• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.07a
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• pp.25-37
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• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.1
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• pp.1-6
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• 2014

The composite anodes of exfoliated graphite (EG) and multiwall carbon nanotube (MWCNT) were fabricated by using the binders with different content of epoxy in Nafion solution. The influence of the epoxy content in the anode binder on the performance of microbial fuel cell (MFC) was examined in a batch reactor. With the increase in the epoxy content in the anode binder, increase in physical binding force was observed, but at the same time an increase in the internal resistance of MFC was also observed. This was due to the increase in activation and ohmic resistance. For the anode binder without epoxy, the maximum power density was $1,892mW/m^2$, but a decrease in maximum power density was observed with the increase in the epoxy content in the anode binder. With the epoxy content of 50% in the anode binder, a decrease in the maximum power density to $1,425mW/m^2$ was observed, which about 75.3% of the anode binder without epoxy is. However, the material consisting of the same amount of epoxy and Nafion solution is a good alternative for anode binder in terms of durability and economics of MFC.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.129-139
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• 1999

Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.247-259
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• 2009

This study is focused on the relationship between whole rock boron contents and metamorphic P-T conditions of metasedimentary rocks from northeastern Yeongnam massif around Samcheok area, Korea. Metamorphic P-T conditions of sillimanite and garnet zones based on the Ti-biotite geothermometer is 553-687$^{\circ}C$ and 582-722$^{\circ}C$ at 4-6 kbar, respectively. In the metasedimentary rocks, boron contents in whole rock decrease with increasing metamorphic grade, from sillimanite zone (9.60-189 ppm B) to garnet zone (2.63-15.97 ppm B), except one sample (90.9 ppm B) from garnet zone containing graphites. Boron depletion in garnet zone has relation with mode of tourmaline which are broken down with increasing metamorphic temperature. Boron contents are indirectly proportional to major and trace elements such as $Al_2O_3$, MgO, $Fe_2O_3$, $K_2O$, Li, Ba, Sc, Co, Cr, Rb and Cs that are abundant in tourmalines. In conclustion, tourmalines and graphite are modulator of boron contents in metasedimentary rocks. In the biotite granitic gneisses, boron contents (2.62-12.2 ppm B) are similar or lower than those of metasedimentary rocks and have no relation with metamorphic P-T conditions.

• Analytical Science and Technology
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• v.8 no.1
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• pp.63-68
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• 1995

For the preparation of pH-selectrode, tribenzylamine, polyvinylchloride, dioctylphthalate, sodium tetraphenylborate and tetrahydrofuran were mixed with 0.02, 0.62, 1.34, 0.02g and 10ml respectively, and added 1g of acetylene black, graphite, silicon carbide or tungsten carbide respectively to improve electric conductivity. The selectrodes of seven kinds were shown linear to hydrogen ion in the range of pH 2 and 9. The best electric conductor for preparation of pH-selectrode based on tribenzylamine as neutral carrier was acetylene black and responded potential of the selectrode to hydrogen ion was shown the values near to theoretical Nernstian slope at $20^{\circ}C$. The interfering effects of the selectrode on hydrogen ion in the presence of alkali and alkaline earth metal ions were shown the better results with less error than glass electrode. The reproducibility and stability were good for use as a selectrode, especially in the presence of fluoride ion.

• Tribology and Lubricants
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• v.11 no.5
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• pp.128-135
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• 1995

