• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.1
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• pp.45-50
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• 2003

Recently, robots technique has been developed remarkably. Emotion recognition is necessary to make an intimate robot. This paper shows the simulator and simulation result which recognize or classify emotions by learning pitch pattern. Also, because the pitch is not sufficient for recognizing emotion, we added acoustic elements. For that reason, we analyze the relation between emotion and acoustic elements. The simulator is composed of the DRNN(Dynamic Recurrent Neural Network), Feature extraction. DRNN is a learning algorithm for pitch pattern.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.344-352
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• 2020

Covertness and performance are very important design goals in the underwater communications. To satisfy both of them, we proposed efficient underwater communication model which combined multiband and direct sequence spread spectrum method in order to improve performance and covertness simultaneously. Turbo coding method with 1/3 coding rates is used for channel coding algorithm, and turbo equalization method which iterately exchange probabilistic information between equalizer and decoder is used for receiver side. After optimal threshold value was set in Rake processing, this paper analyzed the performance by varying the number of chips were 8, 16, 32 and the number of bands were from 1 to 4. Through the simulation results, we confirmed that the performance improvement was obtained by increasing the number of bands and chips. 2~3 dB of performance gain was obtained when the number of chips were increased in same number of bands.

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.24-29
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• 2004

In ocean acoustic tomography (OAT), the pulse compression techniques using M-sequences are employed in the many studies for investigating the ocean structures. M-sequences can provide the good time and Doppler resolution in the process of demodulation using matched-filter. The signal-to-noise (SNR) performance at the output of receiver may be improved by manipulating received signal, i. e. coherently averaging. The processing time can be significantly reduced by using fast hadarmard transform (FHT) or fast Fourier transform (FFT). In this paper, we estimate the multipath arrival structures and delay times using the East Korean Sea experiment data and explore the compensation method for the detrimental effects on performance due to sampling rate error. We also analyze the characteristics of the ocean acoustic channels through scattering function, delay power profile, and time dispersions.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.626-626
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• 2013

P-N 접합에 의해 절연된 게이트를 통해 전류 통로를 제어하는 접합형 전계효과 트랜지스터(Junction Field Effect Transistors; JFETs)는, 입력 임피던스가 크고, 온도에 덜 민감하며, 제조가 간편하여 집적회로(IC) 제조가 용이하고, 동작의 해석이 단순하다는 장점을 가지고 있다. 특히 JFET는 선형적인 전류의 증폭 특성을 가지고 있으며, 잡음이작기 때문에, 감도가 우수한 음향 센서의 증폭회로, 선형성이 우수한 증폭회로, 입력 계측 증폭 회로 등에 주로 사용되고 있다. 기존에 사용되는 JFET 소자는 구조와 제조 공정에 따라서, 컷 오프 전압($V_{cut-off}$)과 드레인-소스 포화 전류($I_{DSS}$)의 변화가 심하게 발생하여, 소자의 전기적 특성 제어가 어렵고, 소자의 수율이 낮다는 문제점이 있다. 본 연구에서는 TCAD 시뮬레이션을 통해 게이트 전압에 의해 채널이 형성되는 채널 층의 상하부에 각각 $Si_xGe_{1-x}$로 이루어진 상부 및 하부 확산 저지층을 삽입한 JFET 소자 형성하여, 게이트 접합부의 접합 영역 확산을 저지하고, 상기 게이트 접합부가 계면에서 날카로운 농도 구배를 갖도록 함으로써, 공정 변화에 따른 전기적 특성의 편차가 작아지는 JFET 소자 구조를 만들어 전기적 특성을 개선하였다. JFET은 채널층에 삽입된 $Si_xGe_{1-x}$ 층의 두께, Ge 함유량 및 n채널층의 두께를 변화하였을 때, off 상태의 게이트-소스 전압이 감소한 반면에 드레인-소스 포화 전류($I_{DSS}$)와 컨덕턴스(gm) 값이 증가하였다. 삽입된 $Si_xGe_{1-x}$층이 Boron이 밖으로 확산되는 현상이 감소하여 채널이 좁아지는 현상을 막아 소자의 전기적 특성을 개선함으로써 제조공정의 변화에 관계없이 컷오프 전압을 정확하고 안정되게 제어할 수 있고 이를 통해 소자의 수율을 높일 수 있을 것으로 기대된다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.223-233
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• 2016

