Automated storage/retrieval systems (AS/RS) remain essential in various industries, including smart factories and distribution centers. This study analyzes the flow time of a twin crane AS/RS (TC-AS/RS) with connected material handling systems such as automated guided vehicles (AGVs). To account for system variability, we developed a discrete-event simulation model considering factors such as arrival and service rates. The simulation data is further analyzed using a G/G/1 queueing model to evaluate system performance. Experimental results show that analyzing TC-AS/RS at the crane-level improves estimation accuracy compared to system-level G/G/1 model. Additionally, the input/output (I/O) configuration significantly impacts flow times, with the Both ends I/O layout help prevent bottlenecks under high demand in the connected material handling system.

The renewable energy has, currently, been used because of its eco-friendly energy such as no emission gas and less environmental pollution. Fuel cell electric vehicle (FCEV) using polymer electrolyte membrane fuel cell (PEMFC) uses the hydrogen as fuel to obtain the power by electrochemical reaction. The objective of this study is to investigate the flow characteristics of the hydrogen according to entrainment ratio for ejector of FCEV through comparison analysis with the air. As the results, the flow of hydrogen in ejector corresponds to turbulence with Reynold number 18,093. The pressure difference of the hydrogen between primary flow and secondary flow in ejector was about 16 times compared with that of the air. The mean velocity of the hydrogen in ejector outlet was faster about 15 times than the air.

Performance of the hydrogen fuel cell system in a compact special vehicle is mainly influenced by the thermal characteristics of heat release through air flow with electrochemical mechanisms. In this study, numerical analysis has been carried out to investigate air flow and heat transfer characteristics near the fuel cell system for various operating conditions. The cooling characteristics around the radiator system depend on air flow generated by vehicle movement, and the effects of vehicle-induced air flow on the velocity and temperature distributions within the heat release system were examined. These results showed that there are quite complicated air flow around the radiator and fan near the fuel cell system in the vehicle cargo area, and its efficient flow field resulted in cooling performance improvement with driving speed. Hence overall heat release characteristics of the hydrogen fuel cell system are strongly associated with various air flow behavior formed around the compact special vehicle including cargo area.

This study aims to provide a basis for selecting the appropriate traffic-flow evaluation indicators by quantitatively analyzing the relative importance of such indicators in mixed traffic environments in which automated vehicles (AVs) and conventional vehicles coexist. As AV technology progresses and its adoption increases, establishing reliable evaluation criteria that accurately reflect the characteristics and performance of traffic systems under transitional conditions is crucial. Thus, approximately 40 domestic and international studies were reviewed in this study, from which 45 evaluation indicators were identified. These indicators were classified into three major categories: mobility, safety, and environment. Five frequently used and representative indicators were selected from each category based on the appearance frequency and relevance. An analytic hierarchy process survey was conducted with a group of transportation experts to derive the relative importance (weights) of both the major categories and individual indicators. The analysis revealed that safety (0.53676) was the most important category, followed by mobility (0.34795) and environment (0.11528). After combining the weights of the categories and sub-indicators, the top three indicators, i.e., time to collision (TTC), time exposed to TTC, and deceleration rate to avoid crashes, appeared to be safety related and associated directly with the collision risk. These findings suggest that, in the early stages of AV deployment, traffic evaluations should prioritize safety considerations over mobility or environmental factors to ensure the successful integration of AVs into existing traffic systems.

In this study, for the design of the impeller and volute casing shape of the water pump for flood prevention, performance was predicted through numerical analysis to secure the theoretical power and hydraulic efficiency of the front well at the discharge well 300m3/h, which is the target design specification, and the flow characteristics of each flow rate were checked and verified. Through the results of this flow analysis, it was possible to secure the basic shape design of the impeller and volute casing of the water pump for flood prevention. In the future, we will perform an interpretation to confirm structural safety according to shape and material.

