• Journal of the Korea Institute of Information and Communication Engineering
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• 제9권3호
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• pp.602-608
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• 2005

We have studied to obtain the SAW filter for the Single Phase Unidirectional Transduce. (SPUDT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulations. Also, we have performed to obtain the properly conditions about impedance matching of the SAW filter for SPUDT. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000A and $3.6{\mu}m$, respectively. And the width of IDT' fingers is $2.4{\mu}m$, and the space between IDT' finger and reflector is $2.0{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.7MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.4dB and standing wave ratio is probably 1.5 after when we have matched impedance.

• Journal of Conservation Science
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• 제29권3호
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• pp.231-241
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• 2013

Analysis of the bronze bodhisattva from Pangyo-dong sites in Seongnam by computed tomography, ICP-AES, metallurgical microscope and SEM-EDS had to know manufacturing technique. And the origin of the raw material, was investigated using TIMS. Results with computed tomography, two bronze bodhisattva produced by lost-wax casting technique with hollow inside and could see the core of the inside. Result of component analysis and microstructure observation, material is alloy of copper-tin-lead and made by casting without artificial treatment. According to lead isotope ratio analysis result of bronze bodhisattva could be made into galena of the Gyeonggi massif in Korea South.

• Progress in Superconductivity
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• 제10권1호
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• pp.45-49
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• 2008

For the development of superconducting fault current limiters (SFCLs), fault current limiting elements were fabricated out of Bi-2212 bulk tubes and tested. The SFCL elements consisted of tube shaped Bi-2212 bulks and metal shunts for the stabilizers. Firstly, the Bi-2212 bulk tubes were processed based on a design of monofilar coils in order to acquire large resistance and high voltage rating. 300 mm-long Bi-2212 tubes were designed to have the current path of 410 cm in length with 24 turns and 41 mm in diameter. The processed monofilar coil, as designed, had 300 A $I_c$ at 77 K. The fabricated superconducting monofilar coils were affixed to Cu-Ni alloy as that of stabilizers. The Cu-Ni alloys were processed to have the same shape of the superconducting monofilar coils. The Cu-Ni coil had resistivity of 32 ${\mu}{\Omega}$-cm at 77 K and 37 ${\mu}{\Omega}$-cm at 300 K. The metal shunts were attached to the outside of the Bi-2212 monofilar coil by a soldering technique. After the terminals made of copper were attached to both ends of the superconductor-metal shunt composite, the gap between the turns and the surface of the elements was filled with an epoxy and a dense mesh made of FRP in order to enhance the mechanical strength. The completed SFCL elements went through fault tests, and we confirmed that the voltage rating of 143 $V_{rms}$ (E =0.35 $V_{rms}$/cm) could be accomplished.

• Journal of Powder Materials
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• 제19권4호
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• pp.247-252
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• 2012

Effect of Cu and $DyF_3$ powder mixing with Cu-free (Nd, Dy)-Fe-B jet-milled powder on the magnetic properties of sintered magnets was investigated. The coercivity of a magnet prepared from the Cu-free (Nd, Dy)-Fe-B powder was about 10 kOe even though the alloy powder already contained some Dy (3.5 wt%). When small copper powder was blended, however, the coercivity of the magnet increased almost 100%, exhibiting about 20 kOe. On the contrary, the coercivity enhancement was moderate, about 4 kOe, when dysprosium content in the sintered magnet was simply increased to 4.9 wt% by the addition of small $DyF_3$3 powder.

• Restorative Dentistry and Endodontics
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• 제18권2호
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• pp.431-445
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• 1993

The purpose of this study was to observe corrosion characteristics of six dental amalgams and was to analyse corrosion products electrochemically. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by using mechanical amalgamator, the triturated mass was inserted into the cylinderical metal mold ($12{\times}10mm$) and was condensed with 160kg/$cm^2$ by using the hydrolic press. The specimen was removed from the mold and was stored at room temperature for 1 week, and was polished with amalgam polishing kit. The anodic and cathodic polarization curve was obtained by using cyclic voltammetric method with 3-electrode potentiostat in saline for each amalgam and Ag, Sn, Cu plate specimen at $37{\pm}0.5^{\circ}C$. The potential sweep range was -1.7V~0. 4V(vs SCE) in working electrode and scan rate was 50mV/s and the exposed surface area of each specimen to the electrolytic solution was $0.79cm^2$. The results were as follows. 1. In anodic-cathodic polarization curve of amalgam specimens, two anodic current rising areas and two cathodic current peaks were obtained at the low Cu amalgam(CF, CS) specimen and three anodic current rising areas and three cathodic current peaks were obtained at the high Cu amalgam (TY, DS, HV) specimen. 2. As this compared with the anodic and cathodic current peak potentials of Sn, Cu and Ag specimen, the first cathodic current peak I c was caused by the reduction of divalent tin salt, second cathodic current peak IIIc results from the reduction of quadravalent tin salt, and third cathodic current peak me results from the reduction of copper salt. 3. As reverse potential sweeping was done repeatedly, anodic current was decreased slightly in all amalgam specimens.

