• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권1호
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• pp.59-66
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• 2013

In this paper, we propose a probabilistic framework for model-based clustering of direction of arrival (DOA) data to obtain stable sound source localization (SSL) estimates. Model-based clustering has been shown capable of handling highly overlapped and noisy datasets, such as those involved in DOA detection. Although the Gaussian mixture model is commonly used for model-based clustering, we propose use of the von Mises mixture model as more befitting circular DOA data than a Gaussian distribution. The EM framework for the von Mises mixture model in a unit hyper sphere is degenerated for the 2D case and used as such in the proposed method. We also use a histogram of the dataset to initialize the number of clusters and the initial values of parameters, thereby saving calculation time and improving the efficiency. Experiments using simulated and real-world datasets demonstrate the performance of the proposed method.

• 산업경영시스템학회지
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• 제26권2호
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• pp.62-67
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• 2003

This paper deals with a First-Come, First-Served queueing model to analyze the behavior of heterogeneous finite source system with a single server Each sources and the processor are assumed to operate in independently Markovian environments, respectively. Each request is characterized by its own exponentially distributed source and service time with parameter depending on the state of the corresponding environment, that is, the arrival and service rates are subject to random fluctuations. Our aim is to get the usual stationary performance measures of the system, such as, utilizations, mean number of requests staying at the server, mean queue lengths, average waiting and sojourn times. In the case of fast arrivals or fast service asymptotic methods can be applied. In the intermediate situations stochastic simulation Is used. As applications of this model some problems in the field of telecommunications are treated.

• Journal of Trauma and Injury
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• 제20권2호
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• pp.96-100
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• 2007

Purpose: Trauma is the 5th most common leading cause of death in Korea, but there has been no appropriate management system for patients until now. We analyzed the main causes of death in trauma patients by comparing the characteristics of those patients with the characteristics of patients who survived. We feel this analysis should have a positive effect on the development of an appropriate trauma management system in Korea. Methods: We retrospectively reviewed trauma patients who had been admitted to the Department of General Surgery from February 2002 to February 2007. We compared several expected risk factors between the mortality and the survival group. Data on the transportation, arrival time at the emergency center, amount of transfusion, initial shock index, cause of death, and initial physical condition according to RTS (Revised trauma score), ISS (Injury severity score) and TRISS (Trauma and Injury Severity Score) were collected. Patients with ISS lower than 12 were excluded. Results: Three hundred sixty-six(366) patients with multiple injuries were included. There were 40 patients in the mortality group and 326 patients in the survival group. The mean arrival time (minutes) to emergency center was longer in the mortality group (137.6 vs 93.6 p 0.04). The total amount of transfusion (ml) was larger in the mortality group (7139 vs 2470 p 0.01). The initial shock index was higher in the mortality group (1.45 vs 1.17 p<0.01). The RTS, ISS, and TRISS were not statistically different between the groups. In the multivariate analysis, mean arrival time and initial shock index were important factors for survival. Conclusion: If the mortality rate of trauma patients is to be reduced, the arrival time at the emergency center should be minimized. Improvement of the emergency medical transfer service system is very important for achieving that.

• Earthquakes and Structures
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• 제1권2호
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• pp.147-162
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• 2010

The ground acceleration measured at a point on the earth's surface is composed of several waves that have different phase velocities, arrival times, amplitudes, and frequency contents. For instance, body waves contain primary and secondary waves that have high frequency content and reach the site first. Surface waves are composed of Rayleigh and Love waves that have lower phase velocity, lower frequency content and reach the site next. Some of these waves could be of more damage to the structure depending on their frequency content and associated amplitude. This paper models critical earthquake loads for single-degree-of-freedom (SDOF) inelastic structures considering evolution of the seismic waves in time and frequency. The ground acceleration is represented as combination of seismic waves with different characteristics. Each seismic wave represents the energy of the ground motion in certain frequency band and time interval. The amplitudes and phase angles of these waves are optimized to produce the highest damage in the structure subject to explicit constraints on the energy and the peak ground acceleration and implicit constraints on the frequency content and the arrival time of the seismic waves. The material nonlinearity is modeled using bilinear inelastic law. The study explores also the influence of the properties of the seismic waves on the energy demand and damage state of the structure. Numerical illustrations on modeling critical earthquake excitations for one-storey inelastic frame structures are provided.