This study investigated the seasonal water quality characteristics of two key environmental flow sources for the Gwangju Stream: the Yeongsan River water supply and effluent from a sewage treatment plant. Monitoring data collected between 2019 and 2023 were analyzed for both sources, and field surveys from October 2023 to June 2024 examined confluence points where environmental flows entered the Gwangju Stream, measuring both main-stream and inflow waters. The Yeongsan River supply recorded its highest spring organic matter levels (mean BOD: 5.2 mg L-1; maximum: 8.7 mg L-1), while the sewage treatment plant effluent exhibited pronounced seasonal variation in total nitrogen (T-N), ranging from a summer low of 8.2 mg L-1 to a winter high of 13.8 mg L-1. Upstream water quality remained stable; however, downstream BOD increased annually by 8.2%, and total phosphorus (T-P) peaked sharply in summer (0.567 mg L-1). Field survey results indicated that in spring, T-N increased by up to 495%, BOD by 182%, and T-P by 290%; in winter, T-N rose by 239%, BOD by 164%, and COD by 73%. These findings reveal marked seasonal variability in the influence of environmental flow sources, with T-N showing the most substantial increase in spring. The results highlight the need for targeted nutrient management strategies, such as increasing the proportion of the plant’s effluent in spring to stabilize nutrient loads and improving its biological treatment efficiency in winter to reduce T-N concentrations. Season-specific measures of this kind can improve water quality and help sustain the ecological integrity of the Gwangju Stream.

지하도로는 폐쇄적인 공간 구조와 내·외부 조도 차이로 인해 지상도로와 다른 교통 환경을 형성하며 이러한 특성은 교 통사고에 영향을 미칠 수 있다. 특히 고속도로 터널에서 사고 발생 시 대형 인명 피해로 이어질 가능성이 크다는 점을 고려할 때 지하도로에서도 유사한 우려가 제기된다. 따라서 지하도로의 교통류 특성을 면밀히 분석하여 안전성을 평가하 고 사고 예방을 위한 효과적인 대책을 마련하는 것이 중요하다. 본 연구에서는 서부간선 지하도로 성산 방면의 14개 VDS 검지기 데이터를 기반으로 지점별 속도 변동성과 교통사고 분석을 통해 안전성을 평가하였고 분석 결과의 시사점 을 바탕으로 지하도로 속도 관리 전략을 설계하였다. 먼저, VDS 검지기 지점별 속도 표준편차와 time-varying-volatility 산출 및 속도의 변동성과 교통사고 데이터 매칭을 통해 사고 개연성과 심각도를 분석하였다. 이후, 사후검정을 통해 속 도 및 속도 변동성 기준으로 동질적 부분집합을 도출하고 회귀분석을 통해 속도 변동성과 교통량·밀도 간의 관계를 규명 하여 속도 변동성을 최소화할 수 있는 최적의 교통량과 밀도를 산출하였다. 분석 결과, 속도 변동성이 큰 구간에서 사고 개연성과 심각도가 높게 나타났으며 지하도로에 구간단속을 적용할 경우 하류부에서 변동성이 증가하는 현상을 확인하 였다. 이를 바탕으로 위험 구간을 식별하고 해당 구간에 가변형 속도 제한 시스템을 적용한 로컬 속도 관리 전략을 제시 하였다. 본 연구의 결과는 지하도로의 사고 예방 및 안전성 향상을 위한 실질적인 속도 관리 전략 설계에 기여할 수 있 을 것으로 기대된다.

Proper Orthogonal Decomposition (POD) is applied to analyze the coherent structure of three-dimensional cylinder wake flow. The flow field data, such as velocity and pressure as functions of time, was obtained by the incompressible CFD analysis. The resulting CFD data was then used to determine eigenvalues, POD modes, and time coefficients through POD process. The flow field was approximately reconstructed using some of lower POD modes. The three-dimensional field reconstructed using the low-order model was found to be in good agreement with the original. This verifies that low-dimensional modeling of complex flow fields is fully possible.

Toilet liquid-type cleaners utilize operating technology that employs buoyancy mechanism to inject uniform amount of cleaning solution. Flow characteristics of velocity and pressure distributions in the flow field of toilet flush cleaner injection device have been analyzed with CFD method. The flow rate decreases near the inlet of the system, where it contacts the container of the cleaning liquid bottle. It then increases near the injection device stopper and decreases again as it moves toward the system outlet The height of the cleaning solution decreases from 12 cm to 3 cm when using the spray device, the average outlet velocity decreases by approximately 73%. The solution level difference increases from 1.616 cm to 3.216 cm, the inlet velocity decreases by approximately 4.1%~5.6%. These predicted results can be widely applied as basic conceptual design data for highly efficient toilet flush cleaner injection device.

