3D 콘크리트 프린팅 기술은 거푸집 없이 콘크리트를 출력하고 제작하여 콘크리트 표면의 대부분이 외기에 노출되고, 이로 인해 콘크리트 내부 수분이 빠르게 증발하고 수축이 크게 발생한다. 또한, 결합 재 대비 낮은 골재 함량과 낮은 물/결합재 비(W/B)를 가지는 사용 배합의 특성상 수축으로 인한 균 열이 발생하기 쉽다. 이러한 3D 콘크리트 프린팅의 수축에 대한 문제는 섬유 혼입을 통해 해결할 수 있고, 부가적으로 적층성 향상의 이점을 얻을 수 있다. 본 연구에서는 이러한 섬유 보강 3D 프린팅 모르타르의 역학적 특성을 살펴보고자 섬유 혼입률을 변수로 실험하였다. 보강 섬유로는 PP섬유를 사 용하였고, 섬유 혼입률 0, 0.2, 0.5, 0.8%를 변수로 실험하였다. 갠트리 방식의 3D 프린터에 30 × 30 mm 사각형 개구부를 가진 노즐을 설치해 1300× 800mm 크기의 직사각형 형태로 모르타르를 출력 하였다. 호퍼 회전속도 6 rpm, 노즐 이동 속도 1500 mm/min을 적용하여 출력하였고, 1층 높이를 30mm로 출력하여 5층 적층하였다. 적층 완료 후 압축강도, 휨인장강도, 층간 부착강도를 측정하기 위 한 시험체를 각각 추출하였고, 28일 수중 양생 후 각 강도실험을 통해 역학적특성을 평가하였다.

3D 프린팅 콘크리트는 임의의 형상을 자유롭게 적층하여 제작할 수 있다는 장점을 가지고 있지만, 노즐의 구조 및 형상에 따라 곡선부의 출력 품질이 달라진다. 또한, 공기중에서 출력한 경우와 수중에 서 출력한 경우 그 품질이 달라진다. 본 연구에서는 고정 마감날을 가진 사각형 노즐을 이용하여 3D 프린팅 모르타르를 수중에서 곡선 형태로 출력하고 적층한 후 출력성능, 적층성능, 및 역학적성능을 평가하였다. 30 × 30 mm 사각형 개구부를 가지고 있고 노즐 끝 양 측면에 고정 마감날이 설치된 노 즐을 사용하였다. 사전 직선 출력시험에서 선정된 조건인 호퍼 회전속도 14 rpm, 노즐 이동 속도 2000 mm/min을 적용하여 출력하였고, 1층 높이를 30mm로 출력하여 5층 적층하였다. 출력 및 적층 결과, 직선부분의 표면은 양호한 반면 곡면부분, 특히 곡률이 큰 곡선부분의 바깥쪽에서 표면균열이 관찰되었다. 직선부분의 치수 일관성은 양호한 반면, 곡률 반경이 작은 곡선부분의 폭 차이가 나타났 다. 곡선부분의 밀도와 압축강도는 직선부분보다 낮았다. 이는 곡선부에서 직사각형 노즐 회전에 따른 재료 토출이 불균일하기 때문인데, 이러한 문제점을 보완할 수 있는 제어 기술 개발이 필요하다.

Regulatory Guide (RG) 1.60 presents the response spectra for the seismic design, especially for the safe shutdown earthquake (SSE), of nuclear power plants. This guide is applicable to a two-step process involving the issuance of construction permits and operating licenses (10 CFR Part 50) as well as the issuance of combined construction and operating licenses (COLs), early site permits (ESPs), and standard plant design certifications (10 CFR Part 52) [1]. New reactor designs, however, require modified design response spectra (MDRS) by broadening the high-frequency range from design response spectra (DRS) in RG 1.60. In order to generate artificial time histories to meet the acceptable criteria described in NUREG-0800 [2], it9s necessary to develop the power spectral density of the MDRS. In this paper, we generate the artificial earthquake time histories of the MDRS for further research.

