the soil resistivity measurements used to create the ground model. Also, we analyzed the change in the general ground resistance characteristics of the copper rod, copper pipe, and carbon rod that are used for grounding. The variation of the grounding resistance with the hydration status was found to be $2.9[{\Omega}]$, $16.5[{\Omega}]$ and $20.1[{\Omega}]$ for the copper rod, copper pipes, and carbon rod, respectively, and the influence of the ground moisture resistance of the carbon rod was found to be the lowest with a value of $141[{\Omega}]$.

The Change and Characteristic of Spacial Structure from Rural Space to Urban Space : The Case of Hwamyeong-Dong of Buk-gu in Busan (농촌에서 도시로의 공간구조 변화와 특성 - 부산 북구 화명동을 중심으로 -)

  • Kong, Yoon Kyung
    • Journal of the Korean association of regional geographers
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    • v.19 no.1
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    • pp.97-110
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    • 2013
  • The purpose of this study is to investigate the change of spacial structure from rural space to urban space and to examine the characteristic of spacial restructure, focusing on the Hwamyeong-Dong of Buk-gu in Busan. Hwamyeong-Dong has changed from rural area to urban area because of spacial expansion owing to industrialization and urbanization. The unique natural environment, rural village, etc. were disappeared and instead the apartment complex, commercial building, and so on were built. For this reason, historic and concrete place were vanished and so the spacial homogenization and uniformization were formed centering around apartment complex. But the singularity of Hwamyeong-Dong exposes in the way that unique history, custom and memory, trace of Hwamyeong-Dong preserved through the support and effort of the residents and that the Daechen stream changed to ecological stream. In addition, Hwamyeong-Dong altered heterogeneous, multi-layered urban space from homogeneous rural space in terms of the apartment supply sectors and scale, the distribution and kind of commercial facility, residents's composition. This has brought about the subdivision, hierarchization of the space as well as the residence, education, culture. Especially, Hwamyeong3-Dong that built to large scale apartment complex are significantly different from Hwamyeong2-Dong. Hwamyeong2-Dong is marginalizing step by step. However, It is found that the residents in Hwamyeong2-Dong are making an effort for liveable place with ecological residential community and educational cultural community as the center.

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Ecological Characteristics and Changes in Plant Community Structure in Mt. Cheongryang, Incheon (인천시 청량산의 생태적 특성과 식생구조의 변화)

  • Lee, Sang-Hee;Han, Bong-Ho;Park, Seok-Cheol
    • Journal of the Korean Institute of Landscape Architecture
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    • v.49 no.2
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    • pp.74-88
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    • 2021
  • In the present study, the characteristics and changes in the vegetation of Mt. Cheongryang, Inchon, were examined to identify and determine appropriate ways to restore the health of the urban forest and to preserve its vegetation. The vegetation of the community of Quercus mongolica (Mongolian oak) on Mt. Cheongryang appeared to decrease in response to the control of the wilt disease of oak trees. The communities of Sorbus alnifolia (Korean mountain ash) and Styrax japonicus (Snowbell tree) have increased. Pinus rigida (Pitch Pine) had its overall territory decrease, but the current state of the Pinus rigida (Pitch Pine) was estimated to be stable due to its dominance as a tree layer species. In regards to Robinia pseudoacacia (Black Locust), the urbanized species of Sorbus alnifolia (Korean mountain ash), and Styrax japonicus (Snowbell tree), their areas have increased with the appearance of Magnolia obovate (Whiteleaf Japanese Magnolia). The biodiversity of Mt. Cheongryang has decreased by simplifying species in the tree layer and understory species thereof, and the initial success of species in marginal areas has increased. The absence of potential succession was attributed to the termination of ecological succession; thereby, the current vegetation structure was concluded to be remaining as it is for the time being. Soil texture in the mountain primarily consisted of sandy loam or loamy sand; the pH of the soil was in the range 4.26-4.86, rendering a mean pH of 4.59. The content of organic matter (O.M.) appeared having a distributing range of 2.18-9.60%, rendering a mean value of 4.33%. To promote species diversity, several methods are suggested, such as prevention of soil acidification, selecting nationally-grown trees from moist soil or valleys for afforestation, preventing species appearing due to urbanization or excessive growth, protecting the understory vegetation and species with hygropreference, and managing the forest to maintain a multi-layered vegetation structure.

