Carbon neutrality by 2050 was declared and are focusing on developing innovative energy technologies aimed at reducing greenhouse gas emissions. Active investment and research are underway in the full-cycle development of hydrogen energy technologies, including hydrogen production, storage, transportation, and utilization, which is gaining attention as a promising future eco-friendly energy source. The storage density of liquid hydrogen is 70.79kg/m3, which is higher than the 41kg/m3 of compressed hydrogen at 700bar, making it more suitable for large-scale storage. To store hydrogen at 20K, insulation technologies such as vacuum insulation, powder insulation, or multi-layer insulation (MLI) are typically required. Consequently, there is active research being conducted on the design of insulation systems and materials. However, research on the design for improving the structural integrity of the supports between the inner and outer tanks remains insufficient. n this study, topology optimization was performed for the support design of a liquid hydrogen storage tank using commercial finite element analysis (FEA) software. The structural safety was validated through structural analysis of a simplified self-designed model.

본 연구는 배수지에서 저수조를 포함한 대수용가의 수도꼭지에 이르는 구간에서 탁도와 잔류염소 농도의 시간적⋅공간적 변화를 분석하였다. 모니터링은 배수지, 중블록 유입 지점, 대수용가 유입 지점, 저수조 유출 지점, 수도꼭지 등 5개 지점에서 수행되었으며, 유량, 잔류염소, 탁도, pH, 전기전도도, 온도를 측정하였다. 연구 결과, 수돗물 이동 경로를 따라 잔류염소 농도는 점차 감소하고 탁도는 증가하는 경향을 보였다. 특히, 비업무시간대에는 수돗물 정체로 인한 수질 저하가 확인되었다. 또한, 저수조의 건전성을 평가하기 위해 반응계수를 산출한 결과, 시간에 따른 저수조 내부 건전성 저하와 수질 악화 가능성이 확인되었다. 본 연구는 수돗물의 이동 거리, 사용 시간대, 유량 변화 및 공급 방식에 따라 수질이 달라질 수 있음을 보여주며, 저수조에 의존하는 지역에서는 안전한 수돗물 공급을 위해 지속적인 모니터링과 관리가 필요함을 시사한다.

Globally, there is a concentrated effort to lead in alternative energy technologies. Among various eco-friendly energy sources and carbon-free fuels, hydrogen energy is gaining attention as a clean energy solution for future industries, as its only byproduct is water. There are two primary storage methods: compressing hydrogen gas at high pressure and storing it as a liquid. Research on insulation, including the structural design of multi-layer Insulation (MLI) and vapor-cooled shield (VCS), as well as the materials used for insulation, has been actively conducted. However, studies focused on improving the structural safety of the supports that sustain the structure between the inner and outer tanks have been limited. In this study, a thermal-structural coupled analysis technique for liquid hydrogen storage tanks was developed using commercial finite element analysis software for the design of support structures for liquid hydrogen storage tanks. Six analytical models were created based on varying the number and diameter of the supports with the constant total volume of the supports and a structurally safe support configuration was proposed.

This study aimed to analyze the behavioral changes and stress responses of cultured leather carp (Cyprinus carpio nudus) for repeated noise exposure. The acoustic stimulus was composed of twenty sets of one second duration noise with an average noise of 147 dB, which was repeated every five minutes. The behavioral changes of the fish were analyzed immediately after noise exposure, three hours, six hours, twelve hours, 24 hours, and 48 hours later. The stress hormone response was also analyzed and compared through blood collection. It was confirmed that the fish were significantly affected by the noise stimulus and unable to be free or adapt to it untill the end of the experiment. The cortisol concentration was also the highest at 38.2 ug/dL after six hours; the glucose concentration did not decrease over time, indicating that stress was maintained and had a significant effect.

In order to prevent disconnection of the hydraulic pump EDV cable, this study judged the vibration generated by the pump as the greatest effect on disconnection, and confirmed the vibration effect. And it had a structure that was vulnerable to vibration because of the wire flow space inside the EDV cable connector. After applying the improved adapter, vibration analysis, excitation test, and bending strength test were performed to confirm the effectiveness of design change and improvement. As a result of vibration analysis, the amount of vibration was reduced by about 10 times compared to the existing product, and the strength increased by about 4 times in the bending strength test was confirmed to increase the effect of preventing disconnection due to vibration.

Advanced technoloigy, according to the development of science, is also applied to weapons systems to prepare for future battles. But the emergence of new technologies leads to DMSMS(Diminishing Manufacturing Source and Material Shortage) because it brings a short life cycle of parts. In particular, DMSMS frequently appear in electronic parts with a short launch cycle for new products. The life support system of K2MBT(Main Battle Tank) is a key functional item related to crew survivability and convenience. Recently, various parts have been cut off on the life support system, requiring a redesign of the Control Box. The K2MBT is not only central to domestic production but also plays a key role in export projects to countries like Poland, making continuous production necessary. This study aimed to ensure the sustainability of component production and reduce maintenance costs by redesigning the control box.

