• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.100-103
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• 2008

COMS(Communication, Ocean and Meteorological Satellite) has multiple payloads; Meteorological Image(MI), Ocean Color Imager(GOCI) and Ka-band communication payloads. MI has 4 IR and 1 visible channel. In order to improve the quality of IR image, two calibration sources are used; black body image and cold space look data. In case of COMS, the space look is performed at 10.4 degree away from the nadir in east/west direction. During space look, SUN or moon intrusions are strictly forbidden, because it would degrade the quality of collected IR channel calibration data. Therefore we shall pay attention to select space look side depending on SUN and moon location. This paper proposes and discusses a simple and complete space look side selection logic based on SUN and moon intrusion event file. Computer simulation has been performed to analyze the performance of the proposed algorithm in term of east/west angular distance between space look position and hazardous intrusion sources; SUN and moon.

• 한국통신학회논문지
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• 제34권2A호
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• pp.107-112
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• 2009

Spectral efficiency of current two-phase cooperative communications protocols is low since in the second time the relay forwards the same signal received from the source to the destination, the source keeps silent in this time. In this paper, we propose a novel cooperative communications protocol where the signal needed to transmit to the destination is sent in both phases, the source and the relay also transmit different signal to the destination thus no loss of spectral efficiency. This protocol performs signal selection based on log-likelihood ratio (LLR) at relay and maximum likelihood (ML) detection at destination. While existing protocols pay for a worse performance than direct transmission in the low SNR regime which is of special interest in ad hoc networks, ours is better over the whole range of SNR. In addition, the proposal takes advantages of bandwidth efficiency, long delay and interference among many terminals in ad hoc network. Simulation results show that the proposed protocol can significantly save total energy for wireless ad hoc networks.

• International Journal of Computer Science & Network Security
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• 제21권6호
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• pp.200-206
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• 2021

Fraud in e-commerce transaction increased in the last decade especially with the increasing number of online stores and the lockdown that forced more people to pay for services and groceries online using their credit card. Several machine learning methods were proposed to detect fraudulent transaction. Neural networks showed promising results, but it has some few drawbacks that can be overcome using optimization methods. There are two categories of learning optimization methods, first-order methods which utilizes gradient information to construct the next training iteration whereas, and second-order methods which derivatives use Hessian to calculate the iteration based on the optimization trajectory. There also some training refinements procedures that aims to potentially enhance the original accuracy while possibly reduce the model size. This paper investigate the performance of several NN models in detecting fraud in e-commerce transaction. The backpropagation model which is classified as first learning algorithm achieved the best accuracy 96% among all the models.

• 한국정보시스템학회지:정보시스템연구
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• 제25권3호
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• pp.175-196
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• 2016

Purpose The development of new products in automobile parts industry plays an important role. Nowadays, automobile industry is one of the most important industries in the world, because automobile industry includes the industries of steel, machinery, electronic, etc. As a result, automobile industry embodies a country's level of development and competitiveness. The purpose of this study is to analyze the relationship between team characteristics such as communication, familiarity, and contiguity, and team performance through TMS in the process of new products development in automobile parts industry. Design/Methodology/Approach Based on real phenomenon of Korean automobile parts industry, this study tried to figure out the influence of TMS between team members for new product development on team performance. Thus, this study adopts communication, familiarity and contiguity as antecedents, and TMS with specialty, credibility and coordination as a mediating variable, and adopts team performance as a dependent variable. The data of questionnaire were collected from team managers who belong to new product development team in automobile parts firms. 171 questionnaires as data unit of group level from 80 Korean automobile parts firms were collected using face-to-face interview methods. Findings This study proved empirically that the relationship between antecedents and TMS has a positive influence, and TMS also has a positive influence on team performance. This study provides the managers an insight that automobile parts companies should pay more attention to set up TMS in order to improve higher performance between their team members for new product development of automobile parts.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권8호
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• pp.2854-2874
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• 2015

This paper presents a game theoretic approach to analyze the public goods (PGs) allocation in peer-to-peer (p2p) networks. In order to reduce the free-riders and promote the cooperation among peers, we propose an incentive mechanism with cooperation-based game theory. In this paper, we regarded the contributed resources by cooperators as public goods (PGs). We also build the PGs allocation in P2P networks to be the optimization problem, and the optimal solution of PGs allocation satisfies the Bowen-Lindahl-Samuelson equilibrium. Firstly, based on the subscriber mechanism, we analyze the feasibility and prove the validity, which can achieve Nash equilibrium. However, this strategy cannot meet to Bowen-Lindahl-Samuelson equilibrium as the free-riders do not pay with their private goods for consuming the PGs. Secondly, based on the Walker mechanism, we analyze the feasibility and prove the validity for the same allocation problem, which meets to Bowen-Lindahl-Samuelson equilibrium and achieves Pareto efficiency within cooperative game. Simulations show that the proposed walker mechanism can significantly improve the network performance of throughout, and effectively alleviate free-riding problem in P2P networks.