Understanding and Applicability of Identity-in-practice Theory (실행 과정에서의 정체성 이론의 이해와 적용 방안)

  • Kim, Jong-Uk;Kim, Chan-Jong
    • Journal of The Korean Association For Science Education
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    • v.41 no.3
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    • pp.267-281
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    • 2021
  • The shift in the perspective on learning as participation draws attention to learners' identity work. This manuscript foregrounds the ongoing and fluid processes of identity, and focuses on the structure surrounding learners where identity work occurs and the expression of individual agency. From the perspective of learning as participation, we introduce Holland et al. (1998) identity-in-practice theory, as the theoretical lens that dialectically describes structure, agency and identity. The concepts representing this theory are 'figured world', 'positionality' and 'authoring self'. The figured world is a web of meaning encompassing the continuous construct/reconstruct through human actions and also exerts as the social force that shapes human actions. 'Positionality' on the other hand, means an understanding of one's social position in the world. The notion of 'authoring self', is a dimension that synthesizes the above two concepts, which describes the improvisation of one's self through the orchestration and collaboration of various social voices. Next, we analyzed and described various cases of this theory that we found within the scope of science education. However, due to the nature of this theory, which takes a sociocultural approach, international research studies cannot be simply applied to the Korean context. Therefore, we sought to expand the applicability of this theory as a methodological tool, by discussing the directions in which this theory can be used in a domestic context. It is intended that the introduction of this theory, which emphasizes multi-layered, continuous and cumulative identity work, will be used as a resource to further expand the horizon of science education reform that is required for the times.

Interactive analysis tools for the wide-angle seismic data for crustal structure study (Technical Report) (지각 구조 연구에서 광각 탄성파 자료를 위한 대화식 분석 방법들)

  • Fujie, Gou;Kasahara, Junzo;Murase, Kei;Mochizuki, Kimihiro;Kaneda, Yoshiyuki
    • Geophysics and Geophysical Exploration
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    • v.11 no.1
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    • pp.26-33
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    • 2008
  • The analysis of wide-angle seismic reflection and refraction data plays an important role in lithospheric-scale crustal structure study. However, it is extremely difficult to develop an appropriate velocity structure model directly from the observed data, and we have to improve the structure model step by step, because the crustal structure analysis is an intrinsically non-linear problem. There are several subjective processes in wide-angle crustal structure modelling, such as phase identification and trial-and-error forward modelling. Because these subjective processes in wide-angle data analysis reduce the uniqueness and credibility of the resultant models, it is important to reduce subjectivity in the analysis procedure. From this point of view, we describe two software tools, PASTEUP and MODELING, to be used for developing crustal structure models. PASTEUP is an interactive application that facilitates the plotting of record sections, analysis of wide-angle seismic data, and picking of phases. PASTEUP is equipped with various filters and analysis functions to enhance signal-to-noise ratio and to help phase identification. MODELING is an interactive application for editing velocity models, and ray-tracing. Synthetic traveltimes computed by the MODELING application can be directly compared with the observed waveforms in the PASTEUP application. This reduces subjectivity in crustal structure modelling because traveltime picking, which is one of the most subjective process in the crustal structure analysis, is not required. MODELING can convert an editable layered structure model into two-way traveltimes which can be compared with time-sections of Multi Channel Seismic (MCS) reflection data. Direct comparison between the structure model of wide-angle data with the reflection data will give the model more credibility. In addition, both PASTEUP and MODELING are efficient tools for handling a large dataset. These software tools help us develop more plausible lithospheric-scale structure models using wide-angle seismic data.