• 한국안전학회지
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• 제27권3호
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• pp.28-35
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• 2012

We investigated the breakdown patterns of silica glass under the various impacts by forensic scientific analysis. The impacts were chosen by thermal and projectiles impact stress. Thermal impacts under the fire were constructed by changing the position of the flame with gas torches. Physical impacts were constructed with the projectiles of slingshots and rifles by changing the size of the projectiles at the surfaces and the initial distance. Also we identified incident angles of the projectiles by analysis of the punching portion at the glass surface. Under the thermal impacts, the breakdown patterns were various by changing the position of the flame. Especially, the configuration of breakdown patterns had radial shape with the position of the flame at the center of the glass sheet. Under the physical impacts by the projectiles, the breakdown patterns had always radial shape.

• 대한안전경영과학회지
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• 제10권4호
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• pp.105-109
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• 2008

The purpose of this study is to distinguish the causes of broken glass on doors or windows when it is originally kept among the remains on the floor in fire site - whether it was broken due to heating or outer power-through test and characteristics of the broken plane including the pattern on the plane. Addition to it, the study tries to find characteristics to judge the point and direction of breakdown through the analysis of glass broken by outer power. With two assumed causes - a) breakdown due to heating and b) breakdown due to outer power-3 pieces of glass plates ($30cm{\times}30cm{\times}5mm$) were tested for each case, getting the results as following: First, for the glass broken due to the change of temperature, the broken plane is of slow and smooth curve without any pattern. Second, for the glass broken due to outer power, with the impact point as the center, the glass shows breakdown of radial type and the side shows breakdown of near-perpendicular type. The far the broken piece is from the impact point, the bigger the size is. The broken piece at the impact point is of long triangle type and the two long planes of the triangle shows semi-arc with the center of breakdown point and the other plane shows opposite pattern. Third, when glass that is damaged by outer power is heated, damaged forms and side patterns of the glass that is damaged by outer power are heated and disappeared.

• 한국재료학회지
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• 제33권12호
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• pp.517-524
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• 2023

BaTiO₃-Poly vinylidene fluoride (PVDF) solution was prepared by adding 0~25 wt% BaTiO₃ nanopowder and 10 wt% PVDF powder in solvent. BaTiO₃-PVDF film was fabricated by spreading the solution on a glass with a doctor blade. The output performance increased with increasing BaTiO₃ concentration. When the BaTiO₃ concentration was 20 wt%, the output voltage and current were 4.98 V and 1.03 ㎂ at an applied force of 100 N. However, they decreased when the over 20 wt% BaTiO₃ powder was added, due to the aggregation of particles. To enhance the output performance, the generator was poled with an electric field of 150~250 kV/cm at 100 ℃ for 12 h. The output performance increased with increasing electric field. The output voltage and current were 7.87 V and 2.5 ㎂ when poled with a 200 kV/cm electric field. This result seems likely to be caused by the c-axis alignment of the BaTiO₃ after poling treatment. XRD patterns of the poled BaTiO₃-PVDF films showed that the intensity of the (002) peak increased under high electric field. However, when the generator was poled with 250 kV/cm, the output performance of the generator degraded due to breakdown of the BaTiO₃-PVDF film. When the generator was matched with 800 Ω resistance, the power density of the generator reached 1.74 mW/m². The generator was able to charge a 10 ㎌ capacitor up to 1.11 V and turn on 10 red LEDs.