• Title/Summary/Keyword: surface replication

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Skeletal myogenic differentiation of human periodontal ligament stromal cells isolated from orthodontically extracted premolars

  • Song, Minjung;Kim, Hana;Choi, Yoonjeong;Kim, Kyungho;Chung, Chooryung
    • The korean journal of orthodontics
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    • v.42 no.5
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    • pp.249-254
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    • 2012
  • Objective: To investigate the stem cell-like characteristics of human periodontal ligament (PDL) stromal cells outgrown from orthodontically extracted premolars and to evaluate the potential for myogenic differentiation. Methods: PDL stromal cells were obtained from extracted premolars by using the outgrowth method. Cell morphological features, self-replication capability, and the presence of cell-surface markers, along with osteogenic, adipogenic, and chondrogenic differentiation, were confirmed. In addition, myogenic differentiation was induced by the use of 5-aza-2'-deoxycytidine (5-Aza) for DNA demethylation. Results: PDL stromal cells showed growth patterns and morphological features similar to those of fibroblasts. In contrast, the proliferation rates of premolar PDL stromal cells were similar to those of bone marrow and adipogenic stem cells. PDL stromal cells expressed surface markers of human mesenchymal stem cells (i.e., CD90 and CD105), but not those of hematopoietic stem cells (i.e., CD31 and CD34). PDL stromal cells were differentiated into osteogenic, adipogenic, and chondrogenic lineages. Myotube structures were induced in PDL stromal cells after 5-Aza pretreatment, but not in the absence of 5-Aza pretreatment. Conclusions: PDL stromal cells isolated from extracted premolars can potentially be a good source of postnatal stem cells for oromaxillofacial regeneration in bone and muscle.

A Study on the Improvement of Optical Efficiency for The 2 inch LGP Considering Injection Molding Characteristics (사출성형 특성을 고려한 2인치 도광판의 광효율 향상에 관한 연구)

  • Do, Y.S.;Hwang, C.J.;Yoon, K.H.
    • Transactions of Materials Processing
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    • v.17 no.5
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    • pp.322-327
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    • 2008
  • LGP is a key component of LCD back light unit because it determines brightness and sharpness of the display image. Usually, it has optical patterns fabricated on the bottom surface. These optical patterns convert point or line sources placed in the side of LGP to plane source at the top surface by changing the propagating direction of the incident light. In the present paper the LiGA-reflow method was applied to fabricate the LGP mold. Furthermore, the optical simulation considering the replication ratio of pattern height was applied to the pattern design. The optical simulation through systematic correction scheme was adopted to find the optimum distribution of pattern density. Finally, the stamper fabricated by this method was installed in the mold and LGP was produced by injection molding. As a result of luminance measurement for the final product, the average luminance and luminance uniformity was measured 3,180 nit and 84%, respectively. Consequently, the mold fabrication method using the LiGA-reflow and optical simulation(CAE) can save the expense and time compared with the existing fabrication methods(laser ablation and chemical etching).

A literature review on RSM-based robust parameter design (RPD): Experimental design, estimation modeling, and optimization methods (반응표면법기반 강건파라미터설계에 대한 문헌연구: 실험설계, 추정 모형, 최적화 방법)

  • Le, Tuan-Ho;Shin, Sangmun
    • Journal of Korean Society for Quality Management
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    • v.46 no.1
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    • pp.39-74
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    • 2018
  • Purpose: For more than 30 years, robust parameter design (RPD), which attempts to minimize the process bias (i.e., deviation between the mean and the target) and its variability simultaneously, has received consistent attention from researchers in academia and industry. Based on Taguchi's philosophy, a number of RPD methodologies have been developed to improve the quality of products and processes. The primary purpose of this paper is to review and discuss existing RPD methodologies in terms of the three sequential RPD procedures of experimental design, parameter estimation, and optimization. Methods: This literature study composes three review aspects including experimental design, estimation modeling, and optimization methods. Results: To analyze the benefits and weaknesses of conventional RPD methods and investigate the requirements of future research, we first analyze a variety of experimental formats associated with input control and noise factors, output responses and replication, and estimation approaches. Secondly, existing estimation methods are categorized according to their implementation of least-squares, maximum likelihood estimation, generalized linear models, Bayesian techniques, or the response surface methodology. Thirdly, optimization models for single and multiple responses problems are analyzed within their historical and functional framework. Conclusion: This study identifies the current RPD foundations and unresolved problems, including ample discussion of further directions of study.

Injection/compression molding for micro pattern (미세패턴 성형을 위한 사출 압축 성형 공정 기술)

  • Yoo Y.E.;Kim T.H.;Kim C.W.;Je T.J.;Choi D.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.100-104
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    • 2005
  • The injection molding is very effective process for various plastic products due to its high productivity. It is also good fur precise products like optical parts. Various thermoplastic materials are also available with this injection molding process. In recent, however, as the overall size of the product increases and micro or nano scale of patterns are applied to the products, we now have some problems such as low fidelity of the replication of the pattern, high molding pressure, or warpage from the in-mold stress. Injection/compression molding is studied to overcome those problems in molding large thin plate with micro pattern array on its surface. An injection compression mold is designed to 3 pieces mold for side gate. We install 4 pressure transducers and 9 thermocouples to measure the melt pressure and surface temperature in the cavity during the process. As a result, the maximum molding pressure for injection compression molding is reduced to 1/3 compared to injection molding and the uniformity of the pressure in the cavity is enhanced by about 15%.