In order to understand the MR fluid flow in the MR damper core, the annular orifice path was simplified into a square channel and the electromagnetic flow was analyzed. For this purpose, the CFD-ACE+ program was used. The temperature and magnetic field of the MR fluid were based on room temperature and orifice wall data, and 2-D steady incompressible laminar flow was assumed. The inlet and outlet of the orifice channel are at atmospheric pressure, and the inflow velocity of the MR fluid is 0.1 m/s. After analyzing the magnetic field of the core, which is a simple model of the 1 stage MR damper, the electromagnetic flow analysis of the MR fluid flowing through the orifice channel was performed. From this, the magnetic field of the orifice channel and the electromagnetic flow of the MR fluid were observed. As the magnetic flux density increased, the flow distribution and velocity of the MR fluid in the channel core changed significantly.

In the development of a digital multi-process welding machine, we aimed to analyze the heat dissipation effects resulting from changes in the transformer's shape. Two installation configurations for the transformer, vertical and horizontal, were proposed. Thermal-flow analysis was conducted for the welding machine, taking into account variations in spacing between each proposed configuration. The results indicated that the shape and spacing of the components did not significantly alter the airflow around the reactor coil, which is the main heat-generating component of the machine. When comparing the heat dissipation effects across models with different transformer spacings, it was observed that models with narrower spacing exhibited improved heat dissipation, while the vertical configuration demonstrated a slightly higher heat dissipation effect overall. Transient analysis revealed the irregularities in internal flow and the resulting scattered temperature distribution over time within the welding machine.

As the importance of the indoor environment increases. As part of a study to improve range hood performance, a flow analysis of chamber casing was conducted. flow analysis was performed by applying Realizable (  ) Model. For flow analysis, “STAR-CCM+” program of “SIEMENS” was used. It was analyzed how changes in inlet velocity, outlet velocity(flow rate) and static pressure increase occur according to changes in the shape of the chamber casing. Flow analysis was performed by changing the shape of the chamber casing limitedly, but the results were not helpful in improving the performance of range hood.

In this study, flow analysis was performed using ANSYS CFX to evaluate the performance of the 30kg hydrogen fuel cell hexa-copter drone in hovering flight. In the case of a hydrogen fuel cell hexa-copter drone, a total of four cooling fans are mounted on the drone's body in two pairs on the left and right to cool the fuel cell module. In order to evaluate the effect of the air flow from the cooling fan on the aerodynamic properties of the hydrogen fuel cell drone as the mounted cooling fan operates, the change in thrust for the case where the cooling fan operates and does not operate was compared and analyzed. Looking at the analysis results, it was found that the presence or absence of the drone's cooling fan had little effect on the drone's thrust through the thrust results for the six wings.

선박용 연료전지 시스템의 스택 온도를 일정하게 유지하기 위한 스택 냉각 시스템은 Close-Loop의 청수 라인과 Open-loop의 해수 라인을 적절하게 조합하여 구성할 수 있다. 청수와 해수의 열 교환량은 스택 냉각 시스템에 설치된 3-way 밸브의 열림 정도로 결 정된다. 냉각 시스템의 청수 라인과 해수 라인 각각의 펌프 토출량과 3-way 밸브의 열림률 관계는 명확하게 규명하기 어려우며, 동시 에 연료전지 스택과 결합 되어 동작하기 때문에 난해한 거동을 보인다. 본 연구에서는 냉각 시스템의 구성 요소들과 연료전지 스택이 결합 되어 동작할 때의 관계를 해석하기 위해 통계적 기법을 적용하였으며 필요 데이터를 확보하기 위해 청수 라인과 해수 라인으로 구성된 30KW 급 PEMFC 시스템을 모델링하고, 다양한 조건으로 시뮬레이션하였다. 펌프의 토출량 변화, 부하 조건의 변동 등의 다양 한 시나리오를 통해 도출된 파라미터들은 3-way 밸브 열림률, 시스템 효율, 동적 응답성 등이며 각각 축 재정의, 정규화 기법 등 통계 적 기법으로 시각화되었다. 따라서 본 연구의 접근 방식을 이용하면, 결합 된 설비들의 관계를 시각적 데이터로 명확하게 확인할 수 있으며, 가동 조건을 변경했을 때의 시스템 효율, 소모전력, 시스템의 정상 작동 여부를 예측할 수 있다. 또한, 이와 같은 방법은 복잡 한 시스템의 특성을 정의하는 기초 연구로서 의미가 있으며 선박의 빅데이터를 처리하는 연구 등으로의 발전 가능성을 확인하였다.

