• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.231-241
• /
• 2005

Laboratory experiments were performed to examine the effects of water content and to see if permittivity had sufficient sensitivity to identify subsurface contamination. Both real and imaginary permittivities of unsaturated sand were strongly governed by the volumetric water content. Especially, a linear relationship between real permittivity and volumetric water content was derived at high frequencies (MHz ranges). Heavy metals in pore fluid result in significant increases in the effective imaginary permittivity, due to ionic conduction, but decreases in the real permittivity arises due to the decreased orientational polarization of water molecules caused by hydration of ions. Clear increase in the effective imaginary permittivity with heavy metal concentration was found to be valuable in the application of electrical methods for detecting heavy metals in the subsurface. However, because the permittivity is primarily dependent on the volumetric water content of soil, pre-evaluation on the volumetric water content is required.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.6
• /
• pp.17-24
• /
• 2018

In this study, static load test and dynamic load test were performed to evaluate pile-filling material (ZA-Soil) of soil-cement injected precast pile method which was developed by using the ash of circulating fluidized boiler as a stimulant for alkali activation reaction of blast furnace slag. As a result of the static load test, the allowable bearing capacity of pile was 1,350 kN, which was the same as the result of using ordinary portland cement. And total settlement was 6.97 mm, and net settlement was 1.48 mm. These are similar to the total settlement, 7.825 mm, and net settlement, 2.005 mm of ordinary portland cement. As a result of the dynamic load test and CAPWAP analysis, the skin friction was 375.0 kN, the end bearing capacity was 3,045.9 kN, and the allowable bearing capacity was 1,368.36 kN. These results are similar to the results of using ordinary portland cement as pile-filling material.

• Journal of Korean Home Economics Education Association
• /
• v.20 no.2
• /
• pp.61-73
• /
• 2008

The purpose of this study was to improve interest and attitude of student's Technology-Home Economics Curriculum and to recognize the change of recognition on Traditional image through Natural Dyeing and Jogakbo making on the unit of making living goods with fabrics in Technology-Home Economics curriculum on first year high school. The abridged result of study following this: First, in Natural Dyeing and Jogakbo making, teaching-learning plan applying LT cooperative studying and learning materials have been developed. Second, after applying the developed lesson plan, the result showed that the change in learning interest and attitude about Technology-Home Economics curriculum was positively improved. After executing the class on Natural Dyeing and Jogakbo making, the interest and concern about tradition were very positively upgraded through the result analyzing the change of recognition on traditional image. Through these results, The Teaching-learning plan and learning materials would show high possibility of application as educational contents about traditional culture in the field of education. After executing the class on making of Natural dyeing and Jogakbo, the learning interest degree and attitude was very positively upgraded, and the recognition on traditional image had been changed to the active and positive recognition.

• Journal of the Korean Institute of Gas
• /
• v.21 no.2
• /
• pp.41-49
• /
• 2017

Recently, as the number of facilities using chemicals is increasing, the amount of handling is rapidly increasing. However, chemical spills are occurring steadily, and if large quantities of chemicals are leaked in time, they are likely to cause major damage. These industrial complexes use information obtained from a number of sensors to detect and monitor leaking areas, and are used in industrial fields by applying existing fixed sensors to robots and drones. Therefore, it is necessary to propose a sensor placement method at the interface for rapid detection and response based on various leaking scenarios reflecting leaking conditions and environmental conditions of the chemical handling process. In this study, COMSOL was used to analyze the actual accident scenarios by applying the medium parameter to the case of chemical leaks. Based on the accident scenarios, the objective function is selected so that the velocity of each robot is calculated by attaching importance to each item of sensor detection probability, sensing time and sensing scenario number. We also confirmed the feasibility of this method of reliability analysis for unexpected leak accidents. Based on the above results, it is expected that it will be helpful to trace back the leakage source based on the concentration data of the portable sensor to be applied later.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.559-562
• /
• 2017

In city, tracing of power transmission lines is difficult due to compound installation of overhead and underground lines, transposition, bad view caused by trees or big buildings. It is hard problem for electrical technician on site to trace power transformers or power lines to serve customers in 3 phase -4 wires power distribution systems. It is necessary that the correct and fast tracing method is required for load balancing among distribution lines. Old technology use to trace off-lines with high power impulse injection. Our proposed method use to trace live lines with very small power high frequency signal injection. Typical power transformers in the distribution system prevent propagating the higher frequency carrier signal. The proposed method uses the limited propagation ability to identify the power transformer to serve customers. Two end communication terminals are required to be synchronized between them for determination on electrically same phases. Challenging issue is to achieve synchronization without GPS providing synchronizing time. A novel power transformer and wire identification system is designed and implemented. The system consists of a transmitter and a receiver with power-line communication module. Some experiments are conducted to verify the theoretical concepts in a big commercial building. Also some simulations are done to help and understand the concepts by using MATLAB Simulink simulator.

