DynamicLabels: 크라우드 피드백을 활용한 머신러닝 레이블 셋 구축 지원 시스템

학위논문(석사) - 한국과학기술원 : 전산학부, 2023.8,[v, 33 p. :]Label set construction --- deciding on a group of distinct labels --- is an essential stage in building a machine learning (ML) application, as a badly designed label set negatively affects other stages such as training dataset construction, model training, and model deployment. Despite its significance, it is challenging for ML practitioners to come up with a well-defined label set, especially when no external references are available. To mitigate this difficulty, ML practitioners often go through multiple iterations to gradually improve their label set. Through our formative study (n=4), we observed that there still remain challenges in collecting helpful feedback and utilizing them to make optimal refinement decisions. To support the iterative refinement, we present DynamicLabels, a system that aims to support a more informed label set-building process with crowd feedback. Crowd workers provide feedback as annotations and label suggestions to the ML practitioner's label set, and the ML practitioner can review the feedback through multi-aspect analysis and see the potential consequences of label refinements. Through a within-subjects study (n=16) using two datasets, we found that DynamicLabels enables better understanding and exploration of the collected feedback and supports a more structured, confident refinement process. The ML practitioners were also able to see surfacing conflicts and edge cases that could have been ignored. In addition, the crowd feedback helped ML practitioners to gain diverse perspectives, spot current weaknesses, and shop from crowd-generated labels. With DynamicLabels, ML practitioners can successfully gain concrete understanding and evidence from the crowd and make informed refinements to iteratively improve the label set.한국과학기술원 :전산학부

인공위성의 고전력밀도 전력시스템에 관한 연구

학위논문(박사) - 한국과학기술원 : 전기및전자공학부, 2023.8,[v, 78 p. :]This dissertation proposes a new control method for solar array regulator (SAR) and a new converter integrating two bus voltage regulators for a satellite's high power density electrical power system. The new control method of SAR proposed in the first study is a direct energy transfer (DET) control that directly charges the battery from the solar array by keeping the buck converter switch of the SAR in the 'ON' state without switching operation. The proposed DET control reduces the conduction loss by eliminating the switching loss and reducing the peak value of the battery charging current. In addition, SAR's conventional controller, maximum power point tracking (MPPT) analog controller and three sensing inductors were removed, and the main inductors were redesigned to be smaller and lighter to reduce weight, volume, and cost. The new converter proposed in the second study is a converter that reduces the number of semiconductor devices by two by integrating a conventional buck converter and a two-switch forward converter. The proposed converter reduced the number of semiconductor devices to reduce weight, volume, and cost. Additionally, zero voltage switching (ZVS) of the switch is achieved to eliminate switching losses. As a result, the proposed DET control method and converter have the advantage of increasing power density in the satellite's electrical power systems.한국과학기술원 :전기및전자공학부

14~24)$ 의 구조와 결합

학위논문(석사) - 한국과학기술원 : 화학과, 2004.8, [ vi, 64 p. ]한국과학기술원 : 화학과

고효율 Two-Stage AC-DC Converter를 위한 전력변환회로들에 대한 설계

학위논문(석사) - 한국과학기술원 : 전기 및 전자공학과, 2012.2, [ iv, 31p ]한국과학기술원 : 전기 및 전자공학과

Experimental Assessment of the Methanol Addition Effect on the Tribological Characteristics of Ni-based Alloy

Currently, the demand for green technologies toward a sustainable future is rapidly increasing due to growing concern over environmental issues. Methanol is biodegradable and can provide clean combustion to reduce sulfur oxide and nitrogen oxide emissions, and therefore it is a candidate fuel for marine engines. However, the effect of methanol on tribological characteristic degradation should be addressed for methanol-fueled engines. In this study, the methanol addition effects on tribological characteristic degradation is experimentally assessed using a pin-on-disk tribo-tester. Ni-based alloy is used as a target material due to its broad applicability as an engine component material. For a lubricant, engine oil with and without methanol are used. The tests are conducted for up to 10,000 cycles under boundary lubrication while the change in friction force is monitored. Additionally, the wear rate is determined based on laser scanning confocal microscope data. An additional test in which methanol is added at regular intervals is performed with an aim to directly observe its effect on friction. Overall, the friction coefficient increases slightly with increasing methanol concentration. Furthermore, the wear rate of the pin and disk increase significantly with methanol addition. The results also indicate that the friction increases instantaneously with methanol addition at the contacting interface. These findings may be useful for better understanding the methanol effect on the tribological characteristics of Ni-based alloys for methanol-fueled engines with improved performance