Glass Fiber Reinforced Polymer (GFRP) shear connectors used in Insulated Concrete Sandwich Wall Panels (ICSWPs) have traditionally been evaluated for composite action based on global stiffness and strength. However, such approaches are limited in capturing local interface behavior and variations in composite action. This study proposes a strain-based shear-flow evaluation method to reflect the local structural behavior of ICSWPs. Theoretical shear flow was analyzed using flexural strain distributions obtained from existing experimental studies. Review of experimental data revealed that composite action decreases under repeated loading due to damage to GFRP shear connectors and interfaces, and that shear flow exhibits nonlinear behavior that is not proportional to the degree of composite action. To evaluate shear flow theoretically, curvature and neutral axis (NA) location were determined from strain distributions using three analytical approaches. Results showed that shear flow was maximized in partial composite action and decreased as composite action increased, with a sharp increase at low composite levels. The proposed approach highlights the importance of considering nonlinear interface shear flow for accurate evaluation of composite action in ICSWPs.

Multi-walled carbon nanotubes (MWCNTs), widely recognized for their excellent electrical, thermal, and mechanical properties, have gained significant attention across various fields. However, aggregation due to their high Van der Waals force limits their processability and applications. Surface functionalization can offer a solution to these limitations and broadens their potential uses. Nevertheless, the low reaction rates of covalent functionalization in conventional batch reactors, caused by MWCNT aggregation, remain a significant challenge to overcome. Moreover, controlling the degree of functionalization in batch reactors is difficult. In this work, we demonstrated covalent functionalization of MWCNT with 4-bromoaniline to produce MWCNT-PhBr with high, controllable degrees of functionalization, using a customized packed-bed flow reactor. The reaction was performed under various conditions, including the reactant injection sequence, reaction time (1–3 h), temperature (60–80 ℃), and concentration of reactant (0.42–1.72 M). The resulting degree of functionalization was controlled within the range of 1.81–5.70 wt%. Notably, the highest degree of functionalization obtained under the optimized flow conditions (5.70 wt% at 70 °C and 1.72 M) represents a 2.11-fold increase compared to that achieved under the optimized batch conditions (2.70 wt% at 60 °C and 0.86 M). These results suggest that the flow system is an efficient and reliable method for synthesizing functionalized MWCNTs with the desired functional group content.

A needle-free automatic injection syringe is a device that delivers drugs into the skin and tissues using a high-speed fluid jet without using an injection needle. This technology is attracting attention as an efficient means of vaccine delivery in the veterinary and livestock fields that reduce the risk of cross-infection and require mass vaccination. In particular, animal vaccination provides various advantages over conventional needle injection methods in terms of worker safety, inoculation speed, and maintenance cost. Among these drivers, Jet Injector Nozzle's flow path design is very important in needleless automatic injection syringes. This paper was conducted to solve the problem of pressure loss at the nozzle discharge side of the existing Jet Injector in designing the flow path of the animal vaccine-free automatic injection syringe nozzle. To this end, CAE was performed and the optimum design of the flow path required by the company was performed, and a large flow rate was possible in the optimal shape design, but this focuses on the nozzle flow path, which requires a review of design additions of cylinders and motors on the rear side.

본 연구에서는 실규모 MLE(Modified Ludzack-Ettinger) 공법 하수처리시설을 대상으로 송풍량 성능을 평가⋅최적화하기 위해 데이터 기반 유입수 성상 분석 프레임워크와 수학적 모델 기반 디지털 트윈(DT, digital twin)을 개발하였다. 국내 기존 하수처리시설 모니터링 체계는 활성슬러지 모델 구동에 필수적인 CODcr 분획 자료가 부족하고, 처리장에서 수행되는 일 1회 채수만으로는 유입수의 시간적 변동성을 반영하기 한계를 가지고 있다. 이를 보완하기 위해 생물반응조 유입수를 대상으로 24시간 채수를 수행하여 계절별 유입 특성을 평가하였다. 또한 이차침전지 처리수를 대상으로 탄소성 및 질소성 생물학적 산소요구량 실험을 진행하였을 때, 잔류 암모니아 1 ㎎/L는 약 4.82 ㎎/L의 NOD(nitrogenous oxygen demand)를 유발하는 것을 파악하였다. 유입수 유기물 성상 및 분획을 추정하기 위해 다항 회귀와 다층 퍼셉트론 기반 모델을 결합하여 적용하였다. 2차 다항 회귀 모델은 TCOD(total COD) 예측에서 R2 0.848의 높은 성능을 보였으나, 비선형성이 큰 용존성 분율 예측에는 한계가 있었다. 이에 MLP(Multi-Layer Perceptron) 모델을 도입한 결과, FCOD(filtered COD)는 R2 0.748, FFCOD(flocculated filtered COD)의 R2 0.698 그리고 VSS(volatile suspended solid) R2 0.933로 신뢰성 있는 예측 정확도를 확보하였다. 예측된 유입수 분획 데이터를 DT 입력값으로 적용하고 7일간의 실제 운영 자료로 검증한 결과, DT 모델은 MAE(mean absolute error) 0.314 ㎎/L, R2 0.721로 질산화 거동을 적절히 재현하였다. 암모니아 기반 송풍 제어(ABAC) 시뮬레이션에서 실제 공급 송풍량이 안정적 질산화를 위한 요구량 대비 평균 13.1% 부족한 것으로 분석되었다. 종합적으로, 본 연구의 데이터 기반 DT 프레임워크는 공정 안정성 및 운전 이해를 정량적으로 평가할 수 있는 지표를 제공하며, 하수처리시설 운영자의 의사결정을 지원하는 진단 도구로서 활용 가능함을 시사한다.

