• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.141-148
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• 2022

In this study, the structural behavior of reinforced concrete members under simultaneous axial and blast loads was analyzed. Nonlinear dynamic analysis verification was performed using the experimental data of panels under fundamental blast load as well as those of reinforced concrete columns subjected to axial and blast loads. Because Autodyn is a program designed only for dynamic analysis, an analysis process is devised to simulate the initial stress state of members under static loads, such as axial loads. A total of 80 nonlinear dynamic finite element analysis procedures were conducted by selecting parameters corresponding to axial load ratios and scaled distances ranging 0%~70% and 1.1~2.0 (depending on the equivalent of TNT), respectively. The structural behavior was compared and analyzed with the corresponding degree of damage and maximum lateral displacement through the changes in axial load ratio and scaled distance. The results show that the maximum lateral displacement decreases due to the increase in column stiffness under axial loads. In view of the foregoing, the formulated analysis process is anticipated to be used in developing blast-resistant design models where structural behavior can be classified into three areas considering axial load ratios of 10%~30%, 30%~50%, and more than 50%.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.5-15
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• 2022

Conventionally, because evaluation methods of the bearing capacity for double steel pipe-concrete composite pile design have not been established, the conventional vertical bearing capacity equations for steel hollow pile are used. However, there are severe differences between the predictions from these equations, and the most conservative one among vertical bearing capacity predictions are conventionally adopted as a design value. Consequently, the current prediction method for vertical bearing capacity of composite pile prediction composite pile causes design reliability and economical feasibility to be low. This paper investigated mechanical behaviors of a new composite pile, with a cross-section composed of double steel pipes filled with concrete (DSCT), vertical bearing capacities were analyzed for several DSCT pile conditions. Axisymmetric finite element models for DSCT pile and surrounding ground were created and they were used to analyze effects on behaviors of DSCT pile pile by embedding depth, stiffness of plugging material at pile tip, height of plugging material at pile tip, and rockbed material. Additionally, results from conventional design prediction equations for vertical bearing capacity at steel hollow pile tip were compared with that from numerical results, and the use of the conventional equations for steel hollow pile was examined to apply to that for DSCT pile.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.243-248
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• 2022

Weight optimization was performed for a rotorcraft shaft system using one-dimensional Euler-Bernoulli beam elements. Torsion, shaft support stiffness such as bearings, flange mass are all considered. To guarantee structural dynamic stability, eigenvalue analysis was performed to avoid critical speed and tooth mesh excitation form the gearbox. The weight optimization was performed by adjusting the thickness and radius while the length of the shaft was fixed, and the optimization process was divided into two stages. In the first, the weight is optimized with the torsional strength constraint. In the second, the difference between the primary mode of shaft and the critical speed is maximized so that the primary mode of the shaft can avoid the critical speed while the constraint on the torsional strength of the shaft is satisfied according to the standard for shaft system stability (AMC P 706-201, 1974). The proposed method was verified by comparing the results of the optimal design using the given one-dimensional beam elements with the stress results of the 3D finite element and the actual manufactured shaft.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.515-524
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• 2022

The turnout system of the sleeper floating tracks (STEDEF) on urban transit is a Anti-vibration track composed of a wooden sleeper embedded in a concrete bed and a sleeper resilience pad under the sleeper. Therefore, deterioration and changes in spring stiffness of the sleeper resilience pad could be cause changes in sleeper support conditions. The damage amount of manganese crossings that occurred during the current service period of about 21 years was investigated to be about 17% of the total amount of crossings, and it was analyzed that the damage amount increased after 15 years of use (accumulated passing tonnage of about 550 million tons). In this study, parameter analysis (wheel position, sleeper support condition, and dynamic wheel load) was performed using a three-dimensional numerical model that simulated real manganese crossing and wheel profile, to analyze the damage type and cause of manganese crossing that occurred in the actual field. As a result of this study, when the voided sleeper occurred in the sleeper around the nose, the stress generated in the crossing nose exceeded the yield strength according to the dynamic wheel load considering the design track impact factor. In addition, the analysis results were evaluated to be in good agreement with the location of damage that occurred in the actual field. Therefore, in order to minimize the damage of the manganese crossing, it is necessary to keep the sleeper support condition around the nose part constant. In addition, by considering the uniformity of the boundary conditions under the sleepers, it was analyzed that it would be advantageous to to replace the sleeper resilience pad together when replacing the damaged manganese crossing.

