Earticle

그동안 차두시간분포를 나타내는 확률분포로 음지수분포, Erlang 분포, 정규분포 등 다양한 단일확률분포들이 사용되어져 왔다. 그러나, 실제 도로에서 차두시간분포의 조사결과는 단일 확률분포로서 설명하기 어려운 경우가 있었다. 본 연구는 차량의 차두시간에 대해 두 개의 정 규분포가 일정한 관련성을 가지고 결합된 복합확률분포의 파라메타에 대해 최우추정법 중 하 나인 EM 알고리즘을 이용하여 추정하는 접근방법을 시도하였다. 이에 대한 분석결과 기존에 알려진 단일확률분포로서 잘 설명되기 어려웠던 차량도착 차두시간 분포를 EM 알고리즘을 이 용하여 복합확률분포의 파라메타를 추정하여 설명하였다. χ2 test 적합도 검정결과, 유의수준 1%에서 통계학적으로 유의성이 확보되어 EM 알고리즘을 이용한 복합확률분포의 파라메타 추 정의 신뢰성이 입증되는 것으로 분석되었다

Various single probability distributions have been used to represent time headway distributions. However, it has often been difficult to explain the time headway distribution as a single probability distribution on site. This study used the EM algorithm, which is one of the maximum likelihood estimations, for the parameters of combined mixture distributions with a certain relationship between two normal distributions for the time headway of vehicles. The time headway distribution of vehicle arrival is difficult to represent well with previously known single probability distributions. But as a result of this analysis, it can be represented by estimating the parameters of the mixture probability distribution using the EM algorithm. The result of a goodness-of-fit test was statistically significant at a significance level of 1%, which proves the reliability of parameter estimation of the mixture probability distribution using the EM algorithm.

To ensure fair packet broadcasting without service disruption in wireless network from one network cell to another is the key to successful mobile services. However, enforcing fair packet broadcasting is challenging because decision policies within the network cell though works efficiently, considerably reduces the energy consumption level. Using MAC protocol, communication framework gets improved by cooperatively localizing the system and achieves space-time synchronization. But redundancy occurs on cellular wireless network for higher energy levels. This work presents the design and implementation of collision free packet broadcasting in wireless network known as Consistent Shortcut Transfigure Path Construction (CSTPC) mechanism. Under this mechanism the main objective is to develop a transfigure path (i.e., alter path) when the link failure occurs during broadcasting (i.e.,) handover the call. Initially, consistent shortcut is created for constructing alter path and when the link gets failed packet handover takes place. Consistent shortcut is created by combining the Midpoint and Simpsons rule procedure. The Midpoint and Simpsons procedure creates the shortcut and with this reduces the rate of energy consumption gradually. Secondly, error rate on call handover is reduced using CSTPC mechanism by applying Estimation of Distribution algorithm. The constructed Estimation of Distribution algorithm in CSTPC mechanism feasibly handover the packets to neighboring base station with minimal error rate. In this way, minimal error rate avoids retransmission of packets due to the collision and path failure. Furthermore, the CSTPC mechanism reduce the energy consumption level on transfigure path construction and also avoids the retransmission of packets (i.e.,) call in wireless network. Experimental work is carried out using factors such as avoidance of retransmission rate, energy consumption rate, and call broadcasting efficiency.

Sarhan and Kundu (2009) introduced a new distribution named as the generalized linear failure rate distribution. This distribution generalizes several well known distributions. The probability density function of the generalized linear failure rate distribution can be right skewed or unimodal and its hazard function can be increasing, decreasing or bathtub shaped. This distribution can be used quite effectively to analyze lifetime data in place of linear failure rate, generalized exponential and generalized Rayleigh distributions. In this paper, we apply the simulated annealing algorithm to obtain the maximum likelihood point estimates of the parameters of the generalized linear failure rate distribution. Simulated annealing algorithm can not only find the global optimum; it is also less likely to fail because it is a very robust algorithm. The estimators obtained using simulated annealing algorithm have been compared with the corresponding traditional maximum likelihood estimators for their risks.

기존의 진화 연산의 한계를 극복하기 위해서 탐색점 분포 학습 알고리즘(Estimation of Distribution Algorithm)이 부각되고 있다. 탐색점 분포 학습 알고리즘은 데이터의 분포를 파악하고, 파악된 분포를 이용해서 새로운 학습 데이터를 생성하는 일련의 과정을 통하여 최적화 문제를 해결하는 방법이다. 그런데, 기존의 탐색점 분포 학습 알고리즘들은 대부분 이진 벡터값을 가지는 최적화 문제들만을 대상으로 하고 있다. 본 논문에서는 비감독 확률 신경망 모델인 헬름홀츠 머신을 이용해서 데이터의 분포를 학습하여 연속 함수 최적화 문제를 해결하는 방법을 개발하였다. 테스트 함수들에 대해서 실수 표현형을 사용한 유전자 알고리즘과 결과를 비교하여 제안하는 방법의 우수성을 검증하였다.

Trip distribution plays an important role in the analysis and network evaluation phases of the transportation and the traffic planing process. In this paper, the authors propose an algorithm for estimating the trip distribution between each pair of zones such as harbours and straits. The algorithm is formulated by using the observed data and introducing the concept of entropy when observed data between harbours were not existed. In order to examine the feasbility , the proposed algorithm is applied to ships on traffic route in Hanryu Sudo and in Korea costal waterway. And also, its validity is examined by comparing another algorithm through statistical test.

본 논문에서는 전영역 탐색기반의 방법에 비하여 예측화질은 거의 같게 유지하면서 불필요한 계산량을 현저히 줄이는 알고리즘을 제안한다. 제안하는 방법은 움직임 벡터의 확률분포에 따라 탐색패턴을 달리하며, 블록매칭 기준의 비교값을 다르게 함으로써 예측화질을 유지하면서 계산량만 효율적으로 감축할 수 있다. 제안한 알고리즘은 기존의 전영역 탐색 기반인 H.264 PDE 고속 알고리즘과 비교하여 예측화질의 저하가 0~0.02dB이며, 소요된 계산량은 20%~30%정도이다. 제안한 알고리즘은 MPEG-2/4 AVC를 이용하는 실시간 비디오 압축 응용분야에 유용하게 사용될 수 있을 것이다.

In the paper, we propose an algorithm that significantly reduces unnecessary computations, while keeping prediction quality almost similar to that of the full search. In the proposed algorithm, we can reduces only unnecessary computations efficiently by taking different search patterns and error criteria of block matching according to distribution probability of motion vectors. Our algorithm takes only 20~30% in computational amount and has decreased prediction quality about 0~0.02dB compared with the fast full search of the H.264 reference software. Our algorithm will be useful to real-time video coding applications using MPEG-2/4 AVC standards.

The ROM (roll over mitigation) system is a next-generation suspension system that can improve vehicle-driving stability and ride comfort. Currently, mass-produced safety systems, such as ESC (electronic stability control) and ECS (electronic control suspension), enable measurements of longitudinal and lateral acceleration as well as yaw rate through inertial sensor clusters, but they lack direct measurements of the roll angle. Therefore, in this paper, a roll angle estimation algorithm from ESC system sensors and tire normal force has been proposed. Furthermore, this study presents a method for roll over mitigation force distribution between the front and rear of a ROM system. Performance and reliability of the roll angle estimation and roll over mitigation force distribution were investigated through simulations. The simulation results showed that the proposed control algorithm and strategy are reliable during vehicle rollovers.