• 한국세라믹학회지
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• 제36권7호
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• pp.718-724
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• 1999

Densification and grain growth behavior of bimodal size distributed alumina powder mixtures were investigated as a function of amount of coarse alumina powder. The specimens which contained coarse alumina powder for 60to 80wt% showed the highest green density. The amount of shrinkage of sintered specimen lineraly decreased with the increase of coarse alumina powder up to the content that showed the highest green density and then further addition of coarse alumina powder led to drastic decrease of shrinkage of specimen. Especially crack-like void were concurrently revealed in the sintered body with addition of coarse alumina powder above 60wt% When the sintering temperature increased up to 1650$^{\circ}C$ the amount of shrinkage of specimen linearly decreased and the grain growth were also retarded with increase of coarse lauminia powder.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.235-238
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• 1999

In a ceramic green body, some degree of nonuniformity in density always presents. These differences in green density will appear as nonuniform shrinkage after sintering takes place. For the complex ceramic bodies with various curves and angles, therefore, it is quite difficult to foresee the final dimensions precisely after sintering. This simulation study shows that, considering the sintering process as a thermal shrinkage phenomenon, the use of NASTRAN enables to predict the precise shape of a sintered body. Based on this result, 'the reverse engineering technique' has been developed that can unfold the exact dimensions of a green body to have the desired shape after sintering. This approach will provide a simple and useful tool for ceramic engineers to fabricate complicate bodies with tight dimensional tolerances.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.822-823
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• 2006

The compaction and sintering behavior of zirconium titanate $(ZrTiO_4)$ was investigated by means of the measurement of sintering density and shrinkage, and the observation of microstructure. With increasing the content of $Al_2O_3$ additive, $Al_2O_3$-modified zirconium titanate samples fired at $1300^{\circ}C$ showed the anisotropic shrinkage behavior that the upper region of sintered body has higher sintering shrinkage than the low region. This difference of sintering shrinkage decreased with increasing firing temperature from 1300 to $1400^{\circ}C$. The SEM micrographs of powder compation show that the anisotropic shrinkage behavior is related with non-uniform density in a uniaxial compaction.

• 대한치과기공학회지
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• 제34권2호
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• pp.113-119
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• 2012

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at $600^{\circ}C$ for 10 hours. Ball milling was performed with 5mm zirconia ball and 60mm polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at $1,500^{\circ}C$ for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470MPa of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680MPa of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780MPa of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block.

• 복식
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• 제57권7호
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• pp.137-152
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• 2007

The purpose of this study is to research on concept, consisting factors, and specialties of theme park' character costumes to understand better about character costumes as well as to establish fundamental research data. The characteristics of character costumes in the theme park are as follows. First, theme park' character costumes are personified so that visitors may feel friendly and have emotional communication with them. Specially, costume that anthropomorphize an animal(85.3%) and silhouette of lozenge style(86.8%) dominated the highest weight. Animal figures are walking upright and wearing human's clothes. They communicate with visitors using mime actions. Second, various types of body proportion is applied to highlight the characteristics of character costume. Most character costumes are applied with unrealistic body proportion. This unrealistic body proportion give abnormal image and looks funny. The important factor is size of their head. Especially, 3.5 body proportion(78.9%) is general. Third, simplification, exaggeration, shrinkage, and modification are other factors. Simplification is applied differently by parts. Pocket, collar details are simplified to clarify the character's image. More simplification can lead to ommission. For their head, peculiar parts look stand out but other parts are simplified to stress their characteristics. Exaggeration is used with shrinkage to give strong impression to visitors. Forms are broken intentionally and they are modified. They look impressive because they are not harmonized. It is unexpected image and induces humor and familiar feelings. Matter of stylization includes exaggeration, shrinkage, modification and movement of actors that have tangible factor of character costume.

• 한국세라믹학회지
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• 제13권2호
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• pp.31-38
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• 1976

Korean tremoitic talc, wollastonite and clay have been used to develop a wall tile body to appropriate to the fast firing process. Some of ceramic properties of the raw materials were investigated by X-ray diffraction, thermal analysis and chemical analysis. The body compositions were formulated from the range of 35~75% tremolitic talc, 0~30% wollastonite and 25~35% plastic clay. Thermal gravity analysis and thermal expansion were tested for each of unfired bodies to study the correlation between thermal dehydration and linear shrinkage during the firing procedure. Linear shrinkage and water absorption of the fired bodies at the various temperature were taken as a measures for determining the proper firing range of the bodies. Increasing the content of wollastonite and firing temperature, the thermal expansion of the fired body showed the gradual decrease, and the thermal expansion curves showed a tendency to straighten. These observations may be resulted from the fact that the amounts of diopside and anorthite formed were gradually increased and those of quartz relatively decreased. The optimum compositions of the wall tile bodies for fast firing are 30% clay, 10~20% wollastonite and 50~60% tremolitic talc.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.150-151
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• 2013

Recently, the internal space organization of the building changes to the frame construction and flat slab construction in the wall type structure. And the use of light weight panel changing the internal joint use easily is increased. Therefore, in this research, the length change characteristic that the magnesium chloride addition rate reaches to the magnesium curing body tries to be studied. It could confirm according to the length change specific result that the magnesium chloride amount of addition reaches to the magnesium oxide curing body to expand. And the thing described below was the large-scale expansion the magnesium oxide addition rate 60%. And it showed up as 50, 40, 30, 20, and order of 10s (%). It could look at to form the hydrate of the SEM picture result needle-shaped of the Hardened.

