Ear piercing has been widely performed for various reasons, but it may cause hypertrophic scarring and its attendant cosmetic problems and/or subjective symptoms, such as pruritus or pain. Many treatment methods have been applied alone or in combination, including surgical excision, steroid injection, compression, radiation, topical silicone application, and so on. Although each modality or combined therapy has its advantages and disadvantages, in the authors' opinion, compressive therapy combined with surgical excision is the most effective method in many respects. However, the peculiar shape of the earlobe does not allow for easy compression. Thus, many compressive devices have been developed that are not wholly satisfactory in terms of effectiveness, appearance, size, or convenience. The authors describe a newly developed method for the treatment of hypertrophic scarring of the earlobe that uses magnetic disks. They treated 47 patients (91 auricles) with a hypertrophic scar on the earlobe that underwent compressive therapy using magnetic disks after surgical excision from April to December 2002. The use of magnetic disks proved effective, and they believe that it offers many advantages as a compressive device.
This paper proposes a predictive control algorithm that includes conduction-mode detection for power factor correction (PFC) converter. In PFC converters, the line current is usually distorted because of the characteristics of the proportional integral (PI) current controller. To improve the quality of the current, the PI current controller requires additional circuits or algorithms. However, because of the optimal duty cycle determined by estimating the next-state current in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM), the proposed predictive control method has a fast dynamic response and accuracy compared to the PI current control method. Moreover, the proposed algorithm can detect the conduction mode without any additional circuitry or mode-detection algorithm using the characteristic of the optimal duty cycle calculated by the predictive control. These advantages of the proposed algorithm improve the quality of the line current for PFC converters. We verify the proposed method by performing experiment using a 1.5 kW PFC converter.
Conventional single-phase Vienna rectifiers employ proportional-integral (PI) controllers which are appropriate for controlling DC components, to regulate their line currents. However, in the regions close to the line current's zero-crossing point, the dynamics of PI controllers are too slow to respond to the reference current, which has an AC component. Hence, the power factor (PF) of the device is degenerated, and total harmonic distortion (THD) increases. A controller with a fast dynamic response is thus required to solve this problem. In this paper, we investigate the use of a model-based predictive controller (MPC), which has a faster dynamic response than a PI controller, to improve the line current quality of a single-phase Vienna rectifier. With this method, the average current in both the continuous current mode (CCM) and the discontinuous current mode (DCM) of operation are controlled using a mode detection method. Moreover, we calculate the optimized duty cycle for the single-phase Vienna rectifier, by predicting the next current state. We verify the operation of the proposed algorithm using a PSIM simulation, and a practical experiment conducted with a 1-kW-rated single-phase Vienna rectifier prototype. With the proposed method, the quality of the line current near the zero-crossing point is improved, and the PF is controlled to unity.
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