• Journal of Ubiquitous Convergence Technology
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• v.2 no.2
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• pp.78-87
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• 2008

Received signal strength indicator (RSSI) is used as one of the ranging techniques to locate dynamic sensor nodes in wireless sensor network. Before it can be used for position estimation, RSSI values must be converted to distances using path loss model. These distances among sensor nodes are combined using trilateration method to find position. This paper presents an idea which attempts to integrate both path loss model and trilateration as one algorithm without going through RSSI-distance conversion. This means it is not simply formulas combination but a whole new model was developed. Several advantages were found after integration: it is able to reduce processing load, and ensure that all values do not exceed the maximum range of 16-bit signed or unsigned numbers due to antilog operation in path loss model. The results also show that this method is able to reduce estimation error while inaccurate environmental parameters are used for RSSI-distance conversion.

• Journal of Engineering Education Research
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• v.13 no.5
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• pp.76-80
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• 2010

In this paper, the Location Compensation Mechanism using equivalent distance rate ($LCM_{edr}$) for localization system based on SDS-TWR (Symmetric Double-Sided Two-Way Ranging) in wireless sensor network is proposed. The performance of the mechanism is experimented in terms of two types of the localization tracking scenarios of indoor and outdoor environments in university campus. From the experimentations, the compensation ratio in the $LCM_{edr}$ is better than that in SDS-TWR about 90% in indoor/outdoor environments in scenario 1 but also is better than that of SDS-TWR about 91.7% in indoor environment and about 100% in outdoor environment in scenario 2 respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.188-195
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• 2010

Unlike using a single sonar platform, using two different sonar platforms can lead to a considerable increase of acoustic aperture in Passive Ranging Sonar(PRS). Values measured from two sonar platforms shall be consistent in order to allow us to rely on such improved aperture. However, obtaining consistent values from a towed array and a frank array is not always simple due to the heading error occurring at towed array. The objective of this paper is to verify a new criterion analyzing the consistency in the measured values of towed array and frank array through computer simulations.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1343-1348
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• 1990

The architecture and functions of a prototype free ranging AGV system are described in this paper. The system has single tricycle configuration - the front wheel is driven and steered simultaneously. The primary position measurement device of this system is the redundant encoder system - an absolute encoder for the steering angle measurement of the front wheel, two incremental encoders for the measurement of the rear wheel rotations. The secondary position measurement device is implemented to reduce the accumulatad error in encoder measurements. The extended Kalman filter is suggested to combine the conflict measurement data for the proper position estimation.

• Speech Sciences
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• v.13 no.2
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• pp.59-72
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• 2006

In the present study, we investigated the grammaticality judgement skills of children with developmental language impairments. The participants included 20 children with language impairments of ages ranging from 7 to 9 years and of IQ's ranging from 71 to 84, and 40 normally developing children. Twenty normal children were matched with the language impaired children in their language ages and the other 20 normal children were matched with the language impaired children in their chronological ages. The children were asked to judge the grammatical correctness of 48 short sentences, half of which were ungrammatical sentences containing incorrect case-markers and the other half were grammatically correct sentences. Four types of case-markers including nominative "i/ga", accusative "ul/lul", locative "e," and instrumental "ro" were systematically changed to generate the ungrammatical sentences. The language impaired children performed worse than both groups of normally developing children in detecting the ungrammatical sentences and in correcting the case-markers of those sentences. In detecting the errors of ungrammatical sentences, the language impaired children exhibited variable performances across the different case-markers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.75-83
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• 2005

NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, which consists of two co-orbiting low altitude satellites, is to measure the Earth gravity field with unprecedented accuracy. Its key instruments include inter-satellite ranging systems and three-axis accelerometers. For the preliminary design and requirements analysis, extensive instrument simulation models are developed. These modeling techniques and orbit-gravity field estimation techniques are described.

• Journal of the Korean Solar Energy Society
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• v.37 no.5
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• pp.1-11
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• 2017

A study on Nacelle Lidar (Light detection and ranging) measurement error and the data reliability verification was carried out at Haengwon wind farm on Jeju Island. For measurement data error processing, the characteristics of Nacelle Lidar measurements were analyzed by dividing into three parts, which are weather conditions (temperature, humidity, atmosphere, amount of precipitation), mechanical movement (rotation of wind turbine blades, tilt variation of Nacelle Lidar) and Nacelle Lidar data availability. After processing the measurement error, the reliability of Nacelle Lidar data was assessed by comparing with wind data by an anemometer on a met mast, which is located at a distance of 200m from the wind turbine with Nacelle Lidar. As a result, various weather conditions and mechanical movement did not disturb reliable data measurement. Nacelle Lidar data with availability of 95% or more could be used for checking Nacelle Lidar wind data reliability. The reliability of Nacelle Lidar data was very high with regression coefficient of 98% and coefficient of determination of 97%.

• The Journal of Korea Robotics Society
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• v.19 no.2
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• pp.169-175
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• 2024

In this study, we developed control system for stable teleoperation of supermicrosurgical robot platform. The supermicrosurgical robot platform is designed to perform precise anastomosis with micro vessels ranging from 0.3 mm to 0.7 mm. The robotic assistance could help more precise manipulation then manual surgery with the help of motion scaling and tremor filtering. However, since the robotic system could cause several vulnerabilities, control system for stable teleoperation should be preceded. Therefore, we first designed control system including inverse kinematics solver, clutch error interpolator and finite state machine. The inverse kinematics solver was designed to minimized inertial motion of the manipulator and tested by applying orientational motion. To make robot slowly converges to the leader's orientation when orientational error was occurred during clutch, the SLERP was used to interpolate the error. Since synchronized behavior of two manipulators and independent behavior of manipulator both exist, two layered finite state machines were designed. Finally, the control system was evaluated by experiment and showed intended behavior, while maintaining low pose error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.569-580
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• 2012

In this paper, an enhanced initial ranging algorithm for large-cell coverage fixed wireless communication system is proposed. In typical wireless communication system such as WiBro, because a round-trip delay between a transmitter and a receiver is within one OFDM (Orthogonal Frequency Division Multiplexing) symbol duration, a frequency-domain differential correlation method is generally used. However, the conventional method cannot be applied due to an increase of a maximum time delay in large-cell system. In case of an accumulative differential method, estimation errors can occur because of frequent sign transitions. In this paper, therefore, we propose an algorithm which can estimate a total timing offset in a ranging channel structure for 15 km cell. The proposed method can improve performance by sign comparison based sign error correction rule between the estimated values and using a weighting scheme based on channel correlation, the number of accumulations, and the noise reduction effect in normalization process. Also, it can estimate the integer timing offset of symbol duration by comparing peak-powers after compensating for the fractional timing offset of symbol duration.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.8-14
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• 2016

High-level conceptual design analysis results of satellite communication system for Korea augmentation satellite system (KASS) satellite communication system, which is a part of KASS and consisted of KASS uplink Stations and two leased GEO is presented in this paper. We present major functions such as receiving correction and integrity message from central processing system, taking forward error correction for the message, modulating and up converting signal and conceptual design analysis for concepts for design process, GEO precise orbit determination for GEO ranging that is additional function, and clock steering for synchronization of clocks between GEO and GPS satellites. In addition to these, KASS requires 2.2 MHz for SBAS Augmentation service and 18.5 MHz for Geo-ranging service as minimum bandwidths as a results of service performance analysis of GEO ranging with respect to navigation payload(transponder) RF bandwidth is presented. These analysis results will be fed into KASS communication system design by carrying out final analysis after determining two GEOs and sites of KASS uplink stations.