In order to determine the future direction of Busan City’s tree planting policy in accordance with changes in automobile fuel and air pollutants, this study selected representative tree species planted in Busan and identified the biogenic volatile organic compounds (BVOCs) emission rate and characteristics of each species. First, representative tree species were selected for each street tree species, forest tree species, and park tree species, and the emission rate and major components of BVOCs were investigated for each tree species. Furthermore, by comparing the ozone generation potential (POCP) for each tree species, tree species with a low emission rate were selected. According to the POCP comparison, P. yedoensis, G. biloba, Z. serrata and C. retusus were selected as roadside tree species, P. densiflora and C. obtusa as forest species, and A. palmatum, C. japonica, and Q. myrsinaefolia were deemed suitable for park species. However, in the case of P. occidentalis, Quercus, and M. glyptostroboides, the emission rates of BVOCs were found to be high. Despite this, these tree species were found to display excellent CO2 absorption and carbon storage. The concentration of NOx in the city center is likely to decrease due to the current trend of transitioning to eco-friendly cars worldwide, resulting in less cars that rely on fossil fuels. Therefore, in the current climate where NOx emissions are still high, planting tree species with a low BVOCs emission rate would be an optimal approach. On the other hand, if the NOx concentration in the city is found to be very low due to changes in automobile fuel use, planting tree species with excellent BVOCs emission capacity and CO2 absorption would be ideal.

양산시 동면 금산리 일원의 공사현장 사면 3개 지점에서 미고결 퇴적층을 절단하는 단층이 확인되었으며, 노두 단면에서 관찰되는 단층의 상세 구조분석을 수행하였다. 이곳 금산리 지점은 기존에 제4기 단층운동이 보고된 가산단층 지점으로부터 북쪽으로 약 0 .6 k m 떨어진 곳에 위치한다. 관찰된 총 6조의 단층들은 14o-32oE 주향을 가지고 3조의 단 층들은 77o-87oNW, 나머지 3조의 단층들은 53o-62oSE로 경사진다. 단층에 의해 절단된 미고결 퇴적층은 동편의 금정산 에서 유래된 선상지 역암으로 주로 화강암 또는 화산암 기원의 직경 0.5m 이상의 거력으로 구성된다. 단층면 상에 발 달하는 단층조선은 역이동성 성분이 포함된 우수향 주향이동단층 운동감각을 지시하며, 이러한 변형특성은 한반도 현생 응력환경인 동북동-서남서 압축응력과 부합한다. 사면에서 관찰되는 기반암과 미고결 퇴적층과의 부정합면을 기준으로 산정한 단층의 겉보기 수직변위는 동편이 15 m, 서편이 1 m이다.

YSZ (Y2O3-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

The blockage rate for three kinds of nets commonly used in agricultural facilities was assessed by using the image acquisition and its relevant processing. By using both empirical relations presented by Idel’chik and Richards and Robinson, and the blockage rate obtained from the image processing, the pressure drop through the nets was predicted and also compared with wind tunnel experiment results. The results of the study showed that the blockage rate of the net was discriminated according to such factors as the magnitude of nets, the existence of inside threads, the thickness and number of threads. In addition, the blockage rate for the incident angle of 0° when the wind blew at the front had the range of 0.22－0.29 (0.22－0.32 when considering whole incident angles from 0° to 45° by 15°). For the nets with the blockage rate of about 30% or below, the prediction by the empirical relations of by Idel’chik and Richards and Robinson showed a little higher pressure drop overall than that of the wind tunnel test, but the use of the empirical relations and the blockage rate could be thought of as providing effectively meaningful guidelines for the safe design of agricultural facilities including nets because the wind tunnel test has been tedious and expensive. Further research and potential application on the prediction technique of the pressure drop, regarding both a subtle deformation by the wind and manufacturing methods with regard to the level of knots and the existence of inside threads, needs to be done for the nets with higher blockage rate.

Li1.5Al0.5Ti1.5(PO4)3 (LATP) is considered to be one of the promising solid-state electrolytes owing to its excellent chemical and thermal stability, wide potential range (~5.0 V), and high ionic conductivity (~10-4 S/cm). LATP powders are typically prepared via the sol-gel method by adding and mixing nitrate or alkoxide precursors with chelating agents. Here, the thermal properties, crystallinity, density, particle size, and distribution of LATP powders based on chelating agents (citric acid, acetylacetone, EDTA) are compared to find the optimal conditions for densely sintered LATP with high purity. In addition, the three types of LATP powders are utilized to prepare sintered solid electrolytes and observe the microstructure changes during the sintering process. The pyrolysis onset temperature and crystallization temperature of the powder samples are in the order AC-LATP > CA-LATP > ED-LATP, and the LATP powder utilizing citric acid exhibits the highest purity, as no secondary phase other than LiTi2PO4 phase is observed. LATP with citric acid and acetylacetone has a value close to the theoretical density (2.8 g/cm3) after sintering. In comparison, LATP with EDTA has a low sintered density (2.2 g/cm3) because of the generation of many pores after sintering.

