• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.123-126
• /
• 2007

Deformation behavior of $Zr_{55}Cu_{30}Al_{10}Ni_5$ (at. %) bulk metallic glass (BMG) fabricated by suction casting method has been investigated at elevated temperatures in this study. The BMG was first verified to have an amorphous structure thru X-ray diffraction (XRD) and differential scanning calorimetry (DSC). A series of compression tests has consequently been performed in supercooled liquid temperature region to investigate the high temperature deformation behavior. A transition from Newtonian to non-Newtonian flow appeared to take place depending upon both the strain rate and test temperature. A processing map based on a dynamic materials model has been constructed to estimate a feasible forming condition for this BMG alloy.

• Korean Journal of Materials Research
• /
• v.15 no.10
• /
• pp.662-666
• /
• 2005

Solid solutions of $(Zr/Ti)O_2$ were prepared in powder form by the coprecipitation technique. After mixing with carbon or exposing to nitrogen gas at elevated temperature, titanium cations selectively diffused out from the oxide compound to form titanium carbide (TiC) or titanium nitride (TiN), respectively. TiN formed strong interfacial contacts between the oxide grains. In contrast, TiC formed as small crystallites on oxide grains but did not bind the matrix grains together. TiN therefore played a role in strengthening the interparticle bonding, but TiC weakened the bonding between grains. Partial diffusion of titanium cations also led to nanolayered structure being formed between the oxide grains, which provided weak interfacial layers that fractured in a step-wise fashion.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.255-258
• /
• 1999

In recent years, the study on the porous concrete which has excellent permeability is actively advanced in the field of architectural and civil engineering. But porous concrete has a reciprocal concept in the aspect of comparative large and continuos void structure and reduction of void for insurance of the necessary strength on the mixing proportion, must have satisfied of the properties of these. Therefore this study is series of experiment for the strength elevation and evaluated the effect according to fine replacement ratio and levels of cement content. As a result, the strength of porous concrete was elevated by an increase of fine replacement ratio and cement content.

• Journal of Hydrogen and New Energy
• /
• v.28 no.1
• /
• pp.24-29
• /
• 2017

A fluorinated polybenzimidazole (FPBI) was synthesized from 3,3-diaminobenzidine (DAB) of tetraamine, 2,2-bis(4-carboxyphenyl)hexafluoropropane of aromatic biscarboxylic acid, and 4,4-sulfonyldibenzoic acid of aromatic biscarboxylic acid in polyphosphoric acid (PPA). A FPBI was easily cast and made into clear films. The structure of condensation polymers and corresponding membranes were analyzed using GPC (gel permeation chromatography), $^1H$-NMR ($^1H$ nuclear magnetic resonance) and FT-IR (fourier transform infrared). TGA (thermogravimetric analysis) analysis showed that the prepared membranes were thermally stable, so that elevated temperature fuel cell operation would be possible. The proton conductivity of the FPBI membranes increased with increasing temperatures in the polymer. A FPBI membrane has a maximum ion conductivity of 45 mS/cm at $90^{\circ}C$ and 100% relative humidity.

• Applied Microscopy
• /
• v.21 no.2
• /
• pp.57-66
• /
• 1991

The main purpose of this paper was to investigate the change of rapidly solidified microstructures and dispersoid behavior according to heat-treatment in the Al-Fe-V-Si-(Mn) alloys. It was found that (111) preferred orientation identified by X-ray diffraction and fine subgrain/large grain were observed in the rapidly solidified Al-Fe-V-Si-(Mn) alloys. Cell boundary of the zone A was composed of the microcrystalline, whereas that of the zone B was amorphous. Decomposition of the Al-Fe-V-Si-(Mn) alloys occurred at about $300^{\circ}C$. These alloys exhibited excellent thermal stability at the elevated temperature. Microstructure of the zone B was more stable than that of the zone A. The spherical dispersoid and 5-fold symmetry phase was also more thermally stable than the amorphous structure of cell boundary.

