• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5401-5421
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• 2016

Both low-density parity-check (LDPC) codes and the multiple access technique of spatially coupling data transmission (SCDT) can be expressed in bipartite graphs. To improve the performance of iterative demodulation and decoding for SCDT, a novel joint sparse graph (JSG) with SCDT and LDPC codes is constructed. Based on the JSG, an approach for iterative joint demodulation and decoding by belief propagation (BP) is presented as an exploration of the flooding schedule, and based on BP, density evolution equations are derived to analyze the performance of the iterative receiver. To accelerate the convergence speed and reduce the complexity of joint demodulation and decoding, a novel serial schedule is proposed. Numerical results show that the joint demodulation and decoding for SCDT based on JSG can significantly improve the system's performance, while roughly half of the iterations can be saved by using the proposed serial schedule.

• Structural Engineering and Mechanics
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• 제59권5호
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• pp.901-920
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• 2016

MeshFree methods have become popular owing to the ease with which high stress gradients can be identified and node density distribution can be reformulated to accomplish faster convergence. This paper presents a strategy for nodal density refinement with strain energy as basis in Element-Free Galerkin MeshFree technique. Two popular flat plate problems are considered for the demonstration of the proposed strategies. Issue of integration errors introduced during nodal density refinement have been addressed by suggesting integration cell refinement. High stress effects around two symmetrical semi-circular notches under in-plane axial load have been addressed in the first problem. The second considers crack propagation under mode I and mode II fracture loading by the way of introducing high stress intensity through line crack. The computational efficacy of the adaptive refinement strategies proposed has been highlighted.

• Earthquakes and Structures
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• 제27권2호
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• pp.127-142
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• 2024

The amount of wave propagation through a rubber concrete construction is the subject of the current investigation. Rubber tire waste was used to make two different types of cement mixtures. One type contains sand substitute in amounts ranging from 15% to 60% of the total volume, while the other has gravel with diameters of 3/8 and 8/15 and 15% sand in the same mixture. A wide variety of concrete forms and compositions were created, and their viscous and solid state characteristics were assessed, along with their short-, medium-, and long-term strengths. Diffusion, density, mechanical strength resistance to compressive force, and ultrasound wave propagation were also assessed. The water-to-cement ratio and plasticizer were used in this investigation. In the second part of the study, an analytical model is presented that simulates the experimental model in predicting the speed of waves and the frequencies accompanying them for this type of mixture. Higher order shear deformation beam theory for wave propagation in the rubberized concrete beam is developed, considering the bidirectional distribution, which is primarily expressed by the density, the Poisson coefficient, and Young's modulus. Hamilton's concept is used to determine the governing equations of the wave propagation in the rubberized concrete beam structure. When the analytical and experimental results for rubber concrete beams were compared, the outcomes were very comparable. The addition of rubber gravel and sandy rubber to the mixture both resulted in a discernible drop in velocities and frequencies, according to the data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.835-840
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• 2000

The objective of the present study is to investigate the characteristics of pressure wave propagation of viscous fluid flow in a circular pipe line. The goal of this study is to select the best frequency of each control factor of a circular pipe. We intend to approach a formalized mathematical model by a very exact and reasonable polynomial for fluid transmission lines. and we computed this mathematical model by computer. The results show that the oil viscosity decreased as the length of the circular pipe increases. and The energy of pressure wave propagation decreased as the pipe diameter decreases. The factor is that density of oil was changed resonant frequency. It has been found the viscosity characteristics is changed largely by length of hydraulic pipe and volume of cavity tank.

• 대한교통학회지
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• 제22권4호
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• pp.147-158
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• 2004

SWP(Stochastic Wave Propagation: 확률파장전파) 모형은 Cellular Automata(CA) 이론을 기반으로한 간략한 차량모형을 이용하여 개별차량의 확률적 형태와 혼잡의 전파를 모사하고, 통계물리학을 기반으로 교통류를 거시적으로 해석한다. SWP모형은 이산적 시공간 구조와 정수형 자료를 이용한 프로그램 지향적 모형구조를 가지며 연산수행속도가 빨라 대규모 가로망의 실시간 시뮬레이션을 가능하게 하였다. 그러나 비현실적인 충돌회피과정으로 인한 자연발생적 혼잡(Spontaneous jam)의 형성 때문에 미시적으로는 혼잡내에서 잠금현상(Lockup)이 발생하여 혼잡내 차량의 저속을 설명할 수 없고, 거시적으로는 혼잡의 밀도와 전파속도를 설명하기 어렵다는 한계를 가지고 있다. 본 연구에서는 비현실적인 차량의 정지과정을 보다 현실적으로 모사하기 위한 정지조작규칙(SMR: Stopping Maneuver Rule)과 혼잡내에서 차량의 낮은 가속을 설명하기 위한 저가속규칙(LAR: Low Acceleration Rule)을 기존의 SWP모형인 NaSch모형에 추가하였다. 이를 통해 미시적으로 보다 현실적인 차량의 정지과정을 모사하면서 혼잡내에서 잠금현상을 방지하고, 거시적으로 혼잡의 밀도와 전파속도를 설명함으로써 보다 다양하게 연속 교통류를 구현하는 모형을 구축하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.889-890
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• 2005

