• Journal of the Korean Society of Industry Convergence
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• v.3 no.4
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• pp.345-351
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• 2000

The change of crystalline structure of drawn PP filaments were investigated. Samples were treated by isothermally annealed after elevated heating from $20^{\circ}C$. Measurements were carried out with XRD for crystallite size and density gradient tube for crystallinity. Isothermally heat treatment were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. in dry oven. The isothermal heat treatment after elevated heating from $20^{\circ}C$ were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. with heating rate of $1^{\circ}C$/min., $5^{\circ}C$/min. and $10^{\circ}C$/min. From the results of this study, it found the following facts. It was found that the crystallinity and crystallite size of (110) plane of sample were increased with increasing of annealed temperature and time. Also crystallinity and crystallite size of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were higher than those of isohtermally annealed samples.

• Journal of the Korean Chemical Society
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• v.67 no.1
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• pp.33-41
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• 2023

Nanocrystallne WO₃ and MoO₃ with several different sizes and crystal structures were prepared by simple acid precipitation and subsequent heat treatment. The photochromic (PC) properties of these samples were comparatively investigated in powder state by monitoring diffuse reflectance spectral changes after bandgap irradiation. The PC effect of hexagonal WO₃ and monoclinic WO₃ strongly depended upon crystallite size rather than crystal structure. The smaller the crystallite size, the better the PC effect. However, orthorhombic WO·H₂O and MoO₃ having hexagonal and orthorhombic structures did not follow this trend. One consistent result for all WO₃ and MoO₃ samples is that the heat treatment in air, which changes crystallinity, whether it changes the crystal structure or only the crystallite size, reduces the PC effect. Since the thermal treatment reduces the surface oxygen defect sites, we believe that the PC effect of WO₃ and MoO₃ depends critically on the surface oxygen defect sites that serve as deep trap sites for photogenerated electrons and oxygen radical holes. We also found that the proton insertion claimed by double charge injection model is not critical for the PC effect.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.47-48
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• 2023

Reinforced concrete structures are an integrated structure in which reinforcing bars are placed on the tensile side of the beam to compensate for concrete that is strong in compression but weak in tension, so that the concrete receives compressive force and the reinforcing bars receive tensile force. It is durable, fire-resistant, economical, and adapts to the shape and dimensions of the structure. It has been widely used for a long time because it can be made freely without restrictions. However, reinforced concrete structures have the disadvantage that cracks occur easily, so they are repaired using a cross-sectional construction method. During this process, problems such as the repair part falling off occurred, so in order to solve the problem, stress changes due to changes in the size of the repair part were examined. As a result, based on the elastic modulus ratio of 1.0, the stress tended to increase as the size of the repair part decreased when it was less than 1.0, and the opposite tendency was seen when it was more than 1.0. This is believed to be due to an increase in the area of the part with a large elastic modulus.

• Journal of Forest and Environmental Science
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• v.31 no.3
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• pp.164-176
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• 2015

Cyathea gigantea is a tree fern distributed throughout humid tropical regions of northeast India and other parts of the country. However, wild populations of this species are largely affected by various natural and anthropogenic activities. Therefore, an attempt was made to study the population structure and regeneration status of C. gigantea in and around greater Itanagar area of Papum Pare district, Arunachal Pradesh. Altogether 45 patches, ranging from 19.63 to $260m^2$ of area, were randomly sampled to study population structure and regeneration status of the species. Population study showed highest number of youngs in the height class of 0.50-0.75 m while, immatures were recorded highest in the height class of 2.0 to 2.5 m. Majority of the matures belonged to 6-9 m height class while it was recorded maximum in the diameter class of 10-15 cm. Average density of C. gigantea was $0.07individuals\;ha^{-1}$ which varied greatly among different patches with a range of 2 to 14. Significant correlations were found between patch size and density of youngs, immatures, matures and total density. Maximum concentration of youngs was observed in patch size $60-140m^2$, while for immatures, it was highest in patch size $20-160m^2$. Similarly, highest concentration of matures was observed in patch size $20-80m^2$ and $80-180m^2$. Population structure of the total population exhibited inverted pyramid shaped distribution. Population structure consisting of youngs, immatures, matures showed that around 60% patches lack of regenerating individuals which depict very poor natural regeneration of the species. Effective conservation strategies are therefore to be formulated to save C. gigantea from the threat of extinction in near future.

