• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.17-23
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• 2002

This paper introduces the spring-mounted odometer system which maintains the correct contact with the pipe wall and measures the distance along the pipe. The odometer wheel is designed to keep contact to the pipelines inner wall and to generate fifty rectangular pulses per one turn(159.5681mm) during pigging. The pipeline has the defects in various types such as buckles, winkles, cracks, dents, welding point and so on. Specially girth welding points which exist each 12m of the pipeline, much affects the operational environment of the odometer. The measurement error of the distance along the pipe is accumulated, for the measurement error of wheel's circumference and the pipeline inner environment. So, this paper proposes the method for the error compensation based on the analysis of the odometer's behavior around the girth welding point of pipe. The experimental results show that developed odometer system can be used for the intelligent pig with good performances.

• Progress in Medical Physics
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• v.10 no.2
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• pp.95-101
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• 1999

The aims of this report are to classify the incorrect data of patients and the errors of dose and dose distribution observed in QA activities on teleradiotherapy chart, and to analyze their frequency. In our department, radiation physicists check several sheets of patient chart to reduce numeric errors before starting radiation therapy and at least once a week, which include history, port diagram, MU calculation or treatment planning summary and daily treatment sheet. The observed errors are classified as followings. 1) Identity of patient, 2) Omitted or unrecorded history sheet even though not including the item related to dose, 3) Omission of port diagram, or omitted or erroneous data, 4) Erroneous calculation of MU and point dose, and important causes, 5) Loss of summary sheet of treatment planning, and erroneous data of patient in the sheet, 6) Erroneous record of radiation therapy, and errors of daily dose, port setup, MU and accumulated dose in the daily treatment sheet, 7) Errors leading inexact dose or dose distribution, errors not administerd even though its possibility, and simply recorded errors, 8) Omission of sign. Number of errors was counted rather than the number of patients. In radiotherapy chart QA from Jun 17, 1996 to Jul 31, 1999, no error of patient identity had been observed. 431 Errors in 399 patient charts had been observed and there were 405 physical errors, 9 cases of omitted or unrecorded history sheet, and 17 unsigned. There were 23 cases (5.7%) of omitted port diagram, 21 cases (5.2%) of omitted data and 73 cases (18.0 %) of erroneous data in port diagram, 13 cases (3.2 %) treated without MU calculation, 68 cases (16.3 %) of erroneous MU, 8 cases (2.0%) of erroneous point dose, 1 case (0.2 %) of omitted treatment planning summary, 11 cases (2.7%) of erroneous input of patient data, 13 cases (3.2%) of uncorrected record of treatment, 20 cases (4.9%) of discordant daily doses in MU calculation sheet and daily treatment sheet, 33 cases (8.1%) of erroneous setup, 52 cases (12.8%) of MU setting error, 61 cases (15.1%) of erroneous accumulated dose. Cases of error leading inexact dose or dose distribution were 239 (59.0 %), cases of error not administered even though its possibility were 142 (35.1 %), and cases of simply recorded error were 24 (5.9 %). The numeric errors observed in radiotherapy chart ranged over various items. Because errors observed can actually contribute to erroneous dose or dose distribution, or have the possibility to lead such errors, thorough QA activity in physical aspects of radiotherapy charts is required.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1167-1172
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• 2017

Desktop computers, which were the main means of Internet use and information activity, were pushed out by smart devices that emphasized mobility and simplicity. The recent information production and consumption activities are performed through smart devices, but there is no input device for smart devices that can fully replace traditional input devices such as full-size PC compatible keyboards. Because of the small size of the virtual keyboard that uses the touch screen of the smart device, typographical error occurs at a high rate. In this paper, we propose a variable virtual keyboard that minimizes the typographical errors of the conventional virtual keyboards. The proposed method minimizes the user 's input error by adjusting the size of each key of the virtual keyboard based on accumulated dataset of position and pressure of the user' s input error even though there is no difference in the key position arrangement of the conventional virtual keyboards.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.459-462
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• 2005

In this paper, we investigate the high precision location estimation algorithm in 2.45GHz band RTLS with multiple tags. The location is estimated in LOS environments, 300m ${\times}$ 300m area, and 2D coordinates adopting a TDOA scheme which is not necessitate the transmission time of tags. We evaluate the average estimation error in distance assuming that tags are randomly distributed and the readers(3${\sim}$8) are uniformly(equal space) placed in test area. In results, average estimation error is 3.12m and 1.47m at reader numbers of 4 and 8, respectively. Minimum estimation error is obtained when the accumulated receiving signal from a tag is 3 or 4 regardless of available reader numbers. The error is less than 3m, satisfies the specification of RTLS.

