• Journal of Applied Reliability
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• v.10 no.1
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• pp.1-9
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• 2010

In general, the performance of a component degrades as time goes by and failure of a component occurs when the performance degradation reaches a pre-specified level. It is difficult to obtain the failure time distribution data or the necessary number of failure data especially for the metal or machine part. Thus, a design of reliability qualification test based on performance distribution is more effective than failure time distribution. In this study, a performance-based reliability qualification test is developed and a numerical example is provided to illustrate the use of the developed reliability qualification test. This approach could be applied to many kinds of metal or machine part whose magnitude of strength could not be evaluated during at any random points but judgement can be made by only failure of the part. Besides, it is also possible that any parts which have a similar failure characteristics could be applicable to the developed reliability qualification test.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.760-767
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• 2006

Underestimation of rock joint shear strength comes from an inadequate consideration of roughness mobilization behavior, which is changed by asperity size as well applied normal load. In this study, we performed rock joint shear tests, and studied the roughness mobilization characteristics related with the scale of normal stress and asperities. Test specimens with artificial triangular asperities were manufactured. The specimens consisted of 3 types, and each type represented unevenness, waviness and total roughness(superposition of unevenness and waviness). The experimental results show that the roughness mobilization characteristics are varied by the scale of normal stress and asperities. Furthermore, the investigation shows that the rate of geometrical component and mechanical component in the total roughness is also varied by the scale of normal stress and asperities. These results suggest that we should consider the roughness mobilization characteristics for the roughness quantification and the shear strength modelling.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.145-146
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• 2018

In this study, the purpose of the study is to determine the depth of damage caused by early frost damage in concrete slab structures under the conditions of external temperature during winter. In other words, we intend to analyze the depth variation of the early frost damage as the thickness of the normal strength concrete slab members changes. As a result, the thinner the component was, the deeper the early frost damage was found to be, and the resulting increase in brightness of the concrete was delayed. and It is analyzed that under this test condition, an early frost damage was created with a thickness of 50 mm for the member and a thickness of 39 mm for the member of 300 mm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.557-564
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• 2002

One of the primary factors like plate structure In ship is redundancy structure that is comparable with ocean structure and frame structure. The more component material becomes buckling collapsed locally the less structure stiffness becomes accordingly. As a result, by increasing the load distribution of any other subsidiary structure continually component member collapses, therefore the structure could be in danger of collapse. So, in order to interpret this phenomenon precisely, the study on boundary condition of the ship's Plate and post-buckling analysis must be considered. In this study, the rectangular plate is compressed by the in-plane load. Buckling ＆ Ultimate strength characteristics we applied to be the elasto-plasticity large deformation by F.E.M. On this basis, elasto-plasticity of the plain plate are investigated. This study proved elasto-plasticity behaviour of tile ship's plate In accordance with boundary condition based on the series analysis In case of the compressive load operation.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.3-9
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• 2013

In ultra high strength concrete, when electric arc furnace oxidizing slag is substituted for sea sand as fine aggregate, compressive strength was improved about 15 MPa. To figure out the cause of the improvement in compressive strength, this study considered the dissolution characteristics of Ca component in fine aggregate and examined the microstructure, porosity, microhardness, and Ca/Si mole ratio on the interface of fine aggregate and paste. And to examine the mechanism of strength improvement resulted from the shape of fine aggregate, this study measured the surface roughness of fine aggregate with AFM. According to the result of this experiment, the mechanisms of strength improvement in ultra high strength concrete resulted from the use of electric arc furnace oxidizing slag as fine aggregate can be divided into chemical and physical mechanisms. In the chemical mechanism, the soluble Ca component contained in electric arc furnace oxidizing slag is dissolved and forms a hydrate between fine aggregate and paste to improve the interlocking strength of fine aggregate-paste. Also, it makes the microstructure around the fine aggregate. And in the physical mechanism, electric arc furnace oxidizing slag has a twice greater surface roughness than sea sand, so the interlocking strength between fine aggregate and paste increases, which contributes to the development of compressive strength.

