• 소성∙가공
• /
• 제13권1호
• /
• pp.53-58
• /
• 2004

The microstructural changes of Al-Zn-Mg-Cu alloy containing Sc during hot extrusion and post heat treatment were investigated. Two kinds of Al-Sc alloys with different alloying elements (B1, B2) were hot extruded to make T-shape bars at extrusion temperature of $380^{\circ}C$, then the bars were solution treated at $480^{\circ}C$ for 2hrs followed by artificial aging at $120^{\circ}C$ for 24hrs. The interior microstructure of as extruded bar consisted of elongated grains, however, fine equiaxed grains were also observed around surface. The microstructural gradient suggested that different restoration process could proceed during the hot extrusion. For B1 and B2, different grain growth behaviors were found around the surface during the post heat treatment. Rapid grain growth behavior was observed for B1 around the surface, however, it was not observed for B2. Orientation pinning, which was related with the evolution of preferred orientation, and precipitation were thought to be responsible for the rapid grain growth.

• 한국주조공학회지
• /
• 제34권5호
• /
• pp.156-161
• /
• 2014

This study is focused on the effect of $Al_2Ca$ as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at $540^{\circ}C$ and $170^{\circ}C$, respectively. Although A356 alloy, which $Al_2Ca$ was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that $Al_2Ca$ added A356 alloy has a certain improvement in oxidation resistance.

• 치위생과학회지
• /
• 제24권2호
• /
• pp.107-114
• /
• 2024

Background: This study aimed to analyze trends in oral health research among people with disabilities. Methods: Data were obtained from 70 oral studies on individuals with disabilities from 2000 to 2024. Keywords were analyzed. Frequency, betweenness centrality, and cluster analyses were performed using NetMiner. Results: The main keywords for oral health research on disabled people were oral health, dental caries, DMFT (decayed-missing-filled-teeth), dental treatment, oral health centers, and disabled children. As a result of the centrality analysis, DMFT had the highest connectivity, followed by disabled children, special care dentistry, oral health behavior, periodontitis, and health insurance. Cluster analysis results of research on disabled people: Group 1, oral diseases and functions of disabled people; Group 2, oral care for disabled children; Group 3, dental treatment for disabled people; Group 4, oral health policy; Group 5, oral care by dental hygienists; and Group 6, conservative dentistry. Conclusion: Considering the increase in the number of disabled people in a super-aging society, research on ways to promote oral health for disabled people, oral health policies, and training of oral health experts for disabled people is required.

• 대한토목학회논문집
• /
• 제11권1호
• /
• pp.29-36
• /
• 1991

장섬유 강화 마그네슘 복합제(FP/ZE41A)의 피로 균열 성장 거동에 대한 열처리 효과를 규명한 것으로 TEM관측에 의해 알루미나 섬유와 마그네슘 복합 매트릭스간의 상호 접변을 완화시키기 위하여 풀림을 실시하였다. 피로 균열 성장 방향에 수직한 섬유와 평행한 섬유들에 대한 피로 균열 성장 거동에 관한 실험을 실시 한 바, 피로 균열 성장 방향에 수직한 시험편의 경우 열처리를 실시한 시험편은 잔류 응력을 제거시키지 않은 시험편에 비해 피로 균열 성장에 대한 더 많은 저항성을 갖고 있음을 알수 있었다. 그러나, 이에 반해 피로 균열 성장 방향에 평행한 시험편의 경우는 잔류 응력을 제거시키지 않은 시험편 이 열처리를 실시한 시험편에 비해 더 많은 피로 균열 성장 저항성을 내포하고 있다는 피로 균열 성장 거동에 대한 차이점을 발견할 수 있었다. 피로 파괴 표면에 대한 연성 파열과 섬유 박리를 SEM관찰한 결과 열처리는 피로균열 성장 거동에서 지적된 바와 같이 섬유와 매트릭스 상호면의 강도를 약화시킨다는 것을 알 수 있었다.