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.

본 연구는 평생교육사의 낙관성과 성취의 관계에서 몰입과 긍정정서 의 매개효과를 살펴보기 위해 실시되었다. K시에 2025년 10월 20일부 터 2025년 11월 18일까지 평생교육사 254명을 대상으로 임의표집하 였다. 분석은 SPSS 26.0 프로그램을 활용하였다. 연구 결과, 평생교육 사의 성취, 낙관성, 몰입, 긍정정서는 모두 평균보다 높은 수준으로 나 타났으며, 각 변인 간에는 정적 상관관계가 확인되었다. 또한 낙관성과 성취의 관계에서 몰입과 긍정정서는 부분 매개효과를 갖는 것으로 나타났다. 이를 통해 몰입과 긍정정서는 평생교육사의 성취를 설명하는 중요 한 심리적 변인임이 확인되었다.

이 연구의 목적은 프리다이빙 참여자의 참여동기와 운동몰입 및 운동지속의도의 관계를 규명함 으로써 프리다이빙 및 관련 산업발전을 위한 세부전략 수립의 기초자료를 제공하는데 있다. 이 연구를 위 해 프리다이빙 동호인 239명을 대상으로 설문조사를 실시하였으며, 이를 분석한 결과는 다음과 같다. 첫 번째, 프리다이빙 참여자의 참여동기 하위요인 중 즐거움요인(t=4.519, p<.001), 정신요인(t=8.173, p<.001)과 사교요인(t=5.220, p<.001)이 프리다이빙 참여자의 운동몰입에 유의한 영향을 미쳤지만, 건강요 인(t=-0.998)은 영향을 미치지 않았다. 두 번째, 프리다이빙 참여자의 참여동기 하위요인 중 사교요인 (t=3.901, p<.001)이 운동지속의도에 유의한 영향을 미쳤지만, 건강요인(t=1.903), 즐거움요인(t=1.073)과 정신요인(-0.745)은 운동지속의도에 영향을 미치지 않았다. 세 번째, 프리다이빙 참여자의 운동몰입은 운 동지속의도에 유의한 영향(t=7.516, p<.001)을 미쳤다.

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 research presents a GRNN(General regression neural network) approach for modeling the high temperature deformation flow behavior of 316L stainless steel under 800℃, 900℃ and 1000℃ and strain rates of 0.0002/s, 0.002/s and 0.02/s. There are many machine learning approaches of modeling the hot deformation of metallic alloys. Among them, the neural network approach is one of the most popular. However, the neural network approach takes a relatively long time and effort to compose and optimize the final model. In this research, GRNN is applied to study its applicability for modeling the hot deformation flow stress behavior. The prediction results were studied by calculating various types of error and observing the distribution of prediction error. The predicted results by the GRNN were very accurate and the GRNN was found to be highly applicable to modeling the flow stress of the hot deformation of 316L stainless steel.

This study examines the influence of the number of orifice stages on flow characteristics using Computational Fluid Dynamics (CFD). Transient simulations were conducted with one to four stages under identical boundary conditions, employing the SST turbulence model. The results show that outlet pressure and pressure hunting behaviors are strongly dependent on the stage number. Single- and two-stage models exhibited periodic pressure oscillations, whereas three- and four-stage models demonstrated irregular or stabilized patterns, with the four-stage configuration achieving the lowest pressure hunting. The maximum velocity increased with the number of stages, with peak values observed at the orifice sections. Similarly, eddy viscosity intensified as the number of stages increased, indicating enhanced turbulent mixing. These findings highlight that the number of orifice stages plays a critical role in determining pressure stability and flow behavior, providing useful insights for the optimal design of orifice-based flow control systems.

