• Wind and Structures
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• v.7 no.3
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• pp.145-158
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• 2004

The evaluation of the accumulation of permanent set for inelastic structures due to wind action is important in establishing a criterion to select a reduced design wind load and in incorporating the beneficial ductile behaviour in wind engineering. A parametric study of the accumulation of the permanent set as well as the ductility demand for bilinear single-degree-of-freedom (SDOF) systems is presented in the present study. The dynamic analysis of the inelastic SDOF system is carried out using the method of Newmark for artificially generated time history of wind speed. Simulation results indicate that the mean of the normalized damage rate is highly dependent on the natural frequency of vibration. This mean value is relatively insensitive to the damping ratio if the damping ratio is larger than 5%. The scatter associated with the accumulation of the permanent set is very significant. The consideration of the postyield stiffness can significantly reduce the accumulation of the permanent set if the ratio of the yield strength to the expected peak response is small. The results also show that the ductility demand due to the wind action over a period of one hour for flexible structures can be much less than that for rigid structures or structures with larger damping ratio if the SDOF systems are designed with a reduced peak response caused by the fluctuating wind.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2040-2047
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• 2001

In this paper, a singularity problem of the state transition matrix is investigated in the spatial propagation when the spatial matrix differential equation is constructed via time finite element analysis. A parametric study shows that the degree of singularity of the state transition matrix depends on the degree of flexibility of the structures. As an alternative to avoid the numerical problems due to the singularity, an analytic solution fur spatial propagation of the flexible structures is proposed. In the proposed method, the spatial properties of the structure are analytically expressed by a combination of transcendental functions. The analytic solution serves fast and accurate results by eliminating the possibility of the error accumulation caused by the boundary condition. Several numerical examples are shown to validate the effectiveness of the proposed methods.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.49-54
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• 2021

The display industry is transitioning from traditional rigid products such as flat panel displays to flexible or wearable ones designed to be folded or rolled. Accordingly, colorless and optically transparent polyimide (CPI) films are one of the prime candidates to substitute traditional cover glass as a passivation layer to accommodate product flexibility. However, CPI films subjected to repetitive pure bending loads inevitably entail an accumulation of residual strain that can eventually cause wrinkles or delamination in the underlying component after a certain number of static and cyclic loading. The purpose of this study is to establish an experimental method to systematically evaluate the bending residual strain of CPI films. Films were monotonically and cyclically wrapped on mandrels of various diameters to ensure a constant strain in each. After unwrapping the wound CPI film, the residual radius of curvature remaining on the film was measured and converted into residual strain. The critical radius of curvature at which residual strain does not remain was about 5 mm, and the residual strain decreased in proportion to the log time. It is expected that flexible displays can be reliably designed using the data between the applied bending strain and the residual strain.

• Journal of Korean Society of Rural Planning
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• v.10 no.1 s.22
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• pp.41-55
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• 2004

The purpose of this study is to investigate a causal relationship between the mode of production and change of rural society. While dominant theories of social change have stressed variation of contingencies and periodical contexts, this theoretical paper drives a new insight paralleling diverse theoretical arguments of each mode of production with rural and urban changes. Investigating the drifts of intellectual ideologies of the mode of production, we get through diverse paradigm shifts of the production accumulation and its trigger effects on rural change. More specifically, the present study investigates change of rural society by way of investigating such fluctuations of societal changes as ancient society, slavery society, feudal society, industrial society, post-industrial society, and information society. We find that transportation and communication technologies have had a key role in the changes, however, the effects of the technologies on social changes have been different between rural- and urban-society. While we take it for granted that flexible accumulation in post-industrial society and time-space compression and informatization in information society will reduce developmental gap between rural- and urban-society, we also found that there have been big differences of actual application of the technologies between theory and reality in each era of mode of production.

• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.292-297
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• 2010

This study was carried out to provide preliminary data to purify contaminated sites by nickel (Ni). After rooted cuttings of Salix reichardtii had been grown in Ni solution (hydroponic culture), pH changes in the solution and the accumulated Ni amount in plant parts were measured and analyzed. When the Ni concentration was low enough for S. reichardtii cuttings to grow well, the pH value of the solution decreased considerably. As the Ni concentration got higher, the plant growth got poorer and the pH value decreased slowly. Roots accumulated the highest Ni amount. Leaves and stems followed after. When stems were older, the accumulated Ni amount was lower. more Ni was accumulated in the plant parts which had more flexible tissue and live cells. As the Ni concentration in solution got higher up to 50.0 ${\mu}mol$/L, so did the Ni accumulation in the plant parts. However, the plant individuals nearly died and the Ni accumulation tended to drop when the Ni concentration in solution was 100.0 ${\mu}mol$/L. The rooted cuttings of S. reichardtii grew poorer as the Ni concentration in solution got higher. The plants in solution with 100.0 ${\mu}mol$/L of Ni were practically dead in four weeks.

