• International Journal of Aeronautical and Space Sciences
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• 제15권1호
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• pp.20-31
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• 2014

This paper deals with the development of a realistic shape optimization of damaged columns that are subjected to conservative and non-conservative forces, using the Genetic Algorithm (GA). The analysis is based on the design of the most optimized shape of the column under the constraint of constant weight, considering the Static, Vibrational, and Flutter characteristics. Under the action of conservative and non-conservative longitudinal forces, an elastic column loses its stability. A numerical analysis based on FEM has been performed on a uniform damaged column, to compute the fundamental buckling load, vibration frequency, and flutter load, under various end restraints. An optimization search based on the Genetic Algorithm is then executed, to find the optimal shape design of the column. The optimized column references the one having the highest buckling load, highest vibration frequency, and highest flutter load, among all the possible shapes of the column, for a given volume. A comparison is then made between the values obtained for the optimized damaged column, and those obtained for the optimized undamaged column. The comparison reveals that the incorporation of damage in the column alters its optimal shape to only a certain extent. Also, the critical load and frequency values for the optimized damaged column are comparatively low, compared with those obtained for the optimized undamaged column. However, these results hold true only for moderate-intensity damage cases. For high intensity damage, the optimal shape may not remain the same, and may vary, according to the severity of damage.

• 비파괴검사학회지
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• 제25권3호
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• pp.178-188
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• 2005

This paper introduces a structural damage identification method to identify 4he multiple directional damages generated within a cylindrical shell by using the measured frequency response function (FRF). The equations of motion for a damaged cylindrical shell are derived. by using a theory of continuum damage mechanics in which a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness. In contrast with most existing vibration-based structural damage identification methods which require the modal Parameters measured in both intact and damaged states, the present method requires only the FRF-data measured at damaged state. Numerically simulated damage identification tests are conducted to verify the feasibility of the Proposed structural damage identification method.

• 대한기계학회논문집A
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• 제29권12권
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• pp.1586-1596
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• 2005

In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the equations of motion of a damaged shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM may require only the FRF-data measured at damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.394-399
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• 2005

In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion fur a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the dynamic equations of the damaged cylindrical shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM requires only the FRF-data measured in damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations fer damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.

• 한국가정과학회지
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• 제5권2호
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• pp.33-43
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• 2002

This study was investigated textural properties of Injulmi affected by milling methods, varieties and added water volume. Sinsunchalbyeo and Hwasunchalbyeo flours were made using Rin-dry milling(PDM) and roll-wet milling(RWM) methods. The proximate composition of waxy rice starches and waxy rice flours were similar. Water binding capacity, soluble carbohydrate and damaged starch of waxy rice flour by RWM: were higher than those of waxy rice flours by PDM. By increasing added water volume, hardness and adhesiveness of Injulmi were decreased. By increasing storage time, hardness of Injulmi was increased, but adhesiveness was decreased. The hardness of Injulmi made from waxy rice flours by PDM was higher than by RDW.

• 보존과학연구
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• 통권30호
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• pp.149-155
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• 2009

Annals of the Joseon Dynasty were composed of 1,229 volumes, and the 475 copies of total annals were wax-treated. Compared to non-wax treated copies, waxed volume of annals were seriously damaged such as crack, stick, discoloration to brown or black, and partially degradation. It is believed that the purpose of wax treatment for some volumes in the annals of the Joseon Dynasty is to prevent paper to deteriorate and to keep for the long time. But, beeswax could be deteriorated itself more rapidly. As a result, the waxed volume was much more damaged than non-waxed volume. Therefore, the investigation of decomposition and deterioration mechanism of beeswax-treated paper which might be used in waxed volume of the annals of the Joseon Dynasty must be done in order to prevent further decomposition and to restore the degraded wax-treated copies of the annals. For basis data of this purpose, physical properties of beeswax-treated paper be analyzed by coating methods. In result, sample products was manufactured reproducibility in lab scale. Specially, beeswax-treated method improved a orientation of papers. And the brushing method was stronger than the dipping method.

