• Composites Research
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• v.29 no.1
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• pp.1-6
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• 2016

Low-speed impact was localized on a stiffened composite structure, using 4 FBG sensors with 100 kHz-sampling rate interrogator and devised localization algorithm. The composite specimen consists of a main spar and several stringers, and the overall size of the specimen's surface is about $0.8{\times}1.2m$. Pre-stored reference data for 247 grid locations and 36 stiffener locations are gathered and used as comparison target for a random impact signal. The proposed algorithm uses the normalized cross-correlation method to compare the similarities of the two signals; the correlation results for each sensor's signal are multiplied by others, enabling mutual compensation. 20 verification points were successfully localized with a maximum error of 43.4 mm and an average error of 17.0 mm. For the same experimental setup, the performance of the proposed method is evaluated by reducing the number of sensors. It is revealed that the mutual compensation between the sensors is most effective in the case of a two sensor combination. For the sensor combination of FBG #1 and #2, the maximum localization error was 42.5 mm, with average error of 17.4 mm.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.6
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• pp.887-891
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• 1995

Nutrient intake data collected by both dietary methods of the 24 hour recall method and the food frequency method from 538 middle school students were analysed to investigate any measurement errors occuring while using these methods. Measurement errors were observed both in terms of differences of average intake and consistancy from the two sources of data used. Wilcoxon signed ranks test was used to test the differences between the two average intakes and Speraman's rank order correlation coefficient was used to test consistancy. As a result, average intake value estimated from the food frequency method tended to be higher than that from the 24 hour recall method. The degree of overestimation varies from one nutrient to another. For instance, carotene showed not only the most significant differences in average intake but also showed the most incoisistancies between the two sets of data. This may imply the validity of nutrient intake as derived from different dietary survey methods varied from one nutrient to another, therefore the selection of dietary survey methods has to be made more cautiously in the case of certainnutrients.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.106-113
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• 2008

The starter motor noise is usually well identified by the customers since it is operated while the engine is quiet, and leaves distinct impressions of the vehicle. In this study the design of experiments(DOE) was applied to the identification of the noise sources of direct drive starter motor since this process usually requires lengthy analysis and elaborate experiments. In the first stage of the test, five controllable factors(alignment and dynamic unbalance of armature, tightening torques of T/bolt and center bracket bolt, and alignment of the center bracket-yoke-rear bracket), excluding static unbalance, are sorted out of all possible factors. Test results showed that the dynamic unbalance and misalignment of armature are the major factors. However, the error level of the first test was relatively high, indicating that there might be some missing major factors. In the second stage test the results showed that both static and dynamic unbalances are the dominant factors contributing to more than 80% of the overall noise, while the misalignment contributes around 12%. Error of the second test was about 4% that could be considered satisfactory. The noise level of the optimal product was predicted to be reduced by 19dBA, and verification test showed the average noise reduction of 16.8dBA with the standard deviation of 3.2dBA, and proved the usefulness of the whole DOE process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.932-939
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• 1998

In this paper, we analyze the performance of a multicode-CDMA system which have been proposed for the multimedia communications. The performance of a multicode-CDMA system, providing good spectrum efficiency as well as serving various bit rates, is analyzed with multipath, frequency selective, slowly fading Rayleigh channel. Also the proposed scheme adopting RAKE receiver with MRC(Maximal Ratio Combine) is advantageous to multipath channel. For a practical channel modeling, the JTC(Joint Technical Committee) recommended channel model(JTC(AIR) 23-065R6) is applied to simulation. The proposed schemehas serial-to-parallel convertor which splits input data stream of 2 Mits/s into 20 branches o 100 kbits/s. From the result of simulation, the case of RAKE receiver with 3 fingers to reduce the system complexity required the relatively large $E_{b}/N_O$ of 0 dB~1.5 dB, compared to the case of RAKE receiver with the number of path finger to keep the average error rate to be $1{\times}10^{-3}$ in channel A.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.6
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• pp.85-94
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• 2010

The objective of this study is to estimate the flood runoff for three guaged stations within Namgang-Dam watershed which are operated by KWATER. For a flood runoff simulation, HEC-HMS was applied and the simulated runoff was compared with observed from 2004 to 2008. The watershed area of Sancheong, Shinan, and Changchon were 693.6 $km^2$, 413.4 $km^2$, and 346.48 $km^2$, respectively. The average runoff ratio of observed runoff for three watersheds were 0.725, 0.418, and 0.586, respectively. The dominant land cover of three watersheds are forest with the value of 71.6 %, 73.1 %, and 82.0 %. Three different cases according to the potential maximum retention of forest areas for calculating the curve number were applied to decrease the error between the simulated and observed. The simulated peak runoff of case 3 which applied the 90 % of potential maximum retention of curve number which is equivalent to AMCI for all the AMCI, AMCII, and AMCIII conditions showed least root mean square error (RMSE). The case 1, which was suggested by previous study, showed high discrepancy between the simulated and observed. Since the forest area consists of more than 70 % for all three watersheds, the application of curve number for forest is critical to improve the estimation errors. Further research is required to estimate the more accurate curve number for forest area.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.83-91
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• 2017

