• International Journal of Highway Engineering
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• v.9 no.4
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• pp.1-9
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• 2007

To decide the number of road lane is very important and related to the 30th design hourly factor in the design of transportation facilities. But, as the quantitative division of road types is difficult, most planner and designer for deciding the 30th design hourly factors have used the fixed values in our country. In this study, we have analyzed the time series property of the design hourly factors in national highways and developed the model capable of estimating the 30th design hourly factors using real data. The presented model is a simple regression model(DHV = K*AADT), which is applied to the division of road lanes(2 or 4 lanes) and the level of AADT(3 levels). As a results, the simple regression model have better performance than the existing method with respect to MAPE and $R^2$. Also, the variations of the 30th design hourly factors are small. The more traffic volume increase, the more the factors decrease. But, the limitation of this study is to use the exiting method estimating the values of the factors, it is subject to study hereafter.

• The Korean Journal of Applied Statistics
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• v.6 no.2
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• pp.201-215
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• 1993

The health status of workers in a foundry was analyzed in a study which consisted of evaluations of respiratory health together with environmental measurements. The results from environmental measurements showed values exceeding permissible exposure limits. A t-test was done with log transformed and untransformed data to examine the statistical significance for the noncompliance with exposure standards. For the analysis of categorical health outcomes, $\chi$-square test with 2 $\times$ 2 tables and logistic regression analysis were employed. For continuous variables, multiple linear regression was done against assessed risk factors. Pros and cons of different parameters in the compliance (or noncompliance) testing were presented. Respiratory function did not show any relation with occupational exposures, which may be due to the healthy worker effects. Strategies for controlling time dependent covariates were discussed in relation to the healthy worker effect. The scope of statistical analysis in occupational health studies is still limited in Korea without a suitable external comparison group such as credible vital statistics for the whole nation. Internal comparisons between different exposure status often result in unstable estimates of effect, and proportional morbidity study is discussed as an alternative potential research tool.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.167-167
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• 2010

반도체는 도핑하지 않으면 대부분 n형을 나타내는 것에 반하여 GaSb는 p형을 보이는 반도체로서, 그 근원은 명확하게 규명되어 있지 않은 상태이다. GaSb의 p형 불순물인 Be은 Ga과 치환 ([$Be_{Ga}$])되므로, p형 전도의 근원으로 추정되는 잔존결함인 [$Ga_{Sb}$]와 그 복합체인 [$Ga_{Sb}-Sb_{Ga}$]와 높은 상관관계를 가질 것으로 예측된다. 본 연구에서는 Be을 도핑한 GaSb:Be 에피층을 MBE 방법으로 성장하여, PL 스펙트럼과 Hall 효과 분석을 통하여 p형 전도의 근원을 조사하였다. 도핑하지 않은 u-GaSb는 DA (deep acceptor)와 함께 A 준위를 나타낸 반면, p-GaSb:Be의 PL 스펙트럼은 Be 도핑농도가 증가함에 따라 FWHM가 줄어들면서 점차 높은 에너지 영역으로 변위하지만 농도가 가장 높은 시료에서는 PL의 FWHM가 증가하면서 에너지는 감소함이 관측되었는데, 이것은 A 피크와 Sb 관련 피크가 경쟁적으로 중첩되어 나타난 현상으로 분석된다. Hall 효과 결과는 유효 전하밀도의 증가에 따라 이동도는 감소하는 전형적인 의존성을 나타내었으며, u-GaSb의 Hall 이동도가 p-GaSb:Be의 값보다 작은 것은 u-GaSb에 잔존하는 DA에 의한 산란 때문으로 해석된다. Gaussian 형태로 분해하여 얻은 A ([$Ga_{Sb}$])와 DA ([$Ga_{Sb}-Sb_{Ga}$]) 및 Be 관련 피크로부터 특정 도핑농도 ($1.2{\times}10^{17}cm^{-3}$)의 시료를 제외한 모든 p-GaSb:Be에는 A 피크가 중첩되고 A와 Be 준위 중간에 Be과의 복합체인 중간상태(intermediate state)인 [$Be^*$]가 존재함이 관측되었는데, 특정 도핑농도에서는 [$Be_{Ga}$]이 우세하지만 더 이상 농도가 증가하면 [$Be_{Ga}$] 준위의 강도는 오히려 감소함을 관측할 수 있었다. 이것은 적정 이상의 Be을 도핑할 경우, A ([$Be_{Ga}$])와 $Be^*([Be_{Ga}-Ga_Sb}])$가 형성 ($A[Ga_{Sb}]+Be{\rightarrow}Be^*[Be_{Ga}-Ga_{Sb}]+[Be_{Ga}]$)됨을 보여 주는 중요한 결과인 것으로 분석된다. A, [Be], [$Be^*$] PL 피크 에너지는 각각 779, 787, 794 meV (오차범위 ${\pm}3\;meV$)이고, [$Be_{Ga}$]의 활성화 에너지는 ($23{\pm}3\;meV$) (20 K)임을 밝혔다.

