This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

The integrity of the disposal repository structure must be guaranteed for few hundreds to few hundred thousand years until toxicity of radioactive waste is surely degraded. Acoustic emission (AE) method is widely utilized to evaluate the integrity of the structure because it can detect crack wave signals of the structures. It is well known that the cracking AE energy is proportional to the volume of the structure (Fractal theory). However, it is hard to destroy whole structures for obtaining AE energy. Therefore, the scaled specimens are prepared to obtain the relationship between volume of the structure and AE energy. The specimens are prepared with same of Wolsong Low and Intermediate Level Radioactive Waste Disposal Center (WLDC) silo concrete recipe. Their diameters are from 50 mm to 150 mm in each 10 mm and their heights are twice of the diameter. One set of 50 mm to 150 mm specimens (11 specimens in one set) are made in single mixers to maintain uniformity. Surface of the specimens are flatten with cement milk to prevent from applying load with eccentricity. The uniaxial compression test is performed by controlling displacement as 0.1 mm/min. The fractal constant is obtained using least square function from volume-cumulative AE energy relationship.

최근에 감에서 떫은맛을 조절하는 AST에 연관된 지역에서 분자 표지들이 개발되었다. 이중에서 sequence characterized amplified region (SCAR) marker는 5R region에 인접한 지역에서 개발되었다. 하지만 이 SCAR마커는 분석 방법이 다소 복잡하고 해석이 어려워 많은 교배실생을 분석할 경우에는 적합하지 않다. 우리는 5R 지역의 sequences에 기반하여 high-resolution melting (HRM)-based 분자 표지를 개발하였다. 개발된 HRM preimer set을 8개 품종의 단감 및 떫은감에 대해 적용한 결과 단감 품종에서는 직선을 나타낸 반면 떫은감 품종에서는 다양한 크기의 곡선으로 나타나서 차이를 확인할 수 있었다. 결과적으로 이번 연구에서 개발된 HRM primer set은 분자 표지를 활용한 감 품종 육성 연구에 매우 효율적으 로 활용될 수 있을 것으로 기대된다.

Commercial ultra-high-strength PAN-based carbon fibers (T1000G) were heat-treated at the temperature range of 2300– 2600 °C under a constant stretching of 600 cN. After continuous high-temperature graphitization treatment, microstructures, mechanical properties and thermal stability of the carbon fibers were investigated. The results show that the T1000G carbon fibers present the similar round shape with a smooth surface before and after graphitization, indicating the carbon fibers are fabricated by dry–wet spinning. In comparison, the commercial high-strength and high-modulus PAN-based carbon fibers (M40JB and M55JB) present elliptical shapes with ridges and grooves on the surface, indicating the carbon fibers are fabricated by wet spinning. After graphitization treatment from 2300 to 2600 °C under a constant stretching of 600 cN, the Young’s modulus of the T1000G carbon fibers increases from about 436 to 484 GPa, and their tensile strength decreases from about 5.26 to 4.45 GPa. The increase in Young’s modulus of the graphitized T1000G carbon fibers is attributed to the increase in the crystallite sizes and the preferred orientation of graphite crystallites along the fiber longitudinal direction under a constant stretching condition. In comparison with the M40JB and the M55JB carbon fibers, the graphitized T1000G carbon fibers are easier to be oxidized, which can be contributed to the formation of more micropores and defects during the graphitization process, thus leading to the decrease in the tensile strength.

The wakes behind a square cylinder were simulated using two-equation turbulence models, k-ε and RNG k-ε models. For comparisons between the model predictions and analytical solutions, we employed three skill assessments:, the correlation coefficient for the similarity of the wake shape, the error of maximum velocity difference (EMVD) of the accuracy of wake velocity, and the ratio of drag coefficient (RDC) for the flow patterns as in the authors’ previous study. On the basis of the calculated results, we discussed the feasibility of each model for wake simulation and suggested a suitable value for an eddy viscosity related constant in each turbulence model. The k-ε model underestimated the drag coefficient by over 40 %, and its performance was worse than that in the previous study with one-equation and mixing length models, resulting from the empirical constants in the ε-equation. In the RNG k-ε model experiments, when an eddy viscosity related constant was six times higher than the suggested value, the model results were yielded good predictions compared with the analytical solutions. Then, the values of EMVD and RDC were 3.8 % and 3.2 %, respectively. The results of the turbulence model simulations indicated that the RNG k-ε model results successfully represented wakes behind the square cylinder, and the mean error for all skill assessments was less than 4 %.

The push-out tests have been conducted on the specimens which consist of the steel beam with U-shape section and the cap-type shear connectors with constant intervals. Existing equations for the evaluation of shear connector strength have been investigated on the basis of test results. The reinforcing bars for longitudinal reinforcement and the penetrative bars for transverse reinforcement didn’t have much effect on the shear capacity of the cap-type shear connector. The larger the width of cap-type shear connector was profiled, the greater the shear strength turned. The shear capacities of cap-type shear connectors with constant intervals were evaluated on the basis of push-out test results, and those were possible to be determined with proper safety margin using the Eurocode 4. The slip capacity of cap-type shear connector was shown to exceed the limit value of 6mm for sufficiently ductile behavior.

