• Korean Journal of Construction Engineering and Management
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• v.13 no.2
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• pp.58-69
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• 2012

In modern society, rooftops and underground spaces are utilized for overcoming a confined space limitation of metropolitan areas. Therefore, floor covering construction is also increasing steadily. From the user's viewpoint, skid resistance performance of floor covering methods is a very important performance criterion for safety and amenity, but an appropriate design and assessment criteria for skid resistance performance are not available. This study presents the skid resistance performance assessment method of floor covering methods considering the sidewalk skid resistance standard of Seoul city and the guideline of the Ministry of Land, Transport and Maritime Affairs(MLTM) of Korea for road safety facilities'installation and maintenance. For this research, three alternatives among urethane floor covering methods are selected and their skid resistance performance is analyzed through an experimental study. The analyzed performance is also evaluated by the skid resistance performance assessment method. Finally, the comprehensive performance assessment including the results of skid resistance performance assessment is conducted by Value Analysis(VA) in order to encourage the construction methods of floor covering which have a high skid resistance performance. As a result of VA, the particle method which the skid resistance performance is improved up to four times more than other alternatives shows the highest performance index of 83.86.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.180-180
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• 2011

하천의 정상적인 기능 및 상태를 유지하기 위하여 필요한 최소유량을 의미하는 하천유지유량은 하천수질보전, 하천생태계보호, 하천경관보전, 염수침입 방지, 하구막힘 방지, 하천시설물 및 취수원보호, 지하수위 유지 등을 감안하여 산정하게 된다. 하천유량 변화는 하천내 동 식물에 영향을 미치며, 특히 고등 생물인 어류의 서식처, 산란장소 및 산란조건 등은 유량 및 수위변화에 민감하게 반응하므로 하천구간별 어류의 서식처 유지에 적절한 수심, 유속 등 수리 조건을 제공할 수 있는 유량을 산정하게 된다. 국내에서는 90년대 후반부터 생태계를 고려한 하천유지유량 개념이 도입되었으며, 어류의 적절한 수생 서식환경 평가를 위해 주로 유량 점증 방법론(IFIM, Instream Flow Incremental Methodology) 개념에 입각한 물리서식처 모형을 이용한 연구가 진행되어 왔다. 본 연구에서는 낙동강수계 13개 지점을 선정하여 어류상 조사를 실시하여 어류의 물리서식처 모형과 수심-유속-유량 관계곡선을 이용한 간단법을 이용하여 생태계 보전을 위한 필요유량을 산정하였다. 어류 물리서식처 모형으로는 어류서식환경 평가에 가장 광범위하게 이용되고, 생태적 특성을 반영할 수 있는 유량점증방법론의 PHABSIM(Physical HABitat SIMulation) 모형을 선택하였다. 현장 모니터링 및 문헌조사를 통해 각 지점별 대표어종을 선정하고, 유량, 수심, 저수로 하천단면, 하상재료와 같은 수리특성을 조사하고, 선정된 한계단면에 대한 유량측정을 실시하였으며, 수심-유속-유량 관계곡선을 통하여 각 지점의 대표어종이 서식할 수 있는 최소유량을 산정하였다. 또한 지점별로 서식처 적합도 지수(HSI, Habitat Suitability Index)와 가중가용면적(WUA, Weighted Usable Area)를 산정하였으며, 이는 PHABSIM 모형의 적용에 이용되었다. 물리서식처 모형과 간단법 적용결과를 비교해본 결과, 모든 지점에서 물리서식처 모형 적용결과가 간단법에 비해 크게 산정되었는데, 이는 간단법이 성어기 서식에 필요한 최소 수리조건을 선택하였지만, PHABSIM의 경우 성어기 어류서식의 최적 수심 및 유속을 이용하여 가중가용면적을 산정하기 때문인 것으로 판단된다. 어류서식과 관련된 많은 관련 데이터가 축적된다면 어류서식처에 맞는 최적의 생태유량을 보다 정확하게 산정할 수 있을 것으로 판단된다.

