• Biomolecules & Therapeutics
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• 제26권5호
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• pp.474-480
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• 2018

Most angiogenesis assays are performed using endothelial cells. However, blood vessels are composed of two cell types: endothelial cells and pericytes. Thus, co-culture of two vascular cells should be employed to evaluate angiogenic properties. Here, we developed an in vitro 3-dimensional angiogenesis assay system using spheroids formed by two human vascular precursors: endothelial colony forming cells (ECFCs) and mesenchymal stem cells (MSCs). ECFCs, MSCs, or ECFCs+MSCs were cultured to form spheroids. Sprout formation from each spheroid was observed for 24 h by real-time cell recorder. Sprout number and length were higher in ECFC+MSC spheroids than ECFC-only spheroids. No sprouts were observed in MSC-only spheroids. Sprout formation by ECFC spheroids was increased by treatment with vascular endothelial growth factor (VEGF) or combination of VEGF and fibroblast growth factor-2 (FGF-2). Interestingly, there was no further increase in sprout formation by ECFC+MSC spheroids in response to VEGF or VEGF+FGF-2, suggesting that MSCs stimulate sprout formation by ECFCs. Immuno-fluorescent labeling technique revealed that MSCs surrounded ECFC-mediated sprout structures. We tested vatalanib, VEGF inhibitor, using ECFC and ECFC+MSC spheroids. Vatalanib significantly inhibited sprout formation in both spheroids. Of note, the $IC_{50}$ of vatalanib in ECFC+MSC spheroids at 24 h was $4.0{\pm}0.40{\mu}M$, which are more correlated with the data of previous animal studies when compared with ECFC spheroids ($0.2{\pm}0.03{\mu}M$). These results suggest that ECFC+MSC spheroids generate physiologically relevant sprout structures composed of two types of vascular cells, and will be an effective pre-clinical in vitro assay model to evaluate pro- or anti-angiogenic property.

• 대한기계학회논문집
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• 제14권3호
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• pp.624-635
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• 1990

본 연구에서는 마멸과정을 선형파괴역학적 관점에서 해석하여, 탄성체의 표면 에 산재되어 있는 표면균열의 전파거동을 마멸과정규명의 입장에서 살펴보고자 한다. 우선 마멸거동에 관한 파괴역학적 접근방식에 의한 마멸이론의 확립을 위해서, 표면균 열이 내부균열보다 그 전파 가능성이 높다고 한 Keer등의 주장에 착안하여 Hertz 접촉 압력하의 경사진 표면균열의 전파거동을 선형파괴역학적으로 해석하고자 한다. 이론 해석에 있어서는 표면균열을 인상전립의 연속분포로 치환하고, 전립밀도분포함수에 관 한 특이적분방정식을 유도해서 Erdogangupta의 방법을 이용하여 그 해를 구하였다.

• 한방재활의학과학회지
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• 제29권1호
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• pp.75-83
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• 2019

Objectives Previous animal studies have shown that mixtures of Cynanchum wilfordii and Phlomis umbrosa extract (IPLUS-CWPU) increases femur length and insulin like growth factor-1 (IGF-1) secretion. IPLUS-CWPU may thus be a promising ingredient in functional foods aimed at growing child's height. The purpose of the study is to investigate the effect of IPLUS-CWPU on height growth in children with short stature. Methods For this purpose, we recruited 90 children aged 4 to 12 years who had heights ranging from the 5th to 25th percentiles of Korean children's growth curve and randomized to either the IPLUS-CWPU or the placebo group. Results The IPLUS-CWPU group showed a significant increase in the change of the height growth compared to the placebo group after 20 weeks of administration (p=0.02). The height growth velosity also showed a statistically significant difference in the test group compared to the placebo group at 10 weeks (p=0.04). The IGF-1 levels showed a tendency to increase in the IPLUS-CWPU group (p=0.08). Moreover, the IPLUS-CWPU significantly increased IGF-1/IGFBP-3 ratio (p=0.02). However, there were no significant differences in blood biochemical parameters including growth hormone, bone age, thyroid stimulating hormone, and osteocalcin levels. Conclusions In conclusion, the data of this trial indicate that IPLUS-CWPU is effective and safe, generally well-tolerated without severe adverse events, in the treatment of children with short stature over a 20 weeks period.