• 한국환경복원기술학회지
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• 제23권6호
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• pp.15-28
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• 2020

Urbanization and industrialization have caused increasing damage to national lands, and ecological restoration has proceeded without any specific assessment of this damage. The purpose of this study is to select indices to assess damaged areas through literature review and panel discussions, and to derive the importance of damaged area assessment indices by analyzing them through the Analytic Hierarchy Process (AHP). This study has derived, via literature review, six types of damage and a total of 18 related assessment indices. A total of 51 responses were collected from surveys and given to experts, and an AHP analysis conducted. As a result of the analysis, "Landform change (0.268)" was of the highest importance, with associated damage types as follows: "Soil contamination (0.193)", "Vegetation damaged (0.149)", "Surface soil loss (0.143)", "Change in soil physiochemical property (0.125)", and "Vegetation decline (0.122)". The analysis determined that the item of the highest importance in the overall assessment of damage was "Slope occurred area (0.100)", and that "Conductivity (0.022)" was of the lowest importance. This study can be presented as a criterion in determining the type and degree of damage in setting priorities for future ecological restoration projects.

• 한국임상수의학회지
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• 제28권4호
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• pp.357-364
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• 2011

To evaluate hepatoprotective effect of Epimedium Koreanum nakai (EKN) on liver-damaged animal model, rats were intoxicated with carbon tetrachloride (1 ml/kg) for 9 weeks orally. Liver-damaged rats were divided into 2 groups: liver-damaged control (LDC) group and EKN group were administered vehicle (saline), EKN extract per os for 4 weeks respectively. Normal control (NC) group was administered saline as the same process of LDC group. The weights of prostate (absolute), testis (relative), epididymis (relative) and packed cell volume (PCV), mean corpuscular volume (MCV) of EKN group significantly (P < 0.05) increased compared with LDC group. But Mean corpuscular hemoglobin (MCH), mean corpusulcar hemoglobin concentration (MCHC) and aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) were significantly (P < 0.01, P < 0.05) decreased. Fibrotic regions in hepatic parenchyma of EKN group significantly (P < 0.01) decreased compared with LDC group and mean diameters of hepatic lobules significantly (P < 0.01) increased. Percentages of degenerative kidney regions and number of degenerative kidney tubules, number of vasodilated atrophic glomerulus of EKN group was significantly (P < 0.01, P < 0.05) decreased compared with LDC group. Number of atrophic seminiferous tubules and epididymal tubules showing oligospermatozoa of EKN group were significantly (P < 0.01) decreased compared with LDC group. In conclusion, EKN extract has a favorable effect on the $CCl_4$-induced liver damage.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.237-240
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• 2004

High strain-rate deformation behavior of NiAl/Ni micro-laminated composites was characterized by split hopkins on pressure bar(SHPB). When the strain rate increased, the compressive stress of micro-laminated composites were increased a little. When the intermetallic volume fraction increased, the compressive stress of micro-laminated composites increased linearly irrespective of strain rate. Absorbed energy during the quasi-static and SHPB tests was calculated from the integrated area of stress-strain curve. Absorbed energy of micro-laminated composites deviated from the linearity in terms of the intermetallic volume fraction but merged to the value of intermetallic as the strain rate increased. This was due to high tendency of intermetallic layer for the localization of shear deformation at high strain rate. Microstructure showing adibatic shear band(ASB) confirmed that the shear strain calculated from the misalignment angle of each layer increased and ASB width decreased when the intermetallic volume fraction. Simulation test impacted by tungsten heavy alloy cylinder resulted that the absorbed energies multiplied by damaged volume of micro-laminated composites were decreased as the intermetallic volume fraction increased. Fracture mode were changed from delamination to single fracture when the intermetallic volume fraction and this results were good matched with previous results[l] obtained from the fracture tests.

• Steel and Composite Structures
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• 제38권5호
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• pp.477-496
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• 2021

The main objective of this paper is to study vibration of sandwich open cylindrical panel with damaged core and FG face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions. It is seen that for the large amount of power-law index "P", increasing this parameter does not have significant effect on the non-dimensional natural frequency parameters of the FG sandwich curved panel. Results indicate that by increasing the value of isotropic damage parameter "D" up to the unity (fully damaged core) the frequency would tend to become zero. One can dictate the fiber variation profile through the radial direction of the sandwich panel via the amount of "P", "b" and "c" parameters. It should be noticed that with increase of volume fraction of fibers, the frequency parameter of the panels does not increase necessarily, so by considering suitable amounts of power-law index "P" and the parameters "b" and "c", one can get dynamic characteristics similar or better than the isotropic limit case for laminated FG curved panels.