• International Journal of Industrial Entomology and Biomaterials
• /
• v.30 no.2
• /
• pp.81-85
• /
• 2015

Recently, many researchers have studied silk sericin because of its high water retention, good wound healing, good cyto-compatibility, and blood-glucose- and cholesterol-lowering effects. Although sericin film can be used in wound dressing and cosmetic packs, its poor mechanical properties have prevented its use in industrial fields. In the present study, sericin was obtained from different silkworm varieties, and the effect of silkworm variety on the structure and properties of sericin was examined. Except for a small difference in serine content, no significant difference in sericin was noted among the silkworm varieties. In addition, silkworm variety almost had no effect on solution viscosity, implying that it does not influence the molecular weight of sericin. Mechanical properties of sericin film were strongly affected by silkworm variety. Wonwon 126 showed the best mechanical properties, while N74 and Geumgwangju displayed the worst properties.

• Journal of Powder Materials
• /
• v.24 no.2
• /
• pp.128-132
• /
• 2017

Harmonic structure materials are materials with a core-shell structure having a shell with a small grain size and a core with a relatively large grain size. They are in the spotlight because their mechanical properties reportedly feature strength similar to that of a sintered powder with a fine grain size and elongation similar to that of a sintered powder with a coarse grain size at the same time. In this study, the tensile properties, microstructure, and stretch-flangeability of harmonic structure SUS304L made using powder metallurgy are investigated to check its suitability for automotive applications. The harmonic powders are made by mechanical milling and sintered using a spark plasma sintering method at 1173 K and a pressure of 50 MPa in a cylindrical die. The sintered powders of SUS304L having harmonic structure (harmonic SUS304L) exhibit excellent tensile properties compared with sintered powders of SUS304L having homogeneous microstructure. In addition, the harmonic SUS304L has excellent stretch-flangeability compared with commercial advanced high-strength steels (AHSSs) at a similar strength grade. Thus, the harmonic SUS304L is more suitable for automotive applications than conventional AHSSs because it exhibits both excellent tensile properties and stretch-flangeability.

• Earthquakes and Structures
• /
• v.12 no.2
• /
• pp.165-175
• /
• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.29 no.1
• /
• pp.39-55
• /
• 1993

Modal Analysis is the process of characterizing the dynamic properties of an elastic structure by identifying its modes of vibration. A mode of vibration is a global property of an elastic structure. That is, a mode has a specific natural frequency and damping factor which can be identified from response data at practically any point on a structure, and it has a characteristic mode shape which identifies the mode spatially over the entire structure. Modal testing is able to be performed on structural and mechanical structure in an effort to learn more about their elastic behavior. Once the dynamic properties of a structure are known its behavior can be predicted and therefore controlled or corrected. Resonant frequencies, damping factors and mode shape data can be used directly by a mechanical designer to pin point weak spots in a structure design, or this data can also be used to confirm or synthesize equations of motion for the elastic structure. These differential equations can be used to simulate structural response to know input forces and to examine the effects of pertubations in the distributed mass, stiffness and damping properties of the structure in more detail. In this paper the measurement of transfer functions in digital form, and the application of digital parameter identification techniques to identify modal parameters from the measured transfer function data are discussed. It is first shown that the transfer matrix, which is a complete dynamic model of an elastic plate structure can be written in terms of the structural modes of vibration. This special mathematical form allows one to identify the complete dynamics of the structure from a much reduced set of test data, and is the essence of the modal approach to identifying the dynamics of a structure. Finally, the application of transfer function models and identification techniques for obtaining modal parameters from the transfer function data are discussed. Characteristics on vibration response of elastic plate structure obtained from the dynamic analysis by Finite Element Method are compared with results of modal analysis.