• 지구물리와물리탐사
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• 제22권2호
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• pp.56-61
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• 2019

셀 기반 유한 차분법을 사용하여 P파 속도와 밀도 변화를 고려한 3차원 시간 영역 음향 파동 전파 모델링에서 성능을 향상시킬 수 있는 방법을 살펴보았다. 일반적인 유한 차분법에서는 격자점에 탄성파 속도 또는 밀도와 같은 물성을 할당하고 계산하지만 셀 기반 유한 차분법에서는 이러한 물성을 격자점 사이의 셀에 할당한다. 격자점에서의 차분식 계산을 위해서는 주변 셀의 물성 평균값을 이용하는데 이로 인해 일반적인 유한 차분법에 비해 계산량이 증가하게 된다. 이 연구에서는 이러한 계산량 문제를 개선하기 위해 메모리를 추가로 사용하여 모델링 시간을 30 % 이상 줄일 수 있었다. 또한 밀도가 제한적으로 변화하는 매질에서 셀 기반 유한 차분법과 일반 유한 차분법을 함께 사용하여 모델링 성능을 추가로 향상시킬 수 있었다.

• 대한전자공학회논문지TE
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• 제42권3호
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• pp.51-56
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• 2005

본 논문에서는 페이딩 채널 환경하에서 OFDM의 BER성능을 개선시키기 위해서 LDPC 부호화된 OFDM 시스템을 제안한다. LDPC 부호는 Sum-Product 알고리즘이나 Belief Propagation 알고리즘으로 알려진 확률적인 전파(Propagation) 알고리즘에 의해서 복호된다. LDPC 부호가 OFDM 시스템에 적용될 때 복호 알고리즘을 수행함에 있어서 복호 횟수를 거듭할수록 성능이 개선된다. 이동통신 시스템에서는, 높은 대역 효율을 요구하므로 다중레벨 변조가 사용된다. 그러나 다중레벨 변조를 갖는 OFDM에 LDPC 부호를 어떠한 방식으로 적용할 것인지에 대해서 명료하지 못하다. 따라서 본 논문에서는 MPSK를 사용한 LDPE Coded OFDM 시스템에 대한 복호 알고리즘에 대해서 언급한다. AWGN 채널 환경과 레일리 페이딩 채널 환경에서의 시뮬레이션 결과는 작은 반복 횟수에 대해서 좋은 BER 성능을 나타낸다.

• ETRI Journal
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• 제32권6호
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• pp.972-975
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• 2010

In this letter, we consider the lossy coding of a non-uniform binary source based on GF(q)-quantized low-density generator matrix (LDGM) codes with check degree $d_c$=2. By quantizing the GF(q) LDGM codeword, a non-uniform binary codeword can be obtained, which is suitable for direct quantization of the non-uniform binary source. Encoding is performed by reinforced belief propagation, a variant of belief propagation. Simulation results show that the performance of our method is quite close to the theoretic rate-distortion bounds. For example, when the GF(16)-LDGM code with a rate of 0.4 and block-length of 1,500 is used to compress the non-uniform binary source with probability of 1 being 0.23, the distortion is 0.091, which is very close to the optimal theoretical value of 0.074.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1478-1480
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• 1998

Inception and propagation of electrical tree and properties of partial discharge(PD) pulses accompanying with tree in low density polyethylene were discussed. We observed the characteristics of process of electrical tree by using optical microscope and investigated the statistical characteristics of the PD pulses by analyzing PD quantities and distribution patterns. The PD pulses were analyzed by q-n, $\phi$-n and $\phi$-q distribution. The statistical operators used were skewness(s), kurtosis(k) and average phase angle. The skewness and average discharge phase angle of PD pulses increased as the Propagation of tree. The kurtosis was about 1.8 at the Inception of tree, but It increased as the propagation of tree.