• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.122-129
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• 2015

Excessive overheating to a manual transmission clutch system under operating conditions can be considered the main reason of its performance degradation. The clutch system has to be ensured with its service life by showing that it passes the extreme tests called anti-fade test and hill start test in a certain design step. In general, design feedbacks from these kinds of the experiments are adapted to the system to enhance its performance. However, it usually takes much time and costs a lot due to the repetition of the tests. In this research, a process to calculate temperature of the clutch system was developed to determine whether the design can be passed the anti-fade test and hill start test in the design phase. The process incorporates many CAE techniques such as heat transfer analysis using 1D dynamic simulation method, system dynamics, CFD and parametric optimization. CFD is utilized to analyze 3-dimensional heat transfer of the clutch system and fluid dynamics of air in the clutch housing. The process was applied for the clutch systems in several vehicle models. The results was compared with those of the experiment. The applicability of the developed process was verified by comparing the predicted results with experimental results.

• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.15-29
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• 2018

The sediment transport process in a river reflects the process of geomorphological change in the watershed, influencesthe river bed variation and the river channel migration, and is a parametric phenomenon that exhibits a dynamic self-adjusting process. Sediment load is divided into bedload and suspended load depending on the dominant mechanism. Quantitative sediment load is important information for solving river problems. Because it is difficult and time consuming to measure bedload, compared to that ofsuspended load, data on the sediment transport load and the research required for the gravel-bed rivers are insufficient. This study is to analyze the ratio of the bedload to the total sediment load in gravel-bed rivers. The sediment load ratio in gravel-bed rivers increases with the flow rate per unit width, and the rate of the bedload varies more rapidly than the suspended load. The sediment transport efficiency coefficient has been affected by the ratio of the flow depth to the mean diameter of particles and has been dependent on the shear velocity Reynolds number. So $A^{\ast}$ and $B^{\ast}$ are introduced to compensate for the uncertainties such as bed materials, sediment transport, and flow velocity distribution, and the coefficient of bedload ratio has been presented. For the sediment load data in experimental channels and rivers, A* was 3.1. The dominant variables of $B^{\ast}$ were $u_*d_m/{\nu}$ in the gravel-bed and h/dm in the sand-bed. When $B^{\ast}$ the is the same, in the experimental channels the coefficient of bedload ratio was affected by the bed forms, but in the rivers it was of little difference between the gravel-bed and sand-bed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.323-330
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• 2010

The time in port for vessels is one of the important factors for analyzing the operation status and the capacity of ports. In addition, the time in port for vessels can be directly used for estimating the greenhouse gas emissions resulted from vessels in port. However, it is unclear which variables can affect the time in port for vessels and what the marginal effect of each variable is. With these challenges in mind, the study analyzes the time in port for vessels arriving and departing port of Busan by using a parametric survival model. The results show that the log-logistic accelerated failure time model is appropriate to explain the time in port for 19,167 vessels arriving and departing port of Busan in 2008, in which the time in port is significantly affected by gross tonnage of vessels, service capacity of terminal, and vessel type. This study also shows that the greenhouse gas emission resulted from full-container vessels, which accounted for about 61% of all vessels with loading/unloading purpose arriving and departing port of Busan in 2008, is about "17 ton/vessel" in the boundary of port of Busan. However, the hotelling greenhouse gas emissions resulted from non-container vessels (3,774 vessels; 20%) are greater than those from the full-container vessels. Hence, it is necessary to take into account more efficient port management polices and technologies to reduce the service time of non-container vessels in port of Busan.

• Tunnel and Underground Space
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• v.8 no.3
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• pp.209-225
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• 1998

Recently, Umbrella Arch Method(UAM), one of the auxiliary techniques for tunnelling, is used to reinforce the ground and improve stability of tunnel face. Because UAM combines the advantages of a modern forepoling system with the grouting injection method, this technique has been applied in subway, road and utility tunnel sites for the last few years in Korea. Also, several research results are reported on the examination of the roles of inserted pipes and grouted materials in UAM. But, because of its empirical design and construction methodology, more qualitative and systematic design sequences are needed. Therefore, above sequences using numerical analysis are proposed and, the effects of some design parameters were studied in this research. In order to acco,mplish these objects, first, the roles of pipe and grouting materials, steel-rib and the others in ground improving mechanism of UAM are clarified. Second, the effects of design parameters are investigated through parametric studies. Design parameters are as follows; 1) ground condition, 2) overburden, 3) geometrical formulation of pipes, 4) grouting region and 5) characteristics of pipes.

