• Title, Summary, Keyword: crystallization

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Influence of final crystallization process on precision of fit of monolithic CAD/CAM-generated restorations by lithium disilicate: A comparative study (리튬 디실리케이트 최종 결정화 과정이 CAD/CAM으로 제조된 수복물의 적합도에 미치는 영향)

  • Kim, Jae-Hong;Kim, Ki-Baek
    • Journal of Technologic Dentistry
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    • v.41 no.4
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    • pp.271-278
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    • 2019
  • Purpose: To quantify the effect of the crystallization process on lithium disilicate ceramic crowns that are fabricated using a computer-aided design/computer-aided manufacturing(CAD/CAM) system, and to determine whether they are clinically acceptable by comparing values before and after the crystallization process. Methods: The maxillary first molar was selected as the abutment for the experiments. Ten working models were prepared. Marginal and internal gap of 4 groups of lithium disilicate crowns(n=10) fabricated with conventional method. Comparison was performed using the silicone replica technique and 3D superimposition analysis. The marginal and internal gaps of the restoration were measured before and after the crystallization process of this prosthesis. The average value of each part(the average of values measured before and after the crystallization) was statistically analyzed using paired t-test(α=0.05). Results: The results from the second phase of this research, which compared the average value of the gap between the marginal and internal fits of the lithium disilicate single crown before and after the crystallization process, indicated that the marginal gap was larger and the internal gap was smaller after the crystallization process, and this difference was statistically significant (P<0.05) in all the parts evaluated. Conclusion: While the shrinkage that occurs during crystallization does affect the marginal and internal fit of the prosthesis, it cannot be concluded to be a major effect because the resultant distortion was within the clinically acceptable range.

Solid Phase Crystallization of LPCVD Amorphous Silicon Thin Films by Alternating Magnetic Flux (교번자속인가에 의한 비정질 실리콘 박막의 결정화거동에 대한 연구)

  • 송아론;박상진;박성계;남승의;김형준
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.459-462
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    • 2000
  • A new method for the fabrication of poly-Si films is reported using by alternating magnetic flux crystallization (AMFC) of LPCVD a-Si films. In this work we have studied the crystallization of LPCVD a-Si films by alternating magnetic flux. A-Si films were 1200$\AA$-thick deposited at 48$0^{\circ}C$ at a total pressure of 0.25Torr using Si$_2$H$_{6}$/H$_2$. After this step, these a-Si films were thermally annealed by Alternating Magnetic Flux at 43$0^{\circ}C$ for 1hours. The annealed films were characterized using X-ray diffraction (XRD), Raman Spectra, Atomic Force Microscopy(AFM). Both alternating magnetic flux crystallization and solid phase crystallization were investigated to compare enhanced crystallization a-Si. We have found that the low temperature crystallization method at 43$0^{\circ}C$ by alternating magnetic flux.x.

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Study on the Crystallization Behavior of the Compatible EVOH/SMA Blends (상용화된 EVOH/SMA 블렌드의 결정화 거동에 관한 연구)

  • Kim, Hyung-Il;Ahn, Byung-Hyun;Park, Soon-Ho
    • Applied Chemistry for Engineering
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    • v.5 no.3
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    • pp.379-384
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    • 1994
  • A series of blends containing ethylene-vinyl alcohol(EVOH) and styrene-maleic anhydride(SMA) copolymers has been produced to study the effect of compatibilization on the crystallization behavior of the dispersed semicrystalline component. The crystallization behavior and the morphology of the blends have been characterized by differential scanning calorimetry(DSC) and scanning electron microscopy(SEM), respectively. Depending on the compatibilization, a part of crystallization of the dispersed phase took place with greater undercooking. Homogeneous crystallization was responsible for the shift of crystallization temperature for those compatibilized blends.

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Thermal behavior and rheology of polypropylene and its blends with poly($\varepsilon$-caprolactone)

  • Chun, Yong-Sung;Minsoo Han;Park, Junghoon;Kim, Woo-Nyon
    • Korea-Australia Rheology Journal
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    • v.12 no.2
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    • pp.101-105
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    • 2000
  • The crystallization behavior of homo polypropylene (PP) and PP in the PP-poly($\varepsilon$-caprolactone) (PCL) blends during isothermal crystallization has been investigated using differential scanning calorimeter (DSC) and advanced rheometric expansion system (ARES). From the storage modulus data of the homo PP and PP-PCL blends during isothermal crystallization, the volume fraction of crystallized material ($X_t$) of the homo PP and PP in the PP-PCL blends was calculated using the various rheological models. The results of $X_t$ of the homo PP and PP in the PP-PCL blends from ARES measurement were compared with the results from DSC. The $X_t$ of the homo PP was found to be higher in the ARES measurement than in the DSC. The crystallization rate of the homo PP was found to be faster in the rheological measurements than in the thermal analysis. The $X_t$ of PP in the PP-PCL blends with various compositions was obtained from the thermal analysis and rheological measurements. The $X_t$ of PP in the PP-PCL blends obtained from the thermal analysis and rheological measurements are not consistent. This discrepancy of $X_t$ may be due to the morphological changes resulted from the different crystallization kinetics of PP in the PP-PCL blends.

