• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.147-154
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• 2000

The influence of the mined-out caves on the stability of the high speed railway tunnel was investigated with a series of geological logging and in-situ tests on the one hand, and with the rock mass classification using the multiple regression analysis on the other hand. The rock mass in this area can be classified as 'fair', and the condition of the discontinuities plays the most important role in the classification of the rock mass. The results of the analysis obtained by the FLAC showed that the western part of the tunnel locating at 50m above the mine cavities could be affected by subsidence associated with a considerable deformation, the magnitude of which might depend on the properties of the rock mass. Key word : multi regression analysis, subsidence, mine cavities

• Journal of the Korea Society for Simulation
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• v.25 no.4
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• pp.93-108
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• 2016

Electric vehicle car sharing (EV-sharing) system is noted as an eco-friendly system of transportation in global warming crisis and has been practically implemented in some cities around the world. However, methodologies to find the efficient operation conditions of EV-sharing systems reflecting a typical characteristic 'charging' have not been fully investigated yet. In the paper a generalized model has been developed to identify optimal level of infrastructure for EV-sharing system which provides the optimum operation efficiency under service level constraints. From the simulation analysis based on the developed model the relationships between the operational variables to describe EV-sharing system have been identified and optimal capacity to maximize the operational efficiency have been found. From the analysis of simulation results it has been found that increases in the number of vehicles and chargers improve the service level until certain value beyond which increasing rate and the efficiency have been reduced. From the cost-revenue analysis the optimal numbers of vehicles and chargers have been identified which maximizes the annual operational profit.

• Korean Journal of Social Welfare
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• v.39
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• pp.5-40
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• 1999

Little is known about unemployment duration and re-employment pattern. This paper empirically examines unemployment duration and re-employment pattern using data by the 1998 national survey about the unemployed and their needs. A parametric survival model(Weibull model) is adopted to identify variables predicting unemployment duration. It is found that the data including people without unemployment insurance as well as people with unemployment insurance fit the Weibull model including the hazard distribution that the hazard of reemployment is increasing at an decreasing rate. Variables that affect unemployment duration are age, householdership, family income, size of prior employment organization, and cause of unemployment. In re-employment pattern, statistically significant variables are age, type of prior employment industry, prior employment pattern, and membership in unemployment insurance. This paper provides a basic knowledge about realities of unemployed individuals in the economic crisis period of Korea, identifies research areas for further research, and develops policy implications for the unemployed.

• Tunnel and Underground Space
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• v.24 no.1
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• pp.67-80
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• 2014

Long-term stability and delayed failure of granite were evaluated through the laboratory test based on Wilkins method and Brazilian disc test (BDT) which yields tensile strength, mode I fracture toughness and subcritical crack growth parameters. Then, the long-term strength of granite was estimated by using analytical models and long-term stability of compressed air-energy storage (CAES) pilot cavern pressurized up to 5 ~ 6 MPa was evaluated using numerical code, FRACOD with the determined subcritical crack growth parameters. The results of test and analyses showed that the subcritical crack growth index, n was determined as 29.39 and the inner pressure of 5 ~ 6 MPa had an insignificant effect on the long-term stability of pilot cavern. It was also found that the measurement and analysis of acoustic emission events can describe the accumulation of damage due to subcritical crack growth quantitatively. That is, AE monitoring can provide the current status of rock under loading if we make an identical installation condition in the field with that of the laboratory test.

• Korean Journal of Heritage: History & Science
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• v.42 no.1
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• pp.122-142
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• 2009

This study explored all domestic and international theories for maintenance and health enhancement of an old and big tree, and carried out the anatomical survey of the operation part of the tree toward he current status of domestic surgery and the perception survey of an expert group, and drew out following conclusion through the process of suggesting its reform plan. First, as a result of analyzing the correlation of the 67 subject trees with their ages, growth status. surroundings, it revealed that they were closely related to positional characteristic, damage size, whereas were little related to materials by fillers. Second, the size of the affected part was the most frequent at the bough sheared part under $0.09m^2$, and the hollow size by position(part) was the biggest at 'root + stem' starting from the behind of the main root and stem As a result of analyzing the correlation, the same result was elicited at the group with low correlation. Third, the problem was serious in charging the fillers (especially urethane) in the big hollow or exposed root produced at the behind of the root and stem part, or surface-processing it. The benefit by charging the hollow part was analyzed as not so much. Fourth, the surface-processing of fillers currently used (artificial bark) is mainly 'epoxy+woven fabric+cork', but it is not flexible, so it has brought forth problems of frequent cracks and cracked surface at the joint part with the treetextured part. Fifth, the correlation with the external status of the operated part was very high with the closeness, surface condition, formation of adhesive tissue and internal survey result. Sixth, the most influential thing on flushing by the wrong management of an old and big tree was banking, and a wrong pruning was the source of the ground part damage. In pruning a small bough can easily recover itself from its damage as its formation of adhesive tissue when it is cut by a standard method. Seventh, the parameters affecting the times of related business handling of an old and big tree are 'the need of the conscious reform of the manager and related business'. Eighth, a reform plan in an institutional aspect can include the arrangement of the law and organization of the old and big tree management and preservation at an institutional aspect. This study for preparing a reform plan through the status survey of the designated old and big tree, has a limit inducing a reform plan based on the status survey through individual research, and a weak point suggesting grounds by any statistical data. This can be complemented by subsequent studies.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.397-402
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• 2003

