• Journal of the Korean Geotechnical Society
• /
• v.21 no.8
• /
• pp.95-105
• /
• 2005

Generally, a modified version of limit equilibrium method can be used to evaluate a slope stability of the geosynthetic reinforced soil slopes. In most cases, resisting effects of geosynthetic reinforcement are dealt with considering an increased shear strength on the potential slip surface. However, it is not clear that the methods satisfy all three equilibrium equations. As we know, the pattern of normal stress distribution along the slip surface is the key factor in calculating the safety factor of slopes. In this study, the new slope stability analysis method in which not only reinforcing effects of geosynthetics can be considered but also all three equilibrium equations can be satisfied was proposed with assuming the normal stress distribution along the slip surface as quadratic curve with horizontal $\chi-coordinate$. A number of illustrative examples, including published slope stability analysis examples for the reinforced and unreinforced soil slopes, loading test of large scale reinforced earth wall and centrifuge model tests on the geotextile reinforced soil slopes, were analyzed. As a result, it is shown that the newly suggested method yields a relatively accurate factor of safety for the reinforced and unreinforced soil slopes.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.8
• /
• pp.107-116
• /
• 2005

Generally, when the stability of the geosynthetic reinforced soil slopes is analyzed, the required tensile forces of each reinforcement layers are calculated from total reinforcement forces which are necessary to retain the equilibrium state of slip mass in which the slip surfaces are assumed to be a linear or bilinear. It is assumed that the reinforcement forces are increased or constant with depth. However, according to the instrumented field data and laboratory model test results, the maximum tensile strain of reinforcement in a reinforced soil slope is developed in a certain elevation, not a bottom of the slope. In the concept of reinforced soil, postulated failure surfaces are the traces of the position in which the reinforcement tensile forces are maximum in the layer, and the reinforcement tensile forces are related to the stress state on the postulated failure surface. Therefore, in this study, based on the distribution of normal stress on the slip surface, a new method for the evaluation of required tensile forces is suggested and a number of the instrumented field data are analyzed by newly suggested method. As a result, it is shown that the newly suggested method produces relatively accurate reinforcement tension forces.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.4
• /
• pp.369-376
• /
• 2003

In this paper, a nonlinear structural analysis for the composite structure composed of the spent nuclear fuel disposal canister and the 50㎝ thick bentonite buffer is carried out to predict the collapse of the canister while the horizontal symmetric sudden rock movement of 10㎝ is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucket-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the canister(cast iron, copper). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffet, the canister structure still endures elastic small strains and stresses below the yield strength. Hence, the 50㎝ thick bentonite buffet can protect the canister safely against the 10㎝ sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the canister structure due to the shear deformation of the bentonite buffer.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.6
• /
• pp.615-624
• /
• 2014

It has been well known the sloshing pressure has complex shape and various patterns. The pattern of sloshing pressure is variously characterized by the pressure amplitude, duration time and skewness. The structural response induced by the sloshing pressure is also affected by the pattern of sloshing pressure and the type of structural members. In order to understand the structural response by the perspective view of categorized pattern, it is more efficient to make simple sloshing pressure pattern than to reflect the complex pressure history. In this study, the sloshing pressures obtained by the small scale model test are simplified with respect to their duration and skewness. Dynamic analyses of Mark-III LNG CCS are then parametrically performed with the consideration of various types of sloshing impact. Meanwhile, the failure pressures given the duration and skewness are investigated after parametric calculations are conducted to investigate the effect of pressure parameters on the structural response.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.8 no.3
• /
• pp.97-111
• /
• 2013

