• Journal of Korean Society of Transportation
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• v.29 no.6
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• pp.97-106
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• 2011

Mode choice model is an essential element for estimating- the demand of new means of transportation in the planning stage as well as in the establishment phase. In general, current demand analysis model developed for the mode choice analysis applies common parameters of utility function in each region which causes inaccuracy in forecasting mode choice behavior. Several critical problems from using common parameters are: a common parameter set can not reflect different distribution of coefficient for travel time and travel cost by different population. Consequently, the resulting model fails to accurately explain policy variables such as travel time and travel cost. In particular, the nonlinear logit model applied to aggregation data is vulnerable to the aggregation error. The purpose of this paper is to consider the regional characteristics by adopting the parameters fitted to each area, so as to reduce prediction errors and enhance accuracy of the resulting mode choice model. In order to estimate parameter of each area, this study used Household Travel Survey Data of Metropolitan Transportation Authority. For the verification of the model, the value of time by marginal rate of substitution is evaluated and statistical test for resulting coefficients is also carried out. In order to crosscheck the applicability and reliability of the model, changes in mode choice are analyzed when Seoul subway line 9 is newly opened and the results are compared with those from the existing model developed without considering the regional characteristics.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.301-317
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• 2002

Recently, a geophysical exploration technology is frequently utilized in the civil engineering field as well as in the resource exploration. It might be important for civil engineers to understand the fundamental theory of seismic survey and limitation of the technique when utilizing these techniques in the civil engineering field. A 3-dimensional migration technique based on the principle of ellipsoid to predict the fractured zone ahead of tunnel face utilizing the tunnel seismic survey was proposed so that the geometry of the fractured zone can be estimated, i.e. the angle between tunnel axis and discontinuity zone, and the dip. Moreover, a numerical analysis technique to simulate the TSP (Tunnel Seismic Prediction) test was proposed in this paper. Based on parametric studies, the best element size, the analysis time step, and the dynamic characteristics of pressure source were suggested to guarantee the stability and accuracy of numerical solution. Example problems on a hypothetical site showed the possibility that the 3-dimensional migration technique proposed in this paper appropriately estimate the 3D-geometry of fractures ahead of tunnel face.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.618-626
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• 2017

This study was conducted to investigate the factors affecting depression in elementary school teachers. The research design was a descriptive study. Methods:Data were collected by questionnaires from 283 elementary school teachers. Data were analyzed using a t-test, ANOVA, a $Scheff{\acute{e}}$ test, correlation analysis, and multiple regression analysis. Results: The mean scores were 2.44, 3.07 and 3.68 out of 5 on Likert scales for burnout, job stress and ego-resiliency, respectively. The mean scores were 1.47 and 2.95 out of 4 on Likert scales for items of depression and job satisfaction, respectively. Teaching experience and class size affected depression significantly. There was a positive correlation between depression and burnout(r=0.465, p<.001), and between depression and job stress(r =.220, p<.001),while a negative correlation was observed between depression and job satisfaction(r=-.249, p<.001), and depression and ego-resiliency(r=-.643, p<.001). Multiple regression analysis showed that ego-resiliency(${\beta}=0.639$), job satisfaction(${\beta}=.141$), burnout(${\beta}=.094$), and job stress(${\beta}=.067$) affected depression in order and the four research variables led to a 42.7% prediction for depression among elementary school teachers. Conclusion: Based on the results of this study, a systematic plan for decreasing job stress and increasing eco-resilience is needed to improve depression among elementary school teachers.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.237-248
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• 2014

Linear cutting test is known to be very effective to determine machine parameters (i.e. thrust force and torque) and to estimate penetration rate of TBM and other operation conditions. Although the linear cutting test has significant advantages, the test is expensive and time-consuming because it requires large size specimen and high load capacity of the testing machine. Therefore, a few empirical prediction models (e.g. CSM, NTNU and QTBM) alternatively adopt laboratory index tests to estimate design parameters of TBM. This study discusses the estimation method of TBM machine parameters and disc cutter consumption using punch penetration test and Cerchar abrasion test of which the researches are rare. The cutter forces and cutter consumption can be estimated by the empirical models derived from the relationship between laboratory test result with field data and linear cutting test data. In addition, the estimation process was programmed through which the design parameters of TBM (e.g. thrust, torque, penetration rate, and cutter consumption) are automatically estimated using laboratory test results.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.12
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• pp.7635-7638
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• 2013

