• 한국재료학회지
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• 제30권9호
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• pp.480-488
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• 2020

The electrocaloric effect can be observed in pyroelectric materials based on conversion between electrical and thermal energy, and can be utilized for the future environment-friendly refrigeration technology. Especially, a strong electrocaloric effect is expected in materials in which field-induced phase transition can be achieved. Emerging fluorite-structure ferroelectrics such as doped hafnia and zirconia, first discovered in 2011, are considered the most promising materials for next-generation semiconductor devices. Besides application of fluorite-structure ferroelectrics for semiconductor devices based on their scalability and CMOS-compatibility, field-induced phase transition has been suggested as another interesting phenomenon for various energy-related applications such as solid-state cooling with electrocaloric effect as well as energy conversion/storage and IR/piezoelectric sensors. Especially, their giant electrocaloric effect is considered promising for solid-state-cooling. However, the electrocaloric effect of fluorite-structure oxides based on field-induced phase transition has not been reviewed to date. In this review, therefore, the electrocaloric effect accompanied by field-induced phase transition in fluorite-structure ferroelectrics is comprehensively reviewed from fundamentals to potential applications.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3493-3505
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• 2023

Reactor containment buildings serve as the last barrier to prevent radioactive leakage due to accidents and their safety is crucial in overpressurization conditions. Thus, the Regulatory Guide (RG) 1.216 has mentioned the global strain as one of failure criteria in the free-field for cylindrical prestressed concrete containment vessels (PCCV) subject to internal pressure. However, there is a limit that RG 1.216 shows the free-field without the specific locations of failure criteria and also the global strain corresponding to only azimuth 135° has been mentioned in NUREG/CR-6685, regardless of the elevations of the structure. Therefore, in order to reevaluate the failure criteria of the 1:4 scaled PCCV, the high fidelity simulation model based on the experimental test was significantly validated in this study, and it was interesting to find that the experimental and numerical result was very close to each other. In addition, for the consideration of the material uncertainties, the Latin hypercube method was used as a statistical approach. Consequently, it was revealed that the radial displacements of various azimuth area such as 120°, 135°, 150°, 180° and 210° at elevations 4680 mm and 6,200 mm can represent as the global deformation at the free-field, obtained from the statistical approach.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2689-2693
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• 2014

The control over microstructure in block copolymer thin films using external electric fields has become an interesting research topic. In this article, the effect of nanoparticle on the microdomain alignments in block copolymer (polystyrene-b-poly(2-vinylpyridine)/nanoparticle (Au) thin films under electric fields has been examined with transmission electron microscopy. The homogeneous dispersion of Au nanoparticles into the block copolymer matrix was achieved by surface modification of nanoparticles with compatible ligands. Compared with the phenomenon seen in the pristine block copolymer thin films, a peculiar alignment behavior was observed in the block copolymer/nanoparticle hybrid thin films under electric fields. In addition, the different pathways observed in the pristine and nanoparticle incorporated block copolymer thin films were also monitored as a function of exposure time. This work can provide the fundamental information for understanding microdomain alignment in block copolymer/nanoparticle thin films under external electric fields.

• 한국주거학회논문집
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• 제16권3호
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• pp.109-117
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• 2005

The purpose of this study is to suggest a basic data of playground design that can arouse various curiosities and interests of children. The 13play areas 'A' kindergartem's playground that parent, music, play equipment, soccer field, water, sand, tunnel, maze, animal, plant, ground hill, bike road, and inner court were evaluated by 16 teachers and 165 children between the age of 4 and 5. POE data of teachers were collected by questionnaire. And children chose and rated very fun and interesting 5 play areas of 13 ones based on the photos. The results were as following. 1) 13 play areas were generally used evenly with diverse purpose. 2) the environment of the play areas was deemed very appropriate. 3) maze area and play equipment area were recognized as the most favored play areas by children. 4) teachers recommended soccer field, plants, maze, tunnel, music area as the most favorable play areas.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.443-446
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• 2002

Wake downstream of an object in the stratified flow has been of long-standing interest in fluid dynamics because of its similarity to geophysical flow over topographical terrains and more recently, concerns about the wake left behind a body moving through the ocean thermocline. Decades of studies of geophysical flow have unveiled that the flow downstream of obstacles in stratified flow consists of attached wake and strong internal waves, or separated, fluctuating wake and persistent late wakes, all of which depend on the flow conditions. Among unique and interesting characteristics of the stratified flow past obstacles is the generation of coherent vortex structure in the late wake far downstream of the object. Without the density stratification, the flow field downstream becomes undisturbed after relatively fast diminishing of the near wake. However, no matter how small the stratification is, the flow field downstream self-develops coherent vortex structures even after diminishing of the near wake. This paper present a computational approach to simulate the generation mechanism of the coherent vortex and analysis of the vortical structure.