• Information Systems Review
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• v.19 no.3
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• pp.69-89
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• 2017

In the information age, the rapid development of information technology provides people with an enriching experience yet also causes them harm because of information security (IS) issues. The IS of smartphones faces great challenges. Although many studies on IS awareness have been conducted, most of them have focused on PCs and do not consider the security issues of smartphones. In this study, we focus on those factors that affect IS awareness for both PCs and smartphones. We also analyze the differences in the impacts of certain factors on PCs and smartphones based on the proposed research model. The results are summarized as follows. First, the understanding of security technique, understanding of IS threat, and IS education have significant impacts on IS awareness for PCs and smartphones, while IS intention has a significant impact on IS awareness for PCs but not for smartphones. Moreover, IS policy has no significant impact on IS awareness. Second, PCs and smartphones show no significant differences in IS awareness, IS threat, and IS intention, but show significant differences in understanding of security technique, IS education, and IS policy.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.81-88
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• 2024

The payload BioCabinet of CAS500-3 is designed for 3D stem cell differentiation, culture, and analysis utilizing bio 3D printing techniques in space. The 3D printing technique was initially developed for orbital use; however, it lacks separate validation for extreme launch vibration environments, necessitating a design that mitigates the launch load on the payload. This paper proposes a passive vibration isolator with a low-stiffness elastic support structure and high damping characteristics to reduce the launch loads affecting the BioCabinet. We explore the high-damping characteristics through the superelastic effects of SMA (Shape Memory Alloys) and a multi-layered structure incorporating viscoelastic tape. The effectiveness of the proposed vibration isolation system was confirmed via launch vibration tests on a qualification model.

• Journal of Acupuncture Research
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• v.25 no.2
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• pp.11-26
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• 2008

목적 : 홍삼약침(藥鍼)이 고혈당 및 지질대사장애에 미치는 개선효과와 그 기전을 조사하고자 한다. 방법 : 홍삼약침(藥鍼)의 anti-diabetic 활성과 그 기전을 C57BL/KsJ db/db mice를 이용하여 관찰하였다. 실험 동물은 대조군(DC), 홍삼약침(藥鍼)군(RGL, RGH) 및 양성대조군(MET, GPZ, PIO)의 6군으로 나누었다. 홍삼약침(藥鍼)군은 $0.2m{\ell}$의 홍삼약침멸(藥鍼滅)을 각각 100mg/kg(RGL) 및 200mg/kg(RGH)씩 인체의 간유(肝兪)($BL_{18}$)에 상응하는 혈위에 1일 1회 10주간 좌우 혈을 번갈아가며 약침 시술하였다. 양성대조군은 metformin 300mg/kg(MET), glipizide 15mg/kg(GPZ) 및 pioglitazone 30mg/kg(PIO)을 각각 1일 1회 10주간 경구투여 하였다. 체중과 혈당은 매주 측정하였다. 실험 10주 후에는 혈액채취로 혈중 glucose, 당화혈색소(HbAlc), insulin, 중성지방(TG), adiponectin, leptin, non-esterified fatty acid(NEFA)를 측정 하였고, 간 조직을 채취하여 조직학적 검사 및 gene expression 분석을 시행하였다. 결과 : 홍삼약침(藥鍼)(RGL, RGH)은 10주 동안 C57BL/KsJ db/db mice의 체중을 증가시키는 부작용은 나타나지 않았다. 홍삼약침(藥鍼)군(RGL, RGH)의 사료섭취량은 대조군과 비슷하였으나 음수량은 증가하였다. 홍삼약침(藥鍼)(RGL, RGH)은 대조군에 비하여 각각 19.8% 및 18.3% 혈당을 낮추었고, 홍삼약침(藥鍼)(RGL)은 insulin resistance를 27.7% 감소시켰으며, 경구내당능 검사의 혈중 glucose에서는 대조군에 비해 홍삼약침(藥鍼)군(RGL, RGH)과 양성대조군(MET, GPZ, PIO)에서 각각 19.8%, 18.3%, 67.7%, 52.3% 및 56.9% 감소시켰다. 당화혈색소(HbAlc)는 홍삼약침(藥鍼)(RGL, RGH), MET, GPZ 및 PIO군에서 대조군에 비하여 각각 11.0%, 6.4%, 18.9%, 16.1% 및 27.9% 감소시켰으며, 혈중 glucose감소와 유사한 경향을 나타내었다. 홍삼약침(藥鍼)(RGL)은 대조군에 비해 TG와 NEFA를 각각 18.8% 및 16.8% 감소시켰고, adiponectin과 leptin을 각각 20.6% 및 12.1% 증가시켰다. 홍삼약침(藥鍼)(RGL, RGH)은 중성지방의 침착으로 인한 간의 질량비 증가를 억제하지 못하였으나, 지방구를 감소시겼음을 관찰할 수 있었다. Microarray 분석에서는 홍삼약침(藥鍼)(RGL, RGH)이 간에서 glycolysis, gluconeogenesis 및 fatty acid beta-oxidation과 관련된 유전자 발현에 영향을 미치는 것으로 나타나 양성대조군 metformin과 유사한 기전을 나타내었다. 요약 : 홍삼약침(藥鍼)은 T2DM동물모델(C57BL/KsJ db/db mice)에서 항당뇨 및 지질대사 개선활성이 있었다. 홍삼약침(藥鍼)은 C57BL/KsJ db/db mice의 간조직에서 lipogenesis억제 및 fatty acid beta-oxidation활성을 통해 혈당 이용을 높이고, insulin sensitivity를 향상시켰다. 또한 유전자 발현분석을 통해 그 기전이 metformin과 유사함을 확인할 수 있었으므로 향후 홍삼약침(藥鍼)의 새로운 약침 기술 개발 근거가 될 수 있을 것으로 사료된다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.4
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• pp.498-506
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• 2014

