• Proceedings of the Korean Geotechical Society Conference
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• 1998.06a
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• pp.147-160
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• 1998

• Geotechnical Engineering
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• v.10 no.2
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• pp.41-56
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• 1994

Under the groundwater level, the tunnel face is affected by the seepage force and the groundwater flow may cause a trouble to the tunnel support systems. The appropriate methods of analysis and design in the tunnel face and the lining, considering groundwater flow according to tunnel drainage condition are presented in this thesis. First, the effect of seepage on the stability of tunnel face was studied. Seepage force was estimated by the 3-D finite element analysis and the stability of tunnel face was checked by analytical method. Furthermore, using the finite difference method the stress and displacement on the face were computed for either case, where the seepage force is or is not considered, and the effect of seepage on the tunnel face stability was evaluated. Second, the effect of seepage force on the tunnel lining when construction is finished and steady state seepage flow occurs was studied and a design methodology considering seepage effect was made. Consequently, in case where the groundwater level remains almost unchanged and the steady state groundwater flow occurs, the proper countermeasures for face staility are required according to the condition of groundwater flow. Moreover, the tunnel lining should be designed and constructed considering the seepage force occuring by the groundwater flow toward the tunnel linings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.89-96
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• 2010

In this paper, we proposed a method about improving face tracking efficiency of face detection for AF system using the faces to the ROI. The conventional face detection system detecting faces based skin color uses the ratio of skin pixels of the present frame to detected face regions of the past frame to track the faces. The tracking method is superior in the stability of the regions but it is inferior in the face tracking efficiency. We proposed a face tracking method using the area of the overlapping region in the detected face regions of the past frame and the present frame to improve the tracking efficiency. The proposed face tracking efficiency demonstration was performed by making a film of face detection with face tracking in real-time and using the moving traces of the detected faces.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.133-144
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• 2004

Pre-reinforcement ahead of a tunnel face using long steel or FRP (Fiberglass Reinforced Plastic) pipes in NATM(New Austrian Tunnelling Method), known as the RPUM(Reinforced Protective Umbrella Method) or UAM (Umbrella Arch Method), is the promising method to sustain the stability of a shallow tunnel face and reduce the ground settlements. In addition, horizontal reinforcing of the face is recently emphasized to improve the stability of the face. However, the characteristics on longitudinal arching around the face have not yet been established quantitatively with the RPUM (crown-reinforcing) and/or the face horizontal reinforcing. In this study, therefore, the behavior of cohesionless soil around the face reinforced by the reinforcing member representing the RPUM and horizontal reinforcing is investigated through two-dimensional laboratory model tests. A series of tests were carried out on various conditions by changing lengths and angles of the reinforcing members. Based on the vertical pressure around the face, the characteristics of longitudinal arching have been found for the case of the non-reinforced and the reinforced.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.91-100
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• 2002

This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.47-51
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• 2013

In this study, we carried out an experimental shield TBM excavation model test using a down-scale device in soft clay, to understand tunnel-face stability properties in relation to changes in slurry pressure. We performed five tests according to tunnel depth (0.5D, 0.75D, 1.0D, 1.25D, 1.5D), and compared theoretical tunnel-face pressure with model test results. The range in theoretical tunnel-face slurry pressure ($P_{min}{\leq}P_{slurry\;pressure}{\leq}P_{max}$), which is determined by earth pressure and water level, was very similar to the model test result. This result was due to the more isotropic condition of the soft clay ground, than of rocky ground.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.3
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• pp.197-204
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• 2006

A large sectional tunnelling method using Shield TBM is expected to be popular as domestic demand of long tunnel gets growing. Although a shield tunnelling method has been recognized as prominent method in consideration of stability and applicability in shallow and poor ground, the cases of accident and constructional trouble have been often happened due to unexpected poor ground condition, or selection and use of improper shield machine. Especially, troubling cases at tunnel face are frequently occurred, so supporting pressure control of tunnel face would be the main issue for securing safer and more efficient tunnel excavation using Shield TBM. In this point, we carried out the numerical feed-back analysis to compare the ground deformation pattern with theoretical result at tunnel face.

• Physical Therapy Rehabilitation Science
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• v.11 no.1
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• pp.43-48
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• 2022

Objective: In the present study, to determine the extent of academic stress and pain from sitting for a long time, we will use a questionnaire to examine the effects of non-face-to-face stress and back pain on college students who have conducted non-face-to-face lectures. Design: Survey research Methods: A questionnaire was conducted using Naver foam to identify academic stress, attitude and time to listen to lectures, and the extent of back pain for college students who are experiencing non-face-to-face lectures. Outcome measures include the scale of academic stress (SAS), the Numeric rating scale (NRS), the Oswestry Disability Index (ODI Korea version) was implemented. The difference in academic stress was analyzed by t-test and one-way ANOVA, and the correlation between academic stress and back pain was analyzed using the Spearman correlation coefficient. In order to examine the academic stress, consistency, and stability, the reliability of the academic stress items was measured by examining the reliability with the Cron-Bach alpha coefficient. Allstatistical significance levels were α=0.05. Results: According to the general characteristics of the subject, there were no statistically significant results compared to gender (P<0.05), but the higher the grade, the higher the stress index, the higher the level of pain. Conclusions: This study confirmed that non-face-to-face lectures caused by COVID-19 have increased academic stress and the resulting increase in back pain in college students.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.9-16
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• 2007

The influence of round length on the tunnel stability and construction cost is well acknowledged by many researchers and engineers but the coherent procedure is not available for its determination. In this study, the behaviour modes of the face and unsupported span was investigated for weak rock tunnel by a small scale model test, PFC3D and FDM analyses in consideration of the round length. Total five types of behaviour modes are defined and quantitative estimation of the behaviour modes was established in terms of the safety factor for the face stability and the conditional chart. Although the proposed method has some restrictions, this method can provide useful information for the optimization of the round length and excavation, especially in design stage.

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.59-63
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• 2007

Radio Frequency Identification (RFID) is a common term for technologies using micro chips that are able to communicate over short-range radio and that can be used for identifying physical objects. RFID technology already has several application areas and more are being envisioned all the time. While it has the potential of becoming a really ubiquitous part of the information society over time, there are many security and privacy concerns related to RFID that need to be solved. This paper proposes a method which could protect private information and ensure RFID's identification effectively storing face feature information on RFID tag. This method improved linear discriminant analysis has reduced the dimension of feature information which has large size of data. Therefore, face feature information can be stored in small memory field of RFID tag. The proposed algorithm in comparison with other previous methods shows better stability and elevated detection rate and also can be applied to the entrance control management system, digital identification card and others.