• The Journal of the Acoustical Society of Korea
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• v.41 no.3
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• pp.359-366
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• 2022

In this paper, we present the Korean menu-ordering Sentence Text-to-Speech (TTS) system using conformer-based FastSpeech2. Conformer is the convolution-augmented transformer, which was originally proposed in Speech Recognition. Combining two different structures, the Conformer extracts better local and global features. It comprises two half Feed Forward module at the front and the end, sandwiching the Multi-Head Self-Attention module and Convolution module. We introduce the Conformer in Korean TTS, as we know it works well in Korean Speech Recognition. For comparison between transformer-based TTS model and Conformer-based one, we train FastSpeech2 and Conformer-based FastSpeech2. We collected a phoneme-balanced data set and used this for training our models. This corpus comprises not only general conversation, but also menu-ordering conversation consisting mainly of loanwords. This data set is the solution to the current Korean TTS model's degradation in loanwords. As a result of generating a synthesized sound using ParallelWave Gan, the Conformer-based FastSpeech2 achieved superior performance of MOS 4.04. We confirm that the model performance improved when the same structure was changed from transformer to Conformer in the Korean TTS.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.957-963
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• 2014

Converter transformers play important roles in high-voltage direct current transmission systems. This paper presents experimental and analysis results of the combined electrical and thermal aging of oil-impregnated paper at pulsating DC voltages. Breakdown voltages and time-to-breakdown of oil-paper specimens were measured by using short-time and constant-stress tests. The breakdown characteristics of combined electrical and thermal aging on insulation system were discussed. According to the relationship between failure time and aging temperature, the two-parameter Weibull model was improved. On the basis of the competing risk algorithm and the improved Weibull model, the two factors failure model was calculated. And the influence of temperature in the insulation system has been analyzed. This model performs better than the two-parameter Weibull model when both time and temperature are considered as variables in estimating the lifetime of oil-paper insulation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.5
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• pp.536-541
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• 1988

The push-pull current-fed DC-to-DC converter has only one energy storage reactor in series with the input for any number of outputs. It is considered that this property of the converter has considerable advantages over other multiple-output circuits. The steady state characteristics of the converter with two outputs is analyzed. It is known that the voltage difference between the two outputs appears by existing the 2nd winding resistance of transformer and there is a region of the duty ratio in which the voltage difference of the converter is smaller than that of the forward converter.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.291-294
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• 2001

This paper presents the circuit modeling and control methods of PWM DC/DC converter with isolated dual outputs. The dual output converter consists of a transformer with a single secondary winding and two switches. The proposed control algorithm is that required inductor current according to the loads is feed-forwarded to the PI current controller. The proposed control method has better response characteristics than conventional PI control method at load change.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.87-90
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• 2003

There are generally two temperature control methods using ac voltage regulators - the phase control method and the on-off control method. The phase control method uses thyristor's angles of extinction for the output power regulation and the on-off control method uses the control of on and off times for the output power regulation. Both of methods have the problems that are the unbalance of the three phase and surge current caused system's destruction. The main object of this study proposes a solution of problems of surge currents and unbalance of three phase when thyristor voltage regulator is switching. To solve the problem, It is proposes that the solution of surge currents is using a tap transformer and an additional switch with adjustable resistance and applies zero crossing of switching voltage of two input line to power load. This method is discuss and verified by computer simulations and experiments.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.385-388
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• 1994

This paper presents a new configure rectifier which has improved input power factor and efficiency for DC arc weldings. Two rectifiers are series connected and they are single-phase full-wave phase controlled rectifiers that use a transformer with two center-tapped secondary. The input power factor can be improved by controlling the each phase of rectifiers sequentially, and then the efficiency can be also improved because the reactive component currents will be reduced. It is confirmed that the proposed rectifiers has about 80% of input power factor and efficiency with the experimental results which are carried out at the output ranges of 100A to 300A.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.69-71
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• 2008

We have developed a current range extension method to obtain the ratio error and phase displacement of a current transformer (CT) by using absolute evaluation method and two different CTs. The method was applied to CTs under test with the current ratios of the range of 5,000 A / 1 A - 20,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Germany using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.351-355
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• 1999

The amount of data stored, processed and transmitted in the multi-media systems has been growing very fast, especially for the image data. For example, it takes 0.75Mbytes to store 512 12 pixels of 24-bit color image. A video signal with 30 frames per second will require 22.5Mbytes of storage space. To solve this problem, we need a good image compression technique. Recently, many researches on the image compression technique based on the wavelet transform are being pursued to overcome the problems of traditional JPEG. This paper describes the architecture and design of two-dimensional wavelet transform circuit. To keep the sire of the circuit small, we tried to minimize the internal storage space by using external SDRAM. This circuit was designed in Verilog-HDL, synthesized using Design Compiler and verified using Verilog-XL.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.372-374
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• 2006

This paper reported the experimental results of the 2 stage converter using a Buck converter and a soft switching dc-to-dc converter that employs two separate transformers. A 2 stage converter module is designed with the specifications of an 3.3V output voltage, 20A output current, 66W output power and 36-75V input voltage. A prototype converter module is successfully implemented within 85.2% efficiency and 3% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.886-890
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• 2003

This paper introduces the combined test results of the traction system for KHST(Korean High Speed Train: hereafter refer to KHST). The main purpose of this combined test is to verify the performance of the traction system that is designed to operate up to maximum 350km/h speed. Combined test system consists of a traction transformer, two AC-DC PWM converters, a PWM Inverter, two traction motors and flywheel system. Flywheel system represents equivalent model of the train inertia. Also traction control system and MASCON Interfaces are included. Various kinds of experiments are performed to prove total traction system performance and detail waveforms are described