• Restorative Dentistry and Endodontics
• /
• 제35권6호
• /
• pp.461-472
• /
• 2010

연구목적: 본 연구는 미세인장결합강도와 파괴인성을 통해 복합 레진 수복물의 수리 시기와 표면 처리 방법에 따른 파괴 거동을 알아보고자 시행되었다. 연구 재료 및 방법: Short rod 시편과 composite resin specimen block을 준비하여 표면 처리 방법에 따라 none-treated, sand blasting, bur roughening 군으로 나누고 이를 다시 즉시군과 2주 지연군으로 나누어 수리했다. 결과: 미세인장결합강도와 파괴인성을 측정한 결과, 두 실험 모두에서 즉시군이 지연군보다 높은 값을 보였다. 기계적 표면 처리군이 none-treated군보다 높은 값을 보였고, sand blasting과 bur roughening 사이에 유의한 차이는 없었다. 파괴인성과 미세인장결합강도는 상관 관계가 없었다. FE-SEM을 보아 수복물의 탈락은 균열 전도와 관계가 있는 것으로 보인다. 결론: 수리된 복합 레진의 파괴 거동 평가에는 파괴인성 실험이 적합하다.

• 한국보건간호학회지
• /
• 제17권1호
• /
• pp.47-57
• /
• 2003

The purpose of this study was to investigate health status and health promoting behaviors of female elderly, and their needs for health-related services in an urban-rural combined city. The data were collected from the subjects registered in senior welfare center and senior citizens' clubs. A total of 119 women were participated in the survey. The results of the study are as follows; 1. The subjects perceived their health status relatively unhealthy. Their health promotion behavior score was 10.82 (range 0-17), and more than $60\%$ of them performed well in smoking and drinking control, regular meal. taking breakfast, and maintaining good relationship with others. 2. The most needed service was health screening followed by health risk assessment, disease diagnosis and treatment. 3. The most demanded education was on dementia prevention, followed by exercise, balanced diet, and maintenance of memorial and mental capability. 4. As the health interest and the health responsibility increased, the need for health service increased as well. Likewise, the health education needs increased as the health interest, health responsibility, and health promotion behavior increased. The results show that the health promotion programs for female elderly need to be focused, primarily, on health screening, health risk assessment, medical services for disease diagnosis and treatment, and health consulting and education. And health consulting and education programs should be designed to promote health interest and health responsibility of female elderly, change positively their attitude to aging, and include education on dementia prevention, exercise and nutrition management. Recommendations are discussed.

• 한국콘텐츠학회논문지
• /
• 제14권6호
• /
• pp.271-280
• /
• 2014

본 연구는 고령화 사회를 맞이하여 노인들의 구강건강상태와 의치필요도를 알아보고자 하였다. '국민건강 영양조사 제5기 1차년도 (2010)원시자료'의 건강설문조사와 구강검진을 활용하여 노인의 주관적 구강건강 수준과 구강관리 행태에 따른 의치필요도를 조사하기 위하여 분석하였다. 목표 모집단을 우리나라에 거주하고 있는 대한민국 국민이며, 65세 이상 노인표본 1,419명을 조사하였다. 연구대상자의 구강건강상태에 따른 의치필요도의 상관관계를 알아보기 위하여 카이제곱검정과 교차비 확률을 이용하여 분석하였다. 연구결과 주관적인 구강건강상태 중 씹기 불편(p<0.001)과 말하기 불편(p<0.001)이 유의미한 관련성이 있는 것으로 검토되었다. 객관적 구강건강상태에서는 치아우식증 유병률(p<0.001)이 있는 노인에서 의치필요도가 높게 나타났다. 구강건강관리 행태에 따른 의치 필요도는 구강위생보조용품을 사용하지 않는 노인과 치과치료를 받지 않는 노인에서 의치필요도가(p<0.001)매우 높은 것으로 검토되었다. 본 연구의 결과로부터 노인의 주관적 객관적 구강건강상태 및 구강건강관리 행태에 따른 의치필요도가 파악되었으며 이러한 결과의 바탕으로 노인의 구강건강상태가 지속적으로 유지 보존될 수 있도록 활발한 구강보건교육 및 전문가 관리가 활발하게 이루어질 수 있도록 프로그램이 계발되어야 할 것이다.

