This study numerically compares optimum solutions generated by element- and node-wise topology optimization designs for free vibration structures, where element-and node-wise denote the use of element and nodal densities as design parameters, respectively. For static problems optimal solution comparisons of the two types for topology optimization designs have already been introduced by the author and many other researchers, and the static structural design is very common. In dynamic topology optimization problems the objective is in general related to maximum Eigenfrequency optimization subject to a given material limit since structures with a high fundamental frequency tend to be reasonable stiff for static loads. Numerical applications topologically maximizing the first natural Eigenfrequency verify the difference of solutions between element-and node-wise topology optimum designs.

This study aimed to determine the optimal planting density for sesame cultivation in a double cropping system after harvesting onion and garlic in the Muan region. It compared the growth, yield, disease susceptibility, and labor hours for two varieties of sesame (Landrace and Geonbaek sesame) at different planting densities. Plant height in the Landrace sesame showed no significant variation with different planting densities, whereas Geonbaek sesame increased in height with higher planting densities. Both cultivars increased the number of viable branches at lower densities. The stem diameter was thicker in Landrace sesame with decreasing planting density, while in the Geonbaek sesame, there was no significant difference in stem diameter regardless of planting density. The number of capsules per plant for the Landrace sesame increased with decreasing density, whereas Geonbaek sesame showed no significant difference. Yield for both cultivars was higher at greater densities. However, the late direct sowing time and shorter cultivation period significantly reduced the yield of sesame cultivated in a double cropping system compared to that of sesame grown in a single cropping system, due to the late direct sowing time and shorter cultivation period. There was no significant difference in disease occurrence based on planting density. Furthermore, although labor hours did not vary with planting density when comparing the labor hours required for cultivating the Landrace sesame and Geonbaek sesame, the latter needed less labor time. This study reveals the optimum planting distance and density for sesame cultivation as a double cropping after harvesting onion and garlic, providing invaluable data for establishing sesame double cropping cultivation techniques.

In this study, we investigated the microstructure and piezoelectric properties of 0.96(K0.456Na0.536)Nb0.95Sb0.05-0.04 Bi0.5(Na0.82K0.18)0.5ZrO3 (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 °C. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d33 = 506 pC/N for one-step specimen sintered at 1,100 °C (one-step 1,100 °C specimen). However, for one-step 1,115 °C specimen, a slight decrease in d33 was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 °C specimen, the two-step specimen exhibited higher piezoelectric coefficients (d33 = 574 pC/N and kp = 0.5) than those of the one-step 1,100 °C specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and twostep specimens showed that despite having a higher g33, the magnetoelectric composite with the one-step 1,100 °C specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest kp. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

In this study, we estimated the distribution density of giant jellyfish in coastal waters of Korea in 2023 and compared the occurrence of giant jellyfish over four years. In May, the giant jellyfish were mainly distributed in the waters of the Yangtze River outflow, and in July, they were highly distributed in the west of Jeju Island and near the south coast of Korea. In addition, when comparing the distribution densities of giant jellyfish in Korea over four years, both acoustic and sighting surveys showed that the highest density of jellyfish occurred in 2021.

This study was conducted to analyze the effects of stand density on fire fuel (FF) changes in a Chamaecyparis obtusa forest. The study site was located in Mt. Munsu in Jeollabuk-do and consisted of a control, 30% thinning treatment (LT), and 50% thinning treatment (HT). Three-year-old seedlings were planted at a density of 3,000 trees ha-1 in 1976, and thinning was carried out in 2000. FF production was measured every 2 months by installing 3 circular litter traps 1.2 m above the ground. Litter bags containing 5 g of each leaf and branch were made and buried in the organic layer to investigate the FF decomposition rate. The decay constant was calculated after 18 months. FF accumulation was measured by collecting dry-weight organic matter from each plot using a square frame (0.09 m2) in September 2018. The FF production in LT and HT was significantly lower than that of the control (P<0.001). The leaf decay constant for HT was significantly lower than that of the control (P<0.05). The FF accumulation in HT was significantly lower than that of the control (P<0.01), but LT was not significantly different from the control. The results of this study showed that thinning decreased FF production.

도농복합시는 1995년 지방자치제가 본격 시행되면서 주민 편의를 증진하고, 도시와 농촌 지역의 균형발전을 목적으로 설치되었다. 본 연구는 우리나라 전체 54개 도농복합시를 대상으로 도시 스프롤 측면에서 도시공간구조를 분석하고자 하였다. 이를 위해 밀도 기반의 도시 스프롤 측정 지수를 적용하여 2000년, 2010년, 2020년 도농복합시의 도시 스프롤을 인구밀도 및 고용밀도의 측면에서 탐색하였다. 분석 결과, 도농복합시의 인구 스프롤은 전반적으로 증가한 반면, 고용 스프롤은 감소하는 경향을 보였다. 그리고 도시 규모별 도농복합시의 도시 스프롤은 차별화되어 진행되었음을 확인하였다.

