• The Journal of Korean Institute of Communications and Information Sciences
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• 제38C권6호
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• pp.531-539
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• 2013

Fingerprinting technique uses the radio signal strength measured reference locations is typically used, although there are many Wi-Fi based location tracking techniques. However, it needs numerous reference locations for precision and accuracy. This paper the analyzes problems of previous techniques and proposes a fingerprinting system using reliability based on a signal strength map. The system collects the signal strength data from a number of reference locations designated by the developer. And then it generates path-loss models to one of the access points for each reference location. These models calculate the predicted signal strength and reliability for a lattice. To evaluate proposed method and system performance, We perform experiments in a $20m{\times}22m$ real indoor environment installed access points. According to the result, the proposed system reduced distance error than RADAR. Comparing the existing system, it reduced about 1.74m.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제30권1C호
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• pp.82-91
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• 2005

This paper introduces an efficient affine projection algorithm(APA) using iterative hyperplane projection. Among various fast converging adaptation algorithms, APA has been preferred to be employed for various applications due to its inherent effectiveness against the rank deficient problem. However, the amount of complexity of the conventional APA could not be negligible because of the accomplishment of sample matrix inversion(SMI). Moreover, the 'shifting invariance property' usually exploited in single channel case does not hold for the application of space-time decision-directed equalizer(STDE) deployed in single-input-multi-output(SIMO) systems. Thus, it is impossible to utilize the fast adaptation schemes such as fast transversal filter(FlF) having low-complexity. To accomplish such tasks, this paper introduces the low-complexity APA by employing hyperplane projection algorithm, which shows the excellent tracking capability as well as the fast convergence. In order to confirm th validity of the proposed method, its performance is evaluated under wireless SIMO channel in respect to bit error rate(BER) behavior and computational complexity.

• Smart Structures and Systems
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• 제26권3호
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• pp.373-390
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• 2020

Hybrid simulation (HS) is a versatile tool for structural performance evaluation under dynamic loads. Although real structural responses are often multiple-directional owing to an eccentric mass/stiffness of the structure and/or excitations not along structural major axes, few HS in this field takes into account structural responses in multiple directions. Multi-directional loading is more challenging than uni-directional loading as there is a nonlinear transformation between actuator and specimen coordinate systems, increasing the difficulty of suppressing loading error. Moreover, redundant actuators may exist in multi-directional hybrid simulations of large-scale structures, which requires the loading strategy to contain ineffective loading of multiple actuators. To address these issues, lately a new strategy was conceived for accurate reproduction of desired displacements in bi-directional hybrid simulations (BHS), which is characterized in two features, i.e., iterative displacement command updating based on the Jacobian matrix considering nonlinear geometric relationships, and force-based control for compensating ineffective forces of redundant actuators. This paper performs performance validation and application of this new mixed loading strategy. In particular, virtual BHS considering linear and nonlinear specimen models, and the diversity of actuator properties were carried out. A validation test was implemented with a steel frame specimen. A real application of this strategy to BHS on a full-scale 2-story frame specimen was performed. Studies showed that this strategy exhibited excellent tracking performance for the measured displacements of the control point and remarkable compensation for ineffective forces of the redundant actuator. This strategy was demonstrated to be capable of accurately and effectively reproducing the desired displacements in large-scale BHS.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제35권10호
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• pp.989-996
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• 2011

An understanding of the concentrated solar flux is critical for the analysis and design of solar-energy-utilization systems. The current work focuses on the development of an algorithm that uses the Monte Carlo ray-tracing method with excellent flexibility and expandability; this method considers both solar limb darkening and the surface slope error of reflectors, thereby analyzing the solar flux. A comparison of the modeling results with measurements at the solar furnace in Korea Institute of Energy Research (KIER) show good agreement within a measurement uncertainty of 10%. The model evaluates the concentration performance of the KIER solar furnace with a tracking accuracy of 2 mrad and a maximum attainable concentration ratio of 4400 sun. Flux variations according to measurement position and flux distributions depending on acceptance angles provide detailed information for the design of chemical reactors or secondary concentrators.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제31권3A호
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• pp.274-281
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• 2006

Sensor network applications need synchronized time extremely such as object tracking, consistent state updates, duplicate detection, and temporal order delivery. This paper describes reliable time synchronization protocol (RTSP) for wireless sensor networks. In the proposed method, synchronization error is decreased by creating hierarchical tree with lower depth and reliability is improved by maintaining and updating information of candidate parent nodes. The RTSP reduces recovery time and communication overheads comparing to TPSN when there are topology changes owing to moving of nodes, running out of energy and physical crashes. Simulation results show that RTSP has about 20% better performance than TPSN in synchronization accuracy. And the number of message in the RTSP is $20%{\sim}60%$ lower than that in the TPSN when nodes are failed in the network. In case of different transmission range of nodes, the communication overhead in the RTSP is reduced up to 40% than that in the TPSN at the maximum.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제27권3A호
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• pp.188-195
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• 2002

The M-algorithm for decoding convolutional codes can significantly reduce the complexity of the Viterbi algorithm by tracking a fixed number of survivor paths in each level of the decoding trellis. It is an easily-implementable algorithm suited for real-time processing of high-speed data. The algorithm, however, generates a sequence of catastrophic errors when the correct path is not included in the set of survivor paths. In this paper, the performance of the M-algorithm obtained from using various decoding complexity levels, frame lengths, and code constraint lengths is presented. The performance gain is quantified when the algorithm is used in conjunction with codes of increased constraint length. In particular, it is demonstrated the gain from the increased code free distance overcompensates the loss from the correct path being excluded from the survivors, when the frame length is short to moderate. Using 64 survivor paths, the signal-to-noise ratio gain obtained by increasing the constraint length from K=7 to K=9, 11, 15 is respectively 0.6, 0.75, and 08dB, when the frame of length L=100 has the frame error rate of 0.01%.

