The Hangang River* is necessary to manage the water environment of severe pollution due to the high density of residential areas, parks, and agriculture and the large population concentrated there. Benthic macroinvertebrates, such as chironomids larvae, are bioindicator species that reflect environmental changes and are crucial for water quality monitoring. In this study, we investigated morphological characteristics and molecular analysis of the chironomids larvae inhabiting the Hangang River area for water environment surveys. For this research, 20 rivers, lakes, and urban area in the Hangang River basin were selected. Chironomids larvae were collected from July to September 2022, and their appearance and characteristics were identified through morphological identification. In addition, phylogenetic analysis was performed based on the mtCOI gene sequences of the collected chironomids larvae, and identification at the genus level was confirmed. As a result, 32 species and 18 genera of 3 subfamilies of Chironomidae larvae were identified, and Stictochironomus sp. dominated most sites (6 sites). The morphological characteristics of the identified chironomids larvae, such as the mentum, ventromental plate, and antenna, were organized into table and pictorial keys, and a Bayesian inference molecular phylogeny was presented. These results provide basic morphological information for genus-level identification and can be used as fundamental information for water quality management. *The public nomenclature following by NGII 2015

In this study, the structural analysis and welding performance experiments were performed to reduce the weight of the semi-automatic TIG welding device. The structural analysis based on finite element method was performed on the lightweight design of the wire feeder's main frame to evaluate the structural safety and straightness of the lightweight frame. To reduce the weight of the welding wire feeder, the step motor was changed to a servo motor and a pinion gear made of lightweight reinforced plastic material was applied. In addition, a new type of welding torch was developed to reduce the weight of the welding torch and to supply more effective fillers. As a result of performing the TIG welding experiment using a prototype of TIG welding device consisting of a lightweight frame, feeding device and welding torch, it was confirmed that the working criteria were satisfied in terms of welding speed, welding bead shape, feeding uniformity and torch durability. The developed lightweight TIG welding device is expected to improve welding productivity and work convenience.

In this study, the deformation of friction stir welding on the aluminum battery housing material(AL6063-T5) applied to the electric vehicle was effectively predicted through experiments and numerical simulations. The temperature data were measured during the friction stir welding experiment, and the numerical simulation was carried out using the experimental temperature data. In the heat transfer analysis, the temperature distribution of the structure over time was calculated using the Reynolds equation. The final friction stir welding deformation was calculated by performing the structural analysis using the calculated temperature distribution data over time. The thermal elasto-plastic analysis was performed according to the friction stir welding process conditions and the welding sequences. Finally, the optimum welding condition was derived that the welding speed is 1000 mm/min and the rotation speed of the tool is 2000 RPM.

본 연구에서는 도그 피스 설치량에 따른 용접 변형 실험을 수행하여 용접 변형 감소 효과를 정량적으로 평가하였고, 도그 피스 설치를 고려한 용접 변형 해석 방법을 제안하였다. 용접 변형 실험 결과, 도그 피스 설치량이 증가할수록 용접 변형이 감소하며 최대 74%의 변형 감소 효과가 있음을 확인하였다. 원판형 열속 모델을 사용한 열탄소성 유한요소 해석을 활용하여 도그 피스 설치를 고려한 용접 변형 해석 방법을 제안하고, 해석 결과와 실험 결과가 좋은 유사성을 보이고 있음을 확인하였다. 본 해석 방법은 현행 도그 피스 설치량에 대한 적정 여부를 평가하거나 도그 피스 사용량을 절감할 수 있는 설치 가이드를 마련하기 위한 해석적 툴로 활용될 수 있다.