• Journal of Computing Science and Engineering
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• v.3 no.2
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• pp.73-87
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• 2009

A hybrid system is a dynamical system in which states can be changed continuously and discretely. Simulation based on numerical methods is the widely used technique for analyzing complicated hybrid systems. Numerical simulation of hybrid systems, however, is subject to two types of numerical errors: truncation error and round-off error. The effect of such errors can make an impossible transition step to become possible during simulation, and thus, to generate a simulation behavior that is not allowed by the model. The possibility of an incorrect simulation behavior reduces con.dence in simulation-based analysis since it is impossible to know whether a particular simulation trace is allowed by the model or not. To address this problem, we define the notion of Instrumented Hybrid Automata (IHA), which considers the effect of accumulated numerical errors on discrete transition steps. We then show how to convert Hybrid Automata (HA) to IRA and prove that every simulation behavior of IHA preserves the discrete transition steps of some behavior in HA; that is, simulation of IHA is sound with respect to HA.

• Journal of the Korean Institute of Gas
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• v.9 no.3 s.28
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• pp.38-43
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• 2005

There is monitored amount operation variables and controlled by operating conditions and loads at many facilities using gas also chemical plants. The process fault which can be indicated by operators, is occurred when the abnormal state was accumulated continuously owing to physical failure, external disturbance or human error. This is studied a Early Warning System which is to estimate process status by real-time monitoring operation variables and to early warning before it will be occurred process fault.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.18-25
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• 2005

Stochastic ground-motion method is adopted to simulate horizontal PGA values for the offshore Uljin earthquake recorded at nationwide seismic stations. For this purpose, the Fourier spectra are calculated at every stations based on comprehensive results of wave propagation and site effect which were previously revealed through inversion process applied to large accumulated spectral D/B. In addition, the apparent source spectrum of the offshore Uljin earthquake is estimated by removing the path and site response from the observed spectra. The distance dependent time-duration model is revised by iteratively fitting the PGA values generated by using the raw spectra data to the observed PGA data. The stochastic ground-motion method predicts the observed PGA values within a error of ${\sigma}_{log10}=0.1$. Transfer functions of a site relative to another site are estimated based on the error residual of the inversion results and used to convert PGA values at multiple stations to expected PGA values at a reference station of TJN. The converted PGA values can be used as basic data to evaluate the ground-motion attenuation relations developed for seismic hazard analysis that concerns the large damaging earthquakes.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.1
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• pp.41-46
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• 2006

Ubiquitous location based services, offer helpful services anytime and anywhere by using real-time location information of objects based on ubiquitous network. Particularly, autonomous mobile robots can be a solution for various applications related to ubiquitous location based services, e.g. in hospitals, for cleaning, at airports or railway stations. However, a meaningful and still unsolved problem for most applications is to develop a robust and cheap positioning system. A typical example of position measurements is dead reckoning that is well known for providing a good short-term accuracy, being inexpensive and allowing very high sampling rates. However, the measurement always has some accumulated errors because the fundamental idea of dead reckoning is the integration of incremental motion information over time. The other hand, a localization system using RFID offers absolute position of robots regardless of elapsed time. We construct an absolute positioning system based on RFID and investigate how localization technique can be enhanced by RFID through experiment to measure the location of a mobile robot. Tags are placed on the floor at 5cm intervals in the shape of square in an arbitrary space and the accuracy of position measurement is investigated . To reduce the error and the variation of error, a weighting function based on Gaussian function is used. Different weighting values are applied to position data of tags since weighting values follow Gaussian function.

• Journal of the Korean Institute of Telematics and Electronics
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• v.16 no.5
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• pp.1-11
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• 1979

Since the second half of 1960's one of the information industry's most vital, yet least-well-understood areas has evolved-Data communications/Computer communications. To successfully realize this field we have to identity and reveal a variety of fundermental characteristics of communications channels and see their high reliability as prerequisites. This paper has accumulated related data from 1973 on, systematically analyzed them and provided some basic back ground and suggestions. Error rate which is the final and external characteristics of communication lines according to channal types, communication types and speed, block length and geographical difference between test points was extensively examined as well as their frequency response and d-c characteristics. The perspective of 9600BPS high speed data communications was also discussed.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.317-325
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• 2022

In this paper, we developed a single frequency-based RRAIM to monitor integrity of the UAM landing vertically in urban area with only low-cost single-frequency GPS receiver. Conventional dual-frequency RRAIM eliminates ionospheric delay through a combination of frequencies. In this study, ionospheric delay was directly modeled. Drift error of residual ionospheric delay is modeled using the previously studied result on ionospheric rates of change. To verify the performance of the proposed RRAIM algorithm, a simulation of vertical landing UAM in urban area was conducted. It was assumed that the protection level at the initial position was calculated through SBAS correction data. During vertical landing, integrity monitored by receiver alone without external correction data. In the 60 sec simulation, the protection level of the proposed RRAIM compared to the conventional RRAIM was calculated to be 140% due to the accumulated ionospheric delay error. Nevertheless, it was confirmed that the final vertical protection level meeting the requirements of LPV-200, which cannot be achieved with single frequency GPS receiver alone.