• Journal of the Korean Geotechnical Society
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• v.25 no.11
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• pp.27-38
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• 2009

In this study, a series of 1 g shaking table model pile tests were carried out in saturated dense and loose sand to evaluate dynamic p-y curves for various conditions of flexural stiffness of a pile shaft, acceleration frequency and acceleration amplitude for input loads. Dynamic p-y backbone curve which can be applied to pseudo static analysis for saturated dense sand was proposed as a hyperbolic function by connecting the peak points of the experimental p-y curves, which corresponded to maximum soil resistances. In order to represent the backbone curve numerically, empirical equations were developed for the initial stiffness ($k_{ini}$) and the ultimate capacity ($p_u$) of soils as a function of a friction angle and a confining stress. The applicability of a p-y backbone curve was evaluated based on the centrifuge test results of other researchers cited in literature, and this suggested backbone curve was also compared with the currently available p-y curves. And also, the scaling factor ($S_F$) to account for the degradation of soil resistance according to the excess pore pressure was developed from the results of saturated loose sand.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.5-13
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• 2008

Laboratory model test with soft silty ground (ML) and polluted silty ground with wastewater and factory waste oil ($ML_p$) was conducted and the applicability of changes of bearing capacity from the increase of pollutants was compared and analyzed with existing findings. As silty ground polluted with wastewater and factory waste oil had increased contents of pollutants, plasticization of ground was fostered compared to soft silt ground due to the influence of pollutants, and characteristics of ground strength decreased. Critical surcharge value of soft silty ground $q_{cr}=4.14c_u$, ultimate bearing capacity value $q_{ult}=9.53c_u$, critical surcharge value of silty ground polluted with wastewater and factory waste oil $q_{cr}=1.78c_u$ and ultimate bearing capacity value $q_{ult}=4.39c_u$. Critical surcharge and ultimate bearing capacity of silty ground polluted with wastewater and factory waste oil were less than those of soft silty ground. It meant that shearing resistance due to the increase of pollutants decreased and rather a smaller value was obtained.

• Geophysics and Geophysical Exploration
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• v.25 no.4
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• pp.189-200
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• 2022

Ground subsidence on urban roads is a social issue that can lead to human and property damages. Therefore, it is crucial to detect underground cavities in advance and repair them. Underground cavity detection is mainly performed using ground penetrating radar (GPR) surveys. This process is time-consuming, as a massive amount of GPR data needs to be interpreted, and the results vary depending on the skills and subjectivity of experts. To address these problems, researchers have studied automation and quantification techniques for GPR data interpretation, and recent studies have focused on deep learning-based interpretation techniques. In this study, we described a hyperbolic event detection process based on deep learning for GPR data interpretation. To demonstrate this process, we implemented a series of algorithms introduced in the preexisting research step by step. First, a deep learning-based YOLOv3 object detection model was applied to automatically detect hyperbolic signals. Subsequently, only hyperbolic signals were extracted using the column-connection clustering (C3) algorithm. Finally, the horizontal locations of the underground cavities were determined using regression analysis. The hyperbolic event detection using the YOLOv3 object detection technique achieved 84% precision and a recall score of 92% based on AP50. The predicted horizontal locations of the four underground cavities were approximately 0.12 ~ 0.36 m away from their actual locations. Thus, we confirmed that the existing deep learning-based interpretation technique is reliable with regard to detecting the hyperbolic patterns indicating underground cavities.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.6
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• pp.621-634
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• 2017

This study is a study on the requirements, resources, and role of policy broker in the policy process. Particular attention was paid to two requirements of legitimacy (official authority, political support) and professionalism (information and expertise, skilled leadership) as the requirements of policy broker. This study analyzed the process of transforming the actor conflicts surrounding the media rep legislative process into a cooperative relationship by being mediated by a strong influential policy broker. Policy brokers can mediate opinions among participating actors and play a role in coordinating conflicting interests. In the mediarep policy process, the policy brokers were unable to resolve conflicts due to lack of legitimacy and expertise in the first phase (legislative grace period) and the second phase (legislative loophole). However, the legitimacy of the six subcommittees of the National Assembly (the legislative period) and the expertise of the Korea Communications Commission were able to succeed in policy-making by acting as a successful policy brokers through complementary activities.

• 한국체육학회지인문사회과학편
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• v.55 no.3
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• pp.43-57
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• 2016

This narrative study aims to describe the experience of P.E. assessment that was conducted by P.E. teachers of Korea Science Academy of KAIST, and interpret the educational significance that was found in the process. The study participants were two P.E. teachers who were selected by decisive case sampling method. Data were collected mainly through official interviews with study participants, and through researcher's field notes, informal interviews, various minutes, students' evaluation of teaching, and emails between the researcher and study participants. Data were analyzed through inductive categorization, and to gain veracity of the study, there were integration of diverse materials, advice and suggestions of fellow researchers, continuous confirmation of study texts by study participants. Study participants, while conducting P.E. assessment in Korea Science Academy of KAIST, experienced effectiveness of evaluation such as qualitative development of P,E. classes in accordance with the simplified assessment, freedom from the chores of handling assessment results, students' improved perceptions of P.E. class, realization of safe classes without excessive competition, and the possibility of giving alternative evaluations to pass/fail system but at the same time experienced limitations such as concerns over gaining validity and reliability of P.E. evaluation, the students' attitude who take lightly of P.E. class, and the reality that teachers cannot fail students. The evaluation experiences of the two P.E teachers were educationally interpreted as encounter with good P.E. classes, invitation to P.E. class criticism, and the start of school P.E. culture that is led by students.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6D
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• pp.737-743
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• 2009