• Journal of Korea Foundry Society
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• 제6권1호
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• pp.12-19
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• 1986

This study was undertaken to understand the formation mechanism of the hard spots in high strength brass. To investigate the behavior of the hard spots in the isothermal liquid state with varying silicon content, the rapidly quenched specimens were obtained by suctioning the melt into the silica tube and water quenching. To examine the growth process of the hard spots with holding time, the unidirectional solidification technique was used. The results of this study are summarized as follows: 1) With the addition of Fe in order to get the effects of grain refinement in high strength brass, the two different type of Fe-rich phases are occurred, which are defined as dendritic and globular phase. The chemical composition of the globular phase was different from that of the dendritic phase in that the globular phase contained Si. 2) With increasing Si content, the Fe-rich phase had a tendency to form globular phase. 3) As the holding time increased in the liquid state, globular was also prone to coalesce. The further growth of globular phase to large size was due to reducing the interfacial energy. 4) The primary phase of copper alloy was nucleated preferentially on the dendritic phase. It was noticeable that the dendritic phase acted as a grain refiner. However, the agglomerate (hard spots) which was composed of the globular phase decreased the mechanical properties of high strength brass. 5) Once the hard spots formed in the high strength brass casting, it was very difficult to remove them. This is due to the fact that their meting temperature is higher than the pouring temperature of high strength brass.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1205-1206
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• 2006

Dispersion-strengthened copper with $TiB_2$ was produced by ball-milling and spark plasma sintering (SPS).Ball-milling was performed at a rotation speed of 300rpm for 30 and 60min in Ar atmosphere by using a planetary ball mill (AGO-2). Spark-plasma sintering was carried out at $650^{\circ}C$ for 5min under vacuum after mechanical alloying. The hardness of the specimens sintered using powder ball milled for 60min at 300rpm increased from 16.0 to 61.8 HRB than that of specimen using powder mixed with a turbular mixer, while the electrical conductivity varied from 93.40% to 83.34%IACS. In the case of milled powder, hardness increased as milling time increased, while the electrical conductivity decreased. On the other hand, hardness decreased with increasing sintering temperature, but the electrical conductiviey increased slightly

• Journal of the Korea Institute of Information and Communication Engineering
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• 제13권12호
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• pp.2662-2670
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• 2009

The effect of the reflector type for the SAW filter on the characteristics of the slanted finger IDT filter have been studied by computer simulation. The IDT was evaporated by Aluminum-Copper alloy. The design condition was optimized by the phase shift of the SAWfilter for WCDMA. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness are $5,000{\AA}$, and the width and the space of reflector are $3.6{\mu}m$ and $2.0{\mu}m$, respectively. Frequency response of the fabricated SFIT filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 8.2MHz. And we could obtain that the return loss is less then 16dB, the ripple characteristics is probably 4dB and the triple transit echo is less then 18dB after when we have matched impedance.

• Resources Recycling
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• 제21권6호
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• pp.45-50
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• 2012

The room-temperature electrodeposition of metallic lithium was investigated from ionic liquid, 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) with lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) as a lithium source. Cyclic voltammograms on gold working electrode showed the possibility of the electrodeposition of metallic lithium, and the reduction current on a gold electrode was higher than the value on platinum and copper. The metallic lithium could be electrodeposited on the gold electrode under potentiostatic condition at -2.4 V (vs. Pt-QRE) and was confirmed by analytical techniques including XRD and SEM-EDS. The dendrite-typed electrodeposits were composed of a metallic lithium and a alloy with gold substrate. And any impurity could be detected except for trace oxygen introduced during handling for the analyses.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제33권3호
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• pp.107-113
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• 2005

A calorimeter of 2-ton thrust level rocket engine chamber has been developed to measure the wall heat flux. The liner of the chamber is made of copper-chromium alloy to maximize the heat transfer performance and structural strength. 1-D design code based on empirical correlations has been used for the prediction of the global thermal characteristics while 3-D CFD has been applied for the verification of local cooling performance. The predicted average wall heat flux at the throat is 43 $MW/m^{2}$ for the combustion chamber pressure of 53 bar. The chamber structure is confirmed to be safe at the pressure of 150 bar through 2-D stress analysis and measurement of the strain of the test species. Finally, the test of pressurizing the calorimeter chamber has been performed with water at the pressure of 150 bar in room temperature environment. No thermal damage has been detected after the hot-fire test in the test nozzle of same cooling performance with the developed calorimeter though the measured throat heat flux is higher than the design value by 10%.