• Earthquakes and Structures
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• 제15권2호
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• pp.203-214
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• 2018

Deflection control in tall buildings is a challenging issue. Connecting of the towers is an interesting idea for architects as well as structural engineers. In this paper, two reinforced concrete core-wall towers are connected by a truss bridge with buckling restrained braces. The buildings are 40 and 60-story. The effect of the location of the bridge is investigated. Response spectrum analysis of the linear models is used to obtain the design demands and the systems are designed according to the reliable codes. Then, nonlinear time history analysis at maximum considered earthquake is performed to assess the seismic responses of the systems subjected to far-field and near-field record sets. Fiber elements are used for the reinforced concrete walls. On average, the inter-story drift ratio demand will be minimized when the bridge is approximately located at a height equal to 0.825 times the total height of the building. Besides, because of whipping effects, maximum roof acceleration demand is approximately two times the peak ground acceleration. Plasticity extends near the base and also in major areas of the walls subjected to the seismic loads.

• 한국정밀공학회지
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• 제18권2호
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• pp.146-151
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• 2001

The effects of slant interface in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity. The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamic stress field around the dynamically propagating inclined interface crack tip in the three point bending specimens. The dynamic load is applied by a hammer dropped from 0.08m high without initial velocity. The dynamic crack propagation velocities and dynamic stresses field around the interface crack tips are investigated. Theoretical dynamic isochromatic fringe loops are compared with the experimental reults. It is interesting to note that the crack propagating velocity becomes comparable to the Rayleigh wave speed of the soft material of a specimen when slant angle decreases.

• 한국가구학회지
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• 제16권2호
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• pp.85-93
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• 2005

There are several way to classify the furniture. The furniture can be classified into use, style, and function, but if the furniture is classified into the way of production, it can be the industrial furniture and the studio furniture. Especially, technology and function of the furniture are important elements in industrial furniture. However, it could be considered artists' character and concept as more important elements in the studio furniture. The studio furniture had come out one of the historical movement in American furniture field after the World War II. This case to apply found objects began to increase after the 1970s. Using objects In furniture design field had built up sprightly after end of 1950s. This expression could be the statement of new expression that essential properties of matter in objects is removed. I try to suggest original and interesting furniture design to apply found objects in this thesis. Especially, I use the Korean traditional objects for the furniture and try to make their essential function to be changed. Also, I focus on furniture design to have formative element in their shapes.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.125-130
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• 1989

In the present study, we described a test to explore the function of optokinetic system which subjected to a full visual field stimulation using two different stimulus images patterns. Our results were interesting in a point of view that the stimulation image pattern had non- neglisible influence on the optokinetic response and that in a bidimensionnel image such as the randomly distributed spots images pattern the linearity of system was assured upto the stimulus velocity of about 50 deg/sec for normal subject. As for measuring human optokinetic after nystagmus, the regular stripes pattern was rather desirable than the randomly distributed spots pattern in this study.

• Journal of Communications and Networks
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• 제12권1호
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• pp.11-18
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• 2010

Diversity-multiplexing tradeoff (DMT) is an efficient tool to measure the performance of multiple-input and multiple-output (MIMO) systems and cooperative systems. Recently, cooperative multicast system with wireless network coding stretched tremendous interesting due to that it can drastically enhance the throughput of the wireless networks. It is desirable to apply DMT to the performance analysis on the multicast system with wireless network coding. In this paper, DMT is performed at the three proposed wireless network coding protocols, i.e., non-regenerative network coding (NRNC), regenerative complex field network coding (RCNC) and regenerative Galois field network coding (RGNC). The DMT analysis shows that under the same system performance, i.e., the same diversity gain, all the three network coding protocols outperform the traditional transmission scheme without network coding in terms of multiplexing gain. Our DMT analysis also exhibits the trends of the three network coding protocols' performance when multiplexing gain is changing from the lower region to the higher region. Monte-Carlo simulations verify the prediction of DMT.