• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.60-69
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• 2013

Purified melanin pigment from Klebsiella sp. GSK was characterized by thermogravimetric, differential thermal, X-ray diffraction and elemental analysis. This melanin pigment is structurally amorphous in nature. It is thermally stable up to $300^{\circ}C$ and emits a strong exothermic peak at $700^{\circ}C$. Its carbon, hydrogen and nitrogen composition is 47.9%, 6.9% and 12.0%, respectively. It was used to scavenge metal ions and free radicals. After immobilizing the pigment and using it to adsorb copper and lead ions, the metal ion adsorption capacity was evaluated by atomic absorption spectroscopy (AAS) and the identity of melanin functional groups involved in the binding of metal ions was determined by Fourier transform infrared (FT-IR) spectroscopy. Batch adsorption studies showed that 169 mg/g of copper and 280 mg/g of lead were adsorbed onto melanin-alginate beads. The metal ion adsorption capacity of the melanin-alginate beads was relatively significant compared to alginate beads. The metal ion desorption capacity of HCl was greater (81.5% and 99% for copper and lead, respectively) than that of EDTA (80% and 71% for copper and lead, respectively). The ability of the melanin pigment to scavenge free radicals was evaluated by inhibition of the oxidation of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and was shown to be about 74% and 98%, respectively, compared with standard antioxidants.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.673-678
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• 2011

With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.89-98
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• 2001

Pb-free wave soldering process of AC Adapter was implemented by six sigma method using Sn-Cu-Ni type solder. The solder joint appearance, microstructural change, a lift-off phenomenon and reliability were evaluated through thermal shock teal. $(Cu,Ni)_6Sn_5$-type intermetallic compound of which thickness is about 5 micron was found at solder joint between Sn-Cu-Ni solder and copper land. After applying the thermal shock test of as-soldered product up to 750 cycles, no crack was found at the solder joint and the newly developed product was superior to conventions; one in terms of productivity and reliability.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.492-494
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• 2000

The rapid increase of electric power demand and the strong requirements for interuptiom-free made most distribution works being done by interruptiom-free work techniques. These trends lead to increase of accident by electric shock. It goes to prove that more than 80% of electric accident is due to the hot line works. Therefore, the countermeasures are very urgent. This paper suggests the improvement to prevent the work accident by interruption-free work through the examination of the present situation of interruption-free work techniques as well as analysing the problems in terms of live-line works and working procedures. These improvement will contribute to reduce the work accident in live-line work and enhance the construction quality by training and managing workers effectively.

• Journal of the Korean institute of surface engineering
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• v.35 no.4
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• pp.218-231
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• 2002

As the environmental regulation worldwide emerges, most notably in Europe and Japan, the elimination of Pb usage in electronic assemblies has been an important issue for microelectronics assembly due to the inherent toxicity of Pb. This has provided an impetus towards the development of Pb-free solders. A major factor affecting alloy selection is the melting point, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation. Other important manufacturing issues are cost, availability, and wetting characteristics. Reliability related properties include mechanical strength, fatigue resistance, coefficient of thermal expansion and reactivity with substrate. In this article, Pb-free solder alloys have been proposed so far have been reviewed and are summarized.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.74-82
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• 2000

The fluxless wetting properties of UBM-coated Si-wafer to the binary lead-free solders(Sn-Ag, Sn-Sb, Sjn-In, Sn0Bi) were estimated by wetting balance method. With the new wettability indices from the wetting curves of one side coated specimen, the wetting property estimation of UBM-coated Si-wafer was possible. For UBM of Si-chip, Au/Cu/Cr UBm was better than au/Ni/TI in the point of wetting time/ At general reflow process temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) was better than that of low melting point one(Sn-Bi, Sn-In). The contact angle of the one side coated Si-plate to the solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• Journal of the Korean Home Economics Association
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• v.33 no.3
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• pp.255-264
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• 1995

This study was the designed to measure skin irritation caused by clothing at free foraldehde have caused a substantial number of cases of dermatitis type. Free formaldehyde levels were observed in infant's sanitatized goods9disposable diapers, cotton-diapers and under wear etc.) at 1992, 1994. The amount of free formaldehyde was measured by means of Acetyle Acetone method(KS K 0611). As the resort, underwear generally gave the highest free formaldehyde level, but disposable diapers and cotton diapers showed the lowest level. The formaldehyde level in intan's clothing lowered in 1994 than 1992, after the enforcement of the level in intant's clothing lowered in 1994 than 1992, after the enforcement of the formaldehyde level control. it was found that 38.7% of infant's sanitatized goods still exceeded th controlled level(A-Ao : 0.05) In the future, research to lower the amount of formaldehyde released form fabrics will also lead to decreased incidence of garment formaldehyde sensitivity. The possibility of a consumer suffering is being in convenienced form a textile-related skin problem will be even lower than it has been in the past.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.126-129
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• 2015

Over the last two decades, quantum dot (QD) solar cells have attracted much attention due to the unique properties of QDs, including band gap tunability, slow hot electron cooling, and multiple exiton generation effect. However, most of the QDs employed in photovoltaic devices contain toxic heavy-metals such as cadmium or lead, which may limit the commercial application. Therefore, recently, heavy-metal-free QDs such as Cu-In-S or Cu-In-Se have been developed for application in solar cells. Here, we review the research trends in heavy-metal-free QD solar cells, mainly focusing on Cu-In-Se QD-sensitized solar cells (QDSC).

• Bulletin of the Korean Mathematical Society
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• v.56 no.1
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• pp.265-276
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• 2019

For a simple implementation, a linear convex splitting scheme was coupled with the Fourier spectral method for the Cahn-Hilliard equation with a logarithmic free energy. However, an inappropriate value of the splitting parameter of the linear scheme may lead to incorrect morphologies in the phase separation process. In order to overcome this problem, we present a nonlinear convex splitting Fourier spectral scheme for the Cahn-Hilliard equation with a logarithmic free energy, which is an appropriate extension of Eyre's idea of convex-concave decomposition of the energy functional. Using the nonlinear scheme, we derive a useful formula for the relation between the gradient energy coefficient and the thickness of the interfacial layer. And we present numerical simulations showing the different evolution of the solution using the linear and nonlinear schemes. The numerical results demonstrate that the nonlinear scheme is more accurate than the linear one.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.381.2-381.2
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• 2002

There is now increasing evidence that free radicals and active oxygen species are involved in a variety of pathological events. often associated with ageing. Free radical-mediated cell damage and free radical attack on polyunsaturated fatty acids result in the formation of lipid radicals. These lipid radicals react readily with molecular oxygen to produce peroxy radicals responsible for initiating lipid peroxidation. The peroxidation of cellular membrane lipid can lead to cell necrosis and considered to be implicated in a number of pathophysiological conditions as well as in the toxicity of many xenobiotics. (omitted)