• 한국대기환경학회지
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• 제16권1호
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• pp.23-35
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• 2000

PM10, which is below 10 ${\mu}{\textrm}{m}$ in a diameter, has a high deposition in the lung or the bronchus by breathing and is generally composed of a lot of organic matters, viruses, algae, mold, and metallic elements that are very toxic to people. This study identified the characteristics of concentration of PM10 and air-borne jmetallic elements produced in the industrial city, Ulsan, and analyzed the correlatuion between sources and generation patterns of PM10 and metallic elements. We classified the five areas(green, residential, heavy traffic, mechanic, and petrochemcal and non-ferrous metal) which might have different characteristics of sources of PM10 and metallic elements. The average concentrations of PM10 in the five areas were as follows(petrochemical and non-ferrous metal(99.9$\mu\textrm{g}$/㎥)>mechanic(77.5 $\mu\textrm{g}$/㎥)>heavy traffic(47.1 $\mu\textrm{g}$/㎥)>residential(39.3 $\mu\textrm{g}$/㎥)>green(32.8 $\mu\textrm{g}$/㎥)). Those of petrochemical and non-ferrous metal areas were higher than other areas. In this study, the average concentration trend of metallic elements contained in PM10 are shown as follows: Fe>Zn>Pb>Cu>Mn>Cr>As>Cd>Sn>Hg, respectively. The metallic elements identified in PM10 showed the highest concentration in the petrochemical and non-ferrous areas. Metal combinations showed that a high correlation among concentrations of heavy metals were as follows: As, Cd and Fe in the residential area; Zn, Mn, Cu and Pb in the mechanical area; and Zn, Cu, As, Pb in the petrochemical and non-ferrous industrial area.

• 한국환경과학회지
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• 제7권5호
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• pp.623-631
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• 1998

Pyrite contained in wasted ore dumps induces a strong acid environment when it contacts oxygenated rainfall. Present research was designed to evaluate the pollution of an area that is supposedly contaminated by pyrite of ore wasted dumps form in Chonju Il Mine. Measured are the pH and selected heavy metal elements in the supposedly polluted hydrologic system. The samples include three types : those collected from the stream waters; those from the stream sediments; and those from the rice field soil scattered over the area. The dispersion path of the pollution source was also traced. The pH of the hydrologic system ranged from 3.44 to 5.46, which clearly indicates that the area is on the acid environment. The pH tends to rise as the distance from the minehead increases. The content of heavy metal elements dissolved in the stream water varies as follows; Mn=69.73~1.99ppm, Cd=0.02~0.03ppm, Zn=0.77~1.18ppm, Cu=0.04~0.13ppm, Pb=0.22~0.32ppm. The stream water in this state may induce serious heavy metal pollution to the agricultural land and the water for human life especially in the villages down the stream. The content of heavy metal elements dissolved in the stream sediment varies as follows; Mn=245.0~4685.0ppm, Cd=10.0~15.0ppm, Zn=105.0~210.0ppm, Cu=65.0~155.0ppm, Pb=90.0~150.0ppm. The content of heavy metal elements dissolved in the rice field soil varies as follows; Mn=185.0~260.0ppm, Cd=10.0~15.0ppm, Zn=135.0~180.0ppm, Cu=65.0~90.0ppm, Pb=100.0~130.0ppm. The pollution index in the stream sediment and the rice field sell is 1.36~2.03, which shows that pollution had already begun all over the area where the samples were collected.

• 대한기계학회논문집
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• 제17권9호
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• pp.2286-2293
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• 1993

The study presents the development of a cost-effective CAD/CAM system for metal moulds by use of personal computer. In the personal CAD/CAM system named DKSYS, metal moulds are defined by the operations of basic elements such as prism, pyramid and sphere, plane, rotational body, and surface elements including curved surface. The internal expression of shape elements in the computer is based on the wire model, which is a set of cross-sectional curves of the shape elements. With the addition of OMS system to CAD/CAM system the optimum cutting condition can be selected automatically. After programming NC information with the form definition and the optimum cutting condition, the metallic mould can be formed by transferring cutting information to CNC machine through DNC system. Using a computer for the above process, it is possible to increase the productivity and reduce the cost.

• 한국해양공학회지
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• 제30권4호
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• pp.334-340
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• 2016

The combustion chamber of a diesel engine is often exposed to a more serious wear and corrosion environment than other parts of the engine because its temperature increases as a result of using heavy oil of low quality. Therefore, repair and built-up welding methods must be performed on worn or corroded parts of the piston crown, exhaust valve, etc. from an economical point of view. In this study, Inconel 718 filler metal was used in repair welding on the groove of a forged steel specimen for a piston crown, along with built-up welding on the surface of another forged steel specimen. Then, the corrosion characteristics of the weld metal zone for the repair welding and the deposited metal zone for the built-up welding were investigated using electrochemical methods in a 35% H₂SO₄ solution. The deposited metal zone indicated better corrosion resistance than the weld metal zone, showing a nobler corrosion potential, higher impedance, and smaller corrosion current density. It is considered that metal elements with good corrosion resistance were generally included in the filler metal, and these elements were also greatly involved in the deposited meta by built-up welding, whereas the weld metal consisted of metal elements mixed with both the filler metal and base metal elements because of the molten pool produced by the repair welding. Finally, it is considered that the hardness of the weld metal was increased by the repair welding, whereas the built-up welding improved the corrosion resistance of the deposited metal.

