AlGaN/GaN high-electron-mobility transistors (HEMTs) are widely employed in power electronics and high-frequency systems because of their high-speed switching and high-power capabilities. However, conventional structures suffer from issues including mobility degradation and device deterioration at elevated temperatures, as well as current collapse and increased gate leakage under high-voltage operation. To address these issues, this work proposes metal-oxidesemiconductor HEMTs (MOS-HEMTs) incorporating an Al2O3/HfO2 stacked gate dielectric. Al2O3 provides excellent chemical stability at the AlGaN interface, reducing interface trap density, while its wide bandgap suppresses electron tunneling and lowers gate leakage. In contrast, HfO2 offers a high dielectric constant, improving oxide capacitance and enhancing charge control even at the same physical thickness. The stacked Al2O3/HfO2 structure leverages the complementary advantages of both materials, enabling threshold voltage stabilization and effective suppression of leakage current. This design mitigates the thermal and electrical reliability concerns of conventional HEMTs and paves the way for high-performance GaN-based devices suited to next-generation high-speed, high-power applications such as artificial intelligence, 5G communication, and LiDAR systems.

Polymeric materials are extensively utilized in various industrial applications, including as gas barriers, fuel cells, sensors, and in semiconductor processes, and are particularly critical to ensure sealing performance in high-pressure gas systems. The diffusivity and solubility of gases within polymers significantly influences their sealing efficacy and is closely related not only to polymer–gas interactions but also to the thermodynamic properties of the gases. Notably, gas solubility exhibits a quantitative correlation with critical temperature, attributed to the condensability of the gas molecules. In this study, the solubility of five pure gases (H2, He, N2, O2, Ar) with varying critical temperatures was quantitatively measured and analyzed under high-pressure conditions (1-10 MPa) in four polymers differing in structure and density. The experiments employed both volumetric and manometric methods to measure gas desorption concentration, with meticulous corrections for minor temperature and atmospheric pressure variations to ensure data accuracy. The results demonstrated that the logarithmic solubility of gases in polymers increases linearly with the gas critical temperature, consistent across all polymer samples. This finding aligns with predictions from the Non-Equilibrium Lattice Fluid (NE-LF) model, which has been shown to accurately describe gas solubility behavior in glassy polymers.

목적 : 본 연구는 발달연령 3세부터 6세에 해당하는 자폐스펙트럼 장애 아동과 일반 아동을 대상으로, 시선 추 적 장치(Eye-Tracker)와 시각장면디스플레이(Visual Scene Displays, VSD)를 활용하여 색 선호도가 시각적 매 끄러움과 시각적 주의집중력에 미치는 영향을 알아보고자 하였다. 방법 : 본 연구의 대상자는 자폐스펙트럼 장애 아동 23명과 일반 아동 28명으로 구성되었다. 시선추적장치(Eye- Tracker)를 사용하여 10가지 색 중 아동이 선호하는 색을 확인하였다. 시각적 매끄러움은 움직이는 목표물의 응시 오차값(mean squared error)으로 측정하였으며, 시각적 주의집중력은 다양한 색 단서(무단서, 선호색 단서, 비선호색 단서)가 제시된 장면에서 관심영역(Area of Interest, AOI)에 대한 응시 횟수로 측정하였다. 결과 : 자폐스펙트럼 장애 아동의 경우, 선호색 단서를 제시했을 때 무단서에 비해 시각적 매끄러움이 유의하게 향상되었으며(p<0.050), 시각적 주의집중력 또한 유의하게 증가하였다(p<0.050). 이러한 차이는 일반 아동에게서 는 나타나지 않았다. 두 집단 모두 성별과 연령에 따라 색 선호도의 차이를 보였다. 결론 : 자폐스펙트럼 장애 아동에게 선호색을 활용한 시각적 자극은 시각적 매끄러움과 시각적 주의집중력을 향 상시키는 데 효과적임을 확인하였다. 이는 아동의 강점을 기반으로 한 중재 및 교육 프로그램 설계에 기초자료로 활용될 수 있을 것으로 기대된다.

Hydrogen has a wide flammability range and rapidly diffuses in air, making precision detection technology essential to prevent explosion risks and ensure system safety as the adoption of hydrogen infrastructure expands. Polymer materials are employed in such infrastructure to seal high-pressure hydrogen, and reliable measurement techniques capable of quantifying trace amounts of hydrogen permeating or leaking through these materials is necessary. In this study, a hydrogen quantification system combining volumetric analysis with image analysis was utilized to evaluate the hydrogen uptake and diffusivity of HDPE (high-density polyethylene), NBR (nitrile butadiene rubber), and EPDM (ethylene propylene diene monomer) under high-pressure conditions. The results indicated that HDPE and NBR samples containing silica filler exhibited hydrogen uptake behavior consistent with Henry’s law, while EPDM samples with carbon black filler demonstrated additional hydrogen adsorption on the carbon black surface. These research results provide a foundation for more precisely evaluating the permeation and leakage behavior of polymers in high-pressure hydrogen environments, and are expected to contribute to the safe and efficient development of hydrogen infrastructure.