• Composites Research
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• v.22 no.5
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• pp.1-7
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• 2009

The vehicle structure of Automated People Mover(APM) made of aluminum honeycomb sandwich with WR580INF4000 glass-fabric epoxy laminate facesheets was evaluated by structural test and finite element analysis. The test of the vehicle structure was conducted according to JIS E 7105. The structural integrity of vehicle structure was evaluated by stress, deflection and natural frequency obtained from dial-gauge and acceleration sensor. And the proposed finite element models were compared with the results of structural test. The results of finite element analysis showed good agreement with those of structural test. Also, in order to improve the stiffness of vehicle structure, the modified underframe model with reinforced side sill was proposed in design stage. The composite vehicle structures with modified underframe model had the improved structural stiffness about 44%.

• Composites Research
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• v.36 no.5
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• pp.369-376
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• 2023

This study focuses on investigating the influence of epoxy polymer crosslinking density, a crucial aspect in composite material matrices, on the yield surface using molecular dynamics simulations. Our approach involved generating epoxy models with diverse crosslinking densities and subjecting them to both uniaxial and multiaxial deformation simulations, accounting for the elasto-plastic deformation behaviors. Through this, we obtained key mechanical parameters including elastic modulus, yield point, and strain hardening coefficient, all correlated with crosslinking conversion ratios. A particularly noteworthy finding is the rapid expansion of the yield surface in the biaxial compression region with increasing crosslinking ratios, compared to the uniaxial tensile region. This unique behavior led to observable yield surface variations, indicating a significant pressure-dependent relationship of the yield surface considering plastic strain and crosslinking conversion ratio. These results contribute to a deeper understanding of the complex interplay between crosslinking density and plastic mechanical response, especially in the aspect of multiaxial deformation behaviors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.141-147
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• 2024

In this study, micro CT images were used to confirm the tensile fracture strength according to the pore distribution characteristics of 3D printed concrete. Unlike general specimens, concrete structures printed by 3D printing techniques have the direction of pores (voids) depending on the stacking direction and the presence of filaments contact surfaces. Accordingly, the pore distribution of 3D printed concrete specimens was analyzed through quantitative and qualitative methods, and the tensile strength by direction was analyzed through a finite element technique. It was confirmed that the pores inside the 3D printed specimen had directionality, resulting in their anisotropic behavior. This study aims to analyze the characteristics of 3D concrete printing specimen and correlate them with simulation-based mechanical properties to improve performance of 3D printed material and structure.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.339-347
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• 2017

The objectives of this study were to analyze ecological characteristics of fish compositions and estimate the optimal ecological flow using the physical habitat simulation system (PHABSIM) in Wonju stream and Boseong river. We sampled fishes using two gears such as casting net and kicknet to determine fish distribution and also measured flow velocity, water depth, bed material at the point where fish collected. Total number of species and individuals sampled were 20 and 2,104, respectively and dominant species was Zacco platypus (39.7%) and subdominant species was Z. koreanus (RA: 15.8%) in Wonju stream. In Boseong river, collected fishes were 1,638 individuals, 28 species. Dominant and sub-dominant species was Z. platypus (RA: 22.0%) and Microphysogobio yaluensis (RA: 17.2%), respectively. For calculating habitat suitability index (HSI), we selected Z. platypus as representative fish species and analyzed water depth and flow velocity. Water depth and flow velocity were 0.2-0.6 m, 0.1-0.3 m/s, respectively in Wonju stream and 0.3-0.6 m, 0-0.3 m/s, respectively in Boseong river. According to the analysis of ecological flow simulation, optimal flow was 1.1 cms and 0.3 cms in Wonju stream and 0.4cms, 2.2cms in Boseong river at up and down stream respectively. WUA (Weighted Usable Area) was 9.5%, 26.6% in Wonju stream and 34.8%, 53.3% in Boseong river at up and down stream respectively.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.405-410
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• 2022

In brachytherapy, a radiation source is inserted into the body to kill tumor tissue. Therefore, it is important to accurately measure the location of the source and the dose distribution. In this study, a dosimeter that can be used for brachytherapy was developed using CsPbBr₃ which is cheaper than the existing detector materials and has a simpler manufacturing process. The CsPbBr₃ dosimeter performance was evaluated by analyzing reproducibility, linearity, and distance dependence in ¹⁹²Ir source. As a result of reproducibility evaluation, the RSD was 1.36%, which satisfies the standard value of 1.5%. As a result of the linearity evaluation, the R² value was 0.9993, which satisfies the standard R² of 0.9990. The distance dependence evaluation showed a signal value that decreased exponentially as the distance increased. The evaluation results show that the CsPbBr₃ dosimeter satisfies the evaluation criteria and can be used as a brachytherapy quality assurance dosimeter.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.198-203
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• 2023