• IE interfaces
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• v.17 no.2
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• pp.190-199
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• 2004

Recently, many enterprises are introducing a workflow management system for the successful implementation of BPR(Business Process Reengineering). Proposed in this study is the workflow management system which has a light-weight component structure and an XPDL(XML Process Definition Language) file interpretation facility. The XPDL is the standard process definition exchange format developed by WfMC(Workflow Management Coalition). The major causes of inefficiency at current implementations of workflow management systems are the centralized workflow engine structure and the use of proprietary workflow definition format among most solutions. The proposed light-weight component structure in this study is the intermediate structure that takes the strength of both centralized and distributed workflow engines. And a prototype workflow system which uses an XPDL process definition file as input is developed through the thorough analysis of functional requirements.

• Journal of Korean Academy of Nursing
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• v.39 no.4
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• pp.584-593
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• 2009

Purpose: The purpose of this study was to investigate the effect of stretching, muscle strengthening, and walking exercise on the cardiopulmonary function and health-related quality of life in hemodialysis patients. Methods: Twenty-one patients in the intervention and the control group participated in the exercise respectively on maintenance hemodialysis at four university hospitals. The exercise was composed of 20 to 60 min per session, 3 sessions a week for 12 weeks. The effect of exercise was assessed by cardiopulmonary function (peak oxygen uptake, peak ventilation, peak respiration rate, maximal heart rate, and exercise duration) using a cycle ergometer. Grip strength was measured by dynamometer, and flexibility was measured by sit and reach measuring instrument. Health-related quality of life was measured using Medical Outcomes Study Short Form-36. Results: Peak oxygen uptake, peak ventilation, peak respiration rate, exercise duration, grip strength, flexibility, and physical component scale were significantly improved in the intervention group after 12 week's exercise compared to the control group. Conclusion: These findings indicate the exercise can improve cardiopulmonary function, grip strength, flexibility, and physical component scale of health-related quality of life in hemodialysis patients.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.142-143
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• 2014

In this study, as to enhance the efficiency and workability, binder contained 3 types of gels have been used to replacement the OPC. Fundamental properties and length change of the concrete have been tested to evaluate the effect of different binders. The following results could be made as the conclusion. When the binder contained 3 types of gels used, the flowability increased, whereas the air content decreased. There showed some different air content when the component of binder changed but the difference was consider as limit. For the strength properties, with the using of binder contained 3 types of gels increased the strength. Specimen of FA20SF5 showed the better strength and lower length change of drying shrinkage than other specimens.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.19-25
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• 2005

Ti6Al4V alloy have been mainly used as implant materials. Ti-6Al-4V alloy instead of pure Ti is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength. But it has been reported recently that vanadium component expresses cytotoxicity and carcinogenicity and aluminium component is related with dementia of Alzheimer type. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study, in addition Ta and Hf were added to Ti-40wt.%Nb alloy to improve its mechanical properties. This paper was described the influence of heat treatment of Ti-40Nb alloys with 2wt%Ta, 2wt%Hf on the mechanical properties. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at 1050$^{\circ}C$ for 24 hr. and then were aged after solution heat treat at $\alpha+\beta$ and $\beta$ regions. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1. The mechanical properties Ti-40wt.%Nb were improved when 2wt.% Ta and 2wt.%Hf were added. 2. The higher tensile strength value and elongation at solution heat treat was higher than solution heat treat and then were aged.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.31-38
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• 2010

Bus manufacturers have tested and studied the dynamic collapse behavior of a bus body structure in rollover since UN ECE established ECE Regulation 66 to provide the requirement for the strength of bus structure. In spite of the costly cycles of practical tests, however, it is still a hard task to meet the rollover regulation by means of local reinforcements in the bus structure. Therefore it is necessary to develop a well designed strategy for the rollover strength implemented in the early stage of vehicle development. In this study, the suitable development method for each design stage from a component to complete body structure was considered to make a well-established development process of a bus body structure for rollover safety. For the efficient approach of the concept design stage, a numerical model based on the plastic hinge theory was used instead of detailed shell models. After setting up the concept design for the component size and geometry, the shell model was used to confirm and optimize the whole structure composition. The process developed in this study was practically used as an effective method to predict the rollover behavior of a new bus body structure.