• The Journal of Advanced Prosthodontics
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• 제1권3호
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• pp.113-117
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• 2009

STATEMENT OF PROBLEM. Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. PURPOSE. The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). MATERIAL AND METHODS. Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad $S\ddot{a}ckingen$, Germany) were prepared in 40 mm (length) $\times$ 4 mm (width) $\times$ 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and $225^{\circ}C$ for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences ($\alpha$= .05). RESULTS. The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below $125^{\circ}C$ for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above $150^{\circ}C$, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. CONCLUSION. The monoclinic phase started to appear after aging treatment above $100^{\circ}C$. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above $175^{\circ}C$. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.

• 대한화장품학회지
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• 제42권3호
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• pp.303-309
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• 2016

연령이 증가함에 따라 피부 내부에서는 콜라겐의 합성 능력이 떨어지고 탄력섬유의 손상 및 matrix metalloproteinase (MMPs) 발현이 증가한다. 본 연구의 목적은 눈가에 주름이 형성되기 전에 연령이 증가할수록 피부 내부에서 피부 노화의 징후가 관찰된다는 것을 확인하고, 피부 내부에서 먼저 발생하는 노화의 징후가 칠엽담 지페노사이드 분획물 함유 크림(칠엽담 지페노사이드 크림)의 효능으로 인해 개선되는 것을 확인하는데 있다. 이에 본 연구에서는 육안으로 눈가에 주름이 관찰되지 않는 21 ~ 34세의 한국 여성 52명을 대상으로 임상 시험을 수행하였다. 이들에게서 연령이 증가함에 따라 피부 외부의 노화 징후가 관찰되지는 않지만 피부 내부에서 노화의 징후가 시작되는 시점을 진피치밀도 측정을 통해 확인하였다. 그리고 육안으로 주름이 관찰되지는 않았지만, 진피치밀도가 감소하는 연령대에서 칠엽담 지페노사이드 크림을 4주 및 8주 사용한 후에 진피치밀도 값이 유의하게 증가함을 확인하였다. 따라서 칠엽담 지페노사이드 크림이 피부 내부에서 먼저 진행되는 노화를 효과적으로 개선하는데 도움을 주며, 이 결과를 토대로 칠엽담 지페노사이드 분획물이 향후 주름 개선기능성 화장품 개발에 활용하기 적합하다고 판단된다.

• 한국작물학회지
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• 제48권4호
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• pp.334-338
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• 2003

The objective of this study was to demonstrate whether or not the deleterious effects of accelerated aging on seed vigour and viability are alleviated by interaction with gamma irradiation. Seeds of soybean (Glycine max L.) were artificially aged and subsequently irradiated with 4 and 8 Gy of gamma irradiation. Germination rate was negatively affected by accelerated aging and positively by gamma irradiation, with a positive interaction of a 3day-seed aging treatment occurring with 4 Gy, possibly suggesting that 4 Gy of gamma irradiation partially offset the adverse effects of seed aging on germination. However, 5-day aged seeds did not gain any benefits from the gamma irradiation. Electrolyte leakage from the seeds increased with the duration in days aged. Irradiation, however, did not impose any effects on the leakage. Respiration rate of the seed with hypocotyl and primary root was significantly low for the aged seeds, but not for the seeds with both irradiation and aging treatments. Accelerated aging decreased the dry weight of the hypocotyl and primary root of the seeds without any measurable effects of irradiation. $\alpha$-Amylase activity decreased with seed aging and positively responded to gamma irradiation. The data is discussed with regard to the possible roles of gamma irradiation for improving the seed vigour and viability of aged seeds.