The recent surge in energy consumption has sharply increased the use of fossil fuels, leading to a steep rise in the concentration of greenhouse gases in the atmosphere. Interest in hydrogen is growing to mitigate the issue of global warming. Currently, hydrogen energy is transported in the form of high-pressure gaseous hydrogen, which has the disadvantages of low safety and energy efficiency. To develop commercial hydrogen vehicles, liquid hydrogen should be utilized. Liquid hydrogen storage tanks have supports between the inner and outer cylinders to bear the weight of the cylinders and the liquid hydrogen. However, research on the design to improve the structural safety of these supports is still insufficient. In this study, through a thermal-structural coupled analysis of liquid hydrogen storage tanks, the model with three supports, which had the lowest maximum effective stress in the outer tank, inner tank, and supports as proposed in the author's previous research, was used to create analysis models based on the diameter of the supports. A structurally safe design for the supports was proposed.

담배, 배추, 고추, 복숭아 등을 가해하는 복숭아혹진딧물은 살충제의 지속적인 사용으로 인해 약제에 대한 저항성이 꾸준히 보고되고 있다. 본 연구에서는 단일처리시 약효가 낮은 약제들을 혼합 처리함으로써 약효의 상승효과를 확인할 수 있었으며, 실내검정에서 높은 혼합효과를 나타 낸 λ-cyhalothrin + flupyradifurone, λ-cyhalothrin + dimpropyridaz, flupyradifurone + chlorfenapyr, flupyradifurone + dimpropyridaz를 포장시험을 통해 검증하였다. 시험 결과, 4종의 혼합제는 복숭아혹진딧물 야외개체군에 대해 97% 이상의 방제가를 보여 약제 저항성 복 숭아혹진딧물 방제에 활용이 가능할 것으로 생각된다.

In this article, improvement of heat screen failure for battle tank is proposed. The heat screen applied to protect a cam sensor from engine heat was cracked by vibrations generated in the engine. To solve this problem, the configuration of the heat screen was changed to a structure that can avoid engine vibration levels. The improved heat screen has first mode frequency at 4,000 RPM band outside the main operating range of the engine, and heat dissipation is at the same level as conventional heat screen. As a result, the improved heat screen secured reliability by improving vibration effects by approximately 163% while maintaining heat dissipation performance.

The main hydraulic pump is a device that generates the hydraulic pressure needed for the K2 tank. It is a pressure-compensated swash plate piston pump that generates the hydraulic power necessary to drive the hydraulic device. Hydraulic pump design changes were made due to frequent failures of the hydraulic pump. As a result of checking the operation records of the hydraulic pump, about 71% of the total engine operation time was in a stationary state where hydraulic pressure was not needed. This has the problem of constantly running when the engine is started, consuming unnecessary endurance time, and generating high noise. In this study, ISG(Idle Stop & Go) was applied to improve operation method. When applying ISG, the pressure can be reduced to about 85% or less in an environment where the operation of the main hydraulic pump is not necessary. So, the lifespan of the main hydraulic pump increases as a result of ISG application, thereby reducing the waste of national funds due to maintenance costs. Also, it is expected to contribute to improving combat power by reducing crew fatigue due to noise reduction.

In this study, numerical analysis was performed on a type IV hydrogen storage tank to analyze the temperature change of hydrogen inside the tank and the filling performance by changing the inlet nozzle outlet angle and the number of outlets. Considering the residual state of charge (SOC) inside the initial tank, the initial pressure was 10 MPa, and the temperature of hydrogen inside the tank and the SOC results were analyzed when hydrogen with a temperature of 233 K was introduced under the conditions of liner, wrap, and outside temperature of 298 K. The results of the analysis showed that the charging completion rate reached the charging limit pressure. The analysis showed that time of filling completion, when the filling limit pressure is reached, the SOC result is about 94% for all geometry change conditions, and the filling completion time increases by 5s as the number of outlets decreases. The temperature change of the wrap area at the end of filling is up to 3.6K, which shows that the outside air temperature has a negligible effect on the hydrogen temperature change inside the tank.

The government declared ‘2050 carbon neutrality’ as a national vision in October 2020 and subsequently pursued the establishment of a ‘2050 carbon neutrality scenario’ as a follow-up response. Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support structures for liquid hydrogen storage tanks, a thermal-structural coupled analysis technique was developed using Ansys Workbench. Analytical models were created based on the number and arrangement of supports to propose structurally safe support designs.

본 연구에서는 ALOHA와 Bow-tie를 활용하여 메탄올 추진 선박의 저장 탱크가 울산항에서의 누출 시나리오를 가정하여 위험도 평가하였다. ALOHA를 이용하여 대안 및 최악의 시나리오를 산정하여 피해 범위를 예측하였다. 독성 영향 범위의 결과(ERPG-2 기준)로는 대안(629m), 최악(817m)로 육상 탱크 터미널의 부두 시설 및 거주 지역까지 포함되는 것으로 확인되었다. 인화성 영향 범위(LEL 10% 기준) 는 대안(126m), 최악(218m) 선박에서만 발생하였으며, 열복사 영향 범위(5.0kW/m2 기준)는 대안(56m), 최악(56m)로 선박에서만 영향을 미쳤 다. 또한, 전문가 집단을 구성하여 Bow-tie 기법을 통하여 예방 대책과 완화 대책을 평가하였다. 대책 유형 분류에서는 Hardware와 Human 으로 구분되었으며, 안전 유효성과 위험 심각성의 결과에서는 “Gas Freeing System”, “Ventilation System”, “Fire-Fighting System이 가장 높은 평가를 받았다. 위의 평가를 토대로 위험도 평가를 도식화하였다.