• 대한치과보철학회지
• /
• 제22권1호
• /
• pp.95-108
• /
• 1984

Even though the tarnishing and corrosion problems characteristic with dental silver-palladium alloy are not yet fully solved, it is recently widely used because of its low cost. However the effects of major alloying elements on the various properties of this system are not fully understood. The object of this research is to clarify the effects of In and Zn additives on the corrosion and tarnishing resistances and precipitation hardening behavior of this sytem, using electrodynamic polarization, immersion, and Vicker's microhardness test and X-ray diffraction and electron probe micro analysis methods. The obtained results were as follows: I. As indium content is increased, both the corrosion resistance in Cl-solution and microhardness are also increased while the tarnishing resistance is decreased. 2. As Zinc content is increased, the corrosion resistance is decreased, but tarnishing resistance is increased 3. At 70Ag-25Pd-2.5Zn-2.5In composition, the precipitation harding behavior was mot significant. The optimum aging temperature was $450^{\circ}C$ and the time was 2 hrs. The resulting specimen of this work carried 180VHN. 4. Under the heat treatment, the changes in the mechanical property are due to the changes in the shape and composition of dendrite matrix, namely, it is because of the precipitation hardening behavior which has been proved by electron probe micro analysis and optical microscopic finding.

• 한국치위생학회지
• /
• 제20권1호
• /
• pp.41-51
• /
• 2020

Objectives: The purpose of this study was to investigate the effects of oral health behaviors of patients with hypertension and diabetic patients on the number of remaining teeth in Korean adults over 45 years of age, furthermore, we also aimed to develop oral health care programs and health promotion for patients with hypertension and diabetes. Methods: Altogether, 1,526 subjects with hypertension and diabetes from the 6th Korean National Health and Nutrition Survey (2013-2015) were analyzed. Results: A multiple logistic regression analysis was performed to determine the effects of oral health behavior and periodontal disease on residual teeth in patients with hypertension and diabetes after adjusting for age. We found 1.53 times the risk of having less than 20 remaining teeth in the group of brushing more than 3 times a day (95% CI: 1.00,2.35, p<0.001), 2.27 times (95% CI: 1.23-4.17, p<0.05) in the group not using the dental floss group 0.05), compared to the group undergoing regular dental check-up (95% CI: 0.93-1.85, p>0.05), compared to the non-smoking group 0.77 times (95% CI: 0.51-1.14, p>0.05), 1.33 times (95% CI: 0.98-1.80, p>0.05) in the drinking group compared to the non-drinking group, in the periodontal disease group, the risk of having less than 20 remaining teeth was 2.19 times higher (95% CI: 1.48-3.24, p>0.001) than in the normal group. Conclusions: As a super-aging society, develops in Korea, the prevalence of hypertension and diabetes will increase gradually. Therefore, an oral health policy should be implemented at the national level for the prevention and treatment of periodontal disease as well as the management of oral health the elderly.

• 한국주조공학회지
• /
• 제21권4호
• /
• pp.239-245
• /
• 2001

Microstructure and mechanical properties of Sn-3.1 wt.%Ag-6.9 wt.%Bi system solders on Cu-substrate were studied. The Sn3.1 wt.%Ag-6.9 wt.%Bi alloy was designed by phase diagram and chemical properties and was prepared by melting in argon atmosphere. The mechanical properties of solder/Cu joints were examined by shear strength test, and also creep test. The microstructure of Sn-3.1 wt.%Ag-6.9 wt.%Bi alloy consists of Bi-rich phase and $Ag_3Sn$ precipitate in {\beta}-Sn$ matrix phase. The shear strength of the joint was decreased with aging treatment. Crack path under shear test was through the solder. Similar crack path change mode was observed at the creep test of solder/Cu joint. The creep behavior of Sn-3.1 wt.%Ag-6.9 wt.%Bi alloy represented the inverse primary creep behavior at all test condition. It is suggested that the inverse primary creep behavior is induced from Bi solute atoms in Sn-matrix. The creep resistance of Sn-3.1Ag-6.9Bi alloy is better than that of Sn-3.5 wt.%Ag alloy at all test conditions.