• Resources Recycling
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• v.11 no.2
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• pp.28-35
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• 2002

A study on the grinding characteristics of metal components in printed circuit boards (PCBs) scrap by a swing-hammer typeimpact mill was conducted. The PCBs scrap crushed to sizes less than 3 mm were pulverized to liberate metal components by the impact mill. The effect of rotation speed of hammer on the grinding characteristics was investigated. The particle size distribution and degree of liberation of metals such as copper and solder were measured. The effect of rotation speed and particle size on the shape sorting of metal Particles from milled PCBs was investigated using an inclined vibrating Plate. At the hammer speed of 61.3 m/s about 80% of the copper particles became larger than 297 $\mu$m while 90% of solder particles was smaller than 297 $\mu$m. In the shape sorting method, the recovery location becomes shorter as the rotation speed of hammer increases. The recovery location for particles larger than 297$\mu$m was shorter than for particles sized between 149$\mu$m and 297$\mu$m. As the recovery location becomes shorter, KI value increases towards unity while $\phi_{c}$ value decreases towards unity indicating the more roundness of metal particles.

• Resources Recycling
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• v.24 no.3
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• pp.76-80
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• 2015

Mobile phone has become one of the essential items in our daily life. In Korea, it is estimated that more than 20 million cell phones are discarded each year due to advancement in technology, thus creating disposal and environmental pollution. In order to conserve the resources, their proper recycling is essential as it contains both valuable and toxic metals. The economics of the recycling will depend on the amount and value of the metals. Therefore, it is necessary to determine the composition of the metals present in the different cell phones. In the present study, a report is presented on the variation of metal content per year of waste mobile phones. A review has been made for the mobile phones manufactured during the period 2000-2009 and metal content of the printed circuit boards (PCBs) by analyzing their metals. An example of the precious metal palladium and of the heavy metal lead shows the decreasing trend.

• Conservation Science in Museum
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• v.28
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• pp.89-108
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• 2022

Among about 500,000 characters in metal types in National Museum of Korea, this study conducts a statistical analysis of 62 metal types from the early Joseon Dynasty, including 33 gabinja (甲寅字) types and 29 eulhaeja (乙亥字) Hangeul types by examining the shape, measuring the specific gravity, and identifying the components based on previously-studied Joseon metal types. Among them, 33 gabinja types and 24 eulhaeja types were made of two-component bronze (copper and tin) (Group A), and four eulhaeja types were produced with three-component bronze (copper, tin and lead). (Group B), and one eulhaeja type was created with two-component bronze (copper and tin) with a high tin content (Group C). By comparing with imjinja (壬辰字) types of the late Joseon Dynasty based on multiple statistical analyses of type components, this study confirms that late-Joseon types have low copper content and high zinc and lead content, and therefore it may be possible to distinguish between the types of early and late Joseon Dynasty.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.379-380
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• 2003

연소나 폐기물 감량화 처리를 위해 이루어지는 소각과정에서 방출되는 대기오염물질은 소각재의 다양한 특성으로 인해 배출물의 특성파악이 매우 어렵고 그로 인해 제어에 많은 어려움을 겪고 있다. 연소 혹은 소각과정에서 에어로졸을 제어하는 것은 대기 중에서 발견되는 중금속성분을 근본적으로 줄이는 기본적인 조치로서 상당히 중요한 역할을 한다(Natusch and Wallace, 1974; Oppelt, 1986; Oberdorster et al., 1995). 본 연구에서는 소각공정에서 금속성 에어로졸 형태로 배연기체 중에 혼합되어 배출되는 여러 가지 금속성분 중 양적으로 많이 배출되는 납성분의 제어를 위한 기초연구를 수행하였다. (중략)

• Conservation Science in Museum
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• v.29
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• pp.111-132
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• 2023

Terahertz radiation cannot pass through metal and therefore reflect and return most signals. Utilizing this property, this study analyzed information on paintings to verify the usage of metal materials on paintings and the scope of their application. First, the study tested specimens of metal-based pigments and synthetic pearl pigments with metallic colors and textures in order to compare basic characteristics of terahertz images, such as signal severance caused by metallic substances, traits reflected in cross-section images, and high degree of reflection. Subsequently, based on the collected information, the study diagnosed various types of paintings including Korean traditional paintings and oil paintings using the terahertz imaging technique to confirm the usage of metal-based pigments in the inner layers of paintings and their scope of application. The terahertz imaging technique could has the potential to provide scientific evidence for previously-undiscovered information and art-historical records about various types of paintings that used metalbased pigments, thereby rendering significant utility for the conservation and authentication of paintings.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.331-336
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• 2004

