• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.89-93
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• 1995

To reduce the redundancy within samples that resulted from uniform sampling method, nonuniform sampling or nonredundant-sample coding methods can be considered. However, it is well known that when conventional nonuniform sampling methods are applied directly to speech signal, the required amount of data is comparable to or mure than that by uniform sampling method like PCM. To overcome this problem, a new nonuniform sampling method is proposed, in which nonuniform sampling is applied to the low-pass filtered speech signal and higher band is compensated by 8 colored Gaussian random noise with various noise levels. By this method, speech signal waveform can be encoded by 1.8 times larger compression ratio than the conventional nonuniform sampling method.

• Korean Journal of Acupuncture
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• v.28 no.4
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• pp.79-89
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• 2011

Objectives : The aim of this study is to propose the W area of pulse (AW) as a new index which can confirm the arteriosclerosis by analyzing parameters of 5-level pressure pulse waveform measurement system for normotensive group according to aging. Methods : We measured radial pulse waveforms of normotensive group (20 to 60 years old) using 3-dimensional pulse imaging analyser (DMP-3000, DAEYOMEDI Co., Korea). And then we analyzed various parameters for sclerosis of the arteries such as Height (h1, h2, h3, h4, h5), Time (t1, t2, t3, t4, t5), AW, AW rate, Total area of pulse (At) and Augmentation Index (AIx). Results : As a result of analyzing parameters according to the aging, h2, h3, AS (systolic area rate to AT), AIx and AW were increased but t2/t, t3/t, t5/t and AD (diastolic area rate to AT) were decreased. Conclusions : We checked blood vessel conditions for normotensive group according to aging and confirmed various parameters. Also, we found that AW was analogous to AIx which has been used for diagnosing arteriosclerosis. Furthermore, we confirmed the usefulness of AW as a new parameter for checking vessel condition and characteristic compared with the AIx.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.581-586
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• 2002

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown by experimentation and confirmed simulation. The experimental results of the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97(%) and an efficiency of 98[%] are also obtained. The new rectifier with no controlled switches meet the harmonic guide lines, resulting in a simple, reliable and low-cost at-to dc converters in comparison with the boost-type current-improving circuits. This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance value is changed by the polarity of current or voltage. And this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit is constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduction and the power factor improvement. Half pulse-width modulated (HPWM) inverter was explained compared with conventional pulse width modulated(PWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.

• Journal of IKEEE
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• v.16 no.4
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• pp.335-342
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• 2012

This paper is studied on a new DCM-ZVS step up-down AC-DC converter of high performance, that is, high system efficiency and power factor correction (PFC). The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit uses a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuits and reduces the number of control components. The input AC current waveform in the proposed converter becomes a quasi-sinusoidal waveform proportional to the magnitude of input AC voltage under constant switching frequency. As a result, the proposed converter obtains low switching power loss and high efficiency, and its input power factor is nearly in unity. The validity of the analytical findings is confirmed by some computer simulation results and experimental results.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.637-646
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• 2022

In this paper the comparative study on the pronunciation of Vietnamese learners and Koreans for the Korean syllable final double consonants was performed. For many errors and the suggested teaching methods related to the pronunciation of the Korean syllable final double consonants that were investigated and analyzed through linguistic research the results of this study by using the analysis tools of speech signal processing were confirmed. Thus, we suggest the new educational method in this paper. Using SVM, which is widely used in machine learning of artificial intelligence the pronunciation of Vietnamese learners and that of Koreans were compared. Being able to obtain the decision hyperplane of the SVM means that Vietnamese learners' pronunciation of the Korean syllable final double consonants is quite different from that of Koreans. Otherwise their pronunciation are pretty similar each other. The new teaching method presented in this paper is not only composed of writing and listening but is included things such as the speech signal waveform in the time domain and its corresponding energy that can be visualized to the learners.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.108-116
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• 2002

This paper presents the measurements and evaluation of voltage waveforms due to human electrostatic discharge(ESD). The principle of operation and design rule of a new device for measuring the ESD fast transient voltages with very fast rise time were described. Peak values and rise time of ESD voltages derived from a charged human body under a variety of experimental conditions were examined. The frequency bandwidth of the proposed voltage measuring system ranges from DC to 400[㎒]. The ESD voltage waveform is nearly equal to the ESD current waveform and the peak amplitude of ESD current waveform is roughly proportional to the ESD voltage in each experimental conditions. A rapid approach results in a discharge voltage with a faster initial rise time than for a slow approach. The voltages caused by direct finger ESDs have an initial slope with a relatively long, 10∼30[ns] rise time, but the amplitude is small. On the other hand, the voltages caused by direct hand/metal ESDs have a steep initial s1ope with 1 ∼3[ns] rise time, but an initial spike is very big. As a consequence, it was found that the ESD voltage and current waveforms strongly depend on the approach speed and material of intruder. These measurement results would be useful to design the ESD protective devices.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.3-14
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• 2016

Recently, researches for new waveforms have been carried in order to satisfy KPI for 5G mobile communication system. UFMC and FBMC are well known as ways to reduce OOB power. In this paper, we analyze spectrum of OFDM, UFMC, and FBMC system under nonlinear HPA environment. And then we evaluate and analyze performance of these systems under the same environment. As simulation results, OOB power of OFDM, UFMC, and FBMC increases with HPA nonlinearity increasement. Especially, OOB power of FBMC is the largest increase due to HPA nonlinearity. Also, BER performance of these systems is degraded by increasement of HPA nonlinearity. Therefore, In this paper, we can confirm that a system with low-complexity and high-speed processing is advantageous, because BER performance and OOB power characteristic of these systems are degraded to similar level, when these systems are implemented in real world.

• Journal of Power Electronics
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• v.4 no.1
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• pp.56-63
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• 2004

A new driving circuit for the SPSS (Single-Pulse Soft-Switching) PFC converter is proposed. The switching device of a SPSS converter switches once in every half cycle of an AC commercial power source. Therefore, it can be solved many problems caused by the high frequency operation. The proposed SPSS converter achieves the soft-switching operation and the EMI noise can be reduced. The resonant capacitor voltage supplies to the resonant inductor even if the input AC voltage is the vicinity of zero cross voltage. Then, the power factor and input current waveform can be improved without delay time. A new driving circuit achieves the operation of SPSS converter by one switching drive circuit. The proposed converter can be satisfied the IEC standard sufficiently

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1151-1156
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• 2007

In this paper, we develop a new conversion method for implementing binary ECG(Electrocardiogram) conversion scheme to improve our previous research works that supported the conversion of binary ECG files into HL7 aECG for enhancing interoperability of ECG data. HL7 aECG is a XML-based standard for interoperability of ECG waveform. To improve the performance of ECG data conversion, we utilize a compilation-based ECG conversion method on binary ECG files. Our new method supports both flexibility of BED-based ECG conversion mechanism and the performance of direct conversion mechanism.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.45-48
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• 1997

The low frequency pulsed MIG welding process of new current waveform control to switch over unit pulse conditions (pulse current, pulse duration) in the fixed cycle was developed and its effect were investigated for aluminium and its alloy. By using this new welding process, the bead appearance having clear ripple pattern, such as TIG welding bead can be obtained and the gap tolerance of lap and butt welding joint can be expanded.