A high-pressure in-situ permeation measuring system was developed to evaluate the hydrogen permeation properties of polymer sealing materials in hydrogen environments up to 100 MPa. This system employs the manometric method, utilizing a compact and portable manometer to measure the permeated hydrogen over time, following high-pressure hydrogen injection. By utilizing a self-developed permeation-diffusion analysis program, this system enables precise evaluation of permeation properties, including permeability, diffusivity and solubility. To apply the developed system to high-pressure hydrogen permeation tests, the hydrogen permeation properties of ethylene propylene diene monomer (EPDM) materials containing silica fillers, specifically designed for gas seal in high-pressure hydrogen environments, were evaluated. The permeation measurements were conducted under pressure conditions ranging from 5 MPa to 90 MPa. The results showed that as pressure increased, hydrogen permeability and diffusivity decreased, while solubility remained constant regardless of pressure. Finally, the reliability of this system was confirmed through uncertainty analysis of the permeation measurements, with all results falling within an uncertainty of 11.2 %.

Gas sensors play a crucial role in monitoring harmful gas concentrations and air quality in real-time, ensuring safety and protecting health in both environmental and industrial settings. Additionally, they are essential in various applications for energy efficiency and environmental protection. As the demand for hydrogen refueling stations and hydrogen fuel cell vehicles increases with the growth of the hydrogen economy, accurate gas concentration measurement technology is increasingly necessary given hydrogen's wide explosion range. To ensure safety and efficiency, gas sensors must accurately detect a wide range of gas concentrations in real-world environments. This study presents two types of gas sensors with high sensitivity, stability, low cost, fast response time, and compact design. These sensors, based on volume and pressure analysis principles, can measure gas filling amounts, solubility, diffusivity, and the leakage of hydrogen, helium, nitrogen, and argon gases in high-density polyethylene charged under high-pressure conditions. Performance evaluation shows that the two sensors have a stability of 0.2 %, a resolution of 0.12 wt･ppm, and can measure gas concentrations ranging from 0.1 wt･ppm to 1400 wt･ ppm within one second. Moreover, the sensitivity, resolution, and measurement range of the sensors are adjustable. Measurements obtained from these sensors of gas filling amounts and the diffusivity of four gases showed consistent results within uncertainty limits. This system, capable of real-time gas detection and characterization, is applicable to hydrogen infrastructure facilities and is expected to contribute to the establishment of a safe hydrogen society in the future.

A technology was developed to measure the hydrogen uptake and diffusivity of polymer materials used in high-pressure hydrogen tanks and pipelines at hydrogen refueling stations. This technology involves charging hydrogen into polymer under a maximum pressure of 90 MPa, followed by depressurization. The polymer material is then placed in a cylinder partially submerged in water, and hydrogen is released from the material. The increase in volume of the released hydrogen causes a decrease in the water level in the cylinder. To track this in real-time, an image analysis algorithm based on the brightness of a crescent-shaped water level image is used to accurately measure the water level and change in hydrogen amount at the same time. This data is then used in a self-developed diffusivity analysis program to evaluate hydrogen uptake and diffusivity. Using this technology, the hydrogen uptake and diffusivity of sulfur-crosslinked nitrile butadiene rubber (NBR) composites containing carbon black and silica fillers were measured from 2 to 90 MPa. Additionally, the relationship between the physical stability of the NBR composites and their hydrogen uptake and diffusivity was investigated. To validate the effectiveness of the technology, an uncertainty analysis of the measurements was conducted, with all results showing an uncertainty within 8 %.

This study aims to estimate the trawl net width based on the design drawing and towing condition of sampling trawl used in past surveys to improve the accuracy of estimation for fishery resources. To this end, the trawl gear was modeled as a flexible structure and numerically analyzed, and the analysis results were subjected to multiple regression analysis. As a result, a model was derived to calculate the net width by the towing conditions. When the towing conditions from past surveys were input into this model, it was confirmed that the net width increased in a natural logarithmic manner with the increase in the warp length and that decreased linearly as the water depth increased at the same warp length. For verification of the model, the theoretical formula of other study and this model were compared. As a result, despite the values of the two were slightly different, the tendency of changing net width by increasing warp length was consistent each other. Therefore, it is thought that the derived model can obtain the net width according to various towing conditions and can contribute to improving the accuracy of fishery resources estimation.

