• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.69-78
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• 2018

The study presented herein focused on the change in hysteretic force-deformation behavior of lead rubber bearings (LRBs). The material model used to idealize response of LRBs under cyclic motion is capable of representing the gradual attrition in strength of isolator unit on account of lead core heating. To identify the effect of loading history on the hysteretic response of LRBs, a typical isolator unit is subjected to cyclic motions with different velocity, amplitude and number of cycles. Furthermore, performance of an LRB isolated single degree of freedom system is studied under different seismic input levels. Finally, the significance of lead core heating effect on LRBs is discussed by considering the current design approach for base isolated structures. Results of this study show that the response of an LRB is governed strongly by the amplitude and number of cycles of the motion and the considered seismicity level.

• Journal of Information Display
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• v.10 no.2
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• pp.49-53
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• 2009

In this study, a very small LED packaging lead frame with a low thermal resistance was developed. The cost of the package process was reduced by the use of many small LED lamps, which increased the light emission efficiency. Compared to the large lead frame lamp, however, the optical property of the small LED packaging lead frame lamp was not sufficiently improved because its reflection structure was changed and its reflection area was reduced. The luminous efficiency of the LED lamp reaches 58 lm/W at the current density of 0.16 A/$cm^2$. Using the LED lamps, 46-inch LCD BLU was manufactured. The BLU-made LED lamps have a low power consumption of 146 W and have a slim (10-mm-thick) BLU, keeping good uniformity in terms of brightness, and maintaining good thermal properties.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.50-55
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• 2002

The transient numerical analysis was performed for vapor cooled current leads. The present numerical modeling considered that there is temperature difference between the copper lead and the helium vapor flow. This numerical modeling was compensated and validated by the experiment with commercially available 100 A current leads. The numerical modeling in this paper described thermal characteristics of overloaded current leads more accurately than the conventional steady state analysis. Proper design of overloaded current leads was suggested by indicating the appropriate overloading factor in the pulse mode operation.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.291-293
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• 2002

In this paper, we fabricated a persistent current mode magnet using Bi-2223 HTS tapes. The coil system consists of double pancake magnet and a persistent current switch and jointed them with solder. Persistent current mode operation of the system was measured experimentally by the decay behavior of the current. We found that resistive component of the system including flux flow resistance lead the exponentially field decay with time.

• Progress in Superconductivity
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• v.10 no.2
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• pp.103-107
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• 2009

$Bi_2Sr_2Ca_1Cu_2O_x$(BSCCO 2212) superconductors for current lead were fabricated by centrifugal melting process(CMP). BSCCO 2212 powder was melted at $1200^{\circ}\C$ in a resistance furnace using a Pt crucible and poured in a rotating cylindrical mold preheated at $550^{\circ}\C$ for 2 hour. The solidified BSCCO-2212 samples were heat-treated by partial melting process in oxygen atmosphere. The current-voltage curves at 77 K of the samples were obtained by transport measurement, and the microstructure was investigated by scanning electron microscope. The $J_c$ values at 77 K of the tubes partially melted at $840^{\circ}C,\;860^{\circ}C\;and\;880^{\circ}C$ were 492, 430 and 398 $A/cm^2$, respectively. It was observed that the plate-like grains in BSCCO 2212 tube was more developed in the sample heat-treated at $840^{\circ}C$. It was found that the critical current of the BSCCO 2212 samples was dependent on the partial melting schedule regarding the grain shape and size of the BSCCO 2212.

• Resources Recycling
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• v.28 no.4
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• pp.3-14
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• 2019

Lead is one of the common non-ferrous metals used in modern industry. The usage of lead continues to increase and has risen from 5 million tonnes per year worldwide in the 1970s to 11 million tonnes in the 2010s. In principle lead is virtually 100 % recyclable as an element without loss of quality. The recycling of lead scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. Therefore production of secondary lead from scrap has been steadily growing and at present it meets approximately 60 % of usage worldwide. Lead scrap (mainly lead-acid battery) is smelted in primary and secondary smelter. Most secondary lead smelting were performed in a shaft-type furnace (blast furnace), rotary furnace and reverberatory furnace. The lead bullion is either cast into ingots and re-melted in refining kettles or refining is performed on the hot lead bullion immediately after production. This work provides an overview of the primary lead production and recycling process.

• Clinical and Experimental Pediatrics
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• v.59 no.3
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• pp.114-119
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• 2016

Purpose: This study aimed to assess the reference values and factors influencing blood lead levels among Korean adolescents. Methods: The study population consisted of 1,585 adolescents (801 males, 784 females; aged 10-19 years) who participated in the Korea National Health and Nutrition Examination Survey 2010-2013. We analyzed blood lead concentrations in relation to demographic/lifestyle characteristics for all participants. "Reference values" of blood lead levels were calculated as the upper limit of the 95% confidence interval of the 95th percentile. Results: The average "reference value" for blood lead concentrations among Korean adolescents was $2.25{\mu}g/dL$ ($2.49{\mu}g/dL$ for males, $2.07{\mu}g/dL$ for females), and the geometric mean of the blood lead concentrations was $1.34{\mu}g/dL$. Males had higher blood lead concentrations than females (male, $1.48{\mu}g/dL$; female, $1.19{\mu}g/dL$; P<0.001). Elementary school students had higher blood lead concentrations than junior and senior high school students ($1.44{\mu}g/dL$ vs. $1.31{\mu}g/dL$, P<0.001). Participants living in detached houses had higher blood lead concentrations than those living in apartments (P<0.001) and current smokers had higher concentrations than nonsmokers or participants with secondhand smoke exposure (P<0.05). Additionally, participants with excessive alcohol consumption had higher levels than non-drinkers (P<0.001). Conclusion: This study provides national reference data on blood lead concentrations stratified by demographic and lifestyle factors among Korean adolescents. Further studies are needed to elucidate the relationship between increased lead exposure and demographic factors including type of housing.

• Proceedings of the KIEE Conference
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• 1984.07a
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• pp.16-18
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• 1984

• Journal of the Korean institute of surface engineering
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• v.24 no.2
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• pp.88-95
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• 1991

The tin-lead alloy was electrodeposited in the low range of peak current density in order to investigate the change of composition and microstructure of them. The Pb content of alloy deposits, which was decreased with increasing average current density, was relatively lower than that of D.C. plated alloy deposit. The preferred orientation of alloy deposit was changed with increasing peak current density and the surface morphology of alloy deposits was closely related to the preferred orientation of them.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.90-90
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• 2008