• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1950-1956
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• 1997

An engineering goal in vibration and noise professionals is to develope quiet machines at the preliminary design stage, and various numerical techniques such as FEM, SEA or BEM are one of the schemes toward the goal. In this paper, the research has been focused on the sensitivity effect of mesh sizes for FEM application so that the optimum size of the mesh that leads to engineering solution within acceptable computing time could be generated. In order to evaluate the mesh size effect, three important parameters have been examined : natural frequencies, number of modes and driving point mobility. First, several lower modes including the fundamental frequency of a 2-D plate structure have been calculated as mesh size changes. Since theoretical values of natural frequencies for a simple structure are known, the deviation between the numerical and theoretical values is obtained as a function of mesh size. The result shows that the error is no longer decreased if the mesh size becomes a quarter wavelength or smaller than that. Second, the mesh size effect is also investigated for the number of modes. For the frequency band up to 1.4 kHz, the structure should have 38 modes in total. As the mesh size reaches to the quarter wavelength, the total count in modes approaches to the same values. Third, a mobility function at the driving point is compared between SEA and FEM result. In SEA application, the mobility function is determined by the modal density and the mass of the structure. It is independent of excitation frequencies. When the mobility function is calculated from a wavelength to one-tenth of it, the mobility becomes constant if the mesh becomes a quarter wavelength or smaller. We can conclude that dynamic parameters, such as eigenvalues, mode count, and mobility function, can be correctly estimated, while saving the computing burden, if a quarter wavelength (.lambda./4) mesh is used. Therefore, (.lambda./4) mesh is recommended in structural vibration analysis.

• The Korean Journal of Cytopathology
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• v.8 no.2
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• pp.120-128
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• 1997

Fine needle aspiration cytology of breast lesion is well known as a simple, economic and effective diagnostic modality. For the evaluation of cytohistologic correlation, 256 cases of cytologic smears and subsequent histologic sections during 2-year period from Jan. 1995 to Dec. 1996 were reviewed. 1. Fifteen cases(5.9%) were proven as insufficient for evaluation, and 13 of them were fibrocystic change histologically. One case of carcinoma exhibiting sufficient amount of aspirates with no malignant cells on smear was regarded as inadequate. 2. Cytohistologic correlation of 240 cases revealed sensitivity 87.0%, specificity 100.0%, positive predictive value 100.0%, negative predictive value 97.0%, false positive rate 0.0% and false negative rate 13.0%. Total diagnostic accuracy is 95.7%. 3. Total 6 cases of negative were due to small amount of aspirates containing scantiness of malignant cells in two and underestimation in four. 4. Diagnostic concordance rates of fibrocystic change and fibroadenoma were 95.5% and 80.0%, respectively. Diagnostic discrepancies were noted in 7 cases of fibrocystic change and 6 cases of fibroadenoma, however, cytologic discrimination of two entities was not easy in seven of them. 5. In a case of phyllodes tumor and a case of duct ectasia, the discrepancy was due to targeting error. Other three cases(lymphoma, adenomyoepithelioma and granulomatous mastitis) were misinterpreted because of poor acquaintance with those entities. Diagnostic accuracy of fine needle aspiration cytology of breast lesions are relatively high. However, good technique on aspiration and adequate interpretation are necessary to reduce the false negative rate and the discrepancy between cytologic and histologic diagnoses.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.160-166
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• 2010

Railroad level crossing systems are used to prevent train from collisions by informing pedestrians and vehicles of approaching trains on the level crossing. The current detection systems mostly use track-based electrical circuits to detect approaching trains. The making and breaking of the circuit when the train wheel passes along the track sends a signal to barriers that restrict access to the track. Unfortunately, this track-based signal system is vulnerable to malfunctions in certain situations. If the rail becomes rusted due to moisture, weather conditions, or infrequent use, the electrical circuit detection system could fail. Such a failure could lead to a train-vehicle or train-pedestrian collision. This paper suggests a replacement of the electrical circuit-based system with an infrared detection system. The research shows that an infrared detection system improves safety by reducing the frequency of detection failure of the alarming circuit to system.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1123-1131
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• 2008

In this study, measurement uncertainty of instrumental neutron activation analysis was evaluated for ambient As concentration in PM2.5. Expanded uncertainties of the measurements were calculated by applying both ISO-GUM approximation and Monte Carlo Simulation(MCS). The estimate of As concentration on a specific day by the Monte Carlo Simulation differed from that of ISO-GUM approximation by less than 4%. Relative expanded uncertainties of As concentrations from a total number of 60 PM2.5 samples were also estimated to be more or less than 10% with 95% confidence level using the Monte Carlo Simulation. Sensitivity test of the measurement uncertainties showed that $\gamma$-ray counting error(62.3%), efficiency(18.5%), air volume(12.3%), neutron flux(2.3%), and absolute gamma-intensity(1.8%) are major factors of uncertainty variations.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.3
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• pp.15-25
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• 2018

