• Speech Sciences
• /
• v.3
• /
• pp.156-166
• /
• 1998

In this paper, I would like to propose a dividing method by estimating the inflection points and the average magnitude energy in speech signals. The method proposed in this paper gave not only a satisfactory solution for the problems on dividing method by zero-crossing rate, but could estimate the feature of the transient period after dividing the starting point and transient period in speech signals before steady state. In the results of the experiment carried out with monosyllabic speech, it was found that even through speech samples indicated in D.C. level, the staring and ending point of the speech signals were exactly divided by the method. In addition to the results, I could compare with the features, such as the length of transient period, the short term energy, the frequency characteristics, in each speech signal.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.12 no.5
• /
• pp.478-491
• /
• 1987

In this paper, an all Digital Phase-Locked Loop(DPLL) has been propoed, which has reduced the phase error by using a half period sampling in order to improve the performance of the conventional DPLL which tracks the phase of incoming sinusoidal signal once per cycle for the Positive Going Zero crossing(PGZC) of the signal. The proposed DPLL tracks the phase of input signal twice per cycle with two samplers for the PGZC. So the loop has a half reduction of the steady state phase error fluctuation ranges without decreasing the lock-range in a whole, comparing with that of the conventional DPLL. Also, it has been known that the proposed loop is rapidly locked to input signal for the same valves of phase differenc between sucessive samples and quantization level. The analytic results of the proposed loop have been verified by computer simulation for the practically requeired conditions.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.615-619
• /
• 2009

This paper is investigated to variation of wave power generation operation rate, operating capacity and output with the wave conditions represented by wave height-period window. By the use of the long-term wave data from 1979 to 2002 which is provided by Korea Ocean Research & Development Institute(KORDI), we calculated the monthly variation of significant wave height(Hs), zero-up crossing period(Tz) and distribution of wave appearance rate. And using the same wave data, it was charted the Hs-Tz and wave-energy scatter diagrams.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.5
• /
• pp.239-246
• /
• 2017

In case of observing only wave height and period in the field, various wave characteristics are mainly calculated by wave by wave analysis method. In this paper, an wave by wave analysis program using MATLAB language is developed. It is possible to perform a function such as 1) correction for mean water level, 2) calculation for zero crossing time, 3) calculation for individual wave height, 4) time interval by using zero upcrossing and downcrossing method. The applicability of the developed program to the data of 0.2 second interval observed by using the WaveGuide Radar installed on HeMOSU-1 was examined. Tidal level variation removal and zero crossing time estimation were determined by linear or quadratic interpolation. It was judged that the Goda method was appropriate for calculating individual wave height, and the method proposed in this study seems to be improved through subsequent research. Due to the fineness of the sample, it can be seen that characteristics of representative waves are different from the results calculated by zero upcrossing and downcrossing method.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.4
• /
• pp.655-669
• /
• 2015

The Overall Motion Sickness Incidence is applied to the hull form optimization of a wave piercing high-speed catamaran vessel. Parametric hull modelling is applied to generate two families of derived hull forms, the former varying the prismatic coefficient and the position of longitudinal centre of buoyancy, the latter instead the demi-hull separation. Several heading angles are analysed in a seaway, considering all combinations of significant wave height and zero-crossing period under two operating scenarios. The optimum hull is generated and vertical accelerations at some critical points on main deck are compared with the parent ones. Finally a comparative analysis with the results obtained for a similarly sized monohull passenger ship is carried out, in order to quantify, by the OMSI, the relative goodness in terms of wellness onboard of monohulls and catamarans, as a function of sea states and operating scenarios.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.10
• /
• pp.56-62
• /
• 2014

When fault currents contain decaying DC offset, the peak value of the fault current in the first cycle of the fault period is higher than the fault current during the steady-state period. To reduce the asymmetric fault current, this paper proposes an operation scheme using the series connection of two hybrid type Superconducting Fault Current Limiters (SFCLs) : an auxiliary SFCL and a main SFCL. The proposed method calculates the fault angle by comparing the zero-crossing time with fault detection time. According to the fault angle calculated, an auxiliary SFCL operates to reduce an asymmetric fault current during half a cycle after fault occurrence. After this process, the fault current is limited by a main SFCL. To confirm the usefulness of the proposed method, case studies using Electro-Magnetic Transients Program (EMTP)/Alternative Transient Program (ATP) Draw are perfomed.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.2 no.2
• /
• pp.75-82
• /
• 1990

