• Journal of Hydrogen and New Energy
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• v.26 no.6
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• pp.554-559
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• 2015

Single cell of PEMFC (polymer electrolyte membrane fuel cell) is composed of bipolar plates, gasket, GDL and the MEA. Bipolar plate's function is the collecting electricity, helping oxygen/hydrogen gas diffuse evenly and draining the water and heat. In this work, we have conducted experiments to low contact resistance and improve the performance of a $25cm^2$ single cell by using metal forms. We have following experimental cases: 1) Conventional graphite serpentine channel bipolar plate; 2) Channel-less bipolar plate with nickel(Ni) based metal foam which coated by various materials. We focused the difference in contact resistance and performance of the single cell with metal foam depending on various coating materials. The experimental results show the similar performance of single cells between with serpentine channel bipolar plates and with channel-less bipolar plate using metal foams. In addition, single cell with metal foam shows potential to higher performance than conventional channel.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.415-421
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• 2018

A location determining method is proposed for critical sliding surface in the stability analysis of the filling materials in karst caves. First, a preliminary location of the sliding surface is determined based on simulation results which includes displacement contour and plastic zone. The sliding surface will locate on the bottom contact interface when the friction angle is relative small. However, a weakened contact interface always becomes the critical sliding surface no matter what the friction angle is. Then when the friction angle becomes larger, the critical sliding surface inside fillings can be determined by a parabola, the coefficient of which increases linearly with the friction angle under the same cohesion. Finally, the critical sliding surface approximately remains unchanged with friction angle. The influence of cohesion is similar to that of friction angle. Although affected by shape, size or position of the karst cave, the critical sliding surface mainly depends on both friction angle and cohesion. Thus, this method is always useful in determining the critical sliding surface.

• The Journal of Pediatrics of Korean Medicine
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• v.29 no.4
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• pp.23-28
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• 2015

Objectives The purpose of this study is to examine the development of PBL Module and the possibility of the evaluation on the Korean medical Pediatrics class. Methods In this study, we examined the 32 case reports (four teams for three years) which were made by the Korean medicine school $4^{th}$ year students, who attended the discussion class. The student read the given materials and identified the purpose of the subjects and selected the learning issues, investigated them. After then they discussed the subjects and made the reports. Results The learning issues by students were similar, the students worked to study them with research papers, books, internet materials and personal subjects. After class, the students showed the change of their thoughts and they could accept the other one. Conclusions This study suggests it is possible that the development of PBL Module and the evaluation on the Korean medical Pediatrics Class.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.269-273
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• 2003

There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.252-263
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• 2006

It is attempted to develop flame retardant polyurethane coatings, which have received significant attention in recent years. It is the purpose of this study to synthesize new reactive polyurethane coatings containing halogen. Lactone based modified polyester polyols, using trichlorobenzoic acid as chlorine moiety (TBAOs) were synthesized. These polyesters were cured with isophorone diisocyanate (IPDI)-isocyanurate at room temperature (TBAPUs). Physical properties of these flame retardant coatings were similar with those of non-flame retardant coatings. The flammability of coatings was strongly dependent on the chlorine contents. We found that the increasing chlorine contents showed better flame retarding properties and that, however, they also resulted in more smog generation during combustion. The detailed results of flammability test using various methods indicated $24{\sim}26%$ in LOI and $3.7{\sim}5.3\;cm$ char length in $45^{\circ}$ Meckel burner method.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.149-156
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• 2013

This study examines the effects of limestone's factors on the fluidity of cement paste when of up to 15%. As the substitution ratio of limestone powder increases, the fluidity of the paste is also improved; however, it has no correlation to the $CaCO_3$ content of the limestone, fineness of the limestone, and fluidity of the pastes. Regardless of clay content of the limestone, it showed a similar mini-slump, so there was no correlation between the clay content and the fluidity of the paste. Also, the total organic carbon content of the limestone and the fluidity of the paste showed no correlation. Regardless of the limestone's grade or fineness, n value of powder gained by using the Rosin-Rammler distribution function showed that the fluidity of the paste increased as the n value reduced. It was also shown that particle size distribution of ordinary Portland cement with limestone powder had a major effect on the fluidity of the paste.