• Journal of Chest Surgery
• /
• v.11 no.2
• /
• pp.185-193
• /
• 1978

Between April 1976 and March 1978, six cases of tricuspid valve replacement were done in the Department of Thoracic Surgery, Seoul National University Hospital. There were 4 men and 2 women and the age of the patients ranged from 17 years of the youngest to 48 years of the oldest. Most of them had characteristic symptoms of tricuspid valve disease, such as a systolic murmur audible over the lower sternum and varying with respiration, pulsatile and distended neck vein, and an enlarged and pulsatile liver. Preoperative functional levels according to NYHA Calcification were class III in 4 cases, and class IV in 2 eases. Most of the cases showed moderate to severe cardiomegaly in chest films and elevated right atrial pressure on preoperative right heart catheterization. Five of them underwent concomittent mitral valve replacement and one pulmonary valvotomy. All of them showed tricuspid insufficiency resulted from massive dilatation of annulus, destructive lesions of valve structure, or both anomalies. One postoperative hospital death was encountered and the cause of death was low out-put syndrome. All survivors showed clinical improvement and cardiomegaly regressed and left hospital in a good condition . *Attendum; Recently 2 more cases of tricuspid valve replacement with mitral valve replacement were done after this review.

• Journal of the Korea Furniture Society
• /
• v.27 no.4
• /
• pp.309-317
• /
• 2016

Recently, Korean society is increaseing "1 person family" phenomenon, which is influenced by changing of young peoples' value, aging society and social economic problems. Increase of single households is a result of complex economic, cultural and social factors. It is because as the individual's financial independence increases due to elevated income and education level, the age of marriage is going up and the individualism, which values the individual's value rather than custom, is spreading. Therefore, this new phenomenon will be impact to between social, economic value structure and living space. An increase with small furnitures are also increasing of R&D and marketing plans for 1 person family. Currently, 1 person family is bigger than last decade and that is requiring more suitable and multi-functional furniture for them. However, in Korea furniture companies are more optimization to traditional family size. Thus, this research explore about developing cheap price sofa bed, which is using at narrow area and small place.

• Steel and Composite Structures
• /
• v.15 no.1
• /
• pp.1-14
• /
• 2013

Predicting the fire resistance of structures has been significantly advanced by full scale fire tests in conjunction with improved understanding of compartmental fire. Despite the progress, application of insulation is still required to parts of structural steelwork to achieve over 60 minutes of fire rating. It is now recognised that uncertainties on insulation properties hinder adaptation of performance based designs for different types of structures. Intumescent coating has recently appeared to be one of most popular insulation types for steel structures, but its design method remains to be confirmed by empirical data, as technical difficulties on the determination of the material properties at elevated temperatures exist. These need to take into account of further physiochemical transitions such as moving boundary and endothermic reaction. The impetus for this research is to investigate the applicability of the conventional differential equation solution which examines the temperature rise on coated steel members by an inorganic intumescent coating, provided that the temperature-dependent thermal/mechanical insulation properties are experimentally defined in lab scale tests.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.12 no.1
• /
• pp.107-114
• /
• 2016

Four cylindrically shaped IHXs(Intermediate Heat Exchangers) are installed in the PHTS(Primary Heat Transfer System) of the PGSFR(Prototype Gen IV Sodium cooled Fast Reactor). As for the IHX, the temperature difference of structure is inevitable result caused by heat transfer between primary coolant sodium and IHTS(Intermediate Heat Transport System) sodium. It is necessary to evaluate the high temperature structural integrity of IHXs which operate at the elevated temperature condition over the creep temperature. In this paper, the high temperature structural integrity of IHX under assumed loading conditions has been reviewed according to ASME code.

• Architectural research
• /
• v.15 no.1
• /
• pp.53-58
• /
• 2013

High strength concrete is being used increasingly in mass structure projects. The purpose of this study is to investigate the influence of temperature during mixing, placing and curing on the strength development, hydration products and pore structures of high strength concrete in mass structures. The experiments were conducted with two different model walls, viz.: 1.5 m and 0.3 m under typical summer and winter weather conditions. The final part of this study deal with the clarification of the relationship between the long-term strength loss and the microstructure of the high strength concrete at high temperatures. Test results indicated that high elevated temperatures in mass concrete structures significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the decomposition of ettringite and increased the total porosity and amount of small pores.