• Journal of the Korean Society for Heat Treatment
• /
• v.15 no.1
• /
• pp.3-8
• /
• 2002

The effect of ADI heat treatment conditions on the core microstructures and mechanical properties of GCD 45 has been investigated. In the case of $25{\ss}{\AE}$ in diameter, it has been found that pearlite structure is not obtained, and the matrix is consisted of graphite, bainite and retained austenite. Upon cooling isothermally from $900^{\circ}C$, the core structure of 35 mm in diameter is converted to pearlite. However, the structure is transformed to bainite after slow cooling from $900^{\circ}C$ to $800^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.297-302
• /
• 2002

This paper investigated the properties of flexural behavior of composite beams (end-Reinforced concrete, center-Steel concrete) according to attaching length of main bars to flange, shear reinforcing length for different types of structure. In the preceding study, structural properties of composite beams were investigated according to shear span to depth ratio, attaching method of main bars and shear reinforcing method. Based on these results, a series of experiments was carried out according to attaching length of main bar ＆ reinforcing length for different types of structure. Consequently, as attaching length of main bar and shear reinforcing length increased, composite beams represented higher strength, ductility index and stress mechanism distributed in connection zone of different types of structure.

• Steel and Composite Structures
• /
• v.24 no.1
• /
• pp.37-52
• /
• 2017

To quantitatively assess the safety against seismic collapse of eccentrically braced steel frame (EBSF) system, 24 typical EBSFs with K-shape and V-shape braces with seismic precautionary intensities 8 and 9 were designed complying with China seismic design code and relative codes to constitute archetype space of this structure system. In the archetype space, the collapse probability of the structural system under maximum considered earthquakes (MCE) was researched. The results show that the structures possess necessary safety against seismic collapse when they respectively encounter the maximum considered earthquakes corresponding to their seismic precautionary levels, and their collapse probabilities increase with increasing seismic precautionary intensities. Moreover, the EBSFs with V-shape braces have smaller collapse probability, thus greater capacity against seismic collapse than those with K-shape braces.

• Elastomers and Composites
• /
• v.50 no.1
• /
• pp.35-48
• /
• 2015

Polyhedral oligomeric silsesquioxane (POSS) is an important inorganic-organic hybrid material with a three-dimensional structure. Polyurethane (PU) is a widely applied polymer that has versatile properties with the change of two phase structure. When POSS is incorporated into PU by physical or chemical methods, many properties can be greatly improved, such as mechanical properties, thermal stability, biodegradation resistance, and water resistance. This paper reviews the recent progress in preparation, structure, and performance of POSS-modified polyurethane from the viewpoint of physical blending and chemical modification.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.3
• /
• pp.63-72
• /
• 1998

This research was intended to evaluate the effect of carboxymethylcellulose(CMC) on the coating structure and surface strength of coated paper prepared with amphoteric latex based coating color. Printability and optical properties of coated papers were compared. The influence of the consolidation behavior of coating color on the coating structure and the surface strength of coated paper was investigated. Compared with the conventional anionic latex, amphoteric latex formed bulkyer, smoother and more porous coating layer, which in turn, restricted binder migration in the coating layers, and facilitated immobilization of coating colors. However, dry pick strength of coated paper was decreased. The addition of CMC to these systems had strongly influenced on. the consolidation behavior and porosity in the dry state, through forming the network structure of coating layers by the interaction with amphoteric latex particles. Thus, printability and optical properties of coated papers were improved. Results indicated that amphoteric latex could be practically applied to the paper coating to improve printability and optical properties of coated papers.

• East Asian Economic Review
• /
• v.18 no.4
• /
• pp.367-394
• /
• 2014

In this study, we examined the fractal structure of the Nikkei225, HangSeng, Shanghai Stock Exchange and Straits Times Index of Singapore. Empirical analysis was performed via non-parametric, semi-parametric long memory tests and also fractal dimension calculations. In order to avoid spurious long memory features, besides the Detrended Fluctuations Analysis (DFA), we also used Smith's (2005) modified GPH method. As for fractal dimension calculations, they were conducted via Box-Counting and Variation (p=1) tests. According to the results, while there is no long memory property in log returns of any index, we found evidence for long memory properties in the volatility of the HangSeng, the Shanghai Stock Exchange and the Straits Times Index. However, we could not find any sign of long memory in the volatility of Nikkei225 index using either the DFA or modified GPH test. Fractal dimension analysis also demonstrated that all raw index prices have fractal structure properties except for the Nikkei225 index. These findings showed that the Nikkei225 index has the most efficient market properties among these markets.