• Geomechanics and Engineering
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• 제28권4호
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• pp.385-396
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• 2022

The accurate determination of the subgrade reaction modulus (K_s) of soil is an important factor for geotechnical engineers. This study estimated the K_s of soft soil improved with floating deep cement mixing (DCM) columns. A novel prediction model was developed that emphasizes the accuracy of identifying the most significant parameters of K_s. Several multi-layer perceptron (MLP) models that were trained using the Levenberg Marquardt (LM) backpropagation method were developed to estimate K_s. The models were trained using a reliable database containing the results of 36 physical modelling tests. The input parameters were the undrained shear strength of the DCM columns, undrained shear strength of soft soil, area improvement ratio and length-to-diameter ratio of the DCM columns. Grey wolf optimization (GWO) was coupled with the MLPs to improve the performance indices of the MLPs. Sensitivity tests were carried out to determine the importance of the input parameters for prediction of K_s. The results showed that both the MLP-LM and MLP-GWO methods showed high ability to predict K_s. However, it was shown that MLP-GWO (R = 0.9917, MSE = 0.28 (MN/m²/m)) performed better than MLP-LM (R =0.9126, MSE =6.1916 (MN/m²/m)). This proves the greater reliability of the proposed hybrid model of MLP-GWO in approximating the subgrade reaction modulus of soft soil improved with floating DCM columns. The results revealed that the undrained shear strength of the soil was the most effective factor for estimation of K_s.

• Geomechanics and Engineering
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• 제31권6호
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• pp.573-582
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• 2022

The geometry of the gravity-type anchorage changes depends on various factors such as the installation location, ground type, and relationship with the upper structure. In particular, the anchorage geometry embedded in the ground is an important design factor because it affects the pull-out resistance of the anchorage. This study examined the effect of four parameters, related to anchorage geometry and embedded ground conditions, on the pull-out resistance in the gravity-type anchorage through two-dimensional finite element analysis, and presented a guide for major design variables. The four parameters include the 1) flight length of the stepped anchorage (m), 2) flight height of the stepped anchorage (n), 3) the anchorage heel height (b), and 4) the thickness of the soil (e). It was found that as the values of m increased and the values of n decreased, the pull-out resistance of the gravity-type anchorage increased. This trend is related to the size of the contact surface between the anchorage and the rock, and it was confirmed that the value of n, which has the largest change rate of the contact surface between the anchorage and the rock, has the greatest effect on the pull-out resistance of the anchorage. Additionally, the most effective design was achieved when the ratio of the step to the bottom of the anchorage (m) was greater than 0.7, and m was found to be an important factor in the pull-out resistance behavior of the anchorage.

• 한국간호교육학회지
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• 제19권4호
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• pp.617-626
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• 2013

Purpose: This study was to investigate the effect of nurses' core competencies and cognition of job competency of senior nurses on work performance. Methods: Three hundred two nurses participated in the study. The collected data were analyzed with SPSS/WIN 20.0. Frequency, t-test, ANOVA and stepwise multiple regression were utilized. Results: The level of nurses' core competencies was 3.65 (${\pm}.40$) points, cognition of job competency of senior nurses was 4.02 (${\pm}.60$) points, and work performance was 4.04 (${\pm}.55$) points. In accordance with the participant's general characteristics, work performance was found to be significant in their age, marital status, educational level, total clinical experience, length of time on the present ward, and their income. Cognition of job competency of senior nurses was found to be the most effective factor in work performance, followed by core competencies and total clinical experience, and these factors accounted for 63.4%. Conclusion: The study suggested that work performance was highly affected by the nurses' core competencies and cognition of job competency of senior nurses. Therefore, effective education programs are required to provide an appropriate experience to both entry-level and experienced nurses, as well as to help in enhancing nurses' and senior nurses competency at the same time.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.499-511
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• 2019

In this study, the axial compressive behavior of novel quadruple C-channel built-up cold-formed steel columns with different slenderness ratio was investigated, using the experimental and numerical analysis. The axial compressive capacity and failure modes of the columns were obtained and analyzed. The finite element models considering the geometry, material and contact nonlinearity were developed to simulate and analyze the structural behavior of the columns further. There was a great correlation between the numerical analyses and test results, which indicated that the finite element model was reasonable and accurate. Then influence of, slenderness ratio, flange width-to-thickness ratio and screw spacing on the mechanical behavior of the columns were studied, respectively. The tests and numerical results show that due to small slenderness ratio, the failure modes of the specimens are generally local buckling and distortional buckling. The axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns decrease with the increase of maximum slenderness ratio. When the screw spacing is ranging from 150mm to 450mm, the axial compressive strength and stiffness of the quadruple C-channel built-up cold-formed steel columns change little. The axial compressive capacity of quadruple C-channel built-up cold-formed steel columns increases with the decrease of flange width-thickness ratio. A modified effective length factor is proposed to quantify the axial compressive capacity of the quadruple C-channel built-up cold-formed steel columns with U-shaped track in the ends.

