• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.372-379
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• 2006

Little attention has been paid to static-strain-dependence of dynamic complex modulus of viscolelastic materials in computational analysisso far. Current commercial Finite Element Method (FEM) codes do not take such characteristics into consideration in constitutive equations of viscoelastic materials. Recent experimental observations that static-strain-dependence of dynamic complex modulus of viscolelastic materials, especially filled rubbers, are significant, however, require that solutions somehow are necessary. In this study, a simple technique of using a commercial FEM code, ABAQUS, is introduced, which seems to be far more cost/time saving than development of a new software with such capabilities. A static-strain-dependent correction factor is used to reflect the influence of static-strains in Merman model, which is currently the base of the ABAQUS. The proposed technique is applied to viscoelastic components of rather complicated shape to predict the dynamic stiffness under static-strain and the predictions are compared with experimental results.

• Journal of Broadcast Engineering
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• v.7 no.1
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• pp.37-44
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• 2002

In this paper. we propose a new video coding scheme with multi-resolution motion compensation and residual quantization. The main functional blocks of the proposed scheme include multi-level wavelet decomposition. motion estimation and motion compensation. raster scanning within each subband. formation of block trees and blocking partitioning. and adaptive arithmetic coding. Although the proposed ceding scheme is simple and requires low computational complexity, it produces bitstreams tilth good features. such as the embedded structure and SNR scalability. Experimental results demonstrate that the proposed coding scheme is quote competitive to and often outperforms other wavelet-based video coding schemes in the literature.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.330-335
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• 2012

This study performed the structure analysis for development and localization of main and nose wheel in Korean Helicopter Program(KHP). Structural stability of wheel is evaluated using ANSYS. Considering wheel and tire interface, Stress analysis was conducted by applying pneumatic of tire, static load, radial load and combined load on main and nose wheel. Considering yield strength at which plastic deformation occurs, simulation results suggest the method which increases structure stability after comparing maximum stress and yield strength.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1011-1016
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• 2004

All the loads in the real world are dynamic loads and it is well known that structural optimization under dynamic loads is very difficult. Thus the dynamic loads are often transformed to the static loads using dynamic factors. However, due to the difference of load characters, there can be considerable differences between the results from static and dynamic analyses. When the natural frequency of a structure is high, the dynamic analysis result is similar to that of static analysis due to the small inertia effect on the behavior of the structure. However, if the natural frequency is low, the inertia effect should not be ignored. Then, the behavior of the dynamic system is different from that of the static system. The difference of the two cases can be explained from the relationship between the homogeneous and the particular solutions of the differential equation that governs the behavior of the structure. Through various examples, the difference between the dynamic analysis and the static analysis are shown. Also the optimization results considering dynamic loads are compared with static loads.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.53-53
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• 2011

자동차용 천연가죽 시트의 제조 공정에서 크롬과 비크롬 Metalic 탄닝제, 식물성 탄닝제, 신탄(Syntan) 및 가지제(Fatliuor) 등의 종류와 함량에 따른 인장강도, 신장율, 정하중 신율, 잔류줄음율 등을 측정하여 특정하중에 따른 콜라겐 섬유 조직의 영구변형율과의 상관관계를 비교 분석해본 결과, 크롬 및 비크롬계 탄닝제에 비해 식물성 탄닝제를 적용하였을 때 조직의 변형율이 적었으며, 리틴닝 공정에서 아크릴계, 레진계 및 단백질계 신탄을 혼합 적용하였을 때 가죽의 배(Belly)부위의 물성 균일화 효과가 우수하였으며, 음이온성 가지제 9%를 사용하여 가죽에 유연성을 부여함으로써 조직이 치밀하고 변형율이 감소되어 내구성이 우수한 결과를 나타내었다.