• Elastomers and Composites
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• v.41 no.3
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• pp.194-204
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• 2006

The effects of the particle size and the structure of carbon blacks on the friction and the wear behavior of filled natural rubber were investigated in this study. The particle size and the structure of carbon black had a significant effect on the wear rates and the worn surface pattern, and the effect of them on abrasion resistance should be considered for the optimum design of desired wear properties. Ten carbon blacks with various sizes and structures are mixed with natural rubber in order to investigate the effects on the wear rate ($W_R$). The friction and the wear behavior were examined by self-made blade type friction-wear abrader, and the ,elation with characteristic parameter (${\psi}=\sqrt{{N_2^2}+{DBP^2}}$), obtained from the particle size and the structure, was studied. The wear rate ($W_R$) had a Power Law relation with the frictional work ($W_f$) and it was inversely proportional to the characteristic parameter of carbon black. It means that smaller particle size and better structure development of carbon black resulted in improved abrasion resistance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.265-268
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• 2005

A new method for measurement of the pore size in a nanohoneycomb structure using atomic force microscopy (AFM) was proposed. Porous type anodic aluminum oxide (AAO) was fabricated as a nanohoneycomb structure to measure the pore size. For measuring pore sizes from AFM images, a criterion was set in porous type AAO. The pore sizes from AFM images were compared with those from SEM images, and the results showed good agreement. The relationship between the pore size and widening time was found to be linear in the range of this study. It was understood as the synchronized effects of the impurity gradient in outer oxide of AAO, mechanical packing and mass transfer increase.

• Korean Institute of Interior Design Journal
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• no.2
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• pp.17-21
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• 1994

The purpose of this study was to compare the spatial structures for household activities according to the house size. multi-Dimentional Scaling analysis was done, using questinonaire data from 349 middle income housewives living in apartment in the area of Captital region. This was an extended article of previous one. In case of house whose size was less than 20 Pyung, washing cloth and bathing behavior took place in the same place whereas in other house size, bathing behavior was incoperated into various behaviors usually shown in the bedroom. The ideal structure in the house of 20 Pyung's showed home office space closer to the bedroom area whereas in others it appeared independently.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.1-8
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• 2016

In this paper, the full-size structural performance test for a lightweight soundproof tunnel composed of partitioned pipe truss members is carried out to investigate the structural performance. In addition, a nonlinear structural analysis of the same finite element model as the full-size testing model is performed to compare the test result. The test and analysis results showed that the lightweight soundproof tunnel ensures the structural safety against wind loads, snow loads and load combinations. As a result, the full-size test and analysis results meet all the design load conditions, hence the proposed lightweight soundproof tunnel is ready for the field application.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.70-73
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• 2000

A finite element analysis model is suggested for analysis of forming process of milli structure whose size is from a few hundreds ${\mu}m$ to a few mm. In this paper, finite element formulation which assemble crystal plasticity theory considering texture development with damage mechanics is developed, since orientation development and growth of micro voids became the primary factors for deformation aspects in large deformation of milli structure. Applying to, extremely, extrusion process of single crystal and extrusion/drawing process of polycrystal milli-size bar, extrusion force, preferred orientation, and damage evolution are examined to understand the characteristics of deformation of milii-size bar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.616-619
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• 2000

The optimum design of a structure requires to determine economical member size and shape of a structure which satisfies the design conditions and functions. In this study, it is attempted to minimize a dead weight of the bogie frame. Therefore, shape optimization is performed for a bolster rib at first and then size optimization for the thickness of top and bottom plate. For the efficient reduction of a weight of a bogie frame, various ellipses centered at a centroid of a bolster rib are made and tried. For the shape optimization, a major axis and an eccentricity of an ellipse are chosen as design variables. From the numerical results of shape and size optimization of a bogie frame, it is known that the weight can be reduced up to 12.476 Y4717.21 kg) with displacement and stress constraints.