This study reviews preceding research for detailed factors to establish development strategies for Korean Hidden Champion firms and classifies strategy factors into internal ones and external ones through specialists' opinions to draw strengths, weaknesses, opportunities and threats of each factor. It also sets hierarchical model to draw up a survey, distributes the survey to groups of specialists and enterprises respectively and then examines consistency ratio. Fifty-four copies of survey whose reliability on responses is secured through examining the consistency ratio are evaluated with their relative importance in factors by using SWOT/AHP technique and their order of priority is determined. Based on their results, development strategies for Korean Hidden Champion firms are established. SWOT/AHP analyses results show that external factors are with the opportunity of industry growth and the threat of intensified competition and market uncertainty and internal factors are with the strength in order of technological competence, construction competence in customer relation and marketing competence. The weakness in the lack of funds, lack of brand awareness in order. This result suggests that external environments of enterprises that more emphasis should be put on the industry growth and aggressive strategies cannot help but be adopted even in a global competition getting fiercer every day are seen more important. Then, it also seems to be thought that the technological competence including R&D and specialization, construction competence in customer relation and marketing competence should internally chosen for strategies to support strategies. The order of priority in development strategies for Korean Hidden Champion firms is drawn as; (i) aggressive S/O strategy which utilizes opportunities by taking advantage of strengths, (ii) W/O strategy which utilizes opportunities by supplementing weaknesses, (iii) diversified S/T strategy which utilizes strengths to make up for threats and (iv) defensive W/T strategy which supplements weaknesses to overcome threats.

• Korean Journal of Social Welfare
• /
• v.58 no.3
• /
• pp.371-398
• /
• 2006

The purpose of this study is to investigate the level of mother's caregiving satisfaction of a person with mental disorder and factors influencing to it as a positive aspect of caregiving experience. A survey conducted upon 231 mothers who live together with their adult-children with mental disorder through community mental health centers, social rehabilitation facilities and day hospitals. Collected data were analysed by t-test, Oneway-ANOVA, hierachical multiple regression analysis, and so on. The results are as follows: 1) The mean of mother's caregiving satisfaction is 3.06 in 5 point scale. Among the total items of the caregiving satisfaction scale, the means of the items 'finding strength through caregiving' and 'personal growth through caregiving' are higher than any others. 2) In the final regression model, statistically significant factors influencing to the caregiving satisfaction are 'the relationship quality between mothers and the mentally disordered', 'perceived social support from family, significant others, and friends', 'marital status of mothers', and 'family income'. Better relationship quality between mothers and the adult children with mental disorder and higher social support from family, significant others, and friends explained higher caregiving satisfaction of mothers. The level of a widow or divorced mother's caregiving satisfaction is higher than married one. The less family income affected to higher caregiving satisfaction. Variables related to mental disorder of adult-children, such as social function, years of mental disorder and frequency of hospitalization were not statistically significant influencing factors to mother's caregiving satisfaction. Through this research, the implications of social work practice were suggested in many ways.

• Journal of the Korean Chemical Society
• /
• v.18 no.4
• /
• pp.223-238
• /
• 1974

CNDO/2 MO theoretical studies and kinetic studies of halide exchange reactions for alkylchloroformates have been carried out in order to investigate structure-reactivity relationship of alkylchloroformates. From the result of energetics, it was concluded that the most stable configuration of alkylchloroformate is that in which alkyl group and chlorine are trans to each other, and that the hindered rotation about the bond between the carbonyl carbon and alkoxy-oxygen bond is attributed to the ${\pi}-$electron delocalization. It has been found that the large charge separation is due to -M effect of carbonyl and alkoxy oxygens and-I effect of chlorine. The order of rates in solvents studied was $(CH_3)_2 > CO > CH_3CN{\gg}MeOH.$$I^->Br^->Cl^-$ in protic solvent, and of Cl^->Br^- >I^-$ in dipolar aprotic solvents. Alkyl group contribution has the decreasing order of $CH_3-> C_2H-{\gg}i-C_3H_7-.$ The solvent effect has been interpreted on the basis of initial and final state contribution. A transition state model has been suggested, and it has been proposed that the most favorable mechanism is the addition-elimination. From the results of activation parameters and electronic properties, an energy profile has been proposed. Structural factors determining reactivities of alkylchloroformates have been shown to be charge, energy level of ${\alpha}^*LUMO$ to C-Cl bond and ${\alpha}^{\ast} $antibonding strength with respect to C-Cl bond in this MO. Charge and polarizability of nucleophile, and the interaction of these effects with solvent structures are also found to be important.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.2
• /
• pp.139-148
• /
• 2017