• 한국농공학회지
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• 제29권4호
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• pp.59-72
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• 1987

Although long-term runoff analysis is important as much as flood analysis in the design of water works, the technological level of the former is relatively lower than that of the latter. In this respect, the precise estimation model for the volume of successive runoff should he developed as soon as possible. Up to now, in Korea, Gajiyama's formula has been widely used in long-term runoff analysis, which has many problems in applying in real situation. On the other hand, in flood analysis, unit hydrograph method has been exclusively used. Therefore, this study aims at trying to apply unit hydrograph method in long-term runoff analysis for the betterment of its estimation. Four test catchment areas were selected ; Maesan area in Namlum river as a representative area of Han river system, Cheongju area in Musim river as one of Geum river system, Hwasun area in Hwasun river as one of Yongsan river system, and Supyung area in Geum river as one of Nakdong river system. In the analysis of unit hydrograph, seperation of effective rainfall was carried out firstly. Considering that effective rainfall and moisture condition of catchrnent area are inside and outside of a phenomenon respectively and the latter is not considered in the analysis, Initial base flow(qb)was selected as an index of moisture condition. At the same time, basic equation(Eq.7) was established, in which qb can take a role as a parameter in relating between cumulative rainfall(P) and cumulative loss of rainfall(Ld). Based on the above equation, computer program for estimation model of qbwas seperately developed according to the range of qb, Developed model was applied to measured hydrographs and hyetographs for total 10 years in 4 test areas and effective rainfall was estimated. Estimation precision of model was checked as shown in Tab- 6 and Fig.8. In the next stage, based on the estimated effective rainfall(R) and runoff(Qd), a runoff distribution ratio was calculated for each teat area using by computerised least square method and used in making unit hydrographs in each test area. Significance of induced hydrographs was tested by checking the relative errors between estimated and measured runoff volume(Tab-9, 10). According to the results, runoff estimation error by unit hydrograph itself was merely 2 or 3 %, but other 2 or 3 % of error proved to be transferred error in the seperation of effective rainfall. In this study, special attentioning point is that, in spite of different river systems and forest conditions of test areas, standardized unit hydrographs for them have very similar curve shape, which can be explained by having similar catchinent characteristics such as stream length, catchinent area, slope, and vegetation intensity. That fact should be treated as important factor ingeneralization of unit hydrograph method.

• KSBB Journal
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• 제10권5호
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• pp.491-498
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• 1995

Cyclodextrin의 고순도 분획, 정제를 위한 CD adsorbent의 제조에 척합한 matnx를 선별하기 위하여 capric acid를 ligand로 각종 이온교환수지를 비교 검토한 결과 DEAE Cellulose가 가장 적합함을 알았다. DEAE Cellulose와 capric acid간의 결합 안정성은 온도, ionic strength의 변화에 영향을 받았으며, ethanol 농도의 변화에는 안정하였다. CD adsorbent의 흡착량, 탈착량, 그리고 ${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD 의 용출양상을 규명하였다. 탄소쇄가 다른 각종 포화, 불포화 fatty acid를 ligand로 하여 specific adsorbent를 제조하였으며, ${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD의 회수율과 분리능을 비교 검토 하였다. 그 결과 steanc a acid는 ${\alpha}$-CD 그리고 linoleic acid는 ${\beta}$-CD에 대하여 높은 회수율과 선택성을 보였으며, 선택성은 fatty acid의 탄소쇄 길이와 이중결합 유무에 의하여 영향을 받았다. Stearic acid와 linoleic acid CD adsorbents를 이용하여 CD 혼합물로부터${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD의 분획양상을 검토하였다.

• 한국인터넷방송통신학회논문지
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• 제11권2호
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• pp.107-112
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• 2011

$n=pq$인 합성수 을 크기가 비슷한 p와 q로 소인수분해하는 것은 매우 어려운 문제이다. 대부분의 소인수분해 알고리즘은 $a^2{\equiv}b^2$ (mod $n$)인 제곱 합동이 되는 ($a,b$)를 소수의 곱 (인자 기준, factor base, B)으로 찾아 $a^2-b^2=(a-b)(a+b)$ 공식에 의거 유클리드의 최대공약수 공식을 적용하여 $p=GCD(a-b,n)$, $q=GCD(a+b,n)$으로 구한다. 여기서 ($a,b$)를 얼마나 빨리 찾는가에 알고리즘들의 차이가 있으며, B를 결정하는 어려움이 있다. 본 논문은 좀 더 효율적인 알고리즘을 제안한다. 제안된 알고리즘에서는 $n+1$을 3자리 소수까지 소인수분해하여 B를 추출하고 B의 조합 $f$를 결정한다. 다음으로, $a=fxy$가 되는 값을 $\sqrt{n}$ < $a$ < $\sqrt{2n}$ 범위에서 구하여 $n-2$의 소인수분해로 $x$를 얻고, $y=\frac{a}{fx}$, $y_1$={1,3,7,9}을 구한다. 제안된 알고리즘을 몇 가지 사례에 적용한 결과 $\sqrt{n}$ < $a$를 순차적으로 찾는 기존의 페르마 알고리즘에 비해 수행 속도를 현격히 단축시키는 효과를 얻었다.