This study investigates the thermo-mechanical behavior and residual stress characteristics of friction stir welding (FSW) in an aluminum inverter housing using finite element analysis (FEA). FSW experiments were first conducted under various tool rotation and traverse speed conditions, and temperature histories were measured using K-type thermocouples. The optimal process condition was identified through tensile testing, and the heat input was estimated by comparing experimental and numerical results. The estimated heat source was incorporated into a transient thermal elasto-plastic analysis to evaluate deformation and residual stresses in an inverter housing model. The results indicated that residual stress distributions varied depending on the welding start position. In particular, when welding started at P3 (near thick ribs and bosses) residual stresses were reduced by approximately 30% compared to P1, owing to the higher local stiffness and enhanced heat dissipation that mitigated temperature gradients. Conversely, welding initiated at P1, a flat region with insufficient reinforcement, resulted in higher stress concentrations. These findings confirm that the welding start position significantly influences residual stress behavior in inverter housings and provide fundamental insights for developing residual stress control strategies in FSW of large-scale components.

The engineered materials arresting system (EMAS) is a safety facility installed at the end of runways to safely stop aircraft when runway overruns occur. The EMAS comprises porous panels composed of specialized materials; however, direct exposure to environmental factors, such as moisture infiltration, freeze–thaw cycles, and ultraviolet radiation, may cause performance degradation. In regions with four distinct seasons and significant temperature variations, such as South Korea, changes in the physical properties and durability of porous panels can pose significant challenges. Therefore, a protective top coating must be applied to EMAS panels to protect the panels from environmental stress and ensure long-term durability. This study presents a preliminary investigation into the development of a high-performance polyureabased top coating to effectively protect the components of an EMAS and crushable concrete panels as well as to maintain the system’s long-term durability and arresting performance. First, optimal formulations were determined via a design study, where the index ratio (the equivalent ratio of polyurea resin to the curing agent) and the NCO content of the isocyanate component were varied. Second, the curing behavior, mechanical properties, and temperature dependence were evaluated. Polyurea—a high-performance elastomer formed by the reaction between isocyanate and amine-based curing agents—exhibits rapid reactivity, complete waterproofing, excellent flexibility, and elasticity, thus satisfying the essential requirements of EMAS top coatings. Considering the balance between stiffness and flexibility, an index ratio of 1.05 and an NCO content of 16.0% were identified as the optimal mix design. Mechanical testing demonstrated a high tensile strength of 20.0 MPa, an outstanding elongation at break of 388%, and a tear strength of 100 N/mm, thus indicating sufficient durability and flexibility to withstand aircraft jet blast and temperature fluctuations. Temperature-dependence tests confirmed that the elongation remained at 136% (at -20 °C) and the tensile-strength ratio at 68% (at 60 °C), thus demonstrating that the coating can maintain stable performance in environments with significant seasonal temperature variations.

As the web game market grows, ensuring service stability through load testing has become increasingly important. Web games comprise a variety of functions with distinct internal logic, ranging from simple data retrieval to complex transaction processing. Therefore, a comparative performance analysis of load-testing tools that accounts for these functional characteristics is crucial for achieving reliable and efficient service operation. This paper evaluates the performance of four widely used load-testing tools—JMeter, k6, Gatling, and Locust—under representative web-game workloads. To emulate realistic database read and write patterns, we implement the core server logic of the web game Pokerogue in a cloud environment rather than simply issuing HTTP requests. We classified workload patterns into write-intensive, read-intensive, and mixed types using distributed tracing, and measured request-generation capability and system resource consumption across five key game functions. Our experiments show that each tool demonstrates distinct strengths depending on the characteristics of individual web-game functions. Specifically, k6 demonstrated high request-generation performance in write-intensive scenarios, while JMeter showed strong performance in read-oriented tasks; Gatling exhibited efficient memory usage in mixed workloads, whereas Locust proved suitable for resource-constrained environments. These results indicate that the selection of a load-testing tool should be informed not only by its request-generation performance but also by the workload characteristics of the target game function. By systematically analyzing function-specific workload patterns together with the performance and resource-usage behavior of each tool, this study aims to provide empirical evidence that can be usefully applied in practical load-testing workflows for web-game services.