• 대한치과보철학회지
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• 제37권6호
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• pp.800-808
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• 1999

To compare several porcelains made by various manufacturers in shrinkage after firing and investigate the effect of condensation on shrinkage, specimens were prepared and the volume of each body was measured by the phase-shifting profilometry. Baseplate wax was cut by $2.5cm{\times}2cm$ and cast in nonprecious metal(Verabond, U.S.A.), then any surfaces of specimens were abrased and polished on the SiC abrasing papers, preparing 120 specimens. Specimens were divided into six groups according to the porcelain used, and the porcelain used in each group were as follows. Group I : Ceramco dentin porcelain Group B : Creation dentin porcelain Group III : Creation margin porcelain Group IV : Vintage margin porcelain Group V : Vita dentin porcelain Group VI : Vintage dentin porcelain Porcelain was built up on the metal plates using a small spoon and then solution matching to each porcelain was added. The six groups are subdivided into a and b. In subgroup a, only excessive solution was absorbed with tissue and in subgroup b, porcelain was condensed sufficiently. When build-up was completed, the shape was measured using the phase-shifting profilometry. After that, specimens were fired in the furnace programed for each porcelain and then their changed shape were measured again. Using the difference between the two above measurements, the ratio of shrinkage was calculated. Obtained results were as follows ; 1. Regardless of condensation, the volume of fired specimens were not different significantly between the two subgroups a and b in the same group. 2. The ratios of shrinkage were significantly higher in the groups porcelain built-up was condensed than in the groups not condensed 3. The ratios of shrinkage were in the range of 36.81-27.19% in the groups porcelain built up was condensed and 44.52-37.54% in the other groups not condensed.

• 한국세라믹학회지
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• 제29권6호
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• pp.419-430
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• 1992

Fabrication possibility of low-shrinkage alumina without oxidation and wetting agent was presented on the basis of observation about oxidation behavior, microstructure and physical characteristics of such reaction agents free Al2O3-Al system. The composition less than Al 10w/o where Al can act as a sintering agent for Al2O3 was excluded. Under the condition of present experiments oxidation of Al2O3-Al system was dependent not on holding time but mainly on oxidation temperature. In thes case of Al powder not comminuted effectively during powder mixing of Al2O3-Al, columnar structure which would act as a hindrance to the densification during sintering developed more during oxidation with higher Al contents, and which made the fabrication of low-shrinkage Al2O3 ceramics impossible. If Al powder was comminuted effectively due to co-mixed Al2O3 characteristics, densification was improved because of no columnar structure and made the fabrication of sintered body with -2.7% dimensional change and 81% relative density possible. As a result, it is possible to fabricate dense low-shrinkage Al2O3 ceramics without oxidation and wetting agent under conditions such as smaller particle size of Al, Al contents below 50v/o, higher green density of Al2O3-Al compact and the use of Al2O3 powder used for high-density ceramics.

• 대한방사선치료학회지
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• 제29권2호
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• pp.109-117
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• 2017

목 적: 두경부 환자가 입체적 세기변조 회전 방사선치료 시 변화하는 체형과 환자 정열 상태를 조사하고 그에 따라 치료 시 발생하는 선량분포의 변화와 적절한 재 CT 모의치료의 필요성을 평가하고자 한다. 대상 및 방법: 근치적 목적으로 방사선 치료를 시행한 두경부암 89명에 대해 입체적 세기변조 방사선치료계획을 수립하고 치료 기간 동안의 체중을 측정하였다. 그 중 10명의 환자에 대하여 체형변화를 평가하였다. ARIA software(Offline review)를 이용하여 ramus, chin, posterior neck, clavicle 등의 landmark를 지정한 후 skin까지의 거리를 측정하여 차이를 분석하였다. 결 과: 남성 60명을 대상으로 치료시행 $17{\pm}4$회에서 re-CT 모의치료를 시행한 결과 체중 감소율이 $-6.47{\pm}3.5%$로 나타났으며, 여성 29명은 경우는 $17{\pm}5$회에서 체중 감소율이 $-5.73{\pm}2.7%$로 나타났다. 피부위축(Skin shrinkage) 변화를 관찰한 결과 대표 landmark에서의 표준편차는 C1(${\pm}0.44cm$), C3(${\pm}0.83cm$), C5(${\pm}1.35cm$)로서 0.5 kg 감소 당 약 1 mm shrinkage 발생함을 알 수 있었다. 치료 횟수에 따른 피부위축은 1~4 fx (변화 없음), 5~13 fx (-2 mm), 14~22 fx(-4 mm), 23~30 fx(-6 mm)로 나타났다. 결 론: 체형이 약 5 mm 변화하게 되면 중심부 선량은 약 3 % 이상 차이나기 시작하게 되므로 적응증치료에 필요한 CT 모의치료를 추가로 진행하여야만 한다. 또한 적극적으로 lower neck의 CT 모의치료 방법 및 set up 방법에 관하여 연구하고 새로운 고정용구(Immobilization device)의 사용도 검토할 필요가 있다.