• Geotechnical Engineering
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• v.13 no.3
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• pp.101-122
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• 1997

A spiting reinforcement system is composed of a series of radially installed reinforcing spites along the perimeter of the tunnel opening ahead of excavation. The reinforcing spill network is extended into the in-situ soil mass both radially and longitudinally The sailing reinforcement system has been successfully used for the construction of underground openings to reinforce weak rock formations on several occasions. The application of this spiting reinforcement system is currently extended to soft ground tunneling in limited occasions because of lack of reliable analysis and design methods. A method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground is presented. The shape of the potential failure wedge for the case of smile-reinforced shallow tunnel is assumed on the basis of the results of three dimensional finite element analyses. A criterion to differentiate the spill-reinforced shallow tunnel from the smile-reinforced deep tunnel is also formulated, where the tunnel depth, soil type, geometry of the tunnel and reinforcing spites, together with soil arching effects, are considered. To examine the suitability of the proposed method of threedimensional stability analysis in practice, overall stability of the spill-reinforced shallow tunnel at facing is evaluated, and the predicted safety factors are compared with results from twotimensional analyses. Using the proposed method of threetimensional limit equilibrium stability analysis of the smile-reinforced shallow tunnel in soft ground, a parametric study is also made to investigate the effects of various design parameters such as tunnel depth, smile length and wadial spill spacing. With slight modifications the analytical method of threeiimensional stability analysis proposed may also be extended for the analysis and design of steel pipe reinforced multi -step grouting technique frequently used as a supplementary reinforcing method in soft ground tunnel construction.

• Journal of Korean Society of Steel Construction
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• v.26 no.2
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• pp.91-103
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• 2014

High performance steel for bridges(HSB 800) with a minimum tensile stress of 800MPa was recently developed. However, the study for local buckling behavior of plate girders considering interactive effects of flanges and webs is still insufficient. In this study, the flange local buckling(FLB) strength of plate girders with HSB 800 was evaluated by nonlinear finite element analysis. The flanges and webs of plate girders having I-section were modeled as 3D shell elements in the nonlinear analysis. Initial imperfection and residual stress were imposed on the plate girder. The high performance steel was modeled as a multi-linear material. Thus, parametric study of compression flanges with a compact, noncompact and slender web was performed. The flange local buckling behavior of plate girders was analyzed, and the nonlinear analysis results were compared with the nominal flexural strength of both AASHTO LRFD(2012) and KHBDC LSD(2012) codes.

• Korean Journal of Childcare and Education
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• v.11 no.1
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• pp.249-267
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• 2015

This study aims to examine the effect of child-centered group play therapy on the improvement of withdrawn preschool children's daily stress, anxiety, peer interaction and EEG variation. The research subjects are 12 children of 3-5 years of age who are over 65T in the social-withdrawal scale of KPRC(Korean Personality Rating Scale for Children). They were recommended by class teachers due to the withdrawal behavior at D kindergarten in Seoul. The experimental group received 12 sessions of the child-centered group play therapy program, twice a week for 35 minutes. But the control group did not receive any of the child-centered group play therapy program. To verify the effects of the program, a Mann-Whitney-U test of the non-parametric was preceded and homogeneity between the two groups was verified. Also, a Wilcoxon's signed-rank test was conducted to check on the pre-to-post changes of daily stress, anxiety, peer-interaction and EEG variation by using SPSS 18.0. The results of this research showed that the child-centered group play therapy program decreases daily stress and anxiety, while it increases positive peer-interaction and the EQ of withdrawal children. The result of this study serves as a baseline data about the effects of child-centered group play therapy for withdrawal children with emotional difficulties.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.44-57
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• 2008