There are records and claims that tung oil was applied to Korean traditional buildings and furniture as finishing paint. Records of the use of tung oil(桐油) exist in the Annals of the Joseon Dynasty(朝鮮王朝實錄) and The Royal Protocols of the Joseon Dynasty(朝鮮王朝儀軌). However, there is also a claim that tung oil was not produced in Korea on its own, and that tung oil was not applied to important buildings such as palaces. Silhak scholar(實學者) Seo Yu-gu says that in Korea, people do not know how to grow tung trees, and boiled perilla oil is called tung oil. If tung oil was used in the Joseon Dynasty, it would be necessary to use tung oil for waterproof coating to preserve current architectural heritage, otherwise, tung oil coating would not be desirable. Analyzing the Yeonggeon Uigwe(營建儀軌) among the Joseon Dynasty's Uigwes shows that tung oil is neither mentioned nor used. In addition, as a result of analyzing the Uigwes mentioned in tung oil, it was found that perilla oil or Myeongyu(明油), not tung oil, was recorded in the actual material used. Therefore, the records of the use of tung oil during the Joseon Dynasty can be seen as records using Myeongyu(明油) or Beopryeon perilla oil(法煉荏油).

본 연구는 보육교사가 지각하는 직무만족, 교육신념, 조직몰입, 역할수행에 대한 인식을 바탕으로 직업적합도와 근무 기관유형에 따른 차이를 알아보고, 주요변수들 간의 구조적 관계를 분석하는 것을 목적으로 하였다. 이를 통해 보육교사 가 자신의 역할수행을 원활하게 수행함으로써 영·유아교육기관이 교육서비스의 질을 향상시킬 수 있는 방안을 모색해보 고자 하였다. 이를 위해 보육교사 339명을 대상으로 설문조사를 실시하였으며, IBM SPSS Statistics 26.0과 AMOS 26.0 프로그램을 활용하여 수집된 자료를 분석하였다. 본 연구의 주요 결과는 다음과 같다. 첫째, 보육교사가 지각하는 직무만 족, 교육신념, 조직몰입의 수준은 보통이었고, 역할수행은 보통 이상으로 나타났다. 둘째, 보육교사는 직업적합도가 높을 수록 직무만족, 교육신념, 조직몰입, 역할수행에 대한 인식이 높았고, 보육교사가 국·공립어린이집에 근무하는 경우, 민간 어린이집 또는 가정어린이집에 근무하는 보육교사보다 직무만족, 조직몰입(정서적몰입), 역할수행에 대한 인식이 높았다. 셋째, 보육교사의 직무만족은 교육신념과 조직몰입에, 교육신념은 역할수행에 정(+)적인 영향을 미치는 반면, 직무만족과 조직몰입은 역할수행에, 교육신념은 조직몰입에 유의한 영향을 미치지 않는 것으로 나타났다. 넷째, 보육교사의 직무만 족이 역할수행에 미치는 영향에서 교육신념은 매개효과가 존재하나, 조직몰입은 매개효과가 유의하지 않은 것으로 나타 났다. 영·유아교육기관의 교육서비스 질을 향상시키기 위해서는 보육교사의 근무환경이 국·공립어린이집 수준으로 개선 되어야 하고, 이를 통해 보육교사의 직무만족과 조직몰입의 수준을 높이는 방안이 마련되어야 하며, 보육교사의 교육신 념을 제고시키기 위한 교육이 필요하다.