Shield TBM, since it was employed for Suyoungman Bay riverbed tunnel of Busan Subway in 2000,has been increasingly adopted in Korea, and in line with growing popularity, the study on Shield TBM has been expanded. However the studies mostly focus on ground condition in a bid to estimate the advancement rate and develop the model for calculating the excavation efficiency, whereas the efforts to analyze the cause of delay and to develop the improvement measures have been neglected. Thus the studies were mostly intended to analyze the schedule slippage focusing on ground conditions, while the study on schedule behind due to equipment itself and related facilities have yet to be attempted in earnest. This study hence was aimed at evaluating the troubles and schedule slippage caused by mechanical elements such as shield TBM equipment and tools and ground conditions, making use of FMEA approach so as to analyze the risk of schedule delay by such elements, thereby proposing the preventive measures to deal with high-risk factors. So, this study suggest the solution to highly ranked trouble factor for the purpose of enhance the efficiency on Shield TBM.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.91-101
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• 2023

In this study, we estimated the concentration of chlorophyll-a (Chl-a) using hyperspectral water surface reflectance in an inland weir (Baekjae weir) and estuarine reservoir (Namyang Reservoir) for monitoring the occurrence of algae in freshwater in South Korea. The hyperspectral reflectance was measured by aircraft in Baekjae Weir (BJW) from 2016 to 2017, and a drone in Namyang Reservoir (NYR) from 2020 to 2021. The 30 reflectance bands (BJW: 400-530, 620-680, 710-730, 760-790 nm, NYR: 400-430, 655-680, 740-800 nm) that were highly related to Chl-a concentration were selected using permutation importance. Artificial neural network based Chl-a estimation model was developed using the selected reflectance in both water bodies. And the performance of the model was evaluated with the coefficient of determination (R²), the root mean square error (RMSE), and the mean absolute error (MAE). The performance evaluation results of the Chl-a estimation model for each watershed was R²: 0.63, 0.82, RMSE: 9.67, 6.99, and MAE: 11.25, 8.48, respectively. The developed Chl-a model of this study may be used as foundation tool for the optimal management of freshwater algal blooms in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.179-186
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• 2008

Pressuremeter test estimates the deformational properties of soil from the relationship between applied pressure and the displacement of cavity wall. It is general to utilize the reloading curve for the estimation of deformational properties of soil because the initial loading curve can be affected by the disturbance caused by boring. On the other hand, the instrumental resolution or the variation of measured data makes it hard to estimate the maximum shear modulus from pressuremeter test results. This study suggested the methodology estimating the maximum shear modulus from pressuremeter test directly, based on the curve fitting of reloading curve. In addition, the difference was taken into account between the stress state around the probe in reloading and that of the in-situ state. Pressuremeter tests were conducted for 15 cases using a large calibration chamber, together with a number of reference tests. The maximum shear moduli taken from suggested method were compared with those from empirical correlation and bender element test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.537-548
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• 2008

Recently, the prestressed unbonded concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with unbonded tendon is different from that of normal bonded PSC beams in that the increment of tendon stress was derived by whole member behavior. The purpose of the present paper is therefore to evaluate the flexural behavior and to propose the equation of ultimate tendon stress by performing static flexural test according to span/depth, concrete compression strength, reinforcement ratio and the effect of existing bonded tendon. From experimental results, for cracking, yielding and ultimate load, the effect of reinforcement ratio was more effective than concrete compression strength, and the beams having high strength concrete had a good performance than having low concrete, but there was no difference between high strength and low strength. And as L/dp was larger, test beams had a long region of ductility. This means that unbonded tendon has a large contribution after reinforcement yielding. Especially, the equation of ACI-318 was not match with test results and had no correlations. After analysis of test results, the equation of ultimate unbonded tendon stress without slip was proposed, and the proposed equation was well matched with test results. So the proposed equation in this paper will be a effective basis for the evaluation of unbonded tendons without slip, analysis and design.

• Issues in Feminism
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• v.10 no.1
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• pp.123-158
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• 2010

For the last several months, abortion debates have sparkled in Korea. The government has escalated the need of active punishment of illegal abortions to solve low fertility problems, while some obstetricians and gynecologist have proclaimed stoppage of illegal abortions suing colleague doctors who has conducted illegal abortions. Women's rights groups and researchers have also responded to the abortion debate claiming that women's decisions over their pregnancy are important in making of abortion policies. To contribute to Korean abortion debates, his paper aims to analyze European experiences of abortion polices in relation to the consequences on women's health. For the analysis of European abortion experiences, three countries - Ireland, U.K, and Netherland -are chosen. These three countries are selected since their legal and social acceptance of abortion and the level of safe abortion system are different. Each country is reviewed by national abortion policy, legal regulation, medical system and the role of civil society. The analysis shows several implications for abortion debates occurring in Korea. Various systematic policy mechanisms - abortion on women' request, abortions without complicated doctor's referrals, transparent and anonymous counseling and information provision regarding abortion, training and education for medical professionals to guarantee high quality abortion, abortions funded publicly for women to improve their access to abortions, steady monitoring and auditing abortion procedures and outcomes for safe abortion and so on - are required in Korean society. Two track procedures - safe abortion on women's request and prevention of unwanted pregnancy - are needed for reproduction of healthy women and society.