• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.89-96
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• 2020

Linked Data allows structured data to be published in a standard way that datasets from various domains can be interlinked. With the rapid evolution of Linked Open Data(LOD), researchers are exploiting it to solve particular problems such as semantic similarity assessment. In this paper, we propose a method, on top of the basic concept of Linked Data Semantic Distance (LDSD), for calculating the Linked Data semantic distance between resources that can be used in the LOD-based recommender system. The semantic distance measurement model proposed in this paper is based on a similarity measurement that combines the LOD-based semantic distance and a new link weight using TF-IDF, which is well known in the field of information retrieval. In order to verify the effectiveness of this paper's approach, performance was evaluated in the context of an LOD-based recommendation system using mixed data of DBpedia and MovieLens. Experimental results show that the proposed method shows higher accuracy compared to other similar methods. In addition, it contributed to the improvement of the accuracy of the recommender system by expanding the range of semantic distance calculation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.175-180
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• 1999

Generally, When we measure of object 3D surfaces with phase shifting shadow moire method, it is use of optical system consist of light source, grating, and ccd camera. At this time, it is important parameter that vertical distance of grating and camera, grating and light source, and horizontal distance of camera and light source. When use camera consist of complex lens vertical distance of grating and camera is unknown parameter. From this cause equivalent wave length of moire fringe is uncertain. In this study, We exactly obtain a vertical distance of grating and camera so improve on measurement accuracy.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.33-39
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• 2015

In conducting indoor positioning by code division multiple access using spread spectrum ultrasonic waves, it is required to detect signals under the influence of near-far problem occurred by difference on signal power, caused by distance between transmitter and receiver. For discussing robustness to the problem, we verified measuring accuracy on distance from an experiment on a real space with a hardware device where our proposed method is mounted. The proposed method performs automatic signal detection by setting threshold level dynamically. As an experimental result, measurable distance were improved by the proposed method, and measurement errors were up to 50mm in distances from 1000mm to 6000mm; therefore, enough accuracy to realize self-localization or navigation for autonomous mobile robot or human was obtained.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.46-50
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• 2014

In this paper, we report a novel algorithm based on phase displacement, which supplements conventional TOF methods for distance measurement using an ultrasonic wave. The proposed algorithm roughly measures the distance between the transmission part and the receiving part by using the initial TOF. Thereafter, the precise distance is determined by measuring the phase displacement value between the synchronizing transmission signal and the signal obtained at the receiving end. A distance measurement experiment using a micrometer was performed to verify the accuracy of the ultrasonic wave sensor system. We found that the mean errors from the one adopting the distance measurement algorithm based on phase displacement varied from a minimum of 0.03 mm to a maximum of 0.09 mm. In addition, the standard deviation varied from a minimum of 0.04 mm to a maximum of 0.07 mm, thus giving a precision of ${\pm}0.1$ mm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.515-519
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• 2021

IEEE 1588 PTP is a precision time protocol in which two systems synchronize without the aid of GPS by exchanging packets including transmission/reception time information. In the time synchronization process, the propagation delay time can be calculated and the distance between the two systems can be measured using this. In this paper, we proposed a method to improve the distance measurement precision less than the modulation symbol period using the timing error information extracted from the preamble of the received packet. Computer simulations show that the distance measurement precision is proportional to the length of the preamble PN sequence and the signal-to-noise ratio.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.2
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• pp.161-168
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• 2015

In this paper, we present an inertial sensor-based gait distance measurement system using accelerometer, gyroscope, and magnetometer. To minimize offset and gain error of inertial sensors, we performed the calibration using the self-made calibration jig with 9 degrees of freedom. For measuring accurate gait distance, we used gradient descent algorithm to remove gravity error and used analysis of gait pattern to remove drift error. Finally, we measured a gait distance by double-integration of the error-removed acceleration data. To evaluate the performance of our system, we walked 10m in a straight line indoors to observe the improvement of removing error which compared un-calibrated to calibrated data. Also, the gait distance measured by the system was compared to the measurement of the Vicon motion capture system. The evaluation resulted in the improvement of $31.4{\pm}14.38%$(mean${\pm}$S.D.), $78.64{\pm}10.84%$ and $69.71{\pm}26.25%$ for x, y and z axis, respectively when walked in a straight line, and a root mean square error of 0.10m, 0.16m, and 0.12m for x, y and z axis, respectively when compared to the Vicon motion capture system.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3099-3103
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• 2011

In measurement of risk voltages; the step and touch voltage, the distance between the current electrode and the ground electrode recedes up to several hundred meters as the scale of grounding system increases. This paper dealt with the measurement method of risk voltage in a restricted space. The risk voltage was analyzed depending on the distance and the direction of the current electrode from the ground electrode in a $10[m]{\times}10[m]$ mesh grounding system. The average value of risk voltages measured at a point 20 [m] away from the current electrode was deviated below 5 [%] from that measured at 100 [m] point. Consequently, the evaluation of risk voltage of a large-scale grounding system buried in a spatially restricted place is available if the current electrode is installed in symmetry to the ground electrode.

• Journal of IKEEE
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• v.13 no.2
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• pp.220-223
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• 2009

A simple measurement system is built to estimate the dual-antenna diversity gain at 2.4GHz easily in open lab environment. To obtain multipath fading propagation channel, the system consists of two transmission horn that placed on opposite direction and a rotating stage mechanically changing the position of test dual-antenna with time over distance greater than one wavelength. Estimated diversity is nearly same as theoretical value such that measured diversity gain of 30mm separated is about 6dB similar to theoretical value of 5.7dB and increases monotonically with the increasing separation distance as predicted by the theory. Proposed measurement system that is simple enough to fit in a small space can evaluate the performance of various dual-antennas with a reasonable accuracy with lower 5% difference between the ten sets of measured waveform distribution and theoretical Rayleigh cumulative distribution.

• Journal of Navigation and Port Research
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• v.35 no.4
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• pp.317-321
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• 2011

In this paper, a foggy-degraded image restoration technique with a physics-based degradation model is proposed for the measurement system. When the degradation model is used for the image restoration, its parameters and a distance from the spreader to the camera have to be previously known. In the proposed image restoration technique, the parameters are estimated from variances and averages of intensities on two foggy-degraded landmark images taken at different distances. Foggy-degraded images can be restored with the estimated parameters and the distance measured by the measurement system. On the basis of the experimental results, the performance of the proposed foggy-degraded image restoration technique was verified.

• Journal of Navigation and Port Research
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• v.28 no.4
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• pp.323-331
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• 2004

This paper introduces a novel approach that can provide the three dimensional information about the movement of a spreader by using two CCD cameras and a laser distance measuring unit in order to derive ALS (Automatic Landing System) in the crane used at a harbor. So far a kind of 2D Laser scanner sensor or laser distance measuring units are used as comer detectors for the geometrical matching between the spreader and a container. Such systems provide only two dimensional information which is not enough for an accurate and fast ALS. In addition to this deficiency in performance, the price of the system is too high to adapt to the ALS. Therefore, to overcome these defects, we proposed a novel method to acquire the three dimensional spreader information using two CCD cameras and a laser distance measuring unit. To show the efficiency of proposed method, real experiments are performed to show the improvement of accuracy in distance measurement by fusing the sensory information of the CCD cameras and a laser distance measuring unit.