• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.339-344
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• 2013

Hot forming using boron steel is currently used for manufacturing low-weight automobile body parts, and a high tensile strength of about 1,500 MPa is obtained after hot forming. However, a high fatigue life is a more important factor than high strength when it is used for automobile suspension parts. A tubular torsion beam axle (TTBA) is one of these suspension parts, and this research deals with the fatigue characteristic of TTBA using hot forming. The low cyclic fatigue life of boron steel is investigated according to the cooling method. In addition, a structural and fatigue analysis of TTBA is performed to predict the fatigue life. The stress concentration that occurs in the tubular torsion beam is found, and the longest fatigue life occurs when rapid cooling is utilized in the TTBA fabrication.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1131-1137
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• 2017

Recently, regulations on fuel efficiency and $CO_2$ emissions have been reinforced in automobile industries. As a result, many companies make an effort to satisfy these regulations by adapting composite materials to the automobile body as well as its components. In particular, the lower control arm in the suspension system is subjected to heavy loads and is designed to be thick to meet operating loads. Therefore, it is essential for the lower control arm to reduce weight and to secure the durability assessment. In this paper, we conducted structural analysis by performing stress and stiffness analysis under given load conditions through finite element analysis, and verified whether it satisfies the load and stiffness conditions. The inertia relief method is adapted to the process of analysis, and the principal stress is used as a criterion for evaluation. Based on these results, the durability assessment is carried out using the stress-life method.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.460-465
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• 2016

Long pipe structures are usually installed in fixtures located with regular intervals or laid underground. Therefore, deflection and deformation could easily occur due to their weight or ground activity. A shape monitoring technique can be used effectively to evaluate the integrity of the pipe structures. Fiber Bragg grating (FBG) sensors, which have an advantage of multiplexing could be used to measure strains at multiple-points of a long structure. In this study, to evaluate the integrity of a pipeline, a shape estimation technique based on strain information was proposed. Furthermore, different experiments were conducted to verify the performance of the proposed technique. Thus, the proposed shape estimation technique can represent the shape according to the deformation of the specimen using the FBGs. Moreover, calculated deflection of the pipeline using the estimation technique showed a good agreement with the actual deflection of the pipeline.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.10
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• pp.1698-1711
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• 2011

Knowledge is often represented as a set of rules or a semantic network in intelligent systems. Recently, ontology has been widely used to represent semantic knowledge, because it organizes thesaurus and hierarchal information between concepts in a particular domain. However, it is not easy to collect semantic relationships among concepts. Much time and expense are incurred in ontology construction. Collective intelligence can be a good alternative approach to solve these problems. In this paper, we propose a collective intelligence approach of Games With A Purpose (GWAP) to collect various semantic resources, such as words and word-senses. We detail how to construct the semantic information model or ontology from the collected semantic resources, constructing a system named FunWords. FunWords is a Korean lexical-based semantic resource collection tool. Experiments demonstrated the resources were grouped as common nouns, abstract nouns, adjective and neologism. Finally, we analyzed their characteristics, acquiring the semantic relationships noted above. Common nouns, with structural semantic relationships, such as hypernym and hyponym, are highlighted. Abstract nouns, with descriptive and characteristic semantic relationships, such as synonym and antonym are underlined. Adjectives, with such semantic relationships, as description and status, illustration - for example, color and sound - are expressed more. Last, neologism, with the semantic relationships, such as description and characteristics, are emphasized. Weighting the semantic relationships with these characteristics can help reduce time and cost, because it need not consider unnecessary or slightly related factors. This can improve the expressive power, such as readability, concentrating on the weighted characteristics. Our proposal to collect semantic resources from the collective intelligence approach of GWAP (our FunWords) and to weight their semantic relationship can help construct the semantic information model or ontology would be a more effective and expressive alternative.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.135-142
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• 2016

Objective: The purpose of this study was to investigate the acute effect of walking on high heels on the behavior of fascicle length and activation of the lower limb muscles. Methods: Twelve healthy inexperienced high heel wearers (age: $23.1{\pm}2.0yr$, height: $162.4{\pm}4.9cm$, weight: $54.4{\pm}8.5kg$) participated in this study. They walked in high heels (7 cm) and barefoot on a treadmill at their preferred speed. During the gait analysis, the lower limb joint kinematics were obtained using a motion analysis system. In addition, the changes in fascicle length and the level of activation of the medial gastrocnemius (MG) were simultaneously monitored using a real-time ultrasound imaging technique and surface electromyography, respectively. Results: The results of this study show that the MG fascicle operates at a significantly shorter length in high heel walking ($37.64{\pm}8.59mm$ to $43.99{\pm}8.66mm$) in comparison with barefoot walking ($48.26{\pm}9.02mm$ to $53.99{\pm}8.54mm$) (p < .05). In addition, the MG fascicle underwent lengthening during high heel walking with relatively low muscle activation while it remained isometric during barefoot walking with relatively high muscle activation. Conclusion: Wearing high heels alters the operating range of the MG fascicle length and the pattern of muscle activation, suggesting that prolonged wearing of high heels might induce structural alterations of the MG that, in turn, hinder normal functioning of the MG muscle during walking.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1323-1330
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• 2013

