• The Journal of the Acoustical Society of Korea
• /
• v.23 no.5
• /
• pp.420-427
• /
• 2004

This paper presents real time implementation of 4kbps EHSX (Enhanced Harmonic Stochastic Excitation) speech coder that combines the harmonic vector excitation coding with time-separated transition coding. The harmonic vector excitation coding uses the harmonic excitation coding for voiced frames and used the vector excitation coding with the structure of analysis-by-synthesis for unvoiced frames, respectively. For transition frames mixed with voiced and unvoiced signal, we use the time-separated transition coding. In this paper. we present the optimization methods of implementation speech coder on the EMS320C6701/sup (R)/ DSP. To reduce the complex for real-time implementation. we perform the optimization method in algorithm by replacing the complex sinusoidal synthesis method with IFFT. and we apply fully pipelines hand assembly coding after converting it from floating source to fixed source. To generate a more efficient code. we also make use or the available EMS320C6701/sup (R)/ resources such as Fastest67x library and memory organization.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.8
• /
• pp.562-569
• /
• 2004

An experiment for observation of the distribution of the seagrass (zostera marina) beds and characteristics of high-frequency backscattering by the photosynthesis was conducted off the coast. Acoustic data were taken as a function of the grazing angles and the relative azimuth angles on the seagrass beds of which bottom type was sandy-mud. The transmitted source signal was a 120 kHz CW waveform. Mapping of the seagrass beds distribution was drawn up using the seagrass backscattering strength with azimuth and grazing angles. The result of the comparison backscattering strength distribution of the seagrass beds was shown to be the similar to the photograph of real seagrass beds. The seagrass backscattering strength was also compared between day and night to verify the effects of the acoustical scattering by the bubbles of Photosynthetic oxygen formed on the seagrass. In these results. it is clear that observation of the seagrass beds between day and night showed the different characteristics because the bubbles of Photosynthetic oxygen affect the acoustical scattering.

• Journal of IKEEE
• /
• v.17 no.3
• /
• pp.275-283
• /
• 2013

In this paper, a 8bit 10Ms/s CMOS Folding and Interpolation analog-to-digital convertor is proposed. The architecture of the proposed ADC is based on a Folding & Interpolation using FR(Folding Rate)=8, NFB(Number of Folding Block)=4, IR(Interpolation Rate)=8. The proposed ADC adopts a preamplifier sharing method to decrease the number of preamplifier by half comparing to the conventional ones. This chip has been fabricated with a 0.35[um] CMOS technology. The effective chip area is $1.8[mm]{\times}2.11[mm]$ and it consumes 20[mA] at 3.3 power supply with 10[MHz] clock. The INL is -0.57, +0.61 [LSB] and DNL is -0.4, +0.51 [LSB]. The SFDR is 48.9[dB] and SNDR is 47.9[dB](ENOB 7.6b) when the input frequency is 100[kHz] at 10[MHz] conversion rate.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.10
• /
• pp.699-705
• /
• 2001

Six types of planar thermal converters from TC 1 to TC 6 were designed and fabricated for the purpose of being used as practical standards to alternating current. The respective voltage responses in air and in a vacuum of TC 6, which has the smallest thermal loss, were about 4.03mV/mW and about 6.38 mV/mW. Thermal time constant of TC 6, which has also the smallest heater thermal inertia, was about 8 ms. The respective variations of AC-DC voltage and current transfer errors from sample to sample, which were measured by FRDC(fast reversed DC) method, were about $\pm$0.41 ~$\pm$0.85 ppm and about $\pm$0.15~$\pm$1.16 ppm in the frequent range of 40 Hz~10 KHz with appling 1 V and 5 mA rms sine waves to the converters. All converters investigated exhibited sufficiently low AC-DC transfer errors to be used as practical standards.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.503-506
• /
• 2001

There are four factors for patient monitoring : electrocardiography, blood pressure, temperature and respiration. While there are a lot of studies of E.C.C (electro-cardiography) monitoring system in the world, the studies of Respiratory system are not enough and leave much to be desired in the country. In this paper, we developed a respiratory system with the electrical impedance change of the lungs depending on the breath. Using the same electrode, we can monitor E.C.C and Respiration simultaneously, so we can monitor a patient's no-breathing state due to the central nerve paralysis in the emergency room easily. In this monitoring system, the analog part was made separated from the digital part for reducing power source noise and protecting patient from electric shock. The analog part consists of the several parts a high-frequency sine-wave generator, all amplifier for amplifying any impedance change signal, an analog processing part for rectifying and filtering. And the digital parts consists of three parts an AD convertor for converting analog signal to digital signal, digital filter, and a digital part for digital signal processing. This system's merits are using the same electrode with E.C.C and developing the multiple patient monitoring system easily.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.5
• /
• pp.79-87
• /
• 2002