• Journal of the Korean association of regional geographers
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• v.8 no.2
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• pp.170-183
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• 2002

Recently it is supposed to be a shift to regional geography. To understand the emergence of the new regional geography, It must be remarked that the progress of capitalist production and consumption change our conceptional apparatus such as representation of space. Region is one of the important mode of representations of space and time. In the Fordist capitalism of 20th century, development is regarded as diffusion of capitalist expansion of western worlds. State must support capitalist growth through regional policies which include constructing of infrastructure and regionalization of spatial division of labour. The regional development theories contributed as ideology and policy tools for state intervention. The region was simply one of the most logical classification tools of organizing geographical informations. In the theories of regional development, the concept of region was reduced to the formal unit of classification. As the transition from Fordism to flexible accumulation, the region is again acquiring its 'identity' and 'authenticity'. In this tendency of the revival of region, it is expected that good achievement could be made in the field of regional geography through relevant research methods. It is also believed one of the available means are historical approaches to the cultural and ecological regions. The historical approaches to cultural and ecological regions are not only correspondent with cultural development strategies of local governments, but also could convey regional identities through both narrativization of place and aestheticization of landscape.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.290.2-290.2
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• 2016

Recently, organic thin-film transistors have been widely researched for organic light-emitting diode panels, memory devices, logic circuits for flexible display because of its virtue of mechanical flexibility, low fabrication cost, low process temperature, and large area production. In order to achieve high performance OTFTs, increase in accumulation carrier mobility is a critical factor. Post-fabrication thermal annealing process has been known as one of the methods to achieve this by improving the crystal quality of organic semiconductor materials In this paper, we researched the properties of pentacene films with X-Ray Diffraction (XRD) and Atomic Force Microscope (AFM) analyses as different annealing temperature in N2 ambient. Electrical characterization of the pentacene based thin film transistor was also conducted by transfer length method (TLM) with different annealing temperature in Al- and Ti-pentacene junctions to confirm the Fermi level pinning phenomenon. For Al- and Ti-pentacene junctions, is was found that as the surface quality of the pentacene films changed as annealing temperature increased, the hole-barrier height (h-BH) that were controlled by Fermi level pinning were effectively reduced.

• Journal of The Korea Institute of Healthcare Architecture
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• v.24 no.4
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• pp.59-67
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• 2018

Purpose: The concept of the Barrier-Free Design has steadily expanded into a basic principle of design, which can provide safe and convenient lives not only limited to the disables, elders, and pregnant women, but also to all members of the society. This is what we now know as the Universal Design. In other words, Barrier-Free Design for all is Architectural Approach of Universal Design. Thus, as a future-oriented alternative to school facilities according to social change, this study suggests basic direction of school building planning and concept of universal design considering school facilities characteristics. Methods: The characteristics of school facilities are understood from the perspective of Universal Design. In addition, a survey is conducted to identify the current state of school facilities. Result: Findings from this study are as follows. First, Universal Design of School Building is an integrated characteristic. Integration is intended to create and manage an integrated environment instead of an individual and one-time approach to installation and maintenance of convenience facilities. Second, It is a flexible characteristic to be sustainable. In other words, they aim to be selectable to respond to change. Third, It is a characteristic of accumulation of outstanding cases. This means that not only individual schools but also entire school spaces will be applied to Universal Design to form a virtuous circle of environment improvement. Implications: The results of this study may serve as a basic concept in the design of school buildings.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.611-617
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• 2017

In this study, it was expected that long-term stability against external mechanical external force could be secured if the phosphor layer had ductility. In this study, a bendable $Gd_2O_2S:Tb$ sensitized paper was fabricated by screen printing method and the image uniformity was evaluated through RMS analysis and histogram analysis to investigate the effect of fatigue accumulation due to long-term external force and repetitive external force. As a result, the dominant pixel area is maintained constant and the relative standard deviation is less than 10% for the long-term external force. However, for the repetitive external force, the dominant pixel area is divided into three areas and the image uniformity is adversely affected. Based on these results, it is suggested that the curved surface detector can be applied by securing the mechanical stability against the existing radiation sensitized paper. However, further studies are needed to apply it to the flexible detector. As a result, flexible radiation sensitizers can be applied to various curved surfaces, and it is expected to be applicable to various fields such as nuclear medicine, medical treatment, and industrial fields in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.262-268
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• 2014

This research introduces the structural design and the validation results of the flexible high speed coupling for 2MW class wind turbine which transmit and cut off torque between gear box and generator. The high speed coupling requires electrical insulation to prevent electrical surface damages on gear box. Therefore glass fiber reinforced plastics is applied to absorb the vibration and deformation of power train and to transmit required torque. Finite element analysis was performed to optimize the thickness and accumulation number of glass fiber reinforced plastics. Torque limiter which cut off the abnormal torque is designed in frictional disc type. The design of the coupling was validated with the performance test of prototype.