Ground subsidence caused by damaged water pipe and sewer is recently increasing due to the aging of city and pipeline in many city. Although many recent studies have verified characteristics of ground subsidence due to wastewater pipe breakdown, research about characteristics of ground subsidence due to water pipe is insignificant. subsidence due to water pipe is insignificant. This study aims to identify the ground failure mechanism caused by water and sewer pipe breakdown. Accordingly, we conducted an indoor model experiment to verify characteristics of ground subsidence considering characteristics of ground and ground failure. The water pipe pressure and velocity head was considered to find out ground subsidence mechanism. Also comparative analysis is conducted by analyzing relative density and fine-grain content considering embedded condition of water pipe. When the relative density and seepage pressure is low, small scale ground subsidence can occur, but when the conditions are opposite, ground subsidence occur in large scale and expands to ground level over time. Furthermore, it is acknowledgeable that ground cavity that is formed after soil run off due to seepage in deep earth, maintains steady strength and stays on the ground level for long period.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.5 no.1
• /
• pp.52-64
• /
• 1995

Robot manipulator is a highly nonlinear-time varying system. Therefore, a lot of control theory has been applied to the system. Robot manipulator has two types of control; one is path planning, another is path tracking. In this paper, we select the path tracking, and for this purpose, propose the intelligent control¬ler which is combined with fuzzy logic and neural network. The fuzzy logic provides an inference morphorlogy that enables approximate human reasoning to apply to knowledge-based systems, and also provides a mathematical strength to capture the uncertainties associated with human cognitive processes like thinking and reasoning. Based on this fuzzy logic, the fuzzy logic controller(FLC) provides a means of converhng a linguistic control strategy based on expert knowledge into automahc control strategy. But the construction of rule-base for a nonlinear hme-varying system such as robot, becomes much more com¬plicated because of model uncertainty and parameter variations. To cope with these problems, a auto-tuning method of the fuzzy rule-base is required. In this paper, the GA-based Fuzzy-Neural control system combining Fuzzy-Neural control theory with the genetic algorithm(GA), that is known to be very effective in the optimization problem, will be proposed. The effectiveness of the proposed control system will be demonstrated by computer simulations using a two degree of freedom robot manipulator.

• The Journal of Korean Academy of Prosthodontics
• /
• v.32 no.4
• /
• pp.484-514
• /
• 1994

Cantilever bridge is widely used by mny clinicians, but its worst mechanical character, so called Class I lever system, makes dentists hesitate to restore the missing tooth with it. Therefore it is important to study stress of the cantilever bridge. In this study, two models of cantilever bridges that restores the missing mandibular second molar with two abutment teeth were constructed. One model was a type of cantilever bridge supported by a normal alveolar bone, the other one was supported by an alveolar bone resorbed to its 1/3 of root length. Maximum bite force(550N) and funtional maximum bite force(300N) were vertically applied to the distal end of the pontic, distal 1/3, and distal half of the pontic. And each force was also applied to centric occlusal contacts as a distributed force. Total 16 loading cases were compared and analyzed with 3-dimensional finite element method. The results were as follows: 1. The stress was concentrated on the joint of the pontic and the retainer, grooves, and distal cervical margin of the posterior retainer. 2. In case of maximum bite force(550N) at the end of the pontic, the risk of fracture at the joint of the pontic and the retainer was high. 3. In case of distributed force in centric occlusion and functional maximum bite force(300N), the stresses were less than the yield strength of the type VI gold for any loading cases. 4. In case of alveolar bone resorption, the occlusal force to the cantilever pontic caused more stress on the root apex and less stress on the alveolar crest region of the distal surface of the posterior abutment. 5. In case of alveolar bone resorption, the displacement was larger than that of normal alveolar bone in all loading cases.