This study explored effects of a sludge-based biochar addition on nitrogen removal of membrane bioreactor (MBR) for wastewater treatment. The membrane fouling reduction by the biochar addition was also investigated. A dose of 3 g/L of the biochar was applied to an MBR (i.e., BC-MBR) and treatment efficiencies of organic matter and nutrient were analyzed. The MBRs with powdered activated carbon (i.e., AC-MBR) and without any additives were also operated in parallel. The average removals of COD and TN were improved with the biochar addition compared to those with the control MBR. Interestingly, operational duration was also increased with biochar addition. The CLSM analysis revealed that biomass amounts of BC-MBR and AC-MBR were reduced by more than 40%, and thickness of the biofilm attached to the membrane surface also was decreased. The physical properties of biochar surfaces were compared with a commercial powdered activated carbon. The specific surface area with 38 m2/g and pore volume with 0.13 cm3/g of the biochar were much smaller than those of the powdered activated carbon, which were 1100 m2/g and 0.67 cm3/g, respectively. Manufacturing conditions for the biochar production needs to be further investigated for enhancing physical properties for adsorption and biological improvement.

나리(Lilium spp.)는 절화, 정원 식물 및 화분 식물과 같은 관상용 가치로 인해 가장 중요한 화훼 작물 중 하나이다. 나 리는 연작으로 인한 환경 스트레스에 민감하며, 환경 스트레 스의 원인 중 하나로는 염 스트레스가 있다. 본 연구는 분홍 색 오리엔탈 나리 'Medusa', 'Lake Carey', 'Ovada'의 생 육 시기별 염스트레스에 따른 표현형 및 색 관련 화합물 함 량 변화를 조사하였다. 염 처리는 생육 시기에 따라 다양한 처리기간(무처리, 발아 전, 발아 후, 전체 생육기간)에 주 1 회 염(8dS･m-1)처리를 실시하였다. 생육 시기별 염스트레스 에 의한 개화의 차이가 있었지만, 전체 생육기간동안 염 스 트레스 처리시 모든 품종에서 개화가 이루어지지 않았다. 염 스트레스 처리 시기에 따라 초장과 꽃의 크기가 감소율이 달 랐으며 'Medusa', 'Lake Carey'는 발아 후 염 처리에서 정 상 개화하였다. 또한, 염스트레스는 꽃과 같은 식물에서 생성 되는 색 관련 화합물인 페놀과 플라보노이드 함량도 시기별 로 차이가 있었다. 품종마다 차이는 있지만, 발아 전이 발아 후 염 처리보다 총 페놀과 총 플라보노이드 함량이 더 낮은 것을 확인하였다. 이 결과는 생육 시기에 따라 염 스트레스 에 의한 나리의 표현형과 화색 관련 화합물의 함량의 변화에 차이가 있었으며 생육초기 염스트레스에 의한 피해가 높은 것으로 판단된다.

도로 건설로 인한 서식지 파편화에 대한 저감방안으로 육교형 생태통로가 건설되고 있기는 하지만 효과성에 대해서는 아직도 논쟁이 있다. 생태통로의 효과성 평가를 위해 족적트랩, 카메라트랩과 같은 모니터링 방법이 실시되고는 있으나 얼마나 많은 개체가 이용하는지 정량적으로 평가하기에는 한계가 있다. 이에 본 연구에서는 생태통로와 인근 지역을 서식지로 이용할 가능성이 큰 소형포유류인 등줄쥐를 대상으로 포획-재포획 방법으로 개체 위치 파악을 통해 생태통로 이용 정도를 도출하고, 트랩 주변 환경 특성을 이용하여 등줄쥐의 생태통로 이용에 미치는 요인을 확인하였다. 등줄쥐의 생태통로 이용도는 격자 단위의 포획지점을 연결하여 이동 거리와 경로를 확인하였고, 생태통로 이용에 미치는 환경 특성은 트랩당 포획 횟수를 종속변수로 한 일반화 선형 모형(Generalized linear model)을 이용하였다. 연구결과, 등줄쥐의 이동 거리는 선행연구와 유사하게 나타났으며, 생태통로를 횡단하는 개체가 나타나지 않음에 따라 등줄쥐는 생태통로를 통로보다는 서식지로 이용함을 확인하였다. 등줄쥐가 생태통로를 이용하는 데 영향을 미친 환경 특성은 층위별 식생피복량(1~2m, 2~8m, 8m 이상), 교목 식생, 트랩 주변 최대 수목 흉고직경, 경사도가 유의하게 나타났다. 이에 따라 생태통로 조성 시 더 많은 교목과 관목을 식재하고, 높은 경사와 절토사면 생성을 방지하여 생태계 내 먹이원으로 이용될 수 있는 등줄쥐 이용도를 높인다면 생태통로의 효과성을 더 높일 수 있을 것으로 예상된다.