With the rapid expansion of the electric vehicle (EV) market, the importance of high-efficiency thermal management systems is increasingly being emphasized. The Octo-valve, a key component in Tesla's integrated thermal management system, plays a pivotal role in controlling the flow of refrigerant and coolant to optimize the efficiency of the heat pump system. This study aims to analyze the detailed internal flow characteristics of a single Octo-valve unit and to explore methods for its performance enhancement. For this purpose, an actual Octo-valve was disassembled, and its internal flow paths were modeled in three dimensions using a high-precision 3D scanner. Based on this model, a numerical analysis was conducted using Computational Fluid Dynamics (CFD) to simulate the thermo-fluid phenomena within the valve. Changes in temperature, pressure distribution, and flow velocity were analyzed under various operating conditions and variables, and the resulting pressure drop was quantified. Furthermore, the influence of these internal flow characteristics on the overall system's Coefficient of Performance (COP) and heat transfer efficiency was evaluated. The findings of this research provide a fundamental understanding of the complex fluid dynamics inside the Octo-valve and offer essential baseline data for the design of next-generation, high-efficiency Octo-valves.

Vascular malformations comprise a spectrum of structural anomalies of blood vessels that may present with variable symptoms and clinical behavior. Among these, venous malformations are the most common low-flow lesions and can involve both cutaneous and mucosal tissues. However, intraoral venous malformations, particularly those arising in the buccal mucosa, are uncommon and may be misdiagnosed as other benign oral lesions. In such cases, subtle clinical findings and nonspecific symptoms can delay diagnosis and appropriate management. Imaging modalities, including Doppler ultrasonography and magnetic resonance imaging, are useful for confirming the low-flow nature of the lesion, delineating its extent, and distinguishing it from other vascular anomalies or soft tissue masses. Therapeutic options range from observation to sclerotherapy, laser treatment, or surgical excision, and must be adapted according to lesion size, location, and symptom burden. This report describes a low-flow venous malformation of the buccal mucosa and outlines the clinical, radiologic, and therapeutic considerations relevant to this rare presentation in the head and neck region. By presenting this case and reviewing the pertinent literature, we aim to raise awareness of buccal venous malformations and provide practical guidance for their evaluation and management.

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.

본 연구에서는 과불화 알킬 사슬이 도입된 산화 그래핀(perfluoroalkyl-grafted graphene oxide, FGO)을 합성하고, 이를 과불소화계 고분자인 나피온(Nafion)에 복합화하여 바나듐 레독스 흐름 전지(vanadium redox flow battery, VRFB)용 이 온 교환 막을 개발하고자 하였다. FGO는 염기성 촉매 하에서 카르복실산기를 함유한 폴리(헥사플루오로프로필렌 옥사이드) (157 FSL, DuPont)의 카르복실산기와 GO의 에폭시기 간 개환 에스터화 반응을 통해 합성하였다. 합성된 FGO를 Nafion 기 지체에 함량을 달리하여 첨가한 복합막(N/FGO_X)을 제조하고, 함수율, 체적 안정성, 수소 이온 전도도, 바나듐 이온 투과도 및 셀 성능을 평가하였다. N/FGO 복합막은 Nafion 단일막 대비 낮은 함수율과 체적 변화율을 보였으며, FGO의 물리적 차단 효과에 의해 바나듐 이온 투과도가 감소하면서도 수소 이온 전도도를 유지하여 우수한 이온 선택도를 나타내었다. VRFB 단 위 셀 평가 결과, FGO가 도입된 복합막은 Nafion 단일막을 적용한 셀 대비 높은 방전 용량, 쿨롱 효율 및 에너지 효율을 유 지하였다.

The purpose of this study is to identify the flow resistance characteristics of the trawl net according to the towing speed of the vessel using two trawl nets designed and manufactured based on 2,000 HP. The trawl net consists of wings, bag and cod-end part, two types with wall area  of 747 m 2 (Sae Dong Baek) and 1,262 m 2 (Dong Baek) with differences in the size of the trawl net. The result of sea experiments are as follows: the flow resistance of trawl net  at the flow velocity  = 1 m/s or higher is affected by the difference in the composition of the cod-end rather than the wing or bag part of the Sae Dong Baek´s trawl net, Dong Baek´s the cod-end part has a  ratio value of 1.19, compared to Sae Dong Baek´s trawl net with a size of 120 m, and Dong Baek´s trawl net is small at 60 mm. Therefore, the water entering into the net cannot easily pass, which is considered to be a factor that increases resistance at the cod-end part. In the result of the experiment, it was found that  decreases exponentially when  increases which makes  . The constant  values when  = 1 m/s were 6.72 and 3.75, and  values were 1.14 and 0.94, showing a difference between the two nets as the flow velocity  increased. The height at the mouth of bottom trawl net decreases exponentially as the current velocity  increases; such height given by   where the constant  and  values are 0.85 for the increase in the flow velocity  and the  value when =1 m/s is 4.35. Therefore, this study investigated the flow resistance characteristics of trawl net at sea. It was possible to obtain more reliable information than previous studies by using a real fishing vessel with advanced underwater measurement devices. As a result, it was possible to analyze the underwater shape change of trawl net and the resulting flow resistance characteristics more quantitatively.