• Journal of Ocean Engineering and Technology
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• v.22 no.2
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• pp.99-105
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• 2008

Ultrasonic nanocrystal surface modification (UNSM) is a method to induce severe plastic deformation to a material surface, so that the structure of the material surface becomes a nanocrystal structure from the surface to a certain depth. It improves the mechanical properties, namely hardness, compressive residual stress, and fatigue characteristics. Specimens of SKD61 were tested to verify the effects of the variation of UNSM static load level on fatigue characteristics. The results were as follows: the grain size of SKD61 treated with UNSM became very fine from the material surface to a $100{\mu}m$ depth. The surface hardness of SKD61 was increased up to 37% after UNSM. And fatigue strength at $10^7$ cycles was increased by 8.3, 11.2, and 17.9% respectively, when the static load levels of UNSM were 4, 6, 8 kgf.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.142-154
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• 1994

In this paper, stochastic imperfection sensitivity analyses of stiffened cylindrical shells under static load are presented. Multimode formulation is performed for the buckling load calculation based on the Donnell's theory and Galerkin approximation. Random imperfection field theory and response surface method are combined with deterministic bucking analysis scheme to perform stochastic imperfection sensitivity analyses of stiffened cylindrical shells considering random geometric imperfection. From the characteristics of probabilistic bucking load, the relation between reliability index and safety parameter can be obtained in addition to the relation between load and reliability index. Those results can be used to determine the range of required safety parameter and acceptable imperfection.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.43-53
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• 2019

It is well-known fact that the stone-mastic asphalt (SMA) mixture has shown superior rut resistance, compared with the dense-graded asphalt (DGA) mixture in highway pavements. However, the SMA is measured to be inferior to DGA mixes when tested by well-known high-temperature test methods, such as the wheel tracking (WT), asphalt pavement analyzer, the Marshall Stability and Kim Test. Therefore, this study examined the reasons why it was measured to be inferior, and devised a potential procedure by which the superiority of SMA could be measured at $60^{\circ}C$. The strength against deformation ($S_D$), which was known to show very high correlation with WT results for DGA mixes, was measured by the Kim Test on the specimen confined in the compacted mold. In standard Kim Test, which used the specimen without confinement, the DGA was measured to show higher $S_D$ than the SMA. But by confining specimen, it was found that the $S_D$ of SMA was measured to be higher than that of DGA. Therefore, the confined static test protocol devised in this study was found to be feasible for evaluating rut resistance of SMA mix.

• Journal of Life Science
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• v.32 no.5
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• pp.340-347
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• 2022

The anti-inflammatory and antioxidant activities of the Ulva lactuca Linnaeus extracts were measured. As a result of the MTT assay of the extract, it was found that the cell viabilities were higher than 90% at all concentrations, and the cell promotion rate exceeded 100% at a certain concentration. Therefore, in all subsequent experiments, the highest concentration was set at 500 ㎍/ml. In the nitric oxide (NO) assay, one of the anti-inflammatory experiments, the Ulva lactuca Linnaeus extracts exhibited inhibitory effects of 16%, 19%, and 62% at concentrations of 5, 50, and 500 ㎍/ml, respectively, compared with the LPS-only group. In tumor necrosis factor-α (TNF-α) assay, the extracts showed inhibitory effects of 16%, 17%, and 27% at concentrations of 5, 50, and 500 ㎍/ml, respectively, compared with the LPS-only group. In the interleukin-6 (IL-6) assay, the extracts also showed inhibitory effects of 15% and 28% at concentrations of 50 and 500 ㎍/ml, respectively, compared with the LPS-only group. In the total polyphenol content assay, the extracts exhibited 8.02, 9.90, and 23.8 mg GAE/g at concentrations of 0.3, 3, and 30 mg/ml, respectively. In the ABTS assay, the extracts exhibited scavenging activities of 2.6, 12.6, and 77.3% at concentrations of 0.3, 3, and 30 mg/ml, respectively. Therefore, it is considered that Ulva lactuca Linnaeus extracts can be used as anti-inflammatory and antioxidant substances for the development of functional foods.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.5-13
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• 2000

In this study, the Disturbed State Concept (DSC) constitutive model is calibrated and modified for steel-sand interface by using the HiS S model for relative intact (Rl) state and the critical state model for the fuBy adjusted (FA) part in the material. The general formulation for implementation is developed. Then, the DSC model with modification for interface is implemented in finite element program based on the generalized Biot's theory. The interface test under one-way monotonic and two-way cyclic loading were numerically simulated using the finite element program modified in this study. The DSC predictions show improved agreement with the observed results from laboratory test. Overall, the computer procedure with the DSC allows relatively improved simulation ofthe soil-structure interaction problems.oblems.