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Superhydrophobic Engineered Surface Based on Nanohoneycomb Structures (나노허니컴 구조물을 이용한 산업용 극소수성 표면 제작)

  • Kim, Dong-Hyun;Park, Hyun-Chul;Lee, Kun-Hong;Hwang, Woon-Bong
    • Composites Research
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    • v.20 no.2
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    • pp.17-20
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    • 2007
  • Superhydrophobic polytetrafluoroethylene ($Teflon^{(R)}$, Dupont) sub-micro and nanostructures were fabricated by the dipping method, based on anodization process in oxalic acid. The polymer sticking phenomenon during the replication creates the sub-microstructures on the negative polytetrafluoroethylene nanostructure replica. This process gives a hierarchical structure with nanostructures on sub-microstructures, which looks like the same structures as lotus leaf and enables commercialization. The diameter and the height of the replicated nano pillars were 40 nm and 40 um respectively. The aspect ratio is approximately 1000. The fabricated surface has a semi-permanent superhydrophobicity, the apparent contact angle of the polytetrafluoroethylene sub-micro and nanostructures is about $160^{\circ}$, and the sliding angle is less than $1^{\circ}$.

Micro/Nano Rheological Characteristics of PMMA in Hot Embossing Process (핫엠보싱 공정에서 PMMA의 마이크로/나노 레올로지 특성)

  • Kim B. H.;Kim K. S.;Ban J. H.;Shin J. K.;Kim H. Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.05a
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    • pp.259-264
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    • 2004
  • The hot embossing process as a method for the fabrication of polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this paper, we carried out experimental studies and numerical simulations in order to understand the viscous flow of polymer film during hot embossing process. As the initial step of quantitating the hot embossing process, simple parametric studies for the embossing conditions have been carried out using high resolution masters which patterned by DRIE process. Under different embossing times and pressures, the viscous flow of PMMA films into micro/nano cavities has been investigated. Also, the viscous flow during the hot embossing process has been simulated by the continuum based FDM analysis considering micro/nano effect, such as surface tension and contact angle.

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Compliant Stage for Nano Patterning Machine (나노 패턴 장비용 컴플라이언스 스테이지)

  • Choi, Kee-Bong;Lee, Jae-Jong
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1065-1068
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    • 2003
  • The nano imprint process is one of the next generation lithography has been mentioned as one of major nanoreplication techniques because it is simple process, low cost, high replication fidelity and relatively high throughput. This process requires a surface contact between a template with patterns and a wafer on a stage. After contact, the vertical moving the template to the wafer causes some directional motions of the stage. Thus the stage must move according to the motions of the template to avoid the damage of the transferred patterns on the wafer. This study is to develop the wafer stage with a passive compliance to overcome the damage. This stage is designed with the concept like that it has a monolithic, symmetry and planar 6-DOF mechanism.

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Flow Behaviors of Polymers in Micro Hot Embossing Process (미세 핫엠보싱 공정에서 폴리머의 유동특성)

  • Ban Jun Ho;Shin Jai Ku;Kim Byeong Hee;Kim Heon Young
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.8 s.173
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    • pp.159-164
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    • 2005
  • The Hot Embossing Lithography(HEL) as a method fur the fabrication of the nanostructure with polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this paper, we carried out experimental studies and numerical simulations in order to understand the viscous flow of the polymer (PMMA) film during the hot embossing process. To grasp the characteristics of the micro patterning rheology by process parameters (embossing temperature, pressure and time), we have carried out various experiments by using the nickel-coated master fabricated by the deep RIE process and the plasma sputtering. During the hot embossing process, we have observed the characteristics of the viscoelastic behavior of polymer. Also, the viscous flow during the hot embossing process has been simulated by the continuum based FDM(Finite Difference Method) analysis considering the micro effect, such as a surface tension and a contact angle.

Candidacidal Effects of Rev (11-20) Derived from HIV-1 Rev Protein

  • Lee, Juneyoung;Lee, Dong Hwan;Lee, Dong Gun
    • Molecules and Cells
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    • v.28 no.4
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    • pp.403-406
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    • 2009
  • Rev is an essential regulatory protein for HIV-1 replication. Rev (11-20) is known as the significant region regarding the function of a nuclear entry inhibitory signal (NIS) of Rev. In this study, anticandidal effects and mechanism of action of Rev (11-20) were investigated. The result exhibited that Rev (11-20) contained candidacidal activities. To understand target site(s) of Rev (11-20), the intracellular localization of the peptide was investigated. The result showed that Rev (11-20) rapidly accumulated in the fungal cell surface. The cell wall regeneration test also indicated that Rev (11-20) exerted its anticandidal activity to fungal plasma membrane rather than cell wall. The fluorescent study using 1,6-diphenyl-1,3,5-hexatriene (DPH) further confirmed the membrane-disruption mechanism(s) of Rev (11-20). The present study suggests that Rev (11-20) possesses significant potential regarding therapeutic agents for treating fungal diseases caused by Candida species in humans.

Replication of High Density Patterned Media (고밀도 패턴드 미디어 성형에 관한 연구)

  • Lee, Nam-Seok;Choi, Yong;Kang, Shin-Ill
    • Transactions of the Society of Information Storage Systems
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    • v.1 no.2
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    • pp.192-196
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    • 2005
  • In this paper, we investigated the possibility of replicating patterned media by nano-injection molding process with a metallic nano-stamper. The original nano-master was fabricated by E-beam lithography and ICP etching process. The metallic nano-stamper was fabricated using a nanoimprint lithography and nano-electroforming process. The nano-patterned substrate was replicated using a nano-injection molding process without additional etching process. In nano-injection molding process, since the solidified layer, generated during the polymer filling, deteriorates transcribability of nano patterns by preventing the polymer melt from filling the nano cavities, an injection-mold system was constructed to actively control the stamper surface temperature using MEMS heater and sensors. The replicated polymeric patterns using nano-injection molding process were as small as 50 nm in diameter, 150 nm in pitch, and 50 nm in depth. The replicated polymeric patterns can be applied to high density patterned media.

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