• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.893-898
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• 2003

This paper proposes a Truncated Type-II Hybrid ARQ scheme and coding techniques using an adaptive modulation system to achieve high throughput data transmission systems for wireless multimedia communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter(m). When the received Eb/No is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received Eb/No is low. The modulation method have been adopted QPSK(Quadrature Phase Shift Keying), 16QAM(Quadrature Amplitude Modulation), 64QAM, 256QAM. Therefore, adaptive modulation systems with truncated type-II hybrid ARQ scheme is proper for wireless multimedia communication system that require high reliability and delay-limited applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.810-816
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• 2001

This paper proposes a Truncated Type-II Hybrid ARQ scheme using an adaptive modulation system to achieve high throughput data transmission systems for mobile communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter(m). When the received $E_bN_0$ is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received $E_bN_0$ is low. The modulation method have been adopted QPSK(Quadrature Phase Shift Keying), 16 QAM(Quadrature Amplitude Modulation), 64 QAM, 256 QAM. Therefore, Adaptive Modulation Systems with Truncated Type-II Hybrid ARQ Scheme is proper for mobile and radio for mobile and radio data communication system that require high reliability and delay-limited applications.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.71-82
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• 2012

In this paper, we propose a license plate detection method with improved Adaboost learning and MCT (Modified Census Transform). The MCT represents the local structure patterns as integer numbered feature values which has robustness to illumination change and memory efficiency. However, since these integer values are discrete, a lookup table is needed to design a weak classifier for Adaboost learning. Some previous research efforts have focused on minimization of exponential criterion for Adaboost optimization. In this paper, a method that uses MCT and improved Adaboost learning based on Newton's optimization to exponential criterion is proposed for license plate detection. Experimental results on license patch images and field images demonstrate that the proposed method yields higher performance of detection rates with low false positives than the conventional method using the original Adaboost learning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.661-667
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• 2001

This paper proposes a Truncated Type-II Hybrid ARQ scheme using an adaptive modulation system to achieve high throughput data transmission systems for DS-CDMA cellular mobile communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter( m). When the received Eb/No is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received Eb/No is low. The modulation method have been adopted QPSK 16QAM, 64QAM, 256QAM. Therefore, adaptive modulation systems with Truncated Type II Hybrid ARQ Scheme is proper for mobile and radio data communication system that require high reliability and delay-limited applications.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.39-58
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• 2024

Tunnel Boring Machines (TBM) use multiple disc cutters to excavate tunnels through rock. These cutters wear out due to continuous contact and friction with the rock, leading to decreased cutting efficiency and reduced excavation performance. The rock's abrasivity significantly affects cutter wear, with highly abrasive rocks causing more wear and reducing the cutter's lifespan. The Cerchar Abrasivity Index (CAI) is a key indicator for assessing rock abrasivity, essential for predicting disc cutter life and performance. This study aims to develop a new method for effectively estimating CAI using rock strength, petrological characteristics, linear regression, and machine learning. A database including CAI, uniaxial compressive strength, Brazilian tensile strength, and equivalent quartz content was created, with additional derived variables. Variables for multiple linear regression were selected considering statistical significance and multicollinearity, while machine learning model inputs were chosen based on variable importance. Among the machine learning prediction models, the Gradient Boosting model showed the highest predictive performance. Finally, the predictive performance of the multiple linear regression analysis and the Gradient Boosting model derived in this study were compared with the CAI prediction models of previous studies to validate the results of this research.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1542-1550
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• 2000

Fiber optic link systems based on SCM scheme are widely used as efficient and economic RF signal links between base station and a central station in mobile communication networks. However, its performance can be seriously limited depending on the operational conditions of not only the optical transmission system but also the wireless link in various environments. In this paper, we propose an analytic model for performance analyses of the SCM fiber optic link for CDMA RF signal transmission in various link environments. We present optimal operational conditions taking account of the nonlinear effects of the optical transmission system, and the multiple access interference produced at the wireless link. It has been shown through the BER analyses in this paper that the selection of optical modulation index of the SCM fiber optic links can be found optimally to minimize the fiber optic link noises and intermodulation distortion due to LD.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.57-62
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• 2019