• Asian Pacific Journal of Cancer Prevention
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• 제17권sup3호
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• pp.269-273
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• 2016

Presently, the world population of the elderly is growing. By improving health hygiene and welfare indicators, mortality and birth rates decrease and life expectancy increases, making the present century the century of elderly. Aging is one of the main risk factors for development of cancer, which itself is the second cause of death in old people. This study was conducted to assess the prevalence of cancer in the elderly covered by the Islamic Republic of Iran Broadcasting (IRIB) insurance program and to obtain suitable programs for cancer screening and early detection, increase patient survival, improve elderly care and to reclaim the cost of treatment in comparison to the national and international statistics. This is a cross-sectional study conducted on all elderly patients diagnosed with malignancy based on their pathology reports. In this study, of the total 75,500 patients covered by IRIB insurance, 17.2% belonged to the elderly group, males accounting for 53.3%. The most common cancers in old men were prostatic cancer (61.3%), colon cancer (10.3%) cancer of the hematologic system, bladder cancer (9.6%), lung cancer (9.1%), thyroid cancer (3.9%) and brain tumors (1.3%). In the elderly women, the most common cancers were breast cancer (80.1%), colon cancer (5.1%), thyroid cancers (4.4%), bladder and hematologic system malignancies (3.6), lung cancer (2.9%) and brain tumors (0.7%). In addition, the prevalence of cancer was almost the same as national and international statistics. With the exception of non-melanoma skin cancer no difference was shown in prevalence of cancer between IRIB elderly patients and the other groups of cancer patients in Iran.

• 대한지역사회영양학회지
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• 제6권5호
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• pp.773-788
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• 2001

The purpose of this study was to investigate the difference in nutrient intake according to the level of self-perception of health status, aging status and life satisfaction of the rural elderly. The factors for the study were surveyed by interview method. The subjects were 270 people(71 male, 129 female) aged over 65 years(73.5 $\pm$ 5.6ys) in the Ham-an area. The obtained results as follows : By evaluation of self-perception of health status, 57.5% of subjects answered they are in a bad health condition. The 91.5% of subjects had diseases(rheumatitis & arthritis 31.4%, cardiovascular disease 20.2%, gastric disease 10.2%). The women had more diseases than the men(p < 0.01). The subjects took medical treatment in private hospital(40.5%) and public health centers(35.0%). The men showed better level of aging status(p < 0.001) and life satisfaction index(p < 0.01) than the worsen. Living with spouse influenced the aging status(p < 0.05) and the more pocket money influenced life satisfaction(p < 0.05) and aging status(p < 0.05). The elderly who eat regularly 3 times a day(p < 0.05) and have a good appetite(p < 0.001) appeared to have positive effect on the self perception of health status and aging status. An increasing level of the self-perception of health status and regular exercise worked to improve aging status(p < 0.001). The habits of smoking and alcohol drinking, however had no effect on any index. The self-perception of health status affected the nutrient intake, but only in female elderly. The aging status and the life satisfaction index related overall positively to the intake of nutrients. In conclusion, the study shows that gender did influence nutrient intake in the elderly. The women who live alone rated lowest in social resources and health condition therefore their nutrient intake was also extremely in deficit. For successful aging, a program for rural elderly is needed, i.e. actions to provide minimum economic life, food delivery and psychological/physical health care through regional public health centers.

• Biomaterials and Biomechanics in Bioengineering
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• 제1권1호
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• pp.51-62
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• 2014

The purpose of this experiment was to evaluate the apatite-formation abilities of low-modulus Ti-7.5Mo substrates treated with NaOH aqueous solutions and subsequent ethyl alcohol aging before soaking them in simulated body fluid. Specimens of Ti-7.5Mo were initially treated with 5 M NaOH at $60^{\circ}C$ for 24 h, resulting in the formation of a porous network structure composed of sodium hydrogen titanate. Afterwards, the specimens were aged in ethyl alcohol at $60^{\circ}C$ for 5 or 10 min, and subsequently immersed in simulated body fluid at $37^{\circ}C$ for 3, 7 and 14 days. Ethyl alcohol aging significantly increased the apatite-forming abilities of Ti-7.5Mo. The amount of apatite deposited on the Ti-7.5Mo after NaOH treatment and subsequent ethyl alcohol aging was much greater, especially after the Ti-7.5Mo specimens were aged for 5 min. Due to its excellent combination of bioactivity, low elastic modulus and low processing costs, the Ti-7.5Mo treated with NaOH aqueous solutions and subsequently aged in ethyl alcohol has promising heavy load-bearing applications.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1398-1401
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• 2005