This study presents the results of compression, drop impact, and vibration durability analyses conducted to evaluate the mechanical reliability of Battery Pack Cases (BPCs) in electric vehicle (EV) systems. BPCs are essential structural components that must endure compressive loads, impact forces, and vibrational fatigue. Finite Element Analysis (FEA) was applied to a representative BPC model to assess deformation, impact resistance, and vibration endurance. The results indicate that the BPC maintained integrity within yield strength limits under compressive loading and effectively absorbed energy under drop impact. Furthermore, Power Spectral Density (PSD) analysis identified stress concentration regions, providing insights for structural optimization. Overall, the findings support the development of lightweight and reliable BPC designs for advanced EV applications.

Ear clamps are components used to securely fasten pipes and hoses in various industrial applications. They achieve clamping force by inducing plastic deformation at the ear region during installation, which can lead to accumulated structural damage and affect fatigue life. Moreover, the fatigue life is influenced by the design shape of the ear. Therefore, in this study, tensile and fatigue tests were conducted on two types of ear clamps with different ear geometries. Finite element analysis (FEA) was performed to obtain the stress distribution around the ear region, and these results were correlated with the experimentally obtained fatigue life. Based on this correlation, an S-N curve for simulation-based fatigue life estimation was established. This approach confirms the possibility of predicting the fatigue life of ear clamps with modified geometries using only finite element analysis, without the need for repeated fatigue testing.

This study proposes empirical formulas for predicting the nonlinear behavior of GIR beam-to-column connections in timber structures to evaluate their structural performance. A database comprising 59 experimental results of GIR connections was collected, and the normality of data distribution was verified. Statistical analysis were conducted to investigate the correlations between input and output parameters. Based on input parameters with high correlation, derived variables were formulated and utilized in a multiple regression analysis to develop empirical formulas for moment capacity and rotation. The R-squared values of the proposed formulas exceeded 0.9, and the predicted initial stiffness and strength closely matched those of experimental results not used in the regression analysis. So the suggested empirical formulas exhibit excellent predictive performance for the nonlinear behavior of GIR beam-to-column connections in timber structures.

Microalgae are efficient fatty acid producers owing to their high photosynthetic activities. They can act as sources of biofuel, feed, and various bioactive compounds. This study aimed to determine optimal culture conditions, including culture medium, temperature, and light intensity, to enhance the biomass and fatty acid content of the indigenous freshwater microalga, Tetradesmus obliquus. Evaluation using a high-throughput photobioreactor revealed that the optimal culture temperature and light intensity were 25°C and 300 μmol m-2 s-1, respectively. Additionally, we optimized components (N, P, and Mg) of the BG-11 medium to enhance the microalgal biomass. Modified BG-11 medium increased the T. obliquus biomass by 37% compared to the standard BG-11 medium. Subsequently, the culture medium was replaced with N- and P-depleted media to determine the abiotic stress factor that could increase the cellular fatty acid content. Notably, fatty acid content was significantly increased from 8.5% up to 14.6% on day 7 of culture in N-deficient (N-P+ and N-P-) media. Sequential optimization effectively increased the biomass by 83% and fatty acid content by >76% in T. obliquus. Our optimization method can be used to enhance the biomass and fatty acid contents of various other microalgae.

아토피 피부염은 만성 염증을 동반한 알레르기성 질환 이며, 일반적으로 Type 2 염증 반응과 관련이 깊다고 알 려져 있다. Corchorus olitorius (C. olitorius)의 아토피 피 부염 치료 효과를 확인하기 위하여 2,4-dinitrochlorbenzene 로 아토피 피부염 모델을 유도한 BALB/c 마우스를 대상 으로 피부 염증 개선도를 육안으로 확인하였으며, 질환 관 련 IgE와 사이토카인(IL-4, IFN-γ and TNF-α)의 수준을 측정 하였다. 7일간의 투여기간동안 양성대조약물인 Dexamethasone 투여군의 체중은 감소하였던 반면에 모든 C. olitorius 투 여군의 체중은 꾸준히 증가하였다. 이와 같은 결과는 C. olitorius이 동물에 위해한 영향이 없었다는 것을 의미한다. C. olitorius 200 mg/kg/day 투여군의 치료 효과가 가장 뛰 어났으며, 모든 C. olitorius 투여군의 염증 관련 면역글로 불린과 사이토카인의 수준은 감소하였다. 따라서, C. olitorius 는 아토피 치료제로 충분히 활용될 수 있다고 판단된다.

