• Tunnel and Underground Space
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• v.6 no.1
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• pp.19-29
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• 1996

Back analysis model, capable of calculating the mechanical properties and the in-situ stresses of jointed rock mass, was developed based on the inverse method using a continuum theory. Constitutive equation for the behavior of jointed rock contains two unknown parameters, elastic modulus of intact rock and stiffness of joint, hence algorithm which determines both parameters simultaneously cannot be established. To avoid algebraic difficulties elastic modulus of intact rock was assumed to be known, since the representative value of which would be quite easily determined. Then, the ratio ($\beta$) of joint stiffness to elastic modulus of intact rock was assigned and back analysis for the behavior of jointed rock was carried-out. The value $\beta$ was repeatedly modified until the elastic modulus from back analysis became very comparable to the predetermined value. The joint stiffness could be calculated by multipling the ratio $\beta$ to the final result of elastic modulus. Accuracy and reliability of back analysis procedure was successfully testified using a sample model simulating the underground opening in the jointed rock mass. Applicability of back analysis model for the underground excavation in practice was also verified by analyzing the mechanical properties of jointed rock in which underground oil storage cavern were under construction.

• Tunnel and Underground Space
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• v.6 no.3
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• pp.209-222
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• 1996

Shut-in pressure, reopenting pressure and fracture orientation are very important parameters to be evaluated precisely in in-situ stress measurement by hydraulic fracturing. Graphical methods on pressure-time curves have been conventionally used, even though these are seriously dependent on subjectivity of interpreters. So there have been many demands on new method to objectivity in determining parameters. We have developed integrated hydrofracturing data processing program (HYDFRAC), based on nonlinear regression analysis and can be invoked under the Window graphical user interface. HYDFRAC consiste of three routines, that is shut-in pressure routine, reopening pressure routine, and fracture delineation routine. Each of routines include independent modules according to parameter determination methods. Its application to field tests ensured both objectivity and facility in determining of hydraulic fracturing parameters. Determining shut-in pressures at each pressurization cycles, we adopted the exponential pressure-decay method(EPD method), the bilinear pressure-decay-rate method (PDR method), and the tangent intersection method in order to find the pressurization-cyclic tendency of shut-in pressures. The estimated pressure by PDR method exists in the range of the upper and lower values by EPD method, and lies near to the upper value more than the lower. Being the pressurization cycle increased, the range of upper and lower limits come to be stabilized gradually. By graphical superposition method and bilinear pressure-accumulated volume method, reopening pressures were determined. Vertical and inclined fracture attitudes were determined by applying the directional statistics and sinusoidal curve fitting, respectively. The results of evaluation of hydrofracturing parameters showed that statistical methods could enhance the objectivity better than graphical methods.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.28-31
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• 2018

이 연구에서는 효율적인 입, 출금 관리를 위해 기존 어플리케이션들의 불편함을 개선한 '입, 출금 관리시스템을 설계 및 구현하였다. 기존 출납관리 어플리케이션은 모든 내역을 사용자가 직접 입력하고 관리하는 방식으로 구현되어 있어서, 다수의 수입, 지출, 이체내역을 직접 입력해야하기 때문에 불편함과 오류들이 발생한다. 또한 남아있는 돈이 어느 계좌에 얼마나 남았는지 알 수 없는 문제점과 동일 은행에 2개 이상의 카드가 있는 경우 인식이 불가능하다는 문제점 역시 발생한다. 이런 문제점들을 개선하기 위해 계좌마다 보유액을 표시하도록 하고, 은행과 카드정보를 연결시켰다. 추가적으로 영수증의 텍스트를 인식해 내역을 저장함으로써 효율적으로 입, 출금 내역을 관리할 수 있도록 하였다. 본 어플리케이션의 기능은 크게 영수증 글자입력을 통한 내역추가, 사용자의 자산내역관리, 계좌 & 체크카드 연동, 더치페이 시스템 등이 있다. 영수증을 카메라로 찍어 필요 정보를 구별해 인식하고 지출 내역을 추가한다. 지출 내역을 추가할 때 필요에 따라 다른 사람들과 내역을 공유할 수 있다. 이 시스템을 통해 사용자는 더욱 쉽고 간편하게 입, 출금내역을 관리할 수 있을 것으로 보인다.

• The Journal of Korean Society for School & Community Health Education
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• v.20 no.2
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• pp.93-107
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• 2019

Objectives: The purpose of this study is to provide basic data on the developement of oral health programs to maintain correct oral health in adolescence by identifying the relevance of health-related behavior and symptom experience to adolescents. Methods: Using the 14th(2018) online survey of youth health behavior, this study was conducted on students in grades1 middle school to grade5 high school in Korea and 30,463 boys, 29,577 girls were selected as the final analysis targets. Results: During the oral disease symptom experience, there was a statistically significant difference in smoking experience with teeth pain controlled general characteristics during eating. Conclusions: It is expected that it will be used as basic dat for the development of oral health programs to maintain the correct oral health status of adolescents by identifying the effects of health-related behaviors and related variables on oral diseases in Korea.