• Korean Journal of Remote Sensing
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• v.24 no.2
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• pp.99-106
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• 2008

A synthetic aperture radar (SAR) system is of great interest in many fields of civil and military applications because of all-weather and luminance free imaging capability. SAR image quality parameters such as spatial resolution, peak to sidelobe ratio (PSLR), and integrated sidelobe ratio (ISLR) can be normally estimated by modeling of impulse response function (IRF) which is obtained from various system design parameters such as altitude, operational frequency, PRF, etc. In modeling of IRF, however, background clutter environment surrounding the IRF is generally neglected. In this paper, analysis method for SAR mage quality is proposed in the real background clutter environment. First of all, SAR raw data of a point scatterer is generated based on various system parameters. Secondly, the generated raw data can be focused to ideal IRF by range Doppler algorithm (RDA). Finally, background clutter obtained from image of currently operating SAR system is applied to IRF. In addition, image quality is precisely analyzed by zooming and interpolation method for effective extraction of IRF, and then the effect of proposed methodology is presented with several simulation results under the assumption of estimation error of Doppler rate.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.507-518
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• 2006

The radiation at $11{\mu}m$ absorbed more than at $12{\mu}m$ when aerosols is loaded in the atmosphere, whereas it will be the other way around when cloud is present. The difference of the two channels provides an opportunity to detect aerosols such as Yellow Sand even with the presence of clouds and at night. However problems associated with this approach arise because the difference can be affected by various atmospheric and surface conditions. In this paper, we has analyzed how the threshold and sensitivity of the brightness temperature difference between two channel (BTD) vary with respect to the conditions in detail. The important finding is that the threshold value for the BTD distinguishing between aerosols and cloud is $0.8^{\circ}K$ with the US standard atmosphere, which is greater than the typical value of $0^{\circ}K$. The threshold and sensitivity studies for the BTD show that solar zenith angle, aerosols altitude, surface reflectivity, and atmospheric temperature profile marginally affect the BTD. However, satellite zenith angle, surface temperature along with emissivity, and vertical profile of water vapor are strongly influencing on the BTD, which is as much as of about 50%. These results strongly suggest that the aerosol retrieval with the BTD method must be cautious and the outcomes must be carefully calibrated with respect to the sources of the error.

• Korean Journal of Social Welfare Studies
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• v.49 no.4
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• pp.65-100
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• 2018

Korean Youth are facing diverse problems. For-instance Korean youth are even called '7 given-up generation' which indicates that they gave up marriage, giving birth, social relationship, housing, dream and the hope. From this point, the study concludes that the influential factors of the alcohol problems of youth should be studied based on the eco social perspectives. And it adopted data-mining methods, using SAS-Enterprise Miner for the analysis, targeting 2538 youths. Specifically, the study analyzed and chose the most predictable model using decision tree analysis, artificial neural network and logistic analysis. As the result, the study found that gender, age, smoking, spouse, family-number, jobsearching and economic participation are statistically significant determinants of alcohol problems of youth. Precisely, those who are male, younger, have the spouse, have less family number, searching jobs, have more income and have the job were more prone to have the alcohol problems. Based on the result, this study proposed the addiction problems targeting youth and etc. and expect to have the contribution on implementing procedures for the alcohol problems.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.303-314
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• 2019