• 한국분말재료학회지
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• 제26권3호
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• pp.251-257
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• 2019

Since the ISO decided to deal with rare-earth elements at the $298^{th}$ Technical Committee (TC) in 2015, Korea has participated in four plenary meetings and proposed four standards as of June 2019. The status of ISO TC 298, the standards covered by the TC, and the standardization strategies of Korea are summarized. Korean delegations are actively engaged in WG2, which deals with recycling, proposing four standards for fostering the rare-earth recycling industry. However, the participation of domestic experts is still low compared with the increase in the number of working groups and the number of standards in TC 298. The aim of this article is to summarize the current status of ISO international standards related to rare-earth elements, to encourage relevant experts to participate in standardization, and to develop international standards that accurately reflect the realities of the industry.

• Advances in nano research
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• 제2권2호
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• pp.77-88
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• 2014

Solvothermal treatment of late transition metal acetylacetonates in a novel medium composed either of pure acetophenone or acetophenone mixtures with amino alcohols offers a general approach to uniform hydrophilic metal nanoparticles with high crystallinity and low degree of aggregation. Both pure metal and mixed-metal particles can be accesses by this approach. The produced materials have been characterized by SEM-EDS, TEM, FTIR in the solid state and by Nanoparticle Tracking Analysis in solutions. The chemical mechanisms of the reactions producing nanoparticles has been followed by NMR. Carrying out the process in pure acetophenone produces palladium metal, copper metal with minor impurity of $Cu_2O$, and NiO. The synthesis starting from the mixtures of Pd and Ni acetylacetonates with up to 20 mol% of Pd, renders in minor yield the palladium-based metal alloy along with nickel oxide as the major phase. Even the synthesis starting from a mixed solution of $Cu(acac)_2$ and $Ni(acac)_2$ produces oxides as major products. The situation is improved when aminoalcohols such as 2-aminoethanol or 2-dimethylamino propanol are added to the synthesis medium. The particles in this case contain metallic elements and pairs of individual metals (not metal alloys) when produced from mixed precursor solutions in this case.

• 로봇학회논문지
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• 제4권4호
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• pp.320-326
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• 2009

This paper proposed a new magnetic field detection algorithm to detect metal pieces in food producing processes. This algorithm can detect mixed metal pieces by sensing magnetic field. Some metal pieces are passed through an over-current circuit to magnetize them. The magnetic field sensor can detect the change in the magnetic field on theconveyor belt caused by the flow of the metal pieces in the food product. However, such a method detects the output of signals that change their amplitude and phase according to the movement of the conveyor belt with the food product, in which the equilibrium of the positive signal that is created in the receiver coil loses its balance due to the magnetized material. This includes not only the signal elements resulting from the effect of the alternating magnetic fields of the mixed metals, but also the signal elements resulting from the effect of the alternating magnetic fields of the examined object itself.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.87-89
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• 2004

Brazing is an indispensable manufacturing technology for liquid rocket engine. In this study, for LRE injector, stainless steel 316L was used of base metal and Ni based MBF-20 of insert metal. The brazing and diffusion was carried out under various conditions. There are solid phase and. residual liquid phase in the brazed joint. With increment of holding time, the amount of solid phase increased and the elements of base metal and insert metal compositionally graded. Boron diffused from insert metal came into base metal and made boride with Cr and Mo at the brazed joint of base metal and insert metal.

• Journal of Welding and Joining
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• 제25권5호
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• pp.45-50
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• 2007

The Ni-base superalloy GTD111 DS is used in the first stage blade of high power land-based gas turbines. Advanced repair technologies of the blade have been introduced to the gas turbine industry over recent years. The effect of the filler metal powder on Transient Liquid Phase bonding phenomenon and tensile mechanical properties was investigated on the GTD111 DS superalloy. At the filler metal powder N series, the base metal powders fully melted at the initial time and a large amount of the base metal near the bonded interlayer was dissolved by liquid inter metal. Liquid filler metal powder was eliminated by isothermal solidification which was controlled by the diffusion of B into the base metal. The solids in the bonded interlayer grew from the base metal near the bonded interlayer inward the insert metal during the isothermal solidification. The bond strength of N series filler metal powder was over 1000 MPa. and ${\gamma}'$ phase size of N series TLP bonded region was similar with base metal by influence of Ti, Al elements. At the insert metal powder M series, the Si element fluidity of the filler metal was good but microstructure irregularity on bonded region because of excessive Si element. Nuclear of solids formed not only from the base metal near the bonded interlayer but also from the remained filler metal powder in the bonded interlayer. When the isothermal solidification was finished, the content of the elements in the boned interlayer was approximately equal to that of the base metal. But boride and silicide formed in the base metal near the bonded interlayer. And these boride decreased with the increasing of holding time. The bond strength of M series filler metal powder was about 400 MPa.

• Journal of Welding and Joining
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• 제24권1호
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• pp.64-70
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• 2006

570MPa grade weldable steels were gas metal arc welded with various heat inputs and interpass temperatures using flux cored wires. Effects of heat input and interpass temperature on the strength and impact toughness of weld metal were investigated in terms of microstructural change, recovery of alloying elements, and the amount of reheated weld metal. Increase of heat input and interpass temperature resulted in decrease of weld metal strength. This is because of the small amount of acicular ferrite, large columnar size and low recovery of alloying elements such as manganese and silicon. In addition to the microstructural change, weld metal toughness was also influenced by the deposition sequence. It increased with an increase of the amount of reheated weld metal.