• 한국IT서비스학회지
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• 제7권2호
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• pp.137-148
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• 2008

This paper measures and compares the traffic of a series of Massively Multi-player On-line Role Playing Game (MMORPG). The purpose of this analysis is to characterize the MMORPG traffic and compare the traffic characteristics of those games caused by the game structure difference between 2D and 3D environment. The target game is 'Lineage I' and 'Lineage II' which represent world's largest MMORPGs in terms of the number of concurrent users. We collect about 280 giga bytes and 1 tera bytes of packet headers, respectively. We compare packet size, packet inter-arrival time and bandwidth usage of these two games. The MMORPG traffic consists of two kinds of packets: client-generated upstream packets and server-generated downstream packets. We observe that the upstream packet size of payload has grown from 9 bytes to 19 bytes, while the average payload size of downstream packets has grown from 37 bytes to 318 bytes. This asymmetry of growing rate is caused by 3D game structure. Packet inter-arrival time becomes shorter from average 2 milliseconds to 58 microseconds. Bandwidth consumption per client has grown from 4 kbps to 20 kbps. We find that there is a linear relationship between the number of users and the bandwidth usage in both case.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.853-859
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• 2022

In this study, we analyzed the instantaneous trajectory generation capability and target arrival rate of a mobile robot by changing the parameter of the TEB (Timed Elastic Band) Local Planner among local planners that affect the instantaneous obstacle avoidance ability of the mobile robot using ROS (Robot Operating System) simulation and real experience. As a result, we can expect a decrease in the target arrival time of the mobile robot through a decrease in the parameter values of the TEB Local Planner's min_obstacle_dist, inflation_dist, and penalty_epsilon. However, if this parameter is reduced too much, the risk of obstacle collision of the moving robot is increases, so it is important to combine the appropriate values to construct the parameter.

• The Journal of Asian Finance, Economics and Business
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• 제3권3호
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• pp.79-91
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• 2016

This paper is the first of its kind using a non-linear approach based on cross-correlation function (CCF) to investigate the information arrival hypothesis in crude palm oil (CPO) futures market. Based on daily data from 1986 to 2010, our empirical results reveal that: First, the volume of volatility is not a proxy of information flow. Second, dependence causality running from current return to future volume in conditional variance exhibit an asymmetric pattern of time span with different signs of correlation between price and volume series. This finding indicates the presence of noise traders' hypothesis of price-volume interaction in CPO futures market. Both findings suggest that this futures market is weak-form inefficiency. In terms of investors' behavior, they tend to change their expectations on current return based on errors made in previous trade in generating abnormal volume in the subsequent period. As implied, it is advisable for the investors devise their future trading strategies according to time span and changes of return.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.28-32
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• 2007

While various methods for sound source localization have been developed, most of them utilize on the time difference of arrival (TDOA) between microphones or the measured head related transfer functions (HRTF). In case of a real robot implementation, the former has a merit of light computation load to estimate the sound direction but can not consider the effect of platform on TDOAs, while the latter can, because characteristics of robot platform are included in HRTF. However, the latter needs large resources for the HRTF database of a specific robot platform. We propose the compensation method which has the light computation load while the effect of platform on TDOA can be taken into account. The proposed method is used with spherical head related transfer function (SHRTF) on the assumption that robot platform, for example a robot head, installed microphones can be modeled to a sphere. We verify that the proposed method decreases the estimation error caused by the robot platform through the simulation and experiment in real environment.

• 산업공학
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• 제23권3호
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• pp.239-245
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• 2010

This paper considers a localization problem of a moving tag on RFID(Radio Frequency Identification) systems, where a positioning engine collects TDOA(Time-difference of Arrival) signal from a target tag to estimate the position of the tag. To localize the tag in the RFID system, we develop two heuristic algorithms and evaluate their performance in the estimation error and computational time by using randomly generated numerical examples. Based upon the performance evaluation, we can conclude our algorithms are valuable for localization the moving target.

• 지구물리와물리탐사
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• 제5권3호
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• pp.193-198
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• 2002

시추공간 파선 토모그래피에 있어서 결과물로 얻어지는 지하의 속도구조를 왜곡시키는 요인으로는 source static, 초동발췌오차 및 부적절한 초기속도 모델에 의한 국부적인 최소값으로의 수렴 등으로 요약된다. 본 논문에서는 이러한 오차생성 요인들 중에서 source static을 자동으로 보정해주는 알고리즘을 소개하고 있다. 소개된 알고리즘은 발췌된 초동자료의 송신기방향으로의 변화를 이용하여 정보정을 자동으로 계산하는 방법으로서, 실제 자료에 대해 적용해 본 결과 매우 만족스러운 결과를 보였으며, 사용자로 하여금 일관되며 자동적인 정보정 적용으로 인해서, 보다 신뢰할 수 있는 속도구조를 얻는데 도움을 줄 수 있을 것으로 예상된다.