Generally it is likely that rock mass properties are expressed not by a mean value but by values with variation due to its characteristic uncertainty. This characteristic is one of the most important parts for the design of undergound structures, but yet to be fully examined. Stochastic finite element method (SFEM) is contrary to deterministic finite element method in its concept as the former has been developed in order to take the randomness of structural systems into account. Using SFEM, the response variability of structural system can be obtained and it leads probabilistic stability of structure to be analyzed. In this study, displacement response variability of circular opening with hydrostatic stress field are analyzed in terms of rock mass properties having a certain mean and a standard deviation using the SFEM. The analyzed response variability shows that the necessity of probabilistic stability analysis of underground structures using reliable mean value and standard deviation of deformation modulus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.229-235
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• 2013

To investigate the effect of the flexible artery wall on the blood flow, three-dimensional numerical simulations were carried out for analyzing the time-dependent incompressible flows of Newtonian fluids constrained by a flexible wall. The Navier-Stokes equations for fluid flow were solved using the P2P1 Galerkin finite element method, and mesh movement was achieved using an arbitrary Lagrangian-Eulerian formulation. The Newmark method was employed for solving the dynamic equilibrium equations for the deformation of a linear elastic solid. To avoid complexity due to the necessity of additional mechanical constraints, we used a combined formulation that includes both the fluid and structure equations of motion to produce a single coupled variational equation. The results showed that the flexibility of the carotid wall significantly affects flow phenomena during the pulse cycle. The flow field was also found to be strongly influenced by the bifurcation angle.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.209-216
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• 2003

The present with in this country, rock bolt installation, shotcrete, and concrete lining in construction order has become accepted as a general tunnelling method in NATM. On the other hand Unlined tunnelling method, which was developed by many countries near Scandinavian Peninsula with hard rocks comparatively, has recently been introduced all over the world, and numerous studies about that have been being devoted to domestic tunnels. Unlined tunnelling method has been developed on the basis of the permanently unsupported openings, and general 7 requirements for them were suggested by Nick Barton. There are no case record about these conditions for Q-system in this country. Therefore, input parameters for Q-system under these conditions were applied to general road tunnel cross-section and numerical analyses for each condition were executed with UDEC-BB, Distinct Element Method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.70-81
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• 2024

In this study, Tridimensional Hybrid Isolation System(THIS) was proposed as a vibration isolator for traffic loads, combining vertical and horizontal isolation systems. Its efficacy in improving serviceability for vertical vibration was analytically evaluated. Firstly, for the analysis, the major vibration modes of the existing apartment were identified through eigenvalue analysis for the system and pulse response analysis for the bedroom slab using commercial structural analysis software. Subsequently, a 16-story model with horizontal, vertical and rotational degrees of freedom for each slab was numerically organized to represent the achieved modes. The dynamic analysis for the measured acceleration from an adjacent ground to high-speed railway was performed by state-space equations with the stiffness and damping ratio of THIS as variables. The result indicated that as the vertical period ratio increased, the threshold period ratio where the slab response started to be suppressed varied. Specifically, when the period ratio is greater than or equal to 5, the acceleration levels of all slabs decreased to approximately 70% or less compared to the non-isolated condition. On the other hand, it was ascertained that the influence of damping ratios on the response control of THIS is inconsequential in the analysis. Finally, the improvement in vertical vibration performance of THIS was evaluated according to design guidelines for floor vibration of AIJ, SCI and AISC. It was confirmed that, after the application of THIS, the residential performance criteria were met, whereas the non-isolated structure failed to satisfy them.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.83-89
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• 2011

A series of full-scale testing was conducted to examine the effect of stairwell pressurization on the pressure differential between the stairwell and the auxiliary room and between the auxiliary room and the residence. Also, flow velocity profiles at open doors were measured. The building tested was a condominium that had twenty floors above the ground and two floors underground. For pressurization of the stairs, a blower was used to supply air into the stairwell at one location underground. Thirteen different cases were tested, and test variables included the number of floors with open doors and the flow rate of the air supply. When the doors on the first floor were open, the pressure differential between the stairwell and the auxiliary room was distributed almost uniformly except for locations near the first floor. When the flow rate was in the range of 180~270 CMM and the doors of one floor were open, the flow velocity could satisfy the requirement of fire safety standards and the stairwell pressure was positive at all levels. However, the minimum pressure requirement (10 Pa) could not always be satisfied. When doors on two floors were open, the flow velocity requirement could be satisfied by increasing the flow rate, but it was found impractical to satisfy the minimum pressure requirement without causing excessive pressure differential in the area near the blower.