This paper evaluates the QE-MMA (Quantized Error-MMA) adaptive equalization algorithm by the number of quantizer in order to compensates the intersymbol interference due to channel in the transmission of high spectral efficient nonconstant modulus signal. In the adaptive equalizer, the error signal is needed for the updating the tap coefficient, the QE-MMA uses the polarity of error signal and correlation multiplier that condered nonlinear finite bit power-of-two quantizing component in order to convinience of H/W implementation. The different adaptive equalization performance were obtained by the number of quantizer, these performance were evaluated by the computer simulation. For this, the equalizer output signal constellation, residual isi, maximum distortion, MSE, SER were applied as a performance index. As a result of computer simulation, it improved equalization performance and reduced equalization noise were obtained in the steady state by using large quantizer bit numbers, but gives slow in convergence speed for reaching steady state.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.539-549
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• 1999

In this paper, the bit error rare (BER) performance of DS/CDMA DQPSK communication system in the presence of multi access interference, impulsive noise and Nakagami fading is investigated. The DS/CDMA DQPSK communication system adopts Maximum Ratio Combining (MRC) diversity reception and error correcting BCH code technique to enhance system performance. Using the derived error probability equation, the error rate performance of DS/CDMA DQPSK communication system has been evaluated and shown in figures to discuss as a function of impulsive index(A), Gaussian noise to impulsive noise power ratio($\Gamma$'), multi access interference(Κ), Nakagami fading parameter(m), the number of diversity branch (Ｌ), the number of error correction symbol (t), PN code sequence length(N) and $E_b/N_0$. The error performance of DS/CDMA-MDPSK signals improve by adopting MRC diversity and BCH(15,7) coding technique in the environment of impulsive noise plus Nagakami fading. From the results, we known that proposed system is affected by multi access interference, impulsive noise and Nakagami fading in radio communication system environment. Also, BER performance of DS/CDMA DQPSK communication system cam be improved increasing either the power of desired signal or the value of Gaussian noise to impulsive noise power ratio. And BCH(15,7) code technique is more effective to restrain the affection of multi access, interference, impulsive noise and Nakagami fading in DS/CDMA DQPSK communication system than MRC diversity reception technique.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.664-666
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• 2004

최근 멀티미디어 인터넷의 확산으로 인해 SIP를 비롯한 음성 및 화상 패킷 전송에 대한 관심이 증대되고 있으며, 이에 대해 인터넷을 통한 음성통신서비스가 전개되고 있다. 또한, 노트북, 핸드폰과 같은 무선 기기에 이러한 음성통신서비스를 제공함으로써 이를 효율적으로 연동하고 제어하기 위한 다양한 표준들이 나타나고 있다. 본 논문에서는 급속하게 발전되고 있는 VoIP 기술 중 세션 제어를 위한 기본 프로토콜 표준인 SIP를 살펴보고, 무선 환경에 이를 적용함으로써 SIP단말이 홈 망을 나간 후 다시 홈 망으로 들어왔을 때의 패킷 손실 및 중단 시간을 이동 단말의 속도에 따라 측정함으로써 무선 환경에서의 음성 트래픽 성능이 어느 정도의 결과를 산출할 수 있는지를 측정한다. 실험 결과 이동 단말이 좀 더 빠르게 움직일 때 더 적은 패킷 손실률이 나왔음을 볼 수 있다.

• The KIPS Transactions:PartB
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• v.9B no.1
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• pp.17-22
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• 2002

A major impediment in using the Dempster-chafer evidence combination scheme is its computational complexity, which in general is exponential since DS scheme allows any subsets over the frame of discernment as focal elements. To avoid this problem, we propose a method called approximate evidence combination scheme. This scheme is applied to a few sample applications and the experiment results are compared with those of VBS. The results show that the approximation scheme achieves a great amount of computational speedup and produces belief values within the range of deviation that the expert allows.