• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.12
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• pp.1321-1328
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• 2015

A radio is a half-duplex voice communication method using the PTT(: Push To Talk), occupy a single line calls during transmission. As an interface between the telephone and the radio, UHF and VHF, for voice communication between the different heterogeneous devices, A device automatically switches between the two devices is required. Therefore, in accordance with the performance of the voice switching apparatus for detecting a voice to be transmitted from an input signal, loss of the audio signal to be transmitted is subjected to Significant influence. Conventional method has the problem responding to noise by setting the level through simple means of amplitude of input signal, in other words, the energy level of the input signal. This paper, by using the audio signal processing techniques, this discriminated what the voice is among the input signal and substantiated a device for the automatic voice transmission between heterogeneous devices. With this proposal, I was confirmed of improvement of performance in the automatic voice switching device, could perform loss-less transmission of voice between heterogeneous devices.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.395-402
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• 1995

The intravoxel spin phases in magnetic resonance imaging (MRI) usually vary due to susceptibility differences of materials to be imaged. The phase variation in the voxel results in a reduction of the signal intensity. This signal intensity reduction is known as the susceptibility effect in MRI and has been studied extensively. In this paper, a new spectral decomposition technique Is proposed and the signal change due to the susceptibility effect can be analyzed. A pulse sequence for the spectral decomposition of the susceptibility was developed and applied to susceptibility imaging of venous blood possessing paramagnetic properties. The computer simulations and their corresponding experimental results obtained using both a phantom and human volunteers are reported. Key words : susceptibility effect in MRI : spectral decomposition of susceptibility effect.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.1-6
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• 2004

This paper proposes on the acoustic signal processing blocking method of Internet pornographicl sites by calculating correlation values between prototype acoustic signals and input acoustic signals. Pre-existing blocking methods mainly focused on directory-based bled(fin and pornographic related words-based blocking. But these methods are not completely blocked the Internet harmful pornographicl sites by several situations. For this, this paper proposes the content-based blocking method which composes of the image-based blocking and the acoustic-based blocking. This paper, mainly, deals with the acoustic -based blocking method. Finally, the effectiveness of this system is demonstrated by several experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.616-624
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• 2019

In order to understand flying aircraft, satellite, missile, etc, a telemetry ground system is used to receive, record, and process the transmitted radio signal from vehicles. In some cases, a line-of-sight communication is not possible along to the trajectory of vehicles, and multipath fading result in a shade area of communication. A number of telemetry ground systems are installed to overcome this limitation, and acquire the transmitted signal seamlessly. The telemetry signals received by multiple independent ground systems have independent probability of errors since they experienced their own communication channels. In other words, we can exploit the independent error characteristics of received signals by processing them in a hybrid method. The optimum hybrid post-process method is proposed in this study, and applied to process telemetry signals acquired from flight tests.

• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.42-47
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• 2000

This paper describes a real-time implementation of a GSM-EFR (Global System for Mobil communications Enhanced Full Rate) speech coder using OakDSP core; a 16bit fixed-point Digital Signal Processor (DSP) by DSP Group, Inc. The real-time implemented speech coder required about 24MIPS for computation and 7.06K words and 12.19K words for code and data memory, respectively. The implemented GSM-EFR speech coder passes all of test vectors provided by ETSI (European Telecommunication Standard Institute), and perceptual speech quality measurement using MNB algorithm shows that the quality of the GSM-EFR speech coder is similar to the one of 32kbps ADPCM. The real-time implemented GSM-EFR speech coder which is the highest bit-rate mode of the GSM-AMR speech coder will be used as the basic structure of the GSM-AMR speech coder which is embedded in MODEM ASIC of IMT2000 asynchronous mode mobile station.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.45-51
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• 2000

This paper describes real-time implementation of a multi-channel G.729A speech coder using a 16 bit fixed-point Digital Signal Processor (DSP) and its application to a Voice Mailing Service (VMS) system. TMS320C549 by Texas Instruments was used as a fixed point DSP chip and a 4 channel G.729A coder was implemented on the chip. The implemented coder required 14.5 MIPS for the encoder and 3.6 MIPS for the decoder at each channel. In addition, memories required by the coder were 9.88K words and 1.69K words for code and data sections, respectively. As a result, the developed VMS system that accommodates two DSP chips was able to support totally 8 channels. Experimental results showed that the our multi-channel coder passes all of test vectors provided by ITU-T.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.198-204
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• 2004

This study suggests a sentence generating method to help those who have language impediment with their communication. The method suggested in this study was constructed into a system in order to be applied to AAC system. AAC system is a personal portable device that generates sentences. Those who have language impediment need another communication method, causes inconvenience when used in a conversation with those who don't have the same trouble. The method of inputting both consonants and vowels can be inconvenient and time consuming for a conversational communication because of the number of the key strokes. The lexical information for the sentence generating of this study defines the user's domain, collects the adequate words and sentences, and extracts and classifies the characteristics of the collected words. The comparison between the number of key strokes for sentence generating using the system and that of inputting consonants and vowels using a keyboard was made in order to evaluate the usefulness the sentence generating method.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.1
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• pp.31-36
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• 2019

A chatbot is an important area of mobile service, which understands informal data of a user as a conversational form and provides a customized service information for user. However, there is still a lack of a service way to fully understand the user's natural language typed query dialogue. Therefore, in this paper, we extract meaningful words, such a region, a food category, and a restaurant name from user's dialogue sentences for recommending a restaurant. and by comparing the extracted words against the contents of the knowledge database that is built from the hashtag for recommending a restaurant in SNS, and provides user target information having statistically much the word-similarity. In order to evaluate the performance of the restaurant recommendation chatbot system implemented in this paper, we measured the accessibility of various user query information by constructing a web-based mobile environment. As a results by comparing a previous similar system, our chabot is reduced by 37.2% and 73.3% with respect to the touch-count and the cutaway-count respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1380-1386
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• 2016

In this paper, we propose and evaluate OFDM(Orthogonal Frequency Division Multiplexing)-SSB(Singe Side Band) for improving spectral efficiency. The proposed system is based on OFDM system using DCT(Discrete Cosine Transform) and DHT(Discrete Hilbert Transform) for SSB modulation, this proposed system transmit a BPSK modulation signal through a single sideband and BPSK modulation signal through the other single sideband. In other words, we design and evaluate the proposed system which transmit two BPSK signal through each other single sideband. Also each BPSK BER performance is similar with theoretical BPSK BER performance. the proposed system transmits BPSK signal using half of spectrum of conventional OFDM system or transmit two BPSK signal in same time.

• Speech Sciences
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• v.7 no.2
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• pp.37-50
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• 2000

This paper describes a test of everyday speech understanding ability, in which a listener's utilization of the context-situational information of speech is assessed, and is compared with the utilization of acoustic-phonetic information. The test items are sentences which are presented in a babble type of noise, and the listener response is the key word in the sentence. The key words are always two-syllabic nouns and the questioning sentences are added to obtain the responding key words. Two types of sentences are used. One is the high-predictable sentences for which the key word is somewhat predictable from the context. The other is the low-predictable sentences for which the key-word cannot be predicted from the context. Both types are included in six 40-item forms of the test, which are balanced for intelligibility, key-word familiarity and predictability, phonetic content, and length. Performance of normally hearing listeners shows significantly different functions for various signal-to-noise ratios. The potential applications of this test, particularly in the assessment of speech understanding ability in the hearing impaired, are discussed.