• Transactions of Materials Processing
• /
• v.21 no.2
• /
• pp.101-106
• /
• 2012

Generally, rapid cure reaction of LED encapsulation silicone resin causes serious defects in cured resin products such as warpage, residual bubbles, and reduced wettablility. In order to prevent residual bubbles in silicone resin, the step cure process was examined in the present paper. Three kinds of step cure processes were applied, and bubble-free phenomenon was observed. Most of the bubbles were removed under $70^{\circ}C$, the minimum temperature for activating cure reaction. In addition, degree of cure(DOC) and temperature distribution were predicted by using FEM analysis of heat transfer. It was concluded that maintaining cure temperature which provide a DOC under 0.5~0.6 effectively reduces residual bubbles.

• Transactions of Materials Processing
• /
• v.24 no.2
• /
• pp.101-106
• /
• 2015

Recently, silicone is being used for LED chip lens due to its good thermal stability and optical transmittance. In order to predict residual stresses, which cause optical birefringence and mechanical warpage of silicone, a finite element analysis was conducted for the curing of silicone during molding. For the analysis of the curing process, a dynamic cure kinetics model was derived based on the results of a differential scanning calorimetry (DSC) testing and applied to the material properties for finite element analysis. Finite element simulation results showed that a step cure cycle reduced abrupt reaction heat and showed a decrease in the residual stresses.

• Elastomers and Composites
• /
• v.34 no.4
• /
• pp.321-331
• /
• 1999

The curing process is the final step in tire manufacturing whereby a green tire built from layers of rubber compounds is formed to the desired shape and the compounds are converted to a strong, elastic materials to meet tire performance needs under elevated pressure and temperature in a press. A numerical optimization procedure was developed to improve product quality in a tire curing process. First, a dynamic constrained optimization problem was formulated to determine the optimal condition of the supplied cure media during a curing process. The objective function is subject to an equality constraint representing the process model that describes the heat transfer and cures kinetic phenomena in a cure press and is subject to inequality constraints representing temperature limits imposed on cure media. Then, the optimization problem was solved to determine optimal condition of the supplied cure media for a tire using the complex algorithm along with a finite element model solver.

• Textile Coloration and Finishing
• /
• v.35 no.4
• /
• pp.246-255
• /
• 2023

In this study, we investigated for natural rubber foam to replace petrochemical-based neoprene foam. Experiments were conducted on vulcanization system and 2-step foaming process of natural rubber. The vulcanization system were EV(Efficient Vulcanization Cure), Semi-EV(Semi-Efficient Vulcanization Cure) and CV(Conventional Vulcanization Cure). In the 2-step foaming process, first molding temperature was 140℃, times were 15, 20, 25, and 30minutes, and the second molding temperature was 160℃, the times 5, 10, 15, and 20minutes. The cure and viscosity characterization were evaluated by oscillating disc rheometer (ODR) and mooney viscosmeter. Various mechanical characteristics, including hardness, tensile strength, elongation at the point of rupture, and tear strength, were quantified. Subsequently, an assessment of alterations in these mechanical attributes was conducted post-immersion in a NaCl solution. In addition degree of volume change was measured after immersing the NR foam in NaCl solution and the low-temperature permanent compression set was evaluated at 4℃. And expansion ratio and shrinkage ratio of NR foam were evaluated for 28 days. As a result the EV vulcanization system showed the least change in physical properties before and after salt water immersion, and the lowest shrinkage ratio for 28 days. In addition it was confirmed that the 2-step foaming optimum condition differed depending on the appropriate vulcanization condition.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.101-107
• /
• 2020

In this paper, step-curing, which includes the change of curing temperature on the curing process, was applied to reduce curing day of HTPB/AP based propellant. This study targets the improvement of productivity of HTPB/AP based solid rocket motor. Comparison of mechanical properties of propellant resulted in the change of normal curing condition (60℃, 5 days) to step-curing condition (60℃, 1 day / 65℃, 3 days). Post-cure test was conducted to determine the impact on the shelf life of the solid rocket motor. The aging characteristics of propellants were analyzed by measuring mechanical properties and thermal expansion factor. To step-cured propellant, accelerated aging test was performed for 12 weeks, followed by tensile test. Sm(bar) and Em(%) were higher than 8 bar and 40% each, showing excellent mechanical properties.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.121-122
• /
• 2002

The main principle of radiation therapy is to deliver optimum dose to tumor to increase tumor cure probability while minimizing dose to critical normal structure to reduce complications. RTP system is required for proper dose plan in radiation therapy treatment. The main goal of this research is to develop dose model for photon, electron, and brachytherapy, and to display dose distribution on patient images with optimum process. The main items developed in this research includes: (l) user requirements and quality control; analysis of user requirement in RTP, networking between RTP and relevant equipment, quality control using phantom for clinical application (2) dose model in RTP; photon, electron, brachytherapy, modifying dose model (3) image processing and 3D visualization; 2D image processing, auto contouring, image reconstruction, 3D visualization (4) object modeling and graphic user interface; development of total software structure, step-by-step planning procedure, window design and user-interface. Our final product show strong capability for routine and advance RTP planning.