The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy were investigated using nano/micro-indentation and mechanical scratching, combined wit optical microscopy and atomic force microscope(AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at $150^{\circ}C$ for different times(0, 2, 4, 8, 10, 16, 24, 36 and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness ($H_V$) and indentation ($H_{IT}$) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

• 보존과학회지
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• 제35권5호
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• pp.416-429
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• 2019

보채는 지류문화재 보존처리의 마지막 단계로 주로 봉채를 사용한다. 본 연구는 지류문화재 보채에 쓰이는 4종의 봉채(본람, 등황, 연지, 대자)를 한지에 채색한 후 채색 양상을 확인하고 인공열화를 통해 색변화 양상을 확인하고자 하였다. 채색 양상을 관찰한 결과 본람·연지·대자는 미세한 안료 입자가 도포되는 형태였으며, 등황은 피막을 형성하였다. 봉채의 X선 회절분석 결과 본람과 연지, 대자에서 석영과 방해석, 납석이 공통적으로 검출되었고, 대자에서 침철석이 추가로 검출되었다. 인공열화 결과 습열열화에서 등황이 노란색에서 주황색으로 변색되었으며, 자외선열화에서는 등황과 연지가 탈색되었다. 결과적으로 봉채로 보채된 지류문화재는 등황이 채색된 경우 알칼리에 의해 주황색으로 변색될 수 있으며, 자외선에 의해 등황과 연지의 탈색이 우선적으로 발생하여 전체적인 색상이 어두워짐을 예측할 수 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.660-669
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• 1998

In this paper the Hardness and Electro-chemical corrosion of the Nimonic 80A superalloy were studied. It aging heat treatments was carried out at $650^{\circ}C$, $700^{\circ}C$, $750^{\circ}C$,$800^{\circ}C$ and $850^{\circ}C$ with different time of 20min , 30min 1hour, 2hours, 4hours, and 16hours additionally 64hours and 128hours at $650^{\circ}C$. The obtained results were as follows; 1. As aging temperature increased the time for the maximum hardness was reduced from 128hours at $650^{\circ}C$ to 30min at $850^{\circ}C$ whereas the highest hardness was reduced from Hv 381 at $650^{\circ}C$ to Hv 321 at $850^{\circ}C$. 2. In the Electro-chemical corrosion test as a function of aging heat treatment time and tem-perature the corrosion potential was reversely proportional to Hardness which indicated the effects of ${\gamma}/{\gamma}'$ coherency of base material and precipitate. 3. Initiation point of the pitting was observed at grain boundary twin boundary and near${\gamma}'$ pre-cipitates. The results of composition analysis by EDS at this point indicated that sulphur originat-ed from 1N $H_2SO_4$ solution was found in depletion at the grain boundaries and the pit which arouse in the near precipitates were lack of Al Ti and Ni which are the main element of ${\gamma}'$ The depletion of such element was cause breakdown of passive film.

• 한국재료학회지
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• 제9권7호
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• pp.695-700
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• 1999

7050 Al합금의 응력부식저항성에 미치는 2단 시효처리의 영향을 미세조직관찰, 전기전도도시험 및 SCF값을 평가함으로써 조사하였다. 최대 경도 이상 과시효에 의해 주 강화상인 η'상이 η상으로 변태되었고, 입내 및 입계에 존재하는 η상의 크기와 간격이 커졌으며 그 결과 응력부식저항성이 증대되었다. 2차 시효시간의 증가에 따라 전기전도도값은 증가되었으나 항복강도의 감소로 인하여 SCF값은 감소되었는데, 이러한 결과는 응력부식저항성의 증가를 의미한다. AMS 4107규격을 기준으로 하였을 때 7050 Al합금 단조재의 적정시효조건은 1차시효가 12$0^{\circ}C$에서 6시간, 2차시효는 $175^{\circ}C$에서 12시간이었다.