PURPOSES : Previously, the expansion state of the concrete pavement in which AAR occurred could not be determined. Because the current situation has not been evaluated, it has been difficult to prepare an appropriate response. In this study, a method for calculating the expansion amount of concrete pavement using the stiffness damage test (SDT) is proposed. METHODS : The SDT method was examined through a literature review. For the laboratory tests, specimens that generated AAR were produced based on the mix design (2018) of the Korea Expressway Corporation. SDT was used to calculate various mechanical properties, and their correlation with the expansion amount was reviewed. RESULTS : Using the SDT, various mechanical properties(elastic modulus, hysteresis area, plastic deformation, plastic deformation index, stiffness damage index, and nonlinear index) were calculated based on the expansion rate of the AAR. The elastic modulus was evaluated as the best predictor of the expansion rate. Thus, if the elastic modulus is calculated using SDT, a prediction equation can be used to calculate the amount of AAR expansion. This equation will need to be supplemented by further research. CONCLUSIONS : SDT was used to confirm that the expansion state due to the AAR of the concrete pavement could be indirectly evaluated. Among the mechanical properties related to SDT, the elastic modulus was found to be the most suitable for predicting the amount of expansion.

This study quantitatively evaluated size selectivity for three netting shapes (T0; regular, T45, T90) and hanging ratio (35%, 70%) of T0 netting used for trawl codend. The size selectivity experiment was performed in a tank using a cube experimental model with a length of 50 cm on one side and 389 experimental individuals, jack mackerel (Trachurus japonicus). In the selectivity analysis, a selectivity curve was created based on the selection ratio using a logistic function, and the 25%, 50%, and 70% selection length and selection range  were obtained. The T0 netting was 19.54 cm when the 50% selective length, which is a selectivity evaluation index, had a hanging ratio of 35%, a selection range of 0.51 cm, and 22.70 cm and 3.08 cm for the hanging ratio of 70%. The T45 netting was 24.34 cm and 2.13 cm, and the T90 netting was 23.51 cm and 2.84 cm. The results of the T45 netting and the T90 netting are similar, and the 50% selection length and selection range were relatively larger than the T0 netting. There was a significant difference in the correlation between the circumference of the inner circle of the mesh by the shape of the netting and the body girth of the experimental individual (Pearson test,      ). There was no significant difference in the correlation between the selection ratio by the T0 netting, T45 netting, and T90 netting with a 70% hanging ratio (one-way ANOVA,   ). The results of this study showed that selectivity such as T45 netting and T90 netting appeared when the hanging ratio, which maximizes the area of T0 netting, was maintained at 70%.

PURPOSES : This study predicts the concentration of suspended road dust (PM10) by analyzing meteorological, traffic, and atmospheric environmental data acquired at various angles, and attains a comprehensive understanding of the influencing factors of suspended road dust. METHODS : Experimental field methods were applied and statistical analyses were conducted. Field experiments were conducted using a vehicle-based measurement of suspended dust (PM10) to measure its concentration at the measurement site while maintaining a constant driving vehicular speed. Statistical analysis demonstrated the effects of the concentration of suspended dust on changes in meteorological and environmental factors and lanes per traffic volume at the time of measurement. Finally, a multiple linear regression model was applied to identify the factors which affected the generation of suspended dust. RESULTS : The analysis of suspended road dust concentrations according to the lanes per traffic volume and environmental factors showed that suspended dust concentrations increased at increasing driving speeds. In addition, the background concentration at the monitoring station was higher at high-wind speeds (>3.0 m/s) than at low-wind speeds (<1.6 m/s), but the suspended dust concentrations were higher at low-wind speeds. During the temperature inversion period from evening to morning, the suspended effects of traffic and meteorological factors were greater than the background concentration at the station. Multiple linear regression analysis showed that excluding yellow-dust days, which are known to affect atmospheric pollution levels, the accuracy of the model improved and resulted in increases in background PM10, vapor pressure, sea-level pressure, visibility, after-rainfall time, and in decreases in insolation and precipitation during low-wind speed conditions. CONCLUSIONS : At low-wind speeds, 5 days after rain, and when the relative humidity was higher than 72%, suspended dust was found to be higher than atmospheric PM10 concentration and may increase at increasing driving speeds and section lane traffic volumes. However, the volume of measured data in this study is limited to determining the patterns of suspended dust, as the silt loading of the operational road or the effects of prominent variables were not considered in this study. However, we identified prominent factors related to road-suspended dust for real-time road-dust predictions.