• The Journal of the Korean dental association
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• v.54 no.5
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• pp.348-355
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• 2016

Ideal autogenous or allogenic bone graft materials should provide 1) stabilization of blood clot, 2) scaffolds for cellular proliferation and differentiation, 3) release of osteogenic growth factors, 4) appropriate resorption profile for remodeling of new bone. Teeth, especially dentin, mostly contain hydroxyapatite and type I collagen which are similar to bone, and could be valuable graft material. Clinically teeth are used as calcined or demineralized forms. Demineralized form of dentin can be more effective as a graft material. But a conventional decalcification method takes time and long treatment time may give negative effects to various osteogenic proteins in dentin. Author used a new clinical method to prepare autogenous teeth, which could be grafted into the removal defects immediately after extraction using vacuum ultrasonic system. The process could be finished within two hours regardless of the form (powder, chip or block). Teeth were processed to graft materials in block, chip, or powder types immediately after extraction. It took 120 minutes to prepare block types and 40 minutes to prepare powder. Clinical cases did not show any adverse response and the healing was favorable. Rapid preparation of autogenous teeth with the vacuum ultrasonic system could make the immediate one-day extraction and graft possible.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.6
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• pp.1027-1031
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• 1994

A method for the process of making fig conserves to prevent the denaturation of ficin (EC3.422.3) that is a proteolytic enzyme in fig (Fixus carica L. ) has been developed. The suutable composition ratio of materials such as, fig, sugar, citric acid and potassium sorbate, to make fig conserves was 1,000, 600 , 1.0 and 0.67g , respectively. to maintain the ficin activity, it was necessary that these materials were heated on 55$^{\circ}C$ and concentrated in the reduced pressure. At a result of sensory evaluation , meat treated with fig was the softest among samples. Then the treated beef with 55$^{\circ}C$ converse, 7$0^{\circ}C$ conserves, sugar and control have been shown the decreased rate respectively. There was significantly different in the effect of tenderness between each group(0.1%) . The nitrogen content of connective tissue was relatively low in the groups of the treated beef with fig and 55$^{\circ}C$ converses, 7$0^{\circ}C$ converses sugar and control , which was similar to the order of the ficin activity. This research revealed that the constituent protein of meat muscle was decomposed by ficin and its solubility was relatively higher than before.

• Journal of Hydrogen and New Energy
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• v.4 no.1
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• pp.11-19
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• 1993

The kinetic studies of the hydrogen induced amorphization in $ErCo_2$ Laves phase is observed by the internal standard method using X-ray diffraction intensities. The activation energy and rate constant exponent for the amorphization in $ErCo_2$ are found to be 26 kcal/mole and 0.78, respectively. From these results, it is believed that the mechanism of the hydrogen induced amorphization in $ErCo_2$ is related to the motion of Co atoms. Though there are many similar physical properties between $ErCo_2$ and $ErNi_2$, the activation energy for the amorphizatin in $ErCo_2$ is larger than that in $ErNi_2$ and the amorphization rate in $ErCo_2$ is slower. It is suggested that these differences of activation energy for the hydrogen induced amorphization and the amorphization rate between $ErCo_2$ and $ErNi_2$ is due to the occurence of structural change on forming crystalline hydride.

• Journal of the Korean Society of Costume
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• v.65 no.1
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• pp.1-14
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• 2015

Magic realism, which originated in the culture of Central and South America, creates a fantastic fictional word by linking unrelated incidents using magical. The purpose of this study was to analyze Tarsem Singh's design characteristics that are based on magic realism in his movies, "The Cell" and "The Fall", and to highlight the artistic values appearing in the films. The research was conducted by observing the characteristics and concept of magic realism based on literature and preceding research, and discovering how Singh expressed these creatively and experimentally within the costumes in his films. The results of the study were as follows: Firstly, magical, legendary and symbolic characteristics appear within the fantasy of magical realism, and common techniques within film costuming include repetition of similar objects, solid silhouettes within scenes, and various decorative materials used for fantastic expression. Secondly, regarding ideality, the destruction of previous ideas and recreation of the present were found with materials and details used in film costuming to destroy previous ideas. Expressions of character through external decoration and depiction of living things as not living were also found. Thirdly, reiteration showed the coexistence of history and legend, reality and fantastic elements, and arrangement of opposing elements.