A wheel loader is a type of construction machinery that is capable of performing a variety of tasks, and demands on its functional diversity and structural reliability are growing. A wheel bearing is one of the core components that determine the life of the loader; taper roller bearings are commonly used for this purpose. The lifetime of a bearing is typically calculated based only on its load and revolution speed. The initial preload of a taper roller bearing is a critical factor that directly affects its endurance life. In this study, the relations between the endurance life and preload characteristics including the amount of preload according to the weight, rotational speed, and thermal modification applied to tapered roller bearings are presented. When the temperature is $100^{\circ}C$, an excessive preload condition is expected compared with that at room temperature, and the durable life decreases by 20.3 %.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.491-497
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• 2017

In recent years, 3D printing has received increasing attention due to its potential for direct fabrication beyond the traditional rapid prototyping. 3D printing has the advantage of being able to manufacture complicated shapes that were thought impossible to produce by traditional manufacturing processes. This advantage has driven applications of 3D printing to direct manufacturing of functional parts, such as lightweight structures and component integration. In this study, a porous shell structure is designed for the purpose of weight reduction and ventilation. Finite element (FE) analyses are performed to compare the effective stiffness of the porous structure with the conventional solid structure. Structural reinforcements are also considered in order to make up the stiffness reduction due to the porosity, and the relevant FE analyses are performed to investigate the effect of the reinforcement design on the bending stiffness. The optimized reinforced structure is then proposed through response surface analysis.

• Fire Science and Engineering
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• v.30 no.1
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• pp.17-23
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• 2016

Membrane structures can be used to create diverse lightweight structural forms using ductile membranes made of coated fabric. Using membrane structures, it is possible to construct large covered spaces relatively quickly and economically, and hence, they are being applied within various applications. The structures are light-weight, transparent, flexible in their application, economical and easy to maintain, and as such, their usage is being expanded. However, despite their prevalence, the standard for membrane material performance in terms of fire safety is still inadequate, and the development of membrane materials with excellent flame resistance performance is being demanded. This study determined flame resistance performance of architectural membranes, including PTFE, PVDF, PVF and ETFE film membranes, through flammability testing and incombustibility testing.

• Fire Science and Engineering
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• v.30 no.1
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• pp.86-95
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• 2016

Weight-bearing building materials are substantially weakened under high temperatures, and this is evident through the collapse of structures once engulfed by fire. Currently, there is no scientific or technological process of evaluating the real-time structural stability of a building whcih is engulfed by flame. There are many building design specifications which aim to reduce the risk of fire, but little consideration given to fire officer safety while operating in a dangerous building. This paper aims to provide direction within building policy in order to ensure the safe evacuation of fire-fighters in case of an impending building collapse. This paper suggests evaluation criteria for buildings which are damaged due to fire, autilizing current information on fire-resistant building design and a fire-resistant capacity.

• Journal of the Korean Regional Science Association
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• v.15 no.1
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• pp.75-92
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• 1999

In this study, the present state of fiscal crisis for local governments after IMF is analyzed, firstly. its implications Characteristics of structural reform of finance after IMF bailout in Korea are examined, secondly. Since Korea was shocked by the currency crisis at the end of 1997, its local governments have also faced fiscal difficulties. The Depression of national and local economies led to decreases in tax revenues of local governments. And these shrunken revenues led to their expenditure cuts. Many investment plans were curtailed, and ordinary expenditures were also reduced sharply. The negative influences of the currency crisis on local government's finances can be examined in terms of fiscal revenue, fiscal spending, and debt burden. As a result many local governments are now experiencing fiscal stress, and some of them are even faced with fiscal crisis although the possibility of extreme measures, such as moratoriums or bankruptcies, is very slim. This is due in part to the weight of debt in local governments' budgets having remained small since the debt of local governments has been controlled by the central government. Another reason is that, central government, which functions as a lender of last resort for the local governments, will pay the debt for them. Also, without a legal system which stipulates the adjudication of bankruptcy for municipalities in Korea, local Korean governments have no legal right to declare bankruptcy. Although not a single municipality has fallen into insolvency, yet, this trend will continue to deepen as the recession continues and may lead to a situation where manu local governments fall into virtual bankruptcy in the near future, and its effects on society, as a whole, will be serious. Therefore, measures to prevent and overcome such an extreme situation are necessary, but both short-and long-term policies should be to cope with the current fiscal crisis and to prevent the deepening of the current situation.