Surface permeability and shallow geological structures play significant roles in shaping the groundwater recharge of shallow aquifers. Surface permeability can be characterized by two concepts, intrinsic permeability and hydraulic conductivity, with the latter obtained from previous near-surface geological investigations. Here we propose a hydraulic equation via the cross-correlation analysis of the rainfall-groundwater levels using a regression equation that is based on the cross-correlation between the grain size distribution curve for unconsolidated sediments and the rainfall-groundwater levels measured in the Gyeongju area, Korea, and discuss its application by comparing these results to field-based aquifer test results. The maximum cross-correlation equation between the hydraulic conductivity derived from Zunker's observation equation in a sandy alluvial aquifer and the rainfall-groundwater levels increases as a natural logarithmic function with high correlation coefficients (0.95). A 2.83% difference between the field-based aquifer test and root mean square error is observed when this regression equation is applied to the other observation wells. Therefore, rainfall-groundwater level monitoring data as well as aquifer test are very useful in estimating hydraulic conductivity.

• Korea journal of population studies
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• v.9 no.2
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• pp.93-105
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• 1986

The historical study reveals that our ancestors had maintained a system which could produce data on the number of population and households as well as on their characteristics. For example, such data on age structure of the population, number of births, number of deaths by age & sex, number of in & out migrants were found in an historical document for the year 755. The main purposes of maintaining the system at that time were taxation and conscription. As the system evolves, another function of identifying the legal status of people was also added. Looking into the figures for those days reveals that ommission rates of the number of population and households were high. Thus, in an effort to obtain a reliable data, the annual population survey system was introduced as of 1 September 1896. This date is now cerebrated as the Statistics Day. Since then, the survey system has been diversified. At the present time, there are three major data sources which produce the statistics on population and households: Civil Registration System (vital statistics), Resident Registratiton System (migration statistics) and Population Census. However, these three systems are found to have some problems to produce the accurate data. There are some inherent problems in the registration systems such as problems in its coverage, accuracies in contents and timeliness in reporting the vital events and publishing the results. The population census has also non-sampling errors such as errors in coverage, response and non-response. Apart from the above mentioned problems, there are also conflicting problems arised from having different three data source. We can find some overlapping problems in laws and difficulties in comparative studies between regions. In the future, these problems should be taken into consideration for the improvement of the quality of statistics on population and households.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.1
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• pp.93-102
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• 2019

In this study, in order to analyze the possibility of observing a typhoon track based on the Global Navigation Satellite System(GNSS), Typhoon NARI, the 11th typhoon of 2007, was analyzed in terms of the typhoon track as well as the local variation of perceptible water over time. The perceptible water was estimated using data obtained from observatories located on the typhoon track from Jeju to the southern coast of Korea for a total of 18 days from September 7(DOY 250) to September 24(DOY 267), 2007, including the period when the observatories were affected by the typhoon at full-scale, as well as one previous week and one following week. The results show that the trend of the variation of perceptible water was similar between the observatories near the typhoon track. Variation of perceptible water over time depending on the development and landing of the typhoon was distinctively observed. Several hours after the daily maximum of perceptible water was found at the JEJU Observatory, the first struck by the typhoon on the typhoon track, the maximum value was found at other observatories located on the southern coast. In the observation period, the time point at which the maximum perceptible water was recorded in each location was almost the same as the time point at which the typhoon landed at the location. To analyze the accuracy of the GNSS-based perceptible water measurement, the data were compared with radiosonde-based perceptible water data. The mean error was 0.0cm, and the root mean square error and the standard deviation were both 0.3cm, indicating that the GNSS-based perceptible water data were highly accurate and precise. The results of the this study show that the GNSS-based perceptible water data may be used as highly accurate information for the analysis of typhoon tracks over time.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1229-1235
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• 2018

We have examined dynamic relationships among water-efficiency, economic growth, electricity generation, and $CO_2$ emissions in Korea using various time-series analysis methods for 1990-2014. While previous studies have been limited to economic growth, $CO_2$ emissions, and electricity generation, this study contributed to explain the relationship between existing variables and water-efficiency. We find that the four variables reach a balanced state in the long run through short-term adjustment, $CO_2$ emissions and economic growth are responsible for water efficiency, and that $CO_2$ emissions, economic growth and water efficiency are the causes of electricity generation. The long-term impact coefficient estimates on water-efficiency show that the increase in electricity generation and the decrease in $CO_2$ emissions increase water-efficiency. Although economic growth has increased water-efficiency, moreover, we have identified an inverted U-shaped relationship between economic growth and water-efficiency, which suggests that economic growth above a certain level reduces the rate of increase in water-efficiency.