A Wave transformation including wave breaking in shallow water region is a non-linear and discontinuous Phenomenon. Therefore, a so-called individual wave analysis (or a wave by wave analysis) rather than spectral approach seems to be adequate to investigate the wave transformation in such regions. In this study, a theoretical joint distribution of wave height, period and wave direction of zero-down crossing waves, which is required in the individual wave analysis in the shallow water region, is derived based on the hypothesis that sea surface is a Gaussian stochastic process and that a band-width of energy spectra is sufficiently narrow. The derived i oint distribution is found to be an effective measure to investigate characteristics of three-dimensional random wave field in shallow water through field measurements.

• Journal of Advanced Marine Engineering and Technology
• /
• v.17 no.5
• /
• pp.71-85
• /
• 1993

The Cycloconverter that the author is going to treat in this paper, has strong advantages over the D.C. Link Inverter in points of chattering torque problem and natural commutation. Thus, the Cycloconverter is expected to be well applied to large and low-speed machines which require better speed control at low frequency. But the control circuit of Cycloconverter has two weak points described as follows. 1) Because of its rather complicated control circuit, it is likely to be illoperating due to unexpected noise signals, thus the higher the accuracy and reliability of the circuit is required to be, the more the circuit may cost. 2) Because the load current is not purely sinusoidal, the Cycloconverter may possibly be destroyed in case of inaccurate convert switching resulted from the difficulties in detecting the load current-zero and the current direction at the moment. In this paper, the author first of all intends to design and build a modified VVVF-type Noncirculating Current Cycloconverter to which recently proposed control methods are applied for improving the circuit simplicity, the control performance, and the system reliability. And then, experiments for observing the output waveforms of the Cycloconverter which is controlled by Singled-Board Computer using 8086 16-bit microprocesser are carried out. Finally the author concludes the result of this study as follows. 1) By replacing the conventional analog control circuits such as Reference Wave Generator, Cosine Timing Wave Generator, and Comparator with softwares, a great circuit simplicity is achieved. 2) The output of the designed Cycloconverter changes its frequency very fast without showing discontinuity of its waveform, and this waveform characteristics enables the smooth speed control of Induction Motor. 3) The design control circuit of Cycloconverter can be applied to the systems of 12 or 24 pulses because of its short processing period.

• The Journal of the Acoustical Society of Korea
• /
• v.13 no.5
• /
• pp.77-82
• /
• 1994

In speech signal processing, it is very important to detect the pitch exactly. Although various methods for detecting the pitch of speech signals have been developed, it is difficult to exactly extract the pitch for wide range of speakers and various utterances. Thus we propose a new pitch detection algorithm which takes advantage of the G-peak extraction. It is a method to detect the pitch period of the voiced signals by finding MZCI (maximum zero-crossing interval) of the G-peak which is defined as cut-off bandwidth rate of LPF (low pass filter). This algorithm performs robustly with a gross error rate of 3.63% even in 0 dB SNR environement. The gross error rate for clean speech is only 0.18%. Also it is able to process all courses with high speed.

• Journal of Ship and Ocean Technology
• /
• v.3 no.3
• /
• pp.1-12
• /
• 1999

Spectral fatigue damage calculations has been performed on four ships in order to assess the effect that the probabilistic modeling of sea states has on the estimated fatigue life. The damage estimation method is based on the Miner- Palmgren fatigue damage formulation and a spectral approach is used to determine the necessary variances of the stress processes. Both the horizontal and vertical hull girder bending induced stress process together with the local water pressure induced stress process is taken into account. The wave scatter diagrams are applied in the calculations and their fatigue severity is assessed by analyzing the results obtained with the ten scatter diagrams and the four ships. All four ships are analyzed both in full load and ballast conditions and while traveling at both full and reduced speed. It is found that the fatigue severity of a wave scatter diagram is dependent on several parameters, some of these being the extreme wave hight extrapolated from the scatter diagram and the mean zero up-crossing period in conjunction with the ship length . Based on these three parameters and expression is derived in order to calculate one single number describing the fatigue severity of a scatter diagram with respect to a certain ship.