In this study, the design of fuel tank for SUVs (sports utility vehicles) was addressed through structural FE-simulation. For safety evaluation, we performed a shape analysis of fuel tank, discovered improvement measures for weak areas, and reflected them in the fuel tank design. Additionally, a strength analysis was conducted and the analysis results were reflected in the design. As a result of analysis through various design changes, it was possible to propose an appropriate fuel tank shape. Additionally, the effect of changes in the shape of the reinforcement and mounting bracket on the stiffness and strength of the fuel tank bracket was investigated.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. However, the low density of hydrogen makes its storage an urgent technical problem for hydrogen energy development. Compared with the density of gas hydrogen, the density of liquid hydrogen is more than 1.5 times higher. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support for liquid hydrogen storage tank, technique of thermal-structural coupled analysis including geometry, mesh, and boundary condition were developed using Ansys workbench, and equivalent stress and deformation distributions were analyzed.

The dissolved air at the bottom layer of the deep aeration tank transforms into fine gas bubbles within the MLSS (Mixed Liquor Suspended Solid) floc when exposed to the atmosphere. MLSS floc flotation occurs when MLSS from the deep aeration tank enters the secondary clarifier for solid-liquid separation, as dissolved air becomes fine air within the MLSS floc. The floated MLSS floc causes a high SS (Suspended Solid) concentration in the secondary effluent. The fine air bubbles within the MLSS floc must be removed to achieve stable sedimentation in the secondary clarifier. Fine bubbles within the MLSS floc can be removed by air sparging. The settleability of MLSS was measured by sludge volume indexes (SVIs) after air sparging MLSS taken at the end of the deep aeration tank. MLSS settling tests were performed at MLSS heights of 200, 300, 400, and 500 mm, and compressed air was fed at the bottom of the settling column with air flow rates of 100, 300, and 500 ml/min at each MLSS height, respectively. Also, at each height and air flow rate, air was sparged for 3, 5, and 7 minutes, respectively. SVI was determined for each height, air flow rate, and sparging time, respectively. Experimental results showed that a 300 mm MLSS height, 300 ml/min air flow rate, and 3 minutes of sparging time were the least conditions to achieve less than 120 ml/g of SVI, which was the criterion for good MLSS settling in the secondary clarifier.

수소는 연소 과정에서 산소와 반응하여 물과 열만을 생성하며 공해 물질이 배출하지 않아 깨끗한 에너지원으로 간주된다. 이러한 특징으로 산업 활동으로 비롯된 대기 오염, 이상 기후 문제 등을 해결 하기 위한 대책안으로써 수소를 활용한 신재생에너지가 세계적으로 주목받고 있다. 이에 따라 선행 연 구에서는 수직형 탱크 구조의 취약부로 평가되는 지지부 단면 변화에 따른 영향성을 평가하기 위해 수소 생산 인프라 현장 조사를 수행한 바 있으며, 현장 조사 중에 현장 설치된 수소 탱크 강재 지지부 의 부식 문제를 확인하였다. 지지부의 부식은 구조물의 전체 강성을 감소시키며, 재난(지진)에 취약해 져 수소 저장 용기가 손상으로 인한 2차 피해로 이어질 수 있다. 이에 따라 본 연구는 선행 연구의 후속 연구로써 강재 지지부의 부식 문제를 개선하고자 고강도-저중량 재료인 CFRP(Carbon Fiber Reinforced Polymer)를 사용한 지지부를 개발하여 수치해석을 통해 CFRP 지지부의 내진 성능평가를 목적으로 한다. 해석에 사용된 수소 탱크는 크게 몸체, 지지부, 기초부, 앵커 볼트로 구성되어 있으며, 지지부는 높이 965mm, 75×75×9.5mm의 L형강 4개로 확인되었다. 지진 하중에 대한 동적 성능을 평가하기 위해 시간이력해석법이 사용되었으며, 적용 동적하중의 경우, ASCE의 ICC-ES에서 제시한 평가 기준에 따라 AC 156 Amplitude 100%의 인공 지진을 적용하였다. 해석 결과, CFRP 지지부와 강재 지지부 상단의 최대 변위가 각각 35.48, 32.54mm로 매우 유사한 것으로 나타났으며, Hashin Damage Criteria를 사용하여 CFRP 지지부의 최대 손상 지수를 측정한 결과 수지의 인장측에서 0.065로 확인되었다. 이는 기준 손상 지수 1 대비 매우 낮은 수준이며, 해석 결과를 종합했을 때 CFRP 지지부는 충분한 안전성을 보이는 것으로 판단된다.