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The study on crystallization for fine particles of Cyclotetramethylene-tetranitramine (Cyclotetramethylene-tetranitramine의 미세 입자 제조를 위한 결정화 연구)

  • Kim, Sung-Il;Chun, Suk-Keun;Park, Du-Goan;Park, Keun-Ho;Park, So-Jin
    • Journal of the Korean Applied Science and Technology
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    • v.24 no.3
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    • pp.219-232
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    • 2007
  • In T-mixer crystallization, supersaturation is generated by mixing of another solvent or non-solvent in order to reduce the solubility of the compound. Also, T-mixer is a type of continuous crystallization. In order to induce micro-mixing, two solutions were mixed rapidly by T-mixer, which formed high supersaturation. As the results, mean size of HMX crystals decreased with increasing de-supersaturation rate $(R_s)$. Eventually, HMX particles ranging from 0.5 to $5{\mu}m$ can be obtained by T-mixer crystallization. Mixing efficiency in T-mixer increased with increasing $R_s$ values. In T-mixer crystallization without surfactants, homogeneous nucleation was formed when S and $R_s$ was over 54 and $1.6{\times}10^3/sec$. In T-mixer crystallization with surfactants, homogeneous nucleation was formed when S and $R_s$ was over 26 and 7.4/sec.

Treatment of shrimp processing wastewater using struvite crystallization process (Struvite 결정화 공정을 이용한 새우가공폐수처리)

  • JEONG, Byung Gon
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.52 no.3
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    • pp.271-275
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    • 2016
  • Recently, pollution problem in coastal water has become more serious and pollution including red tide serves as a main reason for reduction of fishes resources. Particularly, nutrients such as nitrogen and phosphorus are the most serious pollutants. Normally, biological wastewater treatment process is used in removing such nutrients. However, it is difficult to adopt the biological wastewater treatment process to a small-scale fish processing factory in case of using seawater as wash water. Thus, removing nutrients through struvite crystallization is investigated in this study for treating shrimp processing wastewater. Experiments were conducted by varying molar ratio of $Mg^{2+}:NH^4-N:PO^4-P$ from 1:1:1 to 2:1:1. It can be concluded that optimum molar ratio is 1:1:1. Struvite crystallization process is compared with chemical coagulation process using PAC and struvite crystallization process is proven as the more effective process in removing nutrients from wastewater. In view of results obtained from these experiments, struvite crystallization process is a promising method in removing nitrogen and phosphorus from wastewater; however, not so good in removing organics. Thus, struvite crystallization process is suitable as the pre-treatment process in treating shrimp processing wastewater and additional biological process is needed to remove organics.

Effect of Ionic Liquid on Increased Surface Area Crystallization Process for Vancomycin (표면적이 증가된 반코마이신 결정화 공정에서 이온성 액체의 영향)

  • Kim, Sung-Jae;Kim, Jin-Hyun
    • Microbiology and Biotechnology Letters
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    • v.42 no.3
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    • pp.297-301
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    • 2014
  • We examined the effect of ionic liquid on the crystallization efficiency of vancomycin in an increased surface area crystallization with silica gel. The crystallization efficiency was improved by the addition of ionic liquid, [BMIm][$BF_4$]. The addition of ionic liquid (20%, v/v) on the increased surface area crystallization with silica gel dramatically reduced the crystallization time by 6 folds (4 h), compared with the results of the case where the surface area-increasing material and ionic liquid had not been added. In addition, the crystal size of vancomycin was decreased and the crystal quality of vancomycin was improved by increasing the addition of ionic liquid.

Development of spherical crystallization technique and its application to pharmaceutical systems

  • Kawashima, Yoshiaki
    • Archives of Pharmacal Research
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    • v.7 no.2
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    • pp.145-151
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    • 1984
  • A novel agglomeration technique, termed "Spherical Crystallization Process", which can transform directly the fine crystals produced in the crystallization or the reaction process into a spherical shape was developed. By this technique, needle like crystals such as salicylic acid were transformed into free flowing and directly compressible agglomerates. Sphericaly agglomerated aminophyline crystals were obtained directly from the reaction system, which could reduce the preparation processes, e. g. synthesis, crystallization and agglomeration, into only one step. Sodium theophyline monohydrate agglomerates were prepared by salting out, the rate process of which was described by a first order kinetics. Agglomerated crystals of ndw complex of indo-methacin-mepirizole were prepare with this technique; an improved therapeutic effect of the resultant crystals was expected. expected.

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Microwave-Enhanced Low-Temperature Crystallization of Amorphous Silicon Films for TFTs

  • Ahn, Jin-Hyung;Eom, Ji-Hye;Ahn, Byung-Tae
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.177-180
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    • 2002
  • Microwave has been utilized for low-temperature crystallization of amorphous Si films. Microwave annealing lowered the crystallization temperature and shortened the annealing time. The combination of Ni and microwave applications on a-Si films further enhanced the crystallization. The enhancement was due to both reduced nucleation activation energy and growth activation energy.

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Colloidal Crystallization in Microgravity

  • Okubo, Tsuneo
    • Proceedings of the Korean Fiber Society Conference
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    • pp.5-6
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    • 2003
  • Kinetic study on the colloidal crystallization of single component and mixture of different sizes or densities of spheres was made in the exhaustively deionized suspensions and in microgravity, and compared with the results in normal gravity. Colloidal crystallization rates were retarded in microgravity for single component of spheres, whereas rates of alloy crystallization were enhanced substantially in microgravity. The rotational diffusion coefficients of colloids and the formation reaction rates of colloidal silica spheres were also studied in microgravity.

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