Purpose. The aim of this study was to evaluate the proximal contact with a dental floss compared to a celluloid strip and a metal strip in normal dental arch and investigate what the most effective method for measuring is. Materials and methods. The subjects of this study was consisted with 20 healthy adults (10 males and 10 females) who had normal dentition. A dentist with more than 5 years of clinical experience evaluated the proximal contacts using a dental floss method, a celluloid strip method, and a metal strip method. Statistical analysis were performed by the use of Mann-Whitney U test. A P-value < .05 was considered statistically significant in all analysis. In addition, in the evaluation of proximal contact using a dental floss, the measurement of proximal contact using a celluloid strip and a metal strip was compared. Results. 80 % of all proximal contact was proper. Proper proximal contact was observed at the posterior area compared to the anterior area (P < .05). And male had proper proximal contact at the anterior area, female had proper proximal contact at the posterior area (P < .05). The consistency analysis between the results of the celluloid strip and the metal strip experiment on the results obtained from the floss using the consistency scale Kappa index shows that using celluloid strip is more advantageous than using the metal strip. Conclusion. Only 80% of all proximal contact was proper. Using celluloid strips with various thickness for evaluating of proximal contact is considered to be helpful for accurate measuring of proximal contact.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.101-110
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• 2010

Purpose: This study has been conducted in order to examine the oral health status and dental prostheses status, and the effects of dental prostheses to the oral health related quality of life among the elderly using social welfare centers. Material and methods: For this purpose, the researcher conducted a questionnaire survey and oral examination of 275 samples of old persons using 7 social welfare centers located in Daejeon metropolitan city. The oral health related quality of life was measured by GOHAI (Geriatric Oral Health Assessment Index). Results: 1. The less age and the more education and the more subjective economic status and living with spouse of family status, the higher GOHAI showed. 2. Mean age of first using of removable denture is 62.11 years old and average life cycle of removable denture is 10.76years. 57.5% of study subjects use removable denture and complete denture user of study subjects are 13.8%. 3. In the case that they use fixed prostheses rather than removable ones and in the complete denture they use both sides (upper and lower) rather than single side, showed higher GOHAI. 4. In the case that they showed higher degrees of satisfaction with dental prostheses and can use them always and showed no necessity for new dental prostheses and denture adaptation is good, GOHAI showed higher. Conclusion: In order to improve oral health related quality of life among the elderly who have many missing teeth, it is required to restore their masticatory ability to the normal level by restoring the missing teeth which has lost its function through providing proper dental prostheses.

• Journal of the Society of Disaster Information
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• v.19 no.4
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• pp.976-983
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• 2023

Purpose: The dynamic behavior of a bridge structure under seismic loading depends on many uncertainties, such as the nature of the seismic waves and the material and geometric properties. However, not all uncertainties have a significant impact on the dynamic behavior of a bridge structure. Since probabilistic seismic performance evaluation considering even low-impact uncertainties is computationally expensive, the uncertainties should be identified by considering their impact on the dynamic behavior of the bridge. Therefore, in this study, a global sensitivity analysis was performed to identify the main parameters affecting the dynamic behavior of bridges with I-curved girders. Method: Considering the uncertainty of the earthquake and the material and geometric uncertainty of the curved bridge, a finite element analysis was performed, and a surrogate model was developed based on the analysis results. The surrogate model was evaluated using performance metrics such as coefficient of determination, and finally, a global sensitivity analysis based on the surrogate model was performed. Result: The uncertainty factors that have the greatest influence on the stress response of the I-curved girder under seismic loading are the peak ground acceleration (PGA), the height of the bridge (h), and the yield stress of the steel (fy). The main effect sensitivity indices of PGA, h, and fy were found to be 0.7096, 0.0839, and 0.0352, respectively, and the total sensitivity indices were found to be 0.9459, 0.1297, and 0.0678, respectively. Conclusion: The stress response of the I-shaped curved girder is dominated by the uncertainty of the input motions and is strongly influenced by the interaction effect between each uncertainty factor. Therefore, additional sensitivity analysis of the uncertainty of the input motions, such as the number of input motions and the intensity measure(IM), and a global sensitivity analysis considering the structural uncertainty, such as the number and curvature of the curved girders, are required.