The objective of this study was to achieve biological control of green mold disease in Pyogo mushrooms using antagonistic microorganisms. Bacillus subtilis BSM320 cells inhibited mycelial growth by 48–60% against three Trichodermaisolates including T. hazianumisolated from the substrates of Lentinula edodes, showing their antifungal activity.The bacteria were cultured to a high density of 4.2 x 109±113.7 cfu/mlin aqueous extract of composted spent mushroom substrates of L. edodes containing 1% glucose and showed a higher growth rate than that observed when using the commercial medium, Luria-Bertani broth. The bacterial culture showed a 75% protective effect without damaging the mushroom fruiting bodies. These results suggest that B. subtilis BSM320culture is suitable for biological control of green mold disease during mushroom cultivation.

In this study, based on the saturation magnetic flux density experimental values (Bs) of 622 Fe-based bulk metallic glasses (BMGs), regression models were applied to predict Bs using artificial neural networks (ANN), and prediction performance was evaluated. Model performance evaluation was investigated by using the F1 score together with the coefficient of determination (R2 score), which is mainly used in regression models. The coefficient of determination can be used as a performance indicator, since it shows the predicted results of the saturation magnetic flux density of full material datasets in a balanced way. However, the BMG alloy contains iron and requires a high saturation magnetic flux density to have excellent applicability as a soft magnetic material, and in this study F1 score was used as a performance indicator to better predict Bs above the threshold value of Bs (1.4 T). After obtaining two ANN models optimized for the R2 and F1 score conditions, respectively, their prediction performance was compared for the test data. As a case study to evaluate the prediction performance, new Fe-based BMG datasets that were not included in the training and test datasets were predicted using the two ANN models. The results showed that the model with an excellent F1 score achieved a more accurate prediction for a material with a high saturation magnetic flux density.

Metal additive manufacturing (AM) has transformed conventional manufacturing processes by offering unprecedented opportunities for design innovation, reduced lead times, and cost-effective production. Aluminum alloy, a material used in metal 3D printing, is a representative lightweight structural material known for its high specific strength and corrosion resistance. Consequently, there is an increasing demand for 3D printed aluminum alloy components across industries, including aerospace, transportation, and consumer goods. To meet this demand, research on alloys and process conditions that satisfy the specific requirement of each industry is necessary. However, 3D printing processes exhibit different behaviors of alloy elements owing to rapid thermal dynamics, making it challenging to predict the microstructure and properties. In this study, we gathered published data on the relationship between alloy composition, processing conditions, and properties. Furthermore, we conducted a sensitivity analysis on the effects of the process variables on the density and hardness of aluminum alloys used in additive manufacturing.

Aluminum alloy-based additive manufacturing (AM) has emerged as a popular manufacturing process for the fabrication of complex parts in the automotive and aerospace industries. The addition of an inoculant to aluminum alloy powder has been demonstrated to effectively reduce cracking by promoting the formation of equiaxed grains. However, the optimization of the AM process parameters remains challenging owing to their variability. In this study, the response surface methodology (RSM) was used to predict the crack density of AM-processed Al alloy samples. RSM was performed by setting the process parameters and equiaxed grain ratio, which influence crack propagation, as independent variables and designating crack density as a response variable. The RSM-based quadratic polynomial models for crack-density prediction were found to be highly accurate. The relationship among the process parameters, crack density, and equiaxed grain fraction was also investigated using RSM. The findings of this study highlight the efficacy of RSM as a reliable approach for optimizing the properties of AM-processed parts with limited experimental data. These results can contribute to the development of robust AM processing strategies for the fabrication of highquality Al alloy components for various applications.

외부하중을 받는 구조물로부터 계측된 신호의 파워 스펙트럴 밀도함수는 모달 파라미터(고유진동수, 감쇠비)에 대한 상당량 의 정보를 함축하고 있다. 시스템 식별기술은 이러한 신호나 해당 스펙트럼으로부터 모달 파라미터를 추출하는 기법이라고 볼 수 있 다. 파라미터를 추출하는 또 다른 기법으로는 샘플링(신호)을 이용하여한 확률분포의 모수(평균, 분산)를 추정하는 기법이다. 본 연구 에서는 파워 스펙트럼 밀도함수를 확률분포로 치환함으로써 기존 확률통계분야에서 모수를 추출하는 기법(최대우도법)에 의해 모달 파라미터를 추정하는 기법을 제안한다. 모드형상을 추정하는 기법을 개발하고 모드형상에 의해 분해된 모드응답으로부터 고유진동수, 고유감쇠비를 순차적으로 산정하는 기법을 제시한다. 더 나아가, 외부하중이 스펙트럼 해석모델로 치환 가능한 경우에는 이 하중모델 은 통합하여 모델 파라미터까지 산정하는 기법으로 확대한다. 본 연구에서 제시된 기법을 검증하기 위한 수치해석과 실구조물의 응답 에 대한 적용이 이루어졌으며, 검증결과 제안된 모드식별체계가 안정적이며, 신뢰도가 높은 모달파라미터 추정이 가능함을 알 수 있었다.