The objective of this study was to investigate the beneficial effects of mulberry extract (MBE) on blood flow improvement. The $SC_{50}$ value for the DPPH radical scavenging activity of MBE was $89.36{\pm}5.46{\mu}g/mL$. Analysis of the cellular toxicity of MBE on RAW 264.7 and HepG2 cells showed no toxicity under a concentration of 2,500 ${\mu}g/mL$. We found that MBE inhibited the enzyme activity of cyclooxygenase (COX)-2 as well as oxidation of human LDL. Western blotting analysis showed that MBE inhibited protein expression of COX-2 and 5-lipoxygenase in RAW 264.7 cells. In addition, MBE inhibited protein expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in human umbilical vein endothelial cells. Furthermore, MBE reduced the serum levels of total cholesterol and C-reactive protein in a concentration-dependent manner. These results both in vitro and in vivo suggest that MBE can be employed for the improvement of blood flow.

• Journal of Veterinary Clinics
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• v.27 no.4
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• pp.325-329
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• 2010

The osteogenic potential of hydroxyapatite/poly $\varepsilon$-caprolactone composite (HA/PCL) scaffolds with matrigel was evaluated in a rat calvarial defect model. Calvarial defect formation was surgically created in Sprague Dawley rats (n = 18). HA/PCL scaffold was grafted with matrigel (M-HA/PCL group, n = 6) or without matrigel (HA/PCL group, n = 6). A critical defect group (CD group, n = 6) did not received a graft. Four weeks after surgery, bone formation was evaluated with radiography, micro computed tomography (micro CT) scanning, and histologically. No bone tissue formation was radiographically evident in the CD group. Bone tissue was radiographically evident in the HA/PCL and M-HA/PCL groups, however, there was more bone-similar opacity in the M-HA/PCL group. Micro CT analysis revealed that the bone volume of the M-HA/PCL group was higher than the HA/PCL group, however, no significant difference was found between the HA/PCL and M-HA/PCL groups. Bone mineral density in the M-HA/ PCL group was significantly higher than in the HA/PCL group (p < 0.05). Histologically, new bone was formed only from existing bone in the CD group, showing concavity without bone formation in the defect. In the HA/PCL group, new bone formation was only derived from existing bone, while in the M-HA/PCL group the largest bone formation was observed, with new bone tissue forming at the periphery of existing bone and around the HA/PCL scaffold with matrigel. The results indicate that the combination of HA/PCL scaffold with matrigel may be an effective means of enhancing bone formation in critical-sized bone defects.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.1
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• pp.66-75
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• 2014

This study aims to understand environmental factors that determine spatial distribution of macrozoobenthic community in the southern area (ca 100-500 m depth) of East Sea, Korea, known as a candidate site for carbon storage under the seabed. From sixteen locations sampled in the summer of 2012, a total of 158 species were identified, showing density of $843indiv/m^2$ and biomass of $26.2g\;WW/m^2$, with increasing faunal density towards biologically higher diverse locations. Principal component analysis showed that a total of 33 environmental parameters were reduced to three principal components (PC), indicating sediment, bottom water, and depth, respectively. As sand content was increasing, number of species increased but biomass decreased. Six dominant species including two bivalve species favored high concentrations of ${\Omega}$ aragonite and ${\Omega}$ calcite, indicating that the corresponding species can be severely damaged by ocean acidification or $CO_2$ effluent. Cluaster analysis based on more than 1% density dominant species classified the entire study area into four faunal assemblage (location groups), which were delineated by characteristic species, including (A) Ampelisca miharaensis, (B) Edwardsioides japonica, (C) Maldane cristata, (D) Spiophanes kroeyeri, and clearly separated in terms of geography, bottom water and sediment environment. Overall, a discriminant function model was developed to predict four faunal assemblages from five simply-measured environmental variables (depth, sand content in sediment, temperature, salinity and pH in bottom water) with 100% accuracy, implying that benthic faunal assemablages are closed linked to certain combinations of abiotic factors.