Acoustic responses to pressure oscillations in axisymmetric combustion chamber are numerically investigated to examine the qualitative trend of acoustic instability in liquid rocket engine. Chamber operating condition and excitation frequency of oscillating pressure are selected as exciting parameters of acoustic instability. Artificial perturbation is simulated by total-pressure oscillation with sine wave at chamber inlet. Many approximations and simplifications are introduced without losing the essence of acoustic pressure response. First, steady-state solution for each operating condition is obtained and next, transient analysis is conducted. Depending on operating condition and excitation frequency, the distinct response characteristics are brought. Weak-strength flames and high-frequency excitation tend to cause sensitive acoustic pressure response leading to unstable pressure field. These results are analyzed based on the correlation with acoustic pressure responses from the previous works adopting laminar flamelet model.

• Explosives and Blasting
• /
• v.22 no.3
• /
• pp.13-26
• /
• 2004

This work reports results of our study on the dynamic response of buried pipelines depending on their boundary conditions. We have studied behavior of the buried pipelines both along the axial and the transverse direction with a boundary condition of free ends. The buried pipelines are modeled as beams on elastic foundation while the seismic wave as a ground displacement in the form of a sinusoidal wave. The natural frequency, its mode, and the effect of parameters have been interpreted in terms of the free vibration. In order to investigate the response on the earthquake, the resulting frequency and the mode shape obtained from the free vibration have been utilized to derive the mathematical formula for the farced vibration. We have also completed the computer program to simulate the time-displacement graphs of the pipe lines with free ends for both cases of vibrations.

• Journal of Sensor Science and Technology
• /
• v.9 no.4
• /
• pp.288-296
• /
• 2000

Thin-film chromel-alumel multijunction thermal converters with a low output resistance of $64{\sim}85\;{\Omega}$ showed approximately the square law-dependent input-output relation. The voltage responsivities were very low with $0.34{\sim}0.67\;V/W$ in air and $1.15{\sim}1.48\;V/W$ in vacuum, respectively, and the ac-dc voltage transfer error was very large with about +340 ppm in the frequency range of $40\;Hz{\sim}10\;kHz$ in the case of 1 V-input sinewave rms voltage. It can be concluded that the large transfer error of the thermal converter was mainly caused by the low voltage responsivity and the large heat loss due to low output resistance, which implies that the optimization for small ac-dc transfer error is required.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.816-820
• /
• 2011

A method for increasing the difference of side-lobe level in spherical microphone array is presented. In array signal processing, it is known that narrow interval between sensors can increase the difference between main lobe and side-lobe of array response which eventually increase the source recognition capability. Recent commercial array being used, however, have shown certain limitation in using the number of sensors due to its costs and geometrical size of array. To overcome this problem, we have adapted MEMS sensors into spherical microphone array. To check out the improvement, two different types of spherical microphone array were designed. One array is composed with 32 regular instrument microphones and the other one is 85 MEMS sensors. Simulation and experiments were conducted on a sinusoidal noise source with two arrays. The time history data were analyzed with spherical harmonic decomposition and beamforming technique. 85 MEMS sensors array showed the improved side-lobe level suppression by more than 4 dB above the frequency content of 2 kHz compared to 32-sensor array.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.9
• /
• pp.1332-1347
• /
• 1993

Existing instruments are composed independently according to their function and user constructed instrumentation system with those instruments. But in the late 1980s VXI bus enables to construct instrumentation system with various modular type instruments. For an VXI bus system with the word serial protocol, an increase of data size can degrade the system performance. In this paper shared memory protocol is proposed to overcome performance degradation. The shared memory protocol is analyzed using the GSPN and compared with that of the word serial protocol. It is shown that the shared memory protocol has a better performance than the word serial protocol. The VXI bus message based-system with the proposed shared memory protocol is constructed and experimented with signal generating device and FFT analyzing device. Up to 80 KHz input signal the result of FFT analysis is accurate and that result is agree with that of conventional FFT analyzer. In signal generating experiment from 100 KHz to 1.1 GHz sine wave is generated.