Sensorless Control of Voltage Peaks in Class-E Single-Ended Resonant Inverter for Induction Heating Rice Cooker

Single-ended (SE) resonant inverters are widely used as power converters for high-pressure rice cooker induction, with 1200 V insulated-gate bipolar transistors (IGBTs) being used as switching devices for kW-class products. When voltage fluctuations occur at the input stage of an SE resonant inverter, the resonant voltage applied to the IGBT can be directly affected, potentially exceeding the breakdown voltage of the IGBT, resulting in its failure. Consequently, the resonant voltage should be limited to below a safety threshold—hardware resonant voltage limiting methods are generally used to do so. This paper proposes a sensorless resonant voltage control method that limits the increase in the resonant voltage caused by overvoltage or supply voltage fluctuations. By calculating and predicting the resonance voltage through the analysis of the resonance circuit, the resonance voltage is controlled not to exceed the breakdown voltage of the IGBT. The experimental results of a 1.35 kW SE resonant inverter for a high-pressure induction heating rice cooker were used to verify the validity of the proposed sensorless resonant voltage limiting method

Validation of the Korean version of the Metacognitions Questionnaire-Insomnia (MCQ-I) scale and development of shortened versions using the random forest approach

We aimed to validate a Korean version of the Metacognitions Questionnaire-Insomnia (MCQ-I) and develop two shortened versions of the MCQ-I by applying the Random Forest (RF) algorithm. A total of 310 participants responded through an online survey, during April 3–6, 2021, which included rating scales such as the Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), Patient Health Questionnaire-9 (PHQ-9), and the Hospital Anxiety and Depression Scale (HADS), as well as the MCQ-I. After validating the scale, we developed two shortened versions by applying the RF. Finally, we explored the psychometric properties of the shortened versions. The Korean version of the MCQ-I showed good internal consistency based on a Cronbach's alpha of 0.96. Factor analyses showed good model fits for the single structure of the MCQ-I. From the results of the RF, 6 of the 60 items of the MCQ-I were sufficient to distinguish between people with MCQ-I scores above the cut-off value and the rest with high accuracy (AUC>0.97), leading to the 6-item (MCQI-6) version of the MCQ-I. Furthermore, we have also developed a 14-item (MCQI-14) version of the MCQ-I with higher accuracy (AUC>0.98). Both versions were reliable based on their internal consistency (alpha = 0.843 and 0.912), and confirmatory factor analysis showed good model fits for both shortened versions. In addition, good convergent validity of both shortened versions with insomnia, sleep quality, depression, and anxiety were observed. The Korean version of the MCQ-I and two shortened versions (MCQI-6, and MCQI-14) were useful, reliable, and valid tools to evaluate the role of metacognitive beliefs in sleep problems among the Korean population.11Nsciescopu