In this study, a 2D finite-element analysis, using the SEEP/W program, was carried out to estimate the amount of groundwater flawing into a tunnel, as well as the groundwater tables around wetland areas during and after a tunnel excavation through rock mass. Four sites along the Wonhyo-tunnel in Cheonseong Mountain (Gyeongnam, Korea) were analysed, where the model damain of the tunnel included both wetland and fault zone. The anisotropy of the hydraulic conductivities of the rock mass was calculated using the DFN model, and then used as an input parameter for the cantinuum model. Parametric study on the influencing factors was perofrmed to minimize uncertainties in the hydraulic properties. Moreover, the volumetric water content and hydraulic conductivity functions were applied ta the model to reflect the ability of a medium ta store and transport water under both saturated and unsaturated conditions. The conductivity of fault zone was assumed ta be $10^{-5}m/sec\;or\;10^{-6}m/sec$ and the conductivity of grouting zone was assumed as 1/10, 1/50 or 1/100 of the conductivity of rock mass. Totally $6{\sim}8$ cases of transient flow simulation were peformed at each site. The hydraulic conductivities of fault zone showed a significant influence on groundwater inflow when the fault zone crossed the tunnel. Also, groundwater table around wetland maintained in case that the hydraulic conductivity of grouting zone was reduced ta be less than 1/50 of the hydraulic conductivity of rock mass.

• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.5-16
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• 2017

In the present work, a number of advanced three-dimensional (3D) parametric finite element numerical analyses have been conducted to study the behaviour of a single pile in consolidating ground from coupled consolidation analyses. A single pile with typical minimum and maximum ranges of fill height and clay stiffness has been modelled. The computed results demonstrate that the higher the height of the fill above the clay surface and the smaller the stiffness of the clay, the higher the dragloads and the negative skin friction-induced pile settlements. It has been found that the development of dragloads and pile settlement is more governed by the stiffness of the clay rather than the height of the fill. Positive shaft resistance is mobilised only after the average degree of consolidation is larger than 50%. Although the pile is installed when the degree of consolidation is 50% or more, relatively large negative skin friction can nevertheless develop on the pile. On the other hand, when a load is applied on the pile experiencing an increase in the negative skin friction with time during consolidation, the pile undergoes a large increase in the final settlement of up to 95% compared to that of a pile without axial load on the pile head. The allowable pile capacity when there is negative skin friction on the pile is reduced by about 4-11% compared to a pile without negative skin friction.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1249-1249
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• 2022

The facade, an exterior material of a building, is one of the crucial factors that determine its morphological identity and its functional levels, such as energy performance, earthquake and fire resistance. However, regardless of the type of exterior materials, huge property and human casualties are continuing due to frequent exterior materials dropout accidents. The quality of the building envelope depends on the detailed design and is closely related to the back frames that support the exterior material. Detailed design means the creation of a shop drawing, which is the stage of developing the basic design to a level where construction is possible by specifying the exact necessary details. However, due to chronic problems in the construction industry, such as reducing working hours and the lack of design personnel, detailed design is not being appropriately implemented. Considering these characteristics, it is necessary to develop the detailed design process of exterior materials and works based on the domain-expert knowledge of the construction industry using artificial intelligence (AI). Therefore, this study aims to establish a detailed design automation algorithm for AI-based condition-responsive exterior wall panels and their back frames. The scope of the study is limited to "detailed design" performed based on the working drawings during the exterior work process and "stone panels" among exterior materials. First, working-level data on stone works is collected to analyze the existing detailed design process. After that, design parameters are derived by analyzing factors that affect the design of the building's exterior wall and back frames, such as structure, floor height, wind load, lift limit, and transportation elements. The relational expression between the derived parameters is derived, and it is algorithmized to implement a rule-based AI design. These algorithms can be applied to detailed designs based on 3D BIM to automatically calculate quantity and unit price. The next goal is to derive the iterative elements that occur in the process and implement a robotic process automation (RPA)-based system to link the entire "Detailed design-Quality calculation-Order process." This study is significant because it expands the design automation research, which has been rather limited to basic and implemented design, to the detailed design area at the beginning of the construction execution and increases the productivity by using AI. In addition, it can help fundamentally improve the working environment of the construction industry through the development of direct and applicable technologies to practice.