• The KIPS Transactions:PartD
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• 제16D권2호
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• pp.201-212
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• 2009

There are various methods to trace output in software development to verify the consistency and completeness of requirements. Existing studies do present the trace meta-model or automated tools, but fail to list specifically traced output or traced items. Also, in regards to trace tables, which contain traced items, existing studies don‘t consider the whole software development process but merely its sub-process. Given this, the present study suggests an extended requirements tracetable that tracks output from the inception of the project through the architectural design phase to the application delivery, following up on the researcher’s previous study on a tracetable that considered only a sub-process of the whole development process. In addition, in order to address the problem of the tracking process becoming complicated with increased tracefields due to an extended trace table, the researcher suggests a method for normalizing a requirements tracetable that can integrate and separate by development process phase. Apply it to theH system development project of a D company, and this study caseverified application possibility of study, confirmed an effect of a chase to easily find out an error of requirements. Improve precision of a traceto verify consistency of requirements and completeness through this study, and will minimize failure of a software development.

• Journal of Korea Multimedia Society
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• 제12권8호
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• pp.1089-1098
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• 2009

Recently, many researches of making more comfortable input device based on gaze detection technology have been performed in human computer interface. Previous researches were performed on the computer environment with a large sized monitor. With recent increase of using mobile device, the necessities of interfacing by gaze detection on mobile environment were also increased. In this paper, we research about the gaze detection method by using UMPC (Ultra-Mobile PC) and an embedded camera of UMPC based on face and facial feature detection by AAM (Active Appearance Model). This paper has following three originalities. First, different from previous research, we propose a method for tracking user's gaze position in mobile device which has a small sized screen. Second, in order to detect facial feature points, we use AAM. Third, gaze detection accuracy is not degraded according to Z distance based on the normalization of input features by using the features which are obtained in an initial user calibration stage. Experimental results showed that gaze detection error was 1.77 degrees and it was reduced by mouse dragging based on the additional facial movement.

• Journal of the Korean Institute of Intelligent Systems
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• 제20권3호
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• pp.394-399
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• 2010

This paper presents to study the velocity control method of AGV for heavy material transport. Generally, in the industries, fork-type AGV using path tracking requires high stop-precision with performing operations for 20 hours. To obtain the high stop-precision of AGV for heavy material transport, AGV requires driving technic during low speed. Hence, we use encoder with keeping the speed of AGV and study the velocity control method to improve for the stop-precision of AGV. To experiment the proposed the velocity control method, we performed the experiments engaging the pallet located 4m in front of the AGV. In the experimental result, the maximum error of stop-precision was less than 18.64mm, and we verified that the proposed method is able to control stable.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2019년도 학술발표회
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• pp.35-35
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• 2019

본 연구에서는 분포형 수문 모형 Drying Stream Assessment Tool and Water Flow Tracking (DrySAT-WTF)을 활용해 우리나라의 1976년부터 2015년까지의 유출량을 산정하고, 이를 다층퍼셉트론(Multi Layer Perceptron) 인경신경망 모형(Artificial Neural Network Model)에 적용해 미래 유출을 예측하였다. DrySAT-WFT은 전국 표준 유역을 대상으로 하천 건천화 원인 추적 및 평가를 위해 개발된 모형으로 유출모의를 위한 기상자료 외에 건천화 영향 요소를 고려하기 위한 산림 높이, 도로망, 지하수 이용량, 토지이용, 토심 변화에 대한 DB를 적용 가능한 것이 특징이다. DrySAT-WFT를 위한 기상자료로 모의 기간에 대한 일별 강우량, 상대습도, 평균풍속, 평균 및 최고, 최저 기온, 일조시간을 구축하였으며, 연대별 건천화 영향 요소 DB를 구축하여 적용하였다. 전국 다목적 댐 보 12지점의 유량을 활용해 모형의 보정(2005-2010) 및 검증(2011-2015)을 실시한 결과, 평균 결정계수(Coefficient of determination, $R^2$)는 0.76, 모형효율성계수(Nash-Sutcliffe efficiency, NSE)는 0.62, 평균제곱근오차(average root mean square error, RMSE)는 3.09로 신뢰성 있는 유출 모의 결과를 나타내었다. 미래 유출량 예측을 위한 MLP-ANN은 1976년부터 2015년까지의 유출 모의 결과를 Training Set으로 훈련하여 $R^2$가 0.5 이상이 되어 신뢰성을 확보하였고, 2016년부터 2018년까지의 기간을 1개월 단위로 실제 유출량과 예측 유출량을 비교하며 적용성을 검증 및 향상시켰다.