• Journal of the Korean Society of Safety
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• v.37 no.3
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• pp.60-70
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• 2022

The use rate of sports facilities in Korea is increasing every year, which means that accidents are also increasing. However, it is difficult to determine the level of safety management necessary to prevent accidents because there are no measurement tools to evaluate such management of sports facilities. Accordingly, in this study, tools and models to evaluate the safety management level of public sports facilities were developed based on public company management evaluation guidelines and the EFQM Excellence Model. A comparative analysis of the proposed tools and models between local governments showed no difference in awareness of safety management by group. This means that active safety management activities are needed to improve the low level of interest in safety of public sports facilities. We hope that this model will be widely used for the safety management of public sports facilities and to identify improvements and priorities in safety management.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.2
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• pp.171-178
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• 2023

PCM data is result of air-vehicle flight test, this data is distributed for each engineers to analyze its condition. Since line-of-sight between the air-vehicle and the ground receiver cannot always be secured, remote PCM data recording system was claimed to be required. In this paper multi-function PCM data recorder has been described. This PCM data recorder was intended to place on inside of flight object. It can record about two hours in 32 GB SD card with maximum 7 Mbps data rate. RS-422/485 and RJ-45 interface enhanced accessibility for users. 5 V and 1 A power consumption and 19.5 mm × 152.5 mm × 102.3 mm allow to connect with mobile PCM devices. It acquired more than 190-minutes data in 12-times flight test. Also, it achieved military standard environmental test MIL-STD-810G to prove its stability and solidness.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.17-23
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• 1997

A 3-D vision system is developed to evaluate blanks' line up and monitor gap and thickness difference between blanks in tailored blank welding system. A structured lighting method is used for 3-D vision recognition. Images of sheared portion in blanks are irregular according to roughness of blank surface, shape of sheared geometry and blurring. It is difficult to get accurate and reliable informations in the case of using binary image processing or contour detection techniques in real time for such images. We propoe a new energy integration method robust to blurring and changes of illumination. The method is computationally simple, and uses feature restoration concept, different to another digital image restoration methods which aim image itself restoration and may be used in conventional applications using structured line lighting technique. Experimental results show this system measuring repeatability is .+-. pixel for gap and thickness difference in static and dynamic tests. The data are expected to be useful for preview gap control.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.285-288
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• 2022

최근 코로나 확진자가 감소함에 따라 집합금지 명령이 해제되고 단계적 일상 회복이 진행되고 있다. 이에 맞춰 온라인 수업을 진행하던 학교들이 대면 수업으로 전환됨에 따라 학생들이 학교로 돌아오게 되었다. 하지만 학교에 처음 온 학생들은 학교 주변 상권에 대해 잘 모르는 경향이 있다. 본 논문에서는 이러한 학생들의 고민을 줄여주기 위하여 카테고리별로 맞춤 식당을 추천해주는 서비스 개발하였다. Kotlin을 활용한 안드로이드 애플리케이션 형태로 개발하였으며, 네이버 지도를 활용하여 식당의 위치를 알려주도록 하였다. 또한 Firebase를 활용한 게시판을 통해 소통의 창구를 마련하고 간단한 게임 등을 통해 학우들 간의 친밀도를 높일 수 있는 콘텐츠를 제공하였다.

• Advances in nano research
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• v.16 no.5
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• pp.459-472
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• 2024

Nanotechnology is a popular field in the construction industry due to its multiple functions. It mitigates CO₂ emissions and enhances the desirable properties of concrete by replacing small amounts of cement with supplements. This study assess the sustainability impact of using two different nanoparticles partially replacing the cement with 0.3%, 0.6%, 1.0% of nano silica (NS) and 0.03%, 0.045%, 0.06% of Multi-Walled Carbon Nanotubes (MWCNT) in the green concrete mix developement. Nano-sized fragments at the atomic scale tends to modify the properties of concrete. Concrete may increase its strength, durability by adding nanocomposite materials, which will decrease the amount of nano and micropores in structural parts. The strength of the structural elements can be greatly improved and allowing them to withstand higher loads and resist deformation. It improved durability properties by 64.8% in water absorption, 56.4% in acid attack, 78.1% in sulphate attack, and 53.4% in chloride attack. There was an improvement in compressive strength of 37% and split tensile strength of 90%. SEM, FTIR, and XRD investigations have used to look at the microstructural characteristics of nanoconcrete dictated the microstructure characteristics may be made more consistent and dense by adding nanocomposite materials.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.1
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• pp.9-18
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• 2006

This paper describes a new program called GPS_QC needed to check the quality of GPS observations before post-processing so that the surveyors can be improved the precision of GPS data analysis. The GPS_QC was designed to calculate the quality control (QC) parameters such as data gaps, cycle slips, low elevation angle, inonspheric delay, multi-path effects and DOP etc, within the period of GPS observation. It can be used to read and calculate the QC parameters from RINEX files. This program gives users brief statistics, time series plots and graphs of QC parameters. The GPS_QC can simply be performed the quality checking of GPS data that was difficult for surveyors in the field. It is expected that we can be improved the precision of positioning and solved the time consuming problem of GPS observation.