Chironomid larvae in drinking water treatment plants (DWTPs) and tap water lead to highlights the urgent need for effective control measures. The use of combined disinfectant treatments is becoming increasingly common to achieve optimal disinfection efficiency while minimizing residual contamination. This study was conducted to study the effect of combined treatment of disinfectants used in DWTPs on the biological control potential of chironomid larvae. In the experiment, Glytotendipes tokunagai larvae reared according to OECD guidelines were exposed to NaOCl, UV, and O3 complex substances, and biological responses were analyzed using survival rate and body color change as key indicators for 24 hours. The survival rate of larvae exposed to combined disinfectants mostly decreased in a time- and concentration-dependent manner, and lightening of body color was observed. The most significant decrease (53%) of the survival rate was observed to a combination of UV and 4 ppm NaOCl disinfectants and body color change also showed a statistically significant difference compared to the control group (P<0.001). The change in body color is suggested to be a physiological change caused by oxidation of hemoglobin due to exposure to disinfectant complexes. The results of this study contribute to determining the biological impact of combined disinfectant treatment on chironomid larvae of DWTPs, and can be used as data to suggest the biological control potential of disinfectants. In addition, it will provide important information for setting standards for combined disinfectant treatment to improve water quality in the future.

Time-series and spatial analysis of collected odor complaints in Seoul megacity during 2014~2021 were conducted for the characterization of odor complaints emitted from the living environment. The ratio of odor complaints in the environmental complaints was 16.7%, and odor complaints increased 3.3 times from 9,053 cases in 2014 to a maximum of 29,425 cases in 2019. In the time-based evaluation (monthly, daily (day of the week), and hourly variations), the highest number of complaints occurred in June, Monday, and 9:00 AM, respectively. While the lowest number of complaints occurred in December, Sunday, and 3:00 AM, respectively. Among 25 provinces in Seoul megacity, the odor complaints that occurred from 2014 to 2021 were concentrated in Eunpyeonggu. The odor complaints of Seodaemun-gu and Nowon-gu occurred at the highest levels in January-February and June, respectively. Based on the characteristics of odor complaint occurrence according to the above time-series and spatial analyses, more effective odor management and control can be implemented by focusing on those hotspot areas and specific time periods.

최근 지구온난화로 인해 폭우, 눈 등 이상기후가 발생하면서 노면 동결(블랙아이스)로 인한 사고 및 인명피해가 늘어나고 있 는 것이 문제가 되고 있다. 이를 최소화하기 위해 본 연구에서는 다공성 골재인 팽창점토에 열저장이 가능한 상변화물질(PCM)을 적용 하였다. PCM은 상변화 과정에서 열에너지를 흡수, 저장, 방출할 수 있는 소재로 온도에 따른 결빙을 최소화할 수 있다. 따라서 본 연 구에서는 시멘트 복합재에 적용되는 PCM 함침이 가능한 경량골재에 진공함침을 실시하고 기계적, 열적 성능 검증 연구를 수행하였다. 열적 성능을 향상시키기 위해 다중벽탄소나노튜브(MWCNT)와 실리카흄을 첨가하였다. 본 연구에서는 물체의 열적 성능을 측정할 수 있는 DSC 실험을 통해 PCM 함침 경량골재 및 콘크리트 복합체의 열적 성능을 검증하였다. 콘크리트 복합체 제작 후 압축강도 시험 과 열적 성능시험을 실시하였다. 이때 열적 성능을 검증하기 위해 항온항습 챔버를 이용하여 시험을 진행하였다. 압축강도 실험을 통 해 MWCNT의 분삭액을 혼입한 PCM 함침 팽창점토가 적용된 콘크리트 복합체의 평균 압축강도는 24MPa 이상으로 구조물에 적용이 가능함을 확인하였다. 열적 성능시험을 통해 PCM 함침 팽창점토가 적용된 콘크리트 복합체는 영하의 외기온도에서도 영상의 온도를 유지할 수 있음을 확인하였다. 이와 같은 결과를 통해 주거 및 상업 건물 및 다양한 구조물에 적용이 가능할 것으로 판단된다.