고속도로 터널 구간은 일반 도로에 비해 사고 발생 빈도와 심각도가 높으며, 특히 터널 내에서 발생하는 사고나 공사와 같은 돌발 상황은 대기 행렬을 유발해 후미 추돌 위험을 증가시킨다. 본 연구에서는 운전자가 돌발 상황 지점에 접근할 때 선제적으로 대응할 수 있도록, Driving Simulator를 활용하여 다양한 정보를 제공하는 터널 내 교통관리 시스템의 효과를 분석하였다. 분석 대상은 차로 변 경 유도, 속도 감소 유도, 돌발 상황 안내로 구성된 세 가지 교통관리 시스템의 개별 효과와 이들의 통합 운영이 터널의 안전성과 운 영 효율성에 미치는 영향을 포함하였다. 분석 결과, 세 가지 교통관리 시스템을 통해 터널 내 평균 통행 속도가 증가하였으며, 돌발 상황 발생 지점에서 차량의 차로 변경과 감속이 선제적으로 이루어지고 급감속 횟수가 현저히 감소하였다. 본 연구는 터널 내 돌발 상황 발생 시 다양한 정보를 제공함으로써 터널의 안전성과 교통흐름을 개선할 수 있음을 입증하였으며, 특히 여러 시스템을 통합적 으로 운영할 때 그 효과가 극대화됨을 Surrogate Safety Measure를 통해 확인하였다. 이러한 결과는 향후 터널 교통관리에서 단일 시스 템의 기능만을 고려하기보다는, 다양한 교통관리 시스템 간 상호작용을 고려해야 함을 시사한다.

서울시의 대표적인 대중교통 수단인 도시철도를 이용하는 승객 수는 지속적으로 증가하고 있다. 이에 따라 출 퇴근시간대에 열차 내의 혼잡뿐만 아니라 역사내의 혼잡까지 이어져 안전사고가 발생하기도 한다. 본 연구는 역사에서 발생되는 보행흐름의 위험 여부를 판단하기 위해 도로의 교통류에서 활용되고 있는 vehicle accumulation과 travel time 간의 elliptic bivarate relationship을 적용하였다. 또한 보행흐름과 교통류의 혼잡발생 과정을 비교하여 차이점을 규명하였다. 본 연구에서는 도시철도 역사내 CCTV영상을 기반으로 실제 데 이터를 추출하여 역사내 통로에 발생하는 여러 보행흐름을 혼잡강도와 혼잡지속도에 따라 분류하여 비교분석하였다. 혼잡이 발생하는 여러 역의 첨두, 비첨두, 주말등 다양한 시간대의 CCTV 영상을 확보하였고, ByteTrack 방식을 활용하여 객체를 검지하였다. 검지된 보 행흐름을 강도, 지속도에 따라 분류하고 보행 누적량과 평균통행시간을 산출하여 비교분석하였다. 또한, elliptic bivarate relationship의 형태가 교통류와는 어떠한 차이점이 있는지를 규명하고 보행에서의 위험 상황 여부를 그래프를 통해 확인하였다. 분석 결과, 혼잡발생 강도가 높을수록 그래프 타원의 장축이 길게 나타났고, 보도유효폭이 클수록 타원의 기울기가 낮게 나타났다. 또한, 사람들의 평균보 행속도가 클수록 타원이 낮게 위치하였다. 마지막으로 흐름이 바로 해소되지 않고 지속되는 보행흐름의 경우, 일반적인 타원형태에서 우측부분에 타원이 추가로 형성됨을 확인하였다. 교통류와 비교한 결과, 차량의 경우 교통량에 따라 속도가 일정하게 나타나지만, 보 행의 경우 보행량과 속도의 관계가 비교적 불분명하였다.