흰점박이꽃무지[Protaetia brevitarsis seulensis (Kolbe)]의 적정 사육 밀도를 구명하기 위해 상대적으로 발육기간이 긴 3령 유충을 대상으로 밀도 실험을 수행하였다. 3령 유충기부터 번데기까지의 발육기간과 3령 유충부터 성충까지의 발육기간은 모두 30마리 밀도에서 가장 짧았다. 하지만, 번데기에서 성충까지 걸리는 시간은 유의미한 차이가 없었다. 성충의 외형적 특성도 밀도 간 통계적으로 유의미한 차이가 나타났는데, 그중 20마리 밀도 조건에서 사육된 성충은 무게와 체장, 체폭이 가장 우량하였다. 암수의 외형적 특성 차이는 주로 20마리 조건에서 유의미하게 나타났다. 암컷은 밀도 조건에 영향을 받지 않았지만, 수컷의 경우는 모든 외형적 특성에서 밀도에 영향을 받는 것으로 분석되었으며, 특히 20마리 조건은 다른 조건보다 성충의 크기가 큰 것을 확인하였다. 결론적으로, 흰점박이꽃무지의 3령 유충은 3L 사육상자에 30마리 밀도 조건으로 사육하는 것이 효율적이며, 이를 통해 3령에서 성충까지의 발육기간을 단축할 수 있고, 사료 비용도 절감할 수 있다.

본 연구는 주요 참나무류 수종인 신갈나무, 굴참나무, 상수리나무의 임분밀도와 생장과의 관계를 파악하고 수종 간 비교를 통해 생장 유사성 여부를 판별하여 임분밀도관리도 개발 시 주요 참나무류의 생장 예측 모형개발의 방향성을 제시하기 위해 실시하였다. 제7차 국가산림자원조사의 신갈나무, 굴참나무, 상수리나무 우점림과 참나무류 혼효림의 임분생육 자료를 기반으로 수종별 경쟁-밀도효과 곡선을 산출하고 수종 간 교차 적용 후 차우검정(Chow test)을 통해 생장 유사성을 평가하였다. 수종별 경쟁-밀도효과 곡선은 ha당 1,000본에서 평균 재적이 급격히 감소하는 경향을 보이는 역 J자형을 나타내었다. 생장 유사성 평가 결과, 상수리나무와 굴참나무는 유사한 생장 패턴을 보였지만 신갈나무는 상수리나무 및 굴참나무와 생장 패턴에 차이가 있는 것으로 나타났다. 참나무류 혼효림은 굴참나무를 제외한 다른 수종들과 유사한 생장 패턴을 나타내었다.

Environmental DNA (eDNA) can exist in both intracellular and extracellular forms in natural ecosystems. When targeting harmful cyanobacteria, extracellular eDNA indicates the presence of traces of cyanobacteria, while intracellular eDNA indicates the potential for cyanobacteria to occur. However, identifying the “actual” potential for harmful cyanobacteria to occur is difficult using the existing sediment eDNA analysis method, which uses silica beads and cannot distinguish between these two forms of eDNA. This study analyzes the applicability of a density gradient centrifugation method (Ludox method) that can selectively analyze intracellular eDNA in sediment to overcome the limitations of conventional sediment eDNA analysis. PCR was used to amplify the extracted eDNA based on the two different methods, and the relative amount of gene amplification was compared using electrophoresis and Image J application. While the conventional bead beating method uses sediment as it is to extract eDNA, it is unknown whether the mic gene amplified from eDNA exists in the cyanobacterial cell or only outside of the cell. However, since the Ludox method concentrates the intracellular eDNA of the sediment through filtration and density gradient, only the mic gene present in the cyanobacteria cells could be amplified. Furthermore, the bead beating method can analyze up to 1 g of sediment at a time, whereas the Ludox method can analyze 5 g to 30 g at a time. This gram of sediments makes it possible to search for even a small amount of mic gene that cannot be searched by conventional bead beating method. In this study, the Ludox method secured sufficient intracellular gene concentration and clearly distinguished intracellular and extracellular eDNA, enabling more accurate and detailed potential analysis. By using the Ludox method for environmental RNA expression and next-generation sequencing (NGS) of harmful cyanobacteria in the sediment, it will be possible to analyze the potential more realistically.

