Effect of Filler Particle Characteristics on Yield Stress and Plastic Viscosity of Sulfur Composites

Department of Urban and Environmental Engineering (Urban Infrastructure Engineering)Since sulfur has fluidity only at specific temperature (over 115 ??C) and it is very sensitive to the temperature, it is necessary to quantitatively evaluate the workability of sulfur concrete. In this study, we considered the sulfur composite as a suspension of filler particles, which are the blends of cement and fly ash, and investigated the influence of filler properties on the rheology of the sulfur composite in paste level, which made of modified sulfur and fillers. The rheological properties of modified sulfur and sulfur composite are measured by parallel plates and the properties of filler particles were measured by laser diffraction. Bingham model to the selected shear strain rate showed better trends of rheological properties of sulfur composite. Yield stress of sulfur composites is mainly affected by the volume fraction of fillers and the type of fillers. Plastic viscosity is mainly affected by the surface area of fillers in sulfur composite. The rheological results and the Krieger-Dougherty model confirmed the intrinsic viscosity in the model equation is affected by the type of binder regardless of their volume fraction in sulfur composite. Consequently, the sulfur composite follows the suspension-rheology models when the proper content of filler was used, which is less than 30% in sulfur composite, and it implies the suspension theories can be applied to the materials based on the sulfur binder.clos

한국 노인들에서 구강건강 지표에 따른 객관적 저작력

학위논문 (석사) -- 서울대학교 대학원 : 치의학대학원 치의학과, 2021. 2. 김현덕.Objective: To investigate the distribution of objective occlusal force (OF) and its association with oral health indicators (OHI) such as denture status, number of natural teeth (NT), natural and rehabilitated teeth (NRT) among Korean elders after controlling for various confounders encompassing socio-demographic factors, behavioral factors and health factors including oral health. Background: With the global increase in the ageing population, effective oral function including occlusal force is an important goal in geriatric oral health. Many studies have used OHIs such as denture status, NT and NRT as a surrogate of OF. Hence, there is a need to clarify the objective OF according to OHI. Materials and Methods: This cross-sectional study recruited 551 elders from the Sungbook-Gu health education cohort. Occlusal force measured using Prescale II was an outcome variable. OHI assessed by dentists was main explanatory variables. Analysis of covariance and multivariable linear regression models were applied to evaluate the association of OHI with OF. Sex and age group stratified analyses were also applied. Results: OF (Newton[N]) was higher in dentate elders than denture wearers (p<0.05). The adjusted mean occlusal force was 468.3±17.1N for dentate elders, 289.8±28.7N for partial denture wearers, 268.9±47.7N for complete denture wearers. NT showed the highest association with OF (partial r=0.348, p<0.05). OF was higher in males and elders aged less than 75 years. Conclusion: OF was significantly associated with OHI and could be a robust indicator for evaluating overall oral health status among elders.1. 목 적: 고령 인구의 세계적 증가로, 교합력을 포함한 효과적 구강 기능은 노인 구강건강의 중요한 목표이다. 그러나 많은 연구에서 객관적 교합력을 측정하지 않았고,혼란변수들을 또한 보정하지 않았다. 본 연구의 목적은 한국 노인들에서 구강건강지표인 치아상태, 자연치와 재활치수에 따른 객관적 교합력의 분포 및 연관성을 사회인구적 요인,행동 요인 및 구강과 전신건강요인을 보정한 후 평가함이다. 2. 방 법: 성북구 교육 코호트 총 551명의 노인들이 이 단면조사 연구를 위해 모집되었다. 결과변수인 교합력(N)은 프리스케일 필름을 사용하여 측정되였다. 설명변수인 구강건강지표는 훈련된 치의사들에 의해 조사되었다. 설명변수의 결과변수에 대한 연관성 및 영향력 평가를 위해 공분산분석과 다변수 회기분석이 적용되었다. 나아가 성별 및 연령 집단별 층화분석이 수행되었다. 3. 결 과: 객관적 교합력은 자연치보유 노인들에서 틀니장착 노인에서보다 높았다 (p<0.001). 보정된 평균 교합력(N)은 자연치보유 노인에서 468.3±17.1N 이었고 부분틀니장착 노인에서 289.8±28.7 N이었으며 전부틀니장착 노인들에서는 268.9±47.7 N이었다. 자연치아 수, 특히 구치부 자연치아수가 교합력에 가장 영향력이 컸다 (partial r=0.348). 교합력은 남성과 75세미만 노인에서 여성과 75세이상 노인에서보다 더 높았다. 결론적으로,객관적 교합력은 구강건강지표와 유의한 연관성이 있었다. 객관적 교합력은 구강건강 상태를 평가할 수 있는 적절한 도구 및 구강건강 지표가 될 수 있다.1. Introduction 1 1-1. Background 1-2. Objectives 2. Material & Methods 3 2-1. Ethical Considerations and study design 2-2. Participants selection 2-3. Assessment of occlusal force 2-4. Assessment of dental health indicators 2-5. Potential confounders 2-6. Statistical methods and analysis 3. Results 8 3-1. Characteristics of the participants according to denture status 3-2. Crude and adjusted occlusal force according to oral health indicators 3-3. Occlusal force according to sex and age group 3-4. Occlusal force according to denture status with NRT high and moderate group 3-5 Comparison between association impact of oral health indicators on occlusal force. 4. Conclusion 11 5. Discussion 15 Tables and figures 16 References 23 Abstract in Korean 26 Appendix 1(SPSS) Raw Statistics 27 Appendix 2 (STROBE) 88Maste

Vacuum Stability, Perturbativity, EWPD and Higgs-to-diphoton rate in Type II Seesaw Models

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