Background: Sperm-associated antigen 9 (SPAG9) has been recently proposed as a novel biomarker for early diagnosis of several human tumors, including ovarian, cervical and breast cancers. Its clinical value remains to be clarified for endometrial cancer (EC). In this study, we investigated the utility of serum SPAG9 levels in diagnosis of EC and its association with important clinicopathological parameters. Materials and Methods: This cross-sectional study was performed at a tertiary women's referral center in Ankara, Turkey. Preoperative serum samples were collected from patients surgically treated for endometrial cancer between June 2012-April 2013. Similar aged women with a biopsy proven benign endometrium were used as controls. Serum SPAG9 levels were measured with an enzyme-linked immunosorbent assay (ELISA) method and assessed for links with clinicopathological factors. Receiver operating characteristic (ROC) curve analysis was performed to assess power of SPAG9 levels for EC prediction. P values less than 0.05 were considered statistically significant. Results: A total of 63 women with EC and 27 with benign endometrium were included in the study. Mean age in the EC group was $58.7{\pm}1.1$. Median SPAG9 levels in the EC and control groups were 18.3 (range, 12.7-53.8) and 14.1 (range, 4.3-65.3), respectively (p<0.001). A cut-off value of 17 ng/ml for SPAG9 predicted presence of malignant endometrium with 74% sensitivity and 83% specificity [Area under curve (AUC)=0.82, p<0.001]. SPAG9 levels did not demonstrate any significant association with histological type, FIGO stage, tumor grade, size, myometrial invasion, lymphovascular space invasion, cervical involvement, adnexal involvement, peritoneal cytology or lymph node status (all p>0.05). Conclusions: Testing for SPAG9 may be useful for early detection of EC in asymptomatic high-risk women. Its role in post-treatment follow-up and early detection of recurrence should be assessed in future trials.

• Journal of Labour Economics
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• v.42 no.4
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• pp.1-29
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• 2019

This study estimates how changes in the female (aged 25 to 54) labor force participation rate (LFPR) following the historical experiences of the US and Japan would alter the future trend of the female economically active population by 2065, compared to the case in which the LFPR as of 2018 will remain unchanged. According to the results, the female labor force aged 25 to 54 will increase by 14% (about 797,000) and 15% (about 831,000), respectively, by 2042 if the female LFPR should change following the past trends of the US and Japan. In particular, the increase in the labor force is expected to be pronounced among females aged 30 to 44 who currently suffer high rates of job severance. The results of this study strengthen the prediction that the on-going population changes will not reduce much the overall economically active population in the near future. The result of a simulation based on the historical experiences of Japan suggests that, as least in the near future, policy efforts to encourage female labor supply will be more effective in alleviating the potential labor-market impacts of population changes, compared to policies aiming at increasing old-age employment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.347-350
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• 2018

In order for an IoT system to automatically make the house temperature pleasant for the user, the system needs to predict the optimal start-up time of air-conditioner or heater to get to the temperature that the user has set. Predicting the optimal start-up time is important because it prevents extra fee from the unnecessary operation of the air-conditioner and heater. This paper introduces an ANN(Artificial Neural Network) and an IoT system that predicts the cooling and heating time in households using air-conditioner and heater. Many variables such as house structure, house size, and external weather condition affect the cooling and heating. Out of the many variables, measurable variables such as house temperature, house humidity, outdoor temperature, outdoor humidity, wind speed, wind direction, and wind chill was used to create training data for constructing the model. After constructing the ANN model, an IoT system that uses the model was developed. The IoT system comprises of a main system powered by Raspberry Pi 3 and a mobile application powered by Android. The mobile's GPS sensor and an developed feature used to predict user's return.