본 연구는 절화용 튤립(Tulipa spp.) 4품종을 대상으로 재 식밀도에 따른 생장과 발육 특성을 알아보고 광이용효율을 분 석하여 우리나라에서 튤립 촉성재배시 필요한 기초자료를 얻 고자 실시되었다. 절화용 튤립 ‘Novi Sun’, ‘Timeless’, ‘Il de France’, ‘Dow Jones’ 4품종을 대상으로 구근용 재배 상자 (가로×세로×높이; 60cm×40cm×20cm)에 상자당 48, 70, 96개의 구근을 정식하여 저온처리 이후 비닐하우스로 운반되 었다. 그 결과, ‘Novi Sun’과 ‘Timeless’는 온실 이식 이후 35 일 만에 수확되었으며 ‘Il de France’와 ‘Dow Jones’는 그보 다 빠른 30일 만에 수확되었다. 모든 품종에서 재식밀도가 증 가할수록 생체중, 줄기 직경, 엽면적이 감소하였다. 정상개화 율은 96bulbs/box 처리에서 특히‘Novi Sun’ 32.7%과 ‘Timeless’ 4.7%로 감소하였으며 이 두 품종에서 줄기와 꽃의 건물중이 크게 감소하는 것으로 나타났다. 광이용 효율과 밀접 한 지표인 엽면적지수는 재식밀도가 높아질수록 증가하였다. 광합성 효율은 ‘Novi Sun’과 ‘Timeless’의 경우 저광도에서 재식밀도에 따라 큰 차이가 없는 것으로 나타났다. 엽면적 감 소와 형태적인 변화가 작은 ‘Il de France’과 ‘Dow Jones’에 서 광합성 효율이 크게 변화하였다. 재식밀도에 따라 다양한 생육 반응은 유사한 경향은 있으나 품종에 따라 광합성 효율과 동화산물의 분배가 크게 달라지는 것으로 나타났다. 튤립 촉성 재배 시 정상적인 꽃의 발달과 생육 확보를 위해서는 충분한 재식 간격을 확보할 수 있는 재식밀도로 정식해야 한다.

선택적 촉매 환원법(SCR)은 질소산화물(NOx)을 저감하는 매우 효율적인 방법으로 알려져 있으며 발생된 질소산화물(NOx)을 질 소(N2)와 수증기(H2O)로 환원시키는데 촉매 작용을 한다. 질소산화물(NOx) 저감 성능을 결정하는 요소 중 하나인 촉매는 셀 밀도가 증가하 면 촉매효율이 증가하는 것으로 알려져 있다. 본 연구에서는 실습선 세계로호에 설치되어 있는 발전 기관의 배기가스 조건을 모사한 실 험장치를 통하여 100CPSI(60Cell)촉매의 부하에 따른 질소산화물(NOx) 저감 성능을 확인하고 세계로호에 설치되어 있는 25.8CPSI(30Cell) 촉 매의 기존 연구 자료와의 비교를 통해, 셀 밀도가 질소산화물(NOx)의 저감에 미치는 영향에 대하여 고찰하였다. 실험용 촉매는 셀 밀도만 변화를 주었고 형태는 벌집형(honeycomb), 조성물질은 V2O5-WO3-TiO2를 동일하게 사용하여 제작하였다. 실험결과 100CPSI(60Cell) 촉매의 질소산화물(NOx) 농도 저감율은 평균적으로 88.5%이며 IMO specific NOx 배출량은 0.99g/kwh로 IMO Tier III NOx 배출기준을 만족하였다. 25.8CPSI(30Cell) 촉매의 경우, 질소산화물(NOx) 농도 저감율은 78%, IMO specific NOx 배출량은 2.00g/kwh 이었다 두 촉매의 NOx 농도 저감 율과 IMO specific NOx 배출량을 비교하였을 때, 100CPSI(60Cell)촉매가 25.8CPSI(30Cell) 촉매보다, NOx 농도 저감율은 10.5% 높고 IMO specific NOx 배출량은 약 2배 적은 것을 확인하였다. 따라서 촉매의 셀 밀도를 높임으로써 효율적인 탈질효과를 기대할 수 있으며 향후 실선 테스트를 통하여 검증한다면 촉매의 부피 저감을 통한 제작 비용을 줄이고 협소한 선박 기관실을 효율적으로 사용하기 위한 실용적 인 자료로서 기대된다.