• 한국통신학회논문지
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• 제40권9호
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• pp.1741-1753
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• 2015

본 논문에서는 MBR 재생부호인 반복분할 부호의 부분접속수를 향상시킬 수 있는 방법에 대해 소개한다. 향상된 부분접속수를 갖는 반복분할 부호를 부분접속 복구 가능한 반복분할 부호라고 한다. 부분접속 복구 가능한 반복분할 부호의 서로 다른 두 가지 생성 방법을 소개하고 각각을 다양한 성능 척도를 통해 분석한다. 새로운 부호는 반복분할 부호에 비해 낮은 부분접속수를 갖는 대신 저장 가능한 최대 파일 크기나 필요한 저장 노드의 수에서 손해가 발생한다. 다른 부분접속 복구 부호와 비교해 향상된 안정성을 갖고 또한 복구시 심벌 연산이 필요 없는 단순전달 복구를 수행함으로써 복구 복잡도를 낮출 수 있다.

• 한국ITS학회 논문지
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• 제23권2호
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• pp.89-105
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• 2024

버스 이용자의 편의성 제고를 위해 정류장 시설을 개선하는 것은 매우 중요하며, 기 시행된 정류장 개선 사업의 효과를 정량적으로 분석하는 것은 사업의 지속적 확대를 위해 필수적이다. 그럼에도 불구하고 현재는 버스정류장 인프라 개선의 정량적 효과를 추정하는 연구가 전무한 실정이다. 본 연구에서는 정류장 개선에 대한 이용자 만족도에 기반한 조건부 가치측정법을 통해 버스정류장 인프라 개선에 대한 지불의사액과 편익-비용비를 추정했다. 결론적으로 거점지역에 위치한 정류장의 개선은 비용 대비 높은 편익을 달성할 수 있으며, 비거점지역에 위치한 정류장의 개선은 지역주민의 삶의 질 향상에 큰 영향을 미치는 것으로 나타났다. 본 연구의 결과는 버스정류장 시설 개선 사업 확장 시 근거자료로 활용될 것이라 판단된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.610-630
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• 2020

A large number of people suffered from traffic accidents each year, so people pay more attention to traffic safety. However, the traditional methods use laser sensors to calculate the vehicle distance at a very high cost. In this paper, we propose a method based on deep learning to calculate the vehicle distance with a monocular camera. Our method is inexpensive and quite convenient to deploy on the mobile platforms. This paper makes two contributions. First, based on Light-Head RCNN, we propose a new vehicle detection framework called Light-Car Detection which can be used on the mobile platforms. Second, the planar homography of projective geometry is used to calculate the distance between the camera and the vehicles ahead. The results show that our detection system achieves 13FPS detection speed and 60.0% mAP on the Adreno 530 GPU of Samsung Galaxy S7, while only requires 7.1MB of storage space. Compared with the methods existed, the proposed method achieves a better performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2202-2217
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• 2012

The transmission opportunities between nodes in Delay Tolerant Network (DTNs) are uncertain, and routing algorithms in DTNs often need nodes serving as relays for others to carry and forward messages. Due to selfishness, nodes may ask the source to pay a certain reward, and the reward may be varying with time. Moreover, the reward that the source obtains from the destination may also be varying with time. For example, the sooner the destination gets the message, the more rewards the source may obtain. The goal of this paper is to explore efficient ways for the source to maximize its total reward in such complex applications when it uses the probabilistic two-hop routing policy. We first propose a theoretical framework, which can be used to evaluate the total reward that the source can obtain. Then based on the model, we prove that the optimal forwarding policy confirms to the threshold form by the Pontryagin's Maximum Principle. Simulations based on both synthetic and real motion traces show the accuracy of our theoretical framework. Furthermore, we demonstrate that the performance of the optimal forwarding policy with threshold form is better through extensive numerical results, which conforms to the result obtained by the Maximum Principle.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5955-5977
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• 2018

Performance of the interpolation algorithm used in the technique of bi-dimensional empirical mode decomposition directly affects its popularization and application, so that the researchers pay more attention to the algorithm reasonable, accurate and fast. However, it has been a lack of an adaptive interpolation algorithm that is relatively satisfactory for the bi-dimensional empirical mode decomposition (BEMD) and is derived from the image characteristics. In view of this, this paper proposes an image interpolation algorithm based on the particle swarm and fractal. Its procedure includes: to analyze the given image by using the fractal brown function, to pick up the feature quantity from the image, and then to operate the adaptive image interpolation in terms of the obtained feature quantity. All parameters involved in the interpolation process are determined by using the particle swarm optimization algorithm. The presented interpolation algorithm can solve those problems of low efficiency and poor precision in the interpolation operation of bi-dimensional empirical mode decomposition and can also result in accurate and reliable bi-dimensional intrinsic modal functions with higher speed in the decomposition of the image. It lays the foundation for the further popularization and application of the bi-dimensional empirical mode decomposition algorithm.