• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.657-665
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• 2016

Launch Control System(LCS) performs the pre-launch preparation and launch operation during launch campaign. The successful launch operation is basically influenced by hardware and software of LCS. Especially, a trivial errors in control algorithm can cause critical problem or disaster in launch operation. Therefore, the hidden or implicit errors should be distinguished and eliminated by the verification test in advance. In this paper, the design and implementation of hardware and software simulator which have already been used in LCS verification will be introduced. By presenting the detailed design and flowchart-based algorithms, we make other similar systems adopt the implementation philosophies of this paper. Especially, this paper emphasizes that all the simulation algorithms work on the self-controller in LCS without using separated computer or PLC.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.35-41
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• 2010

Since the ad-hoc network allow nodes to communicate each other without infrastructure system and predefined configuration, it comes into the spotlight that is suitable to ubiquitous society. In ad-hoc network, route recovery mechanism is considered important. Normally route recovery is needed to solve the link failure problem because there is no route maintaining system like a router in ad-hoc networks. In this paper we propose BS-AODV(Bidirectional Searching-AODV) route recovery method. The proposed method is a local repair method that can be applied in all of the network area. Unlike a limited local repair method in AODV. the proposed method adopts the bidirectional searching method where the upstream/downstream nodes can send the route maintenance messages. Restricting the flooding of route request messages, the proposed scheme attempts to minimize the costs of local repair, the performance of the proposed scheme is evaluated through the simulations. In two scenarios which variate the node numbers and node speed, the comparison among the proposed scheme, AODV and AOMDV is shown in terms of the control traffic and data delivery ratio.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.692-702
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• 2008

Path planning is gaining more weight in computer games and virtual reality as the number of self-moving characters increases. In the roadmap approach, the map of possible paths is built in advance to plan paths for a character, whose advantage is to provide high-quality paths. On the other hand, a disadvantage is that the road map doesn't reflect properties of characters such as their sizes because they move on the same map once the road map is constructed. In this paper we propose an efficient method to build a different road map for each character so that it can use its own map for path-planning. This method is efficient because the whole map is built once by applying the Visibility Graph regardless of the number of characters and walkable paths are incrementally inserted according to the sizes of characters. The effects of using separate roadmaps are demonstrated through simulations and the trade-offs accompanied with these effects are analyzed.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10b
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• pp.55-57
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• 2001

강화학습은 한 에이전트가 자신이 놓여진 환경으로부터의 보상을 최대화할 수 있는 최적의 행동 전략을 학습하는 것이다. 따라서 강화학습은 입력(상태)과 출력(행동)의 쌍으로 명확한 훈련 예들이 제공되는 교사 학습과는 다르다. 특히 Q-학습과 같은 비 모델 기반(model-free)의 강화학습은 사전에 환경에 대한 별다른 모델을 설정하거나 학습할 필요가 없으며 다양한 상태와 행동들을 충분히 자주 경험할 수만 있으면 최적의 행동전략에 도달할 수 있어 다양한 응용분야에 적용되고 있다. 하지만 실제 응용분야에서 Q-학습과 같은 강화학습이 겪는 최대의 문제는 큰 상태 공간을 갖는 문제의 경우에는 적절한 시간 내에 각 상태와 행동들에 대한 최적의 Q값에 수렴할 수 없어 효과를 거두기 어렵다는 점이다. 이런 문제점을 고려하여 본 논문에서는 로봇 축구 시뮬레이션 환경에서 각 선수 에이전트의 동적 위치 결정을 위해 효과적인 새로운 Q-학습 방법을 제안한다. 이 방법은 원래 문제의 상태공간을 몇 개의 작은 모듈들로 나누고 이들의 개별적인 Q-학습 결과를 단순히 결합하는 종래의 모듈화 Q-학습(Modular Q-Learning)을 개선하여, 보상에 끼친 각 모듈의 기여도에 따라 모듈들의 학습결과를 적응적으로 결합하는 방법이다. 이와 같은 적응적 중재에 기초한 모듈화 Q-학습법(Adaptive Mediation based Modular Q-Learning, AMMQL)은 종래의 모듈화 Q-학습법의 장점과 마찬가지로 큰 상태공간의 문제를 해결할 수 있을 뿐 아니라 보다 동적인 환경변화에 유연하게 적응하여 새로운 행동 전략을 학습할 수 있다는 장점을 추가로 가질 수 있다. 이러한 특성을 지닌 AMMQL 학습법은 로봇축구와 같이 끊임없이 실시간적으로 변화가 일어나는 다중 에이전트 환경에서 특히 높은 효과를 볼 수 있다. 본 논문에서는 AMMQL 학습방법의 개념을 소개하고, 로봇축구 에이전트의 동적 위치 결정을 위한 학습에 어떻게 이 학습방법을 적용할 수 있는지 세부 설계를 제시한다.