Estimating the reference evapotranspiration is an important factor to consider in irrigation system design and agricultural water use. However, there is a limitation in using the FAO Penman-Monteith (FAO P-M) equation, which requires various meteorological data. The purpose of this study is to compare three reference evapotranspiration (ETo) equations in the case of meteorological data missing for 11 study weather stations. Firstly, the FAO P-M equation is used for reference potential evapotranspiration estimation with the actual solar radiation data $R_n$ and the actual vapor pressure $e_a$. Then, in the case of $R_n$, and $e_a$ are missed, the reference evapotranspirations applying FAO P-M, Priestley-Taylor (P-T), Hargreaves (HG) equation were calculated using other meteorological factors. Secondly, MAE, RMSE, $R^2$ were calculated to compare ETo relationship from the ETo equations. From the results, ETo with Hargreaves equation in coastal areas and the Priestley-Taylor equation in the inland areas showed relatively high correlation with FAO P-M when $e_a$ data is missed. In the case of $R_n$ data is missed or two weather data, $e_a$, and $R_n$ data are all missed, $R^2$ value in Priestley-Taylor equation was highest in coastal areas, and $R^2$ values in Hargreaves equation were the high values for 7 inland areas. The results of sensitivity analysis showed that net radiation was the most sensitive for P-T and HG equation, and for FAO P-M, the most sensitive factor was net radiation and relative humidity, air temperature and wind speed were follows. Therefore, in considering of the accessibility to the coast, the types of the missing wether data, and the correlation and the magnitude of error, the reference evapotranspiration equations would be selected in sense of different conditions.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.731-741
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• 2010

In this paper, we propose the methodology of prediction of field strength for a digital television (DTV) receiver by virtue of Recommendation ITU-R P.1546. The curves shown in this recommendation represent the point-to area field strength for 1.0 kW effective radiated power in the 30 MHz ~ 3000 MHz. Based upon the procedures described in this Recommendation, computation results are presented here from the derived formulation of field strength for DTV receiver. To show the validity of this method, some results are compared with the analysis by Okumura-Hata model and it was shown that the error of field strength is in the range of 6.9 ~ 11.5 %. The presented method provides not only the predicted values of field strength for DTV receiving area to check the quality of transmitted signal, but also an appropriate site selection for obtaining good propagation environment. In addition, it can be directly used for analyzing the protection ratio or separated distance for frequency sharing in the same band.

• Journal of Advanced Navigation Technology
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• v.15 no.6
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• pp.1241-1249
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• 2011

There are TOA, TDOA and AOA method to estimate the position of the electromagnetic wave transmitter by using the multiple receivers at the fixed position. Among these methods, AOA method is suitable for the jammer localization system. Because TOA method can be adopted for the clocks of the transmitter and the receiver are synchronized each other, and TDOA method can be only adopted for a broad-band jamming signal. This paper, therefore, analyzes the characteristics of the AOA measurements and the sensitivity of the positioning performance according to the system design parameters. Based on the analyzed results, the jammer localization system to meet the desired performance is designed, and it has been checked that the positioning error for the jammer located at a distance of 10km is lower than 38m through the simulation results.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.30-40
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• 2011

Numerical simulations were carried out to investigate the impact of SST spatial distribution on the result of air quality modeling. Eulerian photochemical dispersion model CAMx (Comprehensive Air quality Model with eXtensions, version 4.50) was applied in this study and meteorological fields were prepared by RAMS (Regional Atmospheric Modeling System). Three different meteorological fields, due to different SST spatial distributions were used for air quality modeling to assess the sensitivity of CAMx modeling to the different meteorological input data. The horizontal distributions of surface ozone concentrations were analyzed and compared. In each case, the simulated ozone concentrations were different due to the discrepancies of horizontal SST distributions. The discrepancies of land-sea breeze velocity caused the difference of daytime and nighttime ozone concentrations. The result of statistic analysis also showed differences for each case. Case NG, which used meteorological fields with high resolution SST data was most successfully estimated correlation coefficient, root mean squared error and index of agreement value for ground level ozone concentration. The prediction accuracy was also improved clearly for case NG. In conclusion, the results suggest that SST spatial distribution plays an important role in the results of air quality modeling on high ozone episode at coastal region.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.17-24
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• 2018

The HEC-HMS model was applied to identify the rainfall-runoff processes for the Anseongchun basin, where the lower part of the stream has been damaged severely by tropical storms in the past. Modeling processes include incorporating with the SCS-CN model for loss, Clark's UH model for transformation, exponential recession model for baseflow, and Muskingum model for channel routing. The parameters were calibrated through an optimization technique using a trial and error method. Sensitivity analysis after calibration was performed to understand the effects of parameters, such as the time of concentration, storage coefficient, and base flow related constants. Two storm water events were simulated by the model and compared with the corresponding observations. Good accuracy in predicting the runoff volume, peak flow, and the time to peak flow was achieved using the selected methods. The results of this study can be used as a useful tool for decision makers to determine a master plan for regional flood control management.

• Journal of Convergence for Information Technology
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• v.10 no.10
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• pp.40-46
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• 2020

With the development of the Internet, users share their experiences and opinions. Since related keywords are used witho0ut considering information such as the general emotion or genre of an unstructured document such as a movie review, the sensitivity accuracy according to the appropriate emotional situation is impaired. Therefore, we propose a system that predicts emotions based on information such as the genre to which the unstructured document created by users belongs or overall emotions. First, representative keyword related to emotion sets such as Joy, Anger, Fear, and Sadness are extracted from the unstructured document, and the normalized weights of the emotional feature words and information of the unstructured document are trained in a system that combines CNN and LSTM as a training set. Finally, by testing the refined words extracted through movie information, morpheme analyzer and n-gram, emoticons, and emojis, it was shown that the accuracy of emotion prediction using emotions and F-measure were improved. The proposed prediction system can predict sentiment appropriately according to the situation by avoiding the error of judging negative due to the use of sad words in sad movies and scary words in horror movies.