• Title/Summary/Keyword: 재료 평가 지수

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Evaluation of Yield Surfaces of Epoxy Polymers Considering the Influence of Crosslinking Ratio: A Molecular Dynamics Study (분자동역학 해석 기반 가교율에 따른 에폭시 폴리머의 항복 표면 형상 평가)

  • Jinyoung Kim;Hyungbum Park
    • 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.

Assessment of Ecological Flowrate and Fish Community to Weir Type in Stream (하천에서 보 형태에 따른 어류군집 구조 및 생태유량 평가)

  • Hur, Jun Wook;Jang, Chang Lae;Kim, Kyu Ho
    • 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.

Development and Feasibility Evaluation of CsPbBr3 Dosimeter for Brachytherapy (근접방사선치료용 CsPbBr3 선량계 제작 및 적용가능성 평가)

  • Yang, Seung-Woo;Park, Sung-Kwang
    • 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.

Evaluation of the proximal contact and comparison of methods for measuring in normal dentition (건강한 자연치열에서 인접면 접촉의 평가 및 측정방법에 따른 비교분석)

  • Ji-Eun Kim;Cheong-Hee Lee
    • 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 effects of dental prostheses to the quality of life among the elderly (일부 노인의 치과보철물 상태가 구강건강관련 삶의 질에 미치는 영향)

  • Hur, Ik-Gang;Lee, Tae-Yong;Dong, Jin-Keun;Hong, Song-Hee
    • 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.

Surrogate Model-Based Global Sensitivity Analysis of an I-Shape Curved Steel Girder Bridge under Seismic Loads (지진하중을 받는 I형 곡선거더 단경간 교량의 대리모델 기반 전역 민감도 분석)

  • Jun-Tai, Jeon;Hoyoung Son;Bu-Seog, Ju
    • 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.

Evaluate spent mushroom substrate for raising bed soil of rice (버섯 수확 후 배지의 수도용 상토로써의 활용가능성 평가)

  • Oh, Tae-Seok;Park, Youn Jin;Kim, Tae-Kwon;Kim, Chang-Ho;Cho, Yong-Koo;Kim, Seong-Min;Shin, Dong-Il;Koo, Han-Mo;Jang, Myoung-Jun
    • Journal of Mushroom
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    • v.13 no.3
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    • pp.250-255
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    • 2015
  • In this study spent mushroom substrate has ingredient raising rice bed soil. spent mushroom substrates are organic content is 60.72% were nitrogen - phosphoric acid - potassium is 1.39 - 0.89 - 0.81% of the chemical characteristics determine. Post-harvested mushroom substrates of the stabilization process, the temperature of the 20 days time progress in the pH of the rise and fall of temperature down were germination index also 77, as identified, Spent mushroom substrate bed soil for raising rice Ingredient to take advantage of the 20 days or more stabilization process needed to be investigated. Rice seed germination characteristic is in the common bed soil for raising rice ingredients manufactured control group and the comparison in spent mushroom substrate is 10% or less of a mixed experimental population of the germination rate is 82% was more than average days to germination and germination energy, even a statistical significant difference is or control group than good level was ok. Growth initial also spent mushroom substrate is 10% or less of a mixed experimental population of shoot dry matter (top) and grave less than control group higher as confirmed spent mushroom substrates are bed soil for raising rice ingredients are likely to take advantage of the high, as was the judge.

Evaluation of the stability of sandblasted, large-grit, acid-etched implants with tapered straight body design (테이퍼드 직선형 SLA 임플란트의 안정성 평가)

  • Kim, Yong-Gun;Lee, Kyu-Bok
    • Journal of Dental Rehabilitation and Applied Science
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    • v.34 no.2
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    • pp.80-88
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    • 2018
  • Purpose: Implant surface modification and implant design are the principle targets for achieving successful primary stability. The aim of this study was to measure implant stability quotient (ISQ) values of sandblasted, large-grit, acid-etched (SLA) implants with tapered straight body design during the healing period, and to determine the various factors affecting implant stability. Materials and Methods: To measure implant stability, resonance frequency analysis (RFA) was performed in 26 patients (13 women and 13 men) with 44 SLA implants with tapered straight body design. Implant stability (ISQ values) was evaluated at baseline and healing abutment connection (12 weeks), and the correlations between RFA and insertion torque (IT), bone quality, and jawbone were determined. Results: The mean ISQ value of the implants was $69.4{\pm}10.2$ at the time of implant placement (baseline) and $81.4{\pm}6.9$ at the time of healing abutment connection (P < 0.05). Significant differences were found between RFA and bone quality and between RFA and jawbone (P < 0.05). No significant differences were found between RFA and IT, insertion area, fixture diameter, and implant length (P > 0.05). Conclusion: ISQ values of SLA implants with tapered straight body design were high at baseline and healing abutment connection. It was concluded that SLA implants with tapered straight body design show improved primary and secondary stability, and that immediate or early loading may be applicable.

The Analysis of Cracks in PSC Girder Using High Flowing Concrete (고유동 콘크리트를 사용한 PSC 거더 균열 분석)

  • Lho, Byeong Cheol;Ahn, Gwang Su;Kwak, Kil Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.126-135
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    • 2013
  • Recently, mass concrete with high flowability are widely used to improve the quality and constructability in the longer span construction of prestressed concrete bridges, but it may induce nonstructural cracks due to the hydration heat and autogenous shrinkage etc. The stresses in concrete were evaluated by various experiments and numerical analysis. The tensile stress in mass concrete was increased in connection with the accumulation of hydration heat. Moreover, large amount of autogenous shrinkage from powder type admixture could add the tensile stress to mass concrete near anchorage zone. The tensile stresses in anchorage zone by heat and autogenous shrinkage exceeded the tensile strength of early stage of concrete, and small amounts of stress increasement were shown in other parts of PSC girder.

A Comparative and Parametric Study of Slope Stability Using a Probability-based Method in Railway Slope (철도 사면에서 확률론적 기법을 이용한 사면안정성 매개변수 비교연구)

  • Choi, Chan-Yong;Kim, Ju-Yong;Eum, Ki-Young
    • Journal of the Korean Geosynthetics Society
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    • v.11 no.4
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    • pp.17-25
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    • 2012
  • In this study, it was carried out reliability analysis and slope stability analysis in a standard cross-sectional embankment on high speed railway. It was confirmed that changing tendency of safety factor with various parameter of each soil materials properties and trends of the probability of failure according to the reliability index. The results have shown that a safety factor were relatively large affected an cohesions and internal friction angle of soil compared to the unit weight of soil. Also, most of the standard cross-sectional embankment in high speed railway was generally evaluated the level of below average (below average) by the reliability analysis according to criterion in US. Army but the 12m height of dry embankment case was shown bad condition as Poor.