Objectives: The purpose of this study was to evaluate the error of the leaf position accuracy of the MLC due to the gravity effect according to the gantry angle by using picket fence test using EPID and GafChromic EBT3 film. Materials and Methods: A 5 cm solid phantom was placed on the table and the SAD was set to 100 cm. The EBT3 film was placed exactly over the solid phantom and covered a 1.5 cm solid phantom and the picket fence test was performed. The EPID was measured under the same conditions as the EBT3 film at SID 100 cm. The gantry angles were measured at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$ in order to evaluate the position of the MLC according to the gantry angle. For the geometric evaluation of the MLC, the leaf position accuracy of the MLC was analyzed using the analysis program. Results: In case of EPID, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.18 mm, 0.31 mm, 0.20 mm, 0.26 mm on the average and the maximum values of the errors were respectively 0.44 mm, 0.54 mm, 0.34 mm, 0.44 mm. In case of EBT3 film, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.19 mm, 0.21 mm, 0.19 mm, 0.31 mm on the average and the maximum values of the errors were respectively 0.35 mm, 0.45 mm, 0.36 mm, 0.48 mm. Conclusion: In this study, we analyzed the position error of the leaf of the MLC according to the gantry angle, and confirmed the position error of the leaf by gravity effect. As a result of comparing the leaf position accuracy using EPID and EBT3 film according to the variation of gantry angle, a larger error occurred in the error analysis method using EPID than that of EBT3 film. Therefore, in the case of IMRT based on MLC, as well as verification of accurate dosimetry should be conducted, it is considered that the quality control and verification for the precise operation of the MLC will be needed. and it is necessary to compare and verify the method of analysis.

• MALSORI
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• no.52
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• pp.161-169
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• 2004

This paper describes the automated call routing for train ticket reservation aid system based on speech recognition. We focus on the task of automatically routing telephone calls based on user's fluently spoken response instead of touch tone menus in an interactive voice response system. Vector-based call routing algorithm is investigated and mapping table for key term is suggested. Korail database collected by KT is used for call routing experiment. We evaluate call-classification experiments for transcribed text from Korail database. In case of small training data, an average call routing error reduction rate of 14% is observed when mapping table is used.

• ETRI Journal
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• v.37 no.1
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• pp.157-164
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• 2015

As GPU power consumption in smartphones increases with more advanced graphic performance, it becomes essential to estimate GPU power consumption accurately. The conventional GPU power model assumes, simply, that a GPU consumes constant power when turned on; however, this is no longer true for recent smartphone GPUs. In this paper, we propose an accurate GPU power model for smartphones, considering newly adopted dynamic voltage and frequency scaling. For the proposed GPU power model, our evaluation results show that the error rate for system power estimation is as low as 2.9%, on average, and 4.6% in the worst case.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.951-954
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• 2000

In this paper, we present a multi-code parallel combinatory CDMA system using bi-orthogonal modulation to reduce envelope variation and improve bit error. .rate (BER) performance. In general, the dynamic range of the amplitude of the transmit signal is very large in the case of conventional multi-code CDMA systems, resulting in severe nonlinear distortion due to high power amplifier and thus significant BER performance degradation. The proposed system exhibits reduction of peak-to-average power ratio (PAPR) of the transmit signal amplitudes and significant performance improvement. We verify the performance of the proposed system by computer simulations under AWGN channel and flat fading channel.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.17-20
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• 2005

In this work, we compared several feature selection methods in the field of spam mail filtering. The proposed fuzzy inference method outperforms information gain and chi squared test methods as a feature selection method in terms of error rate. In the case of junk mails, since the mail body has little text information, it provides insufficient hints to distinguish spam mails from legitimate ones. To address this problem, we follow hyperlinks contained in the email body, fetch contents of a remote web page, and extract hints from both original email body and fetched web pages. A two-phase approach is applied to filter spam mails in which definite hint is used first, and then less definite textual information is used. In our experiment, the proposed two-phase method achieved an improvement of recall by 32.4% on the average over the $1^{st}$ phase or the $2^{nd}$ phase only works.