Design of a vegetation type sound barrier was presented as a noise barrier on the boundary of neighborhood facilities including schools, and apartments. The suggested noise barrier is made of unit blocks that are to be formed by stacking over the wall structure containing the plant and soils in the blocks. The advantage of the vegetation noise barrier is to acquire not only sound absorptive effects of plants and soils, but also sound diffusive effect caused by the irregular surface of the barrier which could eventually mitigate the noise. First, the optimum size of the units to obtain the highest noise reduction was investigated using 1/10 scaled model experiment, and sound attenuation experiments were carried out using a 1/2 mock-up model which is 2 m high and 5 m long. Total 1,137 unit blocks were made of synthetic woods with the size of $10{\times}10{\times}9cm$. These unit blocks were installed on the both side of the 1/2 mock-up steel framed noise barrier. As a result, it was revealed that the block typed vegetation noise barrier has 7 dB higher insertion loss in comparison with the general plane noise barrier. Also, it was found that the appropriate size of unit blocks is $20{\times}20cm$ which has large effect of sound insertion loss.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.193-206
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• 2004

Geophysical data including chirp (3 7 kHz) subbottom profile and detailed bathymetry were obtained over three seamounts in the Ogasawara Fracture Zone (OFZ) of the western Pacific, as a part of manganese crust survey onboard R/V Onnuri in 2003. The OFZ is a 150-km-wide, 600-km-long rift zone, which separates the East Mariana and Pigafetta Basin. The OFZ is unique in that it includes many seamounts (e.g., Magellan Seamounts andseamounts on the Dutton Ridge). The sub-seafloor acoustic echoes obtained near the OFZ were classified into following types on the basis of their characteristics: types I-1(pelagic sediment with parallel or subparallel reflectors), I-2 (pelagic sediment with no internal reflectors), and III-1 (reef build-up complex) on summit; types II-1 and III-2 (basement outcrop) on flank rift zone and upper slope, respectively; type III-3 (slump) on the lower slope and embayment between the flank rift zones; types II-2 (debrite) on the base of slope and basin floor; and types II-3 (turbidite or pelagic sediment) and II-4 (turbidite) on the basin floor. The mass-wasting that produced the complex of type II-2 debrite and III-3 slump on the lower slope and basin may have been caused by (1) strong tensional stress in the OFZ which may cause the numerous fissures or basement faults and (2) complex of the faults on the summit and steep upper slope. The variations in the echo type of pelagic sediment in the summit of seamounts may be related with the changes in the depositional and/or erosional environments. Type I-2 pelagic sediment, which is characterized by a thin and intermittent coverage, was probably deposited at a sheltered area when the current was strong, whereas type I-1 pelagic deposit occurred during a stage of progressive sedimentation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2094-2100
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• 2014

The performance of underwater acoustic communication system is sensitive to the inter-symbol interference due to delay spread develop of multipath signal propagation. Thus, it is necessary technique of equalizer and channel code to eliminate inter-symbol interference. In this paper, underwater acoustic communication system were analyzed by experiment using these techniques on the Kyeong-chun lake, Munkyeong City. Based on the results of experiment, we confirmed that the performance of the proposed iterative BCJR equalization method is improved by increasing the number of iterations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1042-1050
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• 2014

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Turbo Equalization method based on layered Space Time Codes has improved performance compared to conventional UWA communication.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.1-9
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• 2017

The cryogenic nitrogen spray of a swirl injector has been numerically investigated using three dimensional LES turbulence model to analyze the dynamic characteristics under supercritical condition. To predict the precise nitrogen properties under supercritical condition, SRK equation of state, Chung's method for viscosity and thermal conductivity and Takahashi's correlation based on Fuller's theory for diffusion coefficient are implemented. The complex flow structures due to interaction between flow field and acoustic field are observed inside and outside the injector under supercritical condition. FFT, POD, and DMD techniques are employed to understand the coherent structures. By implementing the FFT, the dominant frequencies are identified inside and outside the injector. The coherent flow structures related to the dominant frequencies are visualized using the POD and DMD techniques. In addition, the DMD provides the damping coefficient which is related with the instability prediction.