This study reports the results of an open-ended questionnaire on the experiences of Korean university students who worked on task-based L2 bimodal collaborative writing enhanced by technology. Thirty-six English major students developed a reading text for 2nd-grade middle school students. Using Microsoft TEAMS as the main platform, participants conducted the collaborative writing task using real-time video conferencing, chatting, commenting, file and image posting, and (a)synchronous feedback/revision functions. Participants 1) used multiple tools to maximize their functions, 2) interacted collaboratively in every writing stage to achieve success, and 3) evaluated the quality of collaborative writing more highly than individual writing and perceived the positive impacts of collaborative writing on L2 writing in audience awareness, paraphrasing technique, and linguistic expressions. The levels of visual editing skills and awareness of online image copyright among students varied.

The combustion instability in a dual swirl combustor was investigated experimentally. The effects of thermal power and combustor length on combustion instability were evaluated. Pressure and heat release fluctuation were measured simultaneously. In a conventional combustor, the frequency was decreased with increasing combustor length and decreasing thermal power. However, it showed different results with a dual swirl combustor. In regime 1 where thermal power was relatively high, the results showed same tendency with a conventional combustor. In regime 2 where thermal power was relatively low, the frequency was almost constant with increasing combustor length. It was found that a beating phenomenon occurred with increased combustor length in regime 2 by measuring sound pressure fluctuation. By confirming that beating phenomenon occurs only in regime 2, it is considered that beating phenomenon is the dominant factor of combustion instability in regime 2. This beating phenomenon inside combustion chamber greatly affected to combustion instability. The reason of the beating phenomenon seemed to be the difference oscillating period between main flame and pilot flame.