• The Journal of the Korea Contents Association
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• v.6 no.10
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• pp.163-173
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• 2006

It is frequent to develop the fashion product through predict purchasing needs of consumers in Textile and Fashion Industry. If failed in its prediction, that is, if consumers would not purchase the product, there comes some problems that big sale is inevitable or stock increase tremendously. Otherwise, Quick Response System allows that the company observe the consumer's needs consistently and design products and establish manufacture schedule rapidly so that they could prohibit the products unnecessarily stocked. Consumer's preference is collected and analyzed through the data generated by POS system, and this is provided to the related manufacturer through network in realtime, so that the manufactures could merchandise, produce and provide the products according to the consumer's need. Thus, this study developed POS system-education program, that is, the merchandising of apparel product, product by prediction, retailer, purchase behavior, reduction in stock inventory and product lead time, cooperative system between apparel company and retailer, and conformation to the consumer's needs are included in this program, through binding the new technology in textile and fashion industry for the purpose of Quick Response system.

• The Journal of the Korea Contents Association
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• v.7 no.8
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• pp.21-30
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• 2007

Due to the growth of embedded systems and the development of semi-conductor and storage devices, digital convergence devises is ever growing. Digital convergence devices are equipments into which various functions such as communication, playing movies and wave files and electronic dictionarys are integrated. Example are portable multimedia players(PMPs), personal digital assistants(PDAs), and smart phones. Therefore, these devices need an efficient file system which manages and controls various types of files. In designing such file systems, the size constraint for small embedded systems as well as performance and compatibility should be taken into account. In this paper, we suggest the partial buffer cache technique. Contrary to the traditional buffer cache, the partial buffer cache is used for only the FAT meta data and write-only data. Simulation results show that we could enhance the write performance more than 30% when the file size is larger than about 100 KBytes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1049-1057
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• 2006

Overlay Multicast is an effective method for efficient utilization of system resources and network bandwidth without using hardware customization. Unlike in IP multicast, multicast tree reconstruction is required when non-leaf node leaves or fails. In this paper, we propose a proactive approach to solve this defect by using a resource reservation of the out degrees. This allows children of non-leaf node to connect to its new parent node immediately when its parent node leaves or fails. In our proposal, a proactive route maintenance gives a fast recovery time and reduces a delay effect in the new route. The simulation results show that our proposal takes shorter period of time than the other algorithms to reconstruct a similar tree and that it is a more effective way to deal with a lot of nodes that have lost their parent nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.675-684
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• 2004

There have been several efforts to avoid unnecessary retransmission timeouts (RTOs), which is the main cause for TCP throughput degradation. Unnecessary RTOs can be classified into three groups according to their cause. RTOs due to multiple packet losses in the same window for TCP Reno, the most prevalent TCP version, can be avoided by TCP NewReno or using selective acknowledgement (SACK) option. RTOs occurring when a packet is lost in a window that is not large enough to trigger fast retransmit can be avoided by using the Limited Transmit algorithm. In this Paper, we comparatively analyze these schemes to cope with unnecessary RTOs by numerical analysis and simulations. On the basis of the results in this paper, TCP performance can be quantitatively predicted from the aspect of loss recovery probability. Considering that overall performance of TCP is largely dependent upon the loss recovery performance, the results shown in this paper are of great importance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.671-678
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• 2005

This paper proposed symbol rate method which does not require a priori knowledge on the symbol rate and simplified modulation identification method to classify BPSK, QPSK, 8PSK signal. In order to estimate the unknown symbol rate, sliding FFT and simple moving average to estimate the spectrum of the signals is utilized, and sliding window and decimation, LPF blcok to estimate the proper symbol rate is used. Although conventional modulation ID method must use SNR value as the test statistics, the receiver cannot estimate the SNR value since the receiver cannot know the modulation type at the start of communication, and bit resolution is high due to using nonlinear function such as log, cosh. Therefore, we proposed the simplified fixed SNR value method. The performance of symbol rate estimation and modulation ID is shown using Monte Carlo computer simulation. This paper show that symbol rate estimation also has good performance in low SNR, and proposed simplified fixed SNR method has almost equivalent performance compared to conventional method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.236-242
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• 2010

A GNSS/INS integration system can not provide navigation solutions if there are no available satellites. To overcome this problem, a vision sensor is integrated with this system. Since generally a vision aided integration system uses only feature point to compute navigation solutions, it has a problem in observability. In this case, additional landmarks, which is priory known points, can improve the observability. In this paper, the observability is evaluated using TOM/SOM matrix and Eigenvalues. There are always the observability problems in the feature-point-only case, but the landmark-use case is fully observable after the $2^{nd}$ update time. Consequently the landmarks ensure full observability, so the system performance can be improved.