선박용 연료유가 연소하는 과정에서 배출되는 오염물질은 대기오염을 유발하고 인체에 유해한 영향을 미치는 것으로 알려져 있다. 그에 따라, IMO에서는 선박에서 배출되는 오염물질을 규제하고 있다. 하지만 입자상물질(Particulate matter: PM)에 대한 규제는 아직 논의단계에 있으므로 선제적인 대응이 필요하다. 그러기 위해서는 입자상물질에 대한 기초적인 연구가 필수적이다. 이번 연구에서는 해상용 연료유에서 발생하는 입자상물질의 기초 데이터 구축을 위해 선박 디젤 엔진에 사용되는 연료유의 무차원 광소멸계수(Ke)를 계측하여 분석하였다. 특성 비교를 위해 육상 디젤 엔진에 사용되는 연료유를 같은 방법으로 측정하였다. 두 연료유는 황함유량과 밀도에서 차이가 난다. 무차원 광소멸계수(Ke)는 633 nm의 레이저를 이용하여 광학적인 방법으로 측정하고 중력식 필터법에 의해 채집된 입자상물질의 체적분율을 이용하여 결정하였다. 선박용 연료유에서 배출되는 입자상물질의 무차원 광소멸계수(Ke)는 8.28이고, 육상용 연료유는 8.44 이다. 두 연료유의 무차원 광소멸계수(Ke)는 측정 불확도 범위내에서 거의 유사하였다. 하지만 Rayleigh limit 해법에서 구한 값과의 비교를 통해 광산란 비중이 클 수 있는 부분과 광투과율과 채집질량과의 관계를 통해 광소멸 특성이 상이할 수 있음을 확인하였다.

General D-glass(Dielectric glass) fibers are adaptable to PCBs(Printed circuit boards) because they have a low dielectric constant of about 3.5~4.5. However, very few papers have appeared on the physical characteristics of D-glass fibers. D-glass fibers were fabricated via continuous spinning process using bulk D-glass. In order to fabricate the D-glass, raw materials were put into a Pt crucible, melted at 1650℃ for 2 hrs, and then annealed at 521 ± 10℃ for 2 hrs. We obtained transparent clear glass. The transmittance and adaptable temperature for spinning of the bulk marble glass were characterized using a UV-visible spectrometer and a viscometer. Continuous spinning was carried out using direct melting spinning equipment as a function of the fiberizing temperature in the range of 1368℃ to 1460℃, while the winder speed was between 100 rpm and 200 rpm. We investigated the physical properties of the D-glass fibers. The average diameters of the glass fibers were measured by optical microscope and FE-SEM. The average diameters of the D-glass fibers were 21.36 um at 100 rpm and 34.06 um at 200 rpm. The mechanical properties of the fibers were confirmed using a UTM(Universal materials testing machine). The average tensile strengths of the D-glass fibers were 467.03 MPa at 100 rpm and 522.60 MPa at 200 rpm.

금속 유기 골격체(Metal Organic Framework, 이하 MOF) 종류의 하나인 제올라이트형 이미 다졸레이트 골격체(Zeolitic Imidazolate Framework, 이하 ZIF) 중 ZIF-8은 Zn 금속이온과 imidazole 유기 리간드의 결합으로 이루어져 있다. 본 연구에서는 여러 종류의 용매에서 합성된 ZIF-8의 1차 결정과 2차 입자의 형성이 용매가 가진 특성에 영향을 받는 것을 확인하였다. HBD(hydrogen bond donation) 값이 큰 용매에서 합성된 ZIF-8의 1차 결정은 HBD 값이 작은 용매에서의 것보다 크기가 컸고, 용매의 유전상수의 값이 작을수록 2차 입자의 크기가 큰 ZIF-8이 합성되었다.

In physical engineering, the turbulent flow on the surface roughness is very important. The roughness of the surface changed the distance of the interval. The roughness coefficient occurred with increasing turbulence intensities was stronger. The turbulence intensity away from the roughness in the shape was zero. The variation of turbulence intensity at the experimental flow conditions change was not affected.

MAO ceramic coatings were prepared on AZ61 magnesium alloy for various processing times ranging from 5 to 60 min, in an electrolyte solution based on silicate-fluoride. The mechanical, electrochemical and, microstructural properties and the phase compositions of the coating layers were investigated. In this work, unlike previous studies, coatings with high amounts of the Mag2SiO4 phase were formed which contained small amounts of MgO and MgF2 at a processing condition of 30 min. A microstructural analysis revealed that the porosity of the coatings was reduced considerably with an increase in the processing time, together with a change in the pore geometry from an irregular to a spherical shape. Potentiodynamic polarization and mechanical testing results showed that the coatings acquired after a processing time of 30 min were superior to all of the others.

We made phase-referencing Very Long Baseline Interferometry (VLBI) observations of Galactic 22 GHz H2O maser sources with VLBI Exploration of Radio Astrometry (VERA). We measured the parallax dis- tances of G48.61+0.02, G48.99-0.30, G49.19-0.34, ON1, IRAS 20056+3350, IRAS 20143+3634, ON2N, and IRAS 20126+4104, which are located near the tangent point and the Solar circle. The angular ve- locity of the Galactic rotation at the LSR (i.e. the ratio of the Galactic constants) is derived using the measured parallax distances and proper motions of these sources. The derived value of Ω0 = 28:8  1:7 km s-1 kpc-1 is consistent with recent values obtained using VLBI astrometry but 10% larger than the International Astronomical Union (IAU) recommended value of 25.9 km s-1 kpc-1 = (220 km s-1) / (8.5 kpc).