• Korean Journal of Hospice Care
• /
• v.2 no.1
• /
• pp.182-192
• /
• 2002

Childhood Cancer Foundation of ROC(CCFROC) has been founded since 1982. Its goal is to provide comprehensive care for cancer children and their families. And in turn, under the provision of good and complete care, they can be back to the school and society. To achieve this goal, it needs to get every body's effort of the society together. The foundation has been founder under this concept and tried to fulfil this task. The first step is to educate the public to know that childhood cancer can be cured and the process of treatment is long and expensive. In order to reach this life-saving procedure, campaigns for raising money is most important thing. Then, pediatric hematologists / oncologists try to organize study group, named Taiwan Pediatric Qncology Goupp(TPOG), to make treatment protocols for childhood cancers. Its primary purpose is to increase the cure rate to prove the earlier the diagnosis and treatment, the better the prognosis. The second step is to provide full support of medical expenses and further to give help for emergent need to living. Through the varieties of active exercises of cancer children or families, foundation provides opportunities for them to share the experience during the different periods of diseases. The third step is to extend the scope of training activities for many kinds of personnel who devote to the care for cancer children. On the other hand, it promotes the cooperation or communication with international organizations and sets up recreation playing ground in the communities. The aim is to provide a comprehensive and integrated care for cancer children during their education, breeding and even accomplishment period. Besides the financial support of medical care, it provides social services to give psychological support for children and their families, to strengthen doctor-patients or doctor-families relationship. The foundation provides the mourning religious activities to cherish the memory of their children who passed away and to comfort their sadness. Since the childhood cancer is curable, its treatment should be active, comprehensive and it needs to provide to all cancer children without exception. Indeed, the work of CCFROC should be changed according to the environment and different time period. But, it needs the full support from the society. We hope the scope and content of the work will be more extended and its achievement will be better than now in the future.

• Clinical and Experimental Reproductive Medicine
• /
• v.45 no.2
• /
• pp.75-81
• /
• 2018

Objective: Recapitulation of the spermatogenesis process in vitro is a tool for studying the biology of germ cells, and may lead to promising therapeutic strategies in the future. In this study, we attempted to transdifferentiate Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) into male germ cells using all-trans retinoic acid and Sertoli cell-conditioned medium. Methods: Human WJ-MSCs were propagated by the explant culture method, and cells at the second passage were induced with differentiation medium containing all-trans retinoic acid for 2 weeks. Putative germ cells were cultured with Sertoli cell-conditioned medium at $36^{\circ}C$ for 3 more weeks. Results: The gene expression profile was consistent with the stage-specific development of germ cells. The expression of Oct4 and Plzf (early germ cell markers) was diminished, while Stra8 (a premeiotic marker), Scp3 (a meiotic marker), and Acr and Prm1 (postmeiotic markers) were upregulated during the induction period. In morphological studies, approximately 5% of the cells were secondary spermatocytes that had completed two stages of acrosome formation (the Golgi phase and the cap phase). A few spermatid-like cells that had undergone the initial stage of tail formation were also noted. Conclusion: Human WJ-MSCs can be transdifferentiated into more advanced stages of germ cells by a simple two-step induction protocol using retinoic acid and Sertoli cell-conditioned medium.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.321-322
• /
• 2006

In many manufacturing processes such as web formation, manufacturing of paper and nonwoven, fabric weaving, etc., planar sheets are transported and at the same time appropriate tension is imposed. The input material rolled up on beams is fed by unwinding the beam and the processed is then taken up on beams by winding it. While processed, the planar sheets are thrown under the processing load of impulse form, which causes irregular thickness of the processed sheet. To improve the quality of the product, a dynamic model is needed and the dynamic characteristics is to be analyzed by simulation. This study shows that density variation dynamics of the in-process-sheet in the machine direction can be described at each moment of disturbing impacts in forms of difference equations, while the impacts and tension, the time-dependency of the material properties were taken into account. Simulation showed the most serious variation of the density occurred in the process starting phase. The starting velocity curve with step form showed the least variation of the density. As the time order of the function of the starting velocity cure becomes higher, the density variation gets greater.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.23 no.4
• /
• pp.283-292
• /
• 2007

Two-step or one-step bonding systems generally inhibit curing process of dual-cured core build-up resin composite for their adhesive acidity. In addition this dual-cured core build-up resin composite can be applied to dentin of pulp chamber and root at the time that complete the endodontic treatment. The purpose of this investigation was to determine the influence of sodium hypochlorite on rnicrotensile bond strength of dual-cured core build-up resin composite. Extracted human molars were horizontally sectioned with 1mm thickness using low speed diamond saw. After the sectioned specimens were divided into 8 groups, adhesive systems (Clearfil SE-Bond, Prime&Bond NT[2-step, 1-step], Adper Prompt L-Pop) were then applied with or without sodium hypochlorite pretreatment. The treated specimen was filled with dual-cured core build-up resin composite (Luxacore, DMG corp., German). Then light cured for 40 seconds and soaked in $37^{\circ}C$ water bath for 24 hours. After the treated specimen was grinded with 1mm width and measured rnicrotensile bond strength by testing machine. Additionally 8 teeth were prepared for SEM evaluation. The results were as follows. : NaOCl treated groups generally had lower rnicrotensile bond strength but did not show any difference statistically except Adper Prompt L-Pop. When the teeth were treated by NaOCl, though the difference of applied adhesive system, it had no statistically significant difference within the NaOCl treated groups except the relation of between ClearFil SE-Bond adhesive system and Adper Prompt L-Pop adhesive system. In the SEM evaluation, NaOCl treated groups presented relatively long resin tags and incomplete hybrid layer formation generally.