• Water for future
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• v.29 no.5
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• pp.185-202
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• 1996

The newly-developed method for estimating the instream flow, proposed by the authors (1996), was applied to the main channel reach of the Kum River basin in Korea. Performance of the suggested method was tested through the evaluations of the required flow, instream flow, and river-management flow which were estimated at five main reaches with each representative station. The mean drought flow was used as the object flow to evaluate the minimum instream flow for the mid- and large-size rivers. Water quality prediction by using the QUAL2E model was made for both cases that the planned wastewater treatment facilities may and may not be constructed. The required flow for the fish habitat was evaluated for 9 representative fish species. The instream flows required for the riverine aesthetics at Kong-ju and Puyo scenary points, for river navigation at natural channel conditions, and for current and potential recreation activities were evaluated, respectively. The instream flows required for other items are not quantified. On the whole, it is shown that the instream flow to maintain the natural riverine functions such as fish habitat, and riverine aesthetics govern the upstream reaches of the Kum River, and the artificial riverine functions such as conservation of water quality, navigation and recreations govern the middle and downstream reaches. Especially, it is found that the instream flow requirement depends largely upon the construction of wastewater treatment facilities at the Kum River basin.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.93-101
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• 2017

This study investigate the effect of each type of search volume on the number of Facebook fans and the number of tourists. According to the hierarchy effect model, the effect of communication appears to be the sequentiality of cognition-attitude-behavior. Applying this theory, this study predicted that when consumers who have higher involvement and knowledge on specific cities through search behavior, they will be more active in information search through Facebook fan page subscription and will lead to direct tourism behavior. To verify the prediction, we examined the influences among search volume of Seoul shown in Google Trend, the number of fans of official facebook page named 'Seoul Korea', and the number of foreign tourists. As a result, the type of search keyword was divided into four categories: tourism attraction keyword, natural environment keyword, symbolic keyword, and accessibility keyword. The regression analysis showed that tourism attraction keyword and symbolic keyword have influence on Facebook fanpage 'Like'. In addition, facebook fanpage fan size have mediation effect between search volume and number of tourists. All in all, it would be useful to appeal to foreign tourists with a message that emphasizes tourism attraction and Korea-related contents.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.59-69
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• 2009

The prediction of pressure drop for a droplet flow in a confined micro channel is presented using FE-FTM (Finite Element - Front Tracking Method). A single droplet is passing through 5:1:5 contraction - straight narrow channel - expansion flow domain. The pressure drop is investigated especially when the droplet flows in the straight narrow channel. We explore the effects of droplet size, capillary number (Ca), viscosity ratio ($\chi$) between droplet and medium, and fluid elasticity represented by the Oldroyd-B constitutive model on the excess pressure drop (${\Delta}p^+$) against single phase flow. The tightly fitted droplets in the narrow channel are mainly considered in the range of $0.001{\leq}Ca{\leq}1$ and $0.01{\leq}{\chi}{\leq}100$. In Newtonian droplet/Newtonian medium, two characteristic features are observed. First, an approximate relation ${\Delta}p^+{\sim}{\chi}$ observed for ${\chi}{\geq}1$. The excess pressure drop necessary for droplet flow is roughly proportional to $\chi$. Second, ${\Delta}p^+$ seems inversely proportional to Ca, which is represented as ${\Delta}p^+{\sim}Ca^m$ with negative m irrespective of $\chi$. In addition, we observe that the film thickness (${\delta}_f$) between droplet interface and channel wall decreases with decreasing Ca, showing ${\delta}_f{\sim}Ca^n$ Can with positive n independent of $\chi$. Consequently, the excess pressure drop (${\Delta}p^+$) is strongly dependent on the film thickness (${\delta}_f$). The droplets larger than the channel width show enhancement of ${\Delta}p^+$, whereas the smaller droplets show no significant change in ${\Delta}p^+$. Also, the droplet deformation in the narrow channel is affected by the flow history of the contraction flow at the entrance region, but rather surprisingly ${\Delta}p^+$ is not affected by this flow history. Instead, ${\Delta}p^+$ is more dependent on ${\delta}_f$ irrespective of the droplet shape. As for the effect of fluid elasticity, an increase in ${\delta}_f$ induced by the normal stress difference in viscoelastic medium results in a drastic reduction of ${\Delta}p^+$.