The phase change due to the reflection from target surfaces in a white-light interferometer induces measurement errors when target surfaces are composed of dissimilar materials. We prove that this phase change on reflection as the polarization of the white-light changes causes a shift of both envelope peak position and fringe peak position of several tens of nanometers as the polarization of the white-light changes. In addition, we propose a new equation for white-light interference fringes depending on the polarization of the source.

• Resources Recycling
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• v.21 no.3
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• pp.74-83
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• 2012

Rare earth metals have been made from rare earth compounds which were prepared from rare earth ore concentrates through successive processes such as leaching(i.e. extraction of rare earth elements to liquid media), separation, purification, precipitation. Here, process for treating monazite and bastnasite ore concentrates were briefly reviewed, and metallothermic reduction and fused salt electrolysis methods were introduced as the extraction technologies for rare earth metals.

• KSBB Journal
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• v.16 no.1
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• pp.54-60
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• 2001

The activity of microorganisms is an important factor that determines the efficiency of the bacterial recovery of precious metals from low-grade ore. Metal-leaching microorganisms must have a tolerance, within the concentration levels encountered to leached metals. In this study, the tolerance levels of Thiobacillus ferroxidans to the single and mixed metal ions systems, composed of $Zn^{2+}$, $Cu^{2+}$, $Ni^{2+}$, and $Cd^{2+}$ were investigated. When single metal ions of $Zn^{2+}$ (10~60 g/L), $Cu^{2+}$ (1~6 g/L), $Ni^{2+}$ (1~6 g/L), or $Cd^{2+}$ (1~6 g/L) were added to the growth medium of T. ferrooxidans, the iron oxidation rate of this bacterium was not significantly inhibited. The maximum inhibition percentage observed on the iron oxidation rate of T. ferrooxidans was approximately 50% in the medium supplemented with two or three mixed metal ions of $Cu^{2+}$, $Ni^{2+}$, and $Cd^{2+}$. However, when $Zn^{2+}$ was also added to the medium with the other metal ions, the inhibitory effect on the iron oxidation activity of T. ferroxidans was remarkably increased.

• Resources Recycling
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• v.19 no.3
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• pp.9-15
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• 2010

Domestic gold mine tailings, generally, contain a lot of non-metallic silica and clay minerals. These minerals can be separated from the tailings by various physical separation methods and used as raw materials for cements and ceramic products. In these physical separation procedures, metallic complex sulfides, in which Au and metallic constituents such as Pb, As and Fe were concentrated, were obtained as a by-product. These metallic constituents should be removed or separated from the by-product to extract Au efficiently. In this work, removal and separation processes of Pb, As, and Fe from the by-product were investigated. Pb was removed to under 3% by using alkaline oxidative leaching at the leaching condition of $120^{\circ}C$, 2M NaOH, 100psi $Po_2$, 250r.p.m., 4 wt.% solid and 30 min. leaching time. The leached residue was roasted and separated magnetically to obtain a non-magnetic product contained <0.2% As, <3% Fe and high concentrated Au more than 8,000 ppm.

• Journal of Conservation Science
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• v.22
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• pp.109-120
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• 2008

Understanding the whole knowledge of ceramics is essential for a person in charge of conservation of ceramics since their methods of manufacturing or materialistic features have very close relationship with their damaging process. Also, various executions of repair and restoration dealing with any damage in use have to be looked into. The information attained through those studies finds damaging causes of ceramics, which becomes a critical element when choosing a proper conservation treatment method and utilizes as indispensable data for permanent preservation. As part of scrutinizing materials of repair and restoration, this study examines the purpose, date, and the constituents of the materials used in metal bound rims adhered to the brim of ceramics. Among the subjected ceramics, the metal bound rims possible to scientific analysis were gone through element analyses with Portable ${\bullet}\"{I}$-XRF Spectrometer and SEM-EDS while the ingredients of the ceramics difficult to analyze were inferred by eye inspection of exhibition catalogues. The results of this study confirm that metal bound rims consisted of diverse materials were adhered to the brim of ceramics.