• The KIPS Transactions:PartD
• /
• v.15D no.6
• /
• pp.793-802
• /
• 2008

The development methods which utilize OSSs have been tried as new alternative to solve limits of the previous software developments such as the quality of software, and time and cost of developments. Especially, small and medium companies are suffering from difficulty in applying large-scale development methodology whenever they develop softwares. Therefore, in the current situation that demand for small-scale development methodology is increasing, the methods of utilizing OSSs can become an efficient way to save costs and reduce a development period. Accordingly, analysis of open-source is no fixed procedure or method to utilize open-source for software developments in the field. In this thesis, to solve such problems, we propose the procedures and methods for identifying and selecting suitable open-source, and effective methods for improvement and integration through least modification on the basis of synthesis of existing researches and experiences in development projects. For selection of OSSs, we did identify correct requirements for the software to be developed, investigate the open-source just matching with such requirements, draw a candidate index, establish assessment criteria, and the consequently present a method to select OSSs. And, we deduced the validity and improvement of each detailed activity from practical application to an actual project and assessment.

• KDI Journal of Economic Policy
• /
• v.36 no.3
• /
• pp.121-168
• /
• 2014

After analyzing and finding the explaining factors about the "Effect of My Mom's Friend's Son (MMFS Effect)" with online-surveyed data, we introduce this concept into the conventional job search theory to develop it further. We try to estimate its effects on the hazard rate of youth pre-employment duration with some proxy variables such as his/her parents' schooling, living with parents dummy, increasing rate of consumer price index representing the burdens of parents, monthly temporary/daily workers ratio, relative ratio of quarterly 90th percentile urban household income, monthly average wage differentials between the workers of large and small firms, etc. The results confirm us the fact that so called "MMFS Effect" has been effective enough and strengthened up to recently. The conventional job search theory should be extended to be able to introduce the influencing effects of other person's success, for instance MMFS's success, on the job search behavior of youths, too.

• Korean Journal of Environment and Ecology
• /
• v.26 no.1
• /
• pp.113-124
• /
• 2012

The purpose of this study is to analyze community members' perception due to impacts on use and development of Dulegil in Bukhansan National Park. The study was conducted by questionnaire survey sent to community members of the vicinity of Dulegil. Average score of positive impact on the local community was 3.2. Positive impacts mentioned by community members were 'heightened pride in their community with increased community image' and 'improvement of landscape and natural environment.' Improved residents' awareness of landscape and natural environment indicated that Dulegil almost accomplished intended goal of preservation of ecosystem. However, actual effects on ecosystem preservation and local economy were not perceptible yet. Score of negative impact was 2.8 on average. 'Traffic congestion' and 'increase in noise level' were considered the most serious among the negative impacts. Environmental pollution and destruction of vegetation in the lowland were deemed relatively bad. Regarding resident awareness of community, those in their 50s and older were quite satisfied with the community. However, young people showed lower level of satisfaction. In order to satisfy all ages, infrastructure and programs for the youth should be in place. To minimize negative awareness of impacts of Dulegil, visitor's attitude should be changed, and education and training on the value and mind set of horizontal hiking are required.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.1
• /
• pp.83-91
• /
• 2017

In case of estimation of settlement for the piled-raft foundation, it is necessary to consider interaction among raft, piles and soil. But, simple analytic methods usually are not applicable to considering this complicated interaction. In this study, a computer-based approximate analytic method, HDPR, was developed in consideration of above mentioned interaction in order to analysis of settlement for the piled-raft foundation. The finite element method was applied to raft analysis by means of the Mindlin plate theory, and soil and piles were modeled as springs which were connected with their raft. The linear spring which can consider multi layered soil and the non-linear spring were applied to soil springs and pile springs, respectively. The raft-piles-soil interaction was reflected to each spring. In order to verify the developed analytic method, it was compared and analyzed with 3D FEM analysis, existing approximate analytic method and site monitoring data. As a result, the developed analytic method showed reasonable results of settlement estimations of raft and piles for each case. From a practical point of view, it is confirmed that this analytic method is able to apply for analysis and design of the piled-raft foundation.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.6
• /
• pp.959-972
• /
• 2017

In evaluation of blast-induced vibration, peak particle velocity (PPV) is generally calculated by using attenuation relation curve. Calculated velocity is compared with the value in legal requirements or the standards to determine the stability. Attenuation relation curve varies depending on frequency of test blasting, geological structure of the site and blasting condition, so it is difficult to predict accurately using such an equation. Since PPV is response value from the ground, direct evaluation of the structure is impractical. Because of such a limit, engineers tend to use the commercial numerical analysis program in evaluating the stability of the structure more accurately. However, when simulate the explosion process using existing numerical analysis program, it's never easy to accurately simulate the complex conditions (fracture, crushing, cracks and plastic deformation) around blasting hole. For simulating such a process, the range for modelling will be limited due to the maximum node count and it requires extended calculation time as well. Thus, this study is intended to simulate the elastic energy after fractured zone only, instead of simulating the complex conditions of the rock that results from the blast, and the analysis of response characteristics of the velocity depending on shape and size of the fractured zone was conducted. As a result, difference in velocity and attenuation character were calculated depending on fractured zone around the blast source appeared. Propagation of vibration tended to spread spherically as it is distanced farther from the blast source.