Atomic force microscopy/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales, ranging from atomic and molecular to microscales. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation, detection of material transfer, and boundary lubrication and for nanofabrication/nanomachining purposes. Micro/nanotribological studies of single-crystal silicon, natural diamond, magnetic media (magnetic tapes and disks) and magnetic heads have been conducted. Commonly measured roughness parameters are found to be scale dependent, requiring the need of scale-independent fractal parameters to characterize surface roughness. Measurements of atomic-scale friction of a freshly-cleaved highly-oriented pyrolytic graphite exhibited the same periodicity as that of corresponding topography. However, the peaks in friction and those in corresponding topography were displaced relative to each other. Variations in atomic-scale friction and the observed displacement has been explained by the variations in interatomic forces in the normal and lateral directions. Local variation in microscale friction is found to correspond to the local slope suggesting that a ratchet mechanism is responsible for this variation. Directionality in the friction is observed on both micro- and macro scales which results from the surface preparation and anisotropy in surface roughness. Microscale friction is generally found to be smaller than the macrofriction as there is less ploughing contribution in microscale measurements. Microscale friction is load dependent and friction values increase with an increase in the normal load approaching to the macrofriction at contact stresses higher than the hardness of the softer material. Wear rate for single-crystal silicon is approximately constant for various loads and test durations. However, for magnetic disks with a multilayered thin-film structure, the wear of the diamond like carbon overcoat is catastrophic. Breakdown of thin films can be detected with AFM. Evolution of the wear has also been studied using AFM. Wear is found to be initiated at nono scratches. AFM has been modified to obtain load-displacement curves and for nanoindentation hardness measurements with depth of indentation as low as 1 mm. Scratching and indentation on nanoscales are the powerful ways to screen for adhesion and resistance to deformation of ultrathin fdms. Detection of material transfer on a nanoscale is possible with AFM. Boundary lubrication studies and measurement of lubricant-film thichness with a lateral resolution on a nanoscale have been conducted using AFM. Self-assembled monolyers and chemically-bonded lubricant films with a mobile fraction are superior in wear resistance. Finally, AFM has also shown to be useful for nanofabrication/nanomachining. Friction and wear on micro-and nanoscales have been found to be generally smaller compared to that at macroscales. Therefore, micro/nanotribological studies may help def'me the regimes for ultra-low friction and near zero wear.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.120-120
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• 1998

Boron nitride (BN) films have attracted a growing interest for a variety of t technological applications due to their excellent characteristics, namely hardness, c chemical inertness, and dielectrical behavior, etc. There are two crystalline phases 1551; of BN that are analogous to phases of carbon. Hexagonal boron nitride (h-BN) has a a layered s$\sigma$ucture which is spz-bonded structure similar to that of graphite, and is t the stable ordered phase at ambient conditions. Cubic boron nitride (c-BN) has a z zinc blende structure with sp3-bonding like as diamond, 따ld is the metastable phase a at ambient conditions. Among of their prototypes, especially 삼Ie c-BN is an i interesting material because it has almost the same hardness and thermal c conductivity as di없nond. C Conventionally, significant progress has been made in the experimental t techniques for synthesizing BN films using various of the physical vapor deposition 밍ld chemical vapor deposition. But, the major disadvantage of c-BN films is that t they are much more difficult to synthesize than h-BN films due to its narrow s stability phase region, high compression stress, and problem of nitrogen source c control. Recent studies of the metalorganic chemical vapor deposition (MOCVD) of I III - V compound have established that a molecular level understanding of the d deposition process is mandatory in controlling the selectivity parameters. This led t to the concept of using a single source organometallic precursor, having the c constituent elements in stoichiometric ratio, for MOCVD growth of 삼Ie required b binary compound. I In this study, therefore, we have been carried out the growth of h-BN thin f films on silicon substrates using a single source precursors. Polycrystalline h-BN t thin films were deposited on silicon in the temperature range of $\alpha$)() - 900 $^{\circ}$C from t the organometallic precursors of Boron-Triethylamine complex, (CZHs)3N:BRJ, and T Tris(dimethylamino)Borane, [CH3}zNhB, by supersonic molecular jet and remote p plasma assisted MOCVD. Hydrogen was used as carrier gas, and additional nitrogen w was supplied by either aDlIDonia through a nozzle, or nitrogen via a remote plasma. T The as-grown films were characterized by Fourier transform infrared spectroscopy, x x-ray pthotoelectron spectroscopy, Auger electron spectroscopy, x-ray diffraction, t transmission electron diffraction, optical transmission, and atomic force microscopy.roscopy.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.315-319
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• 2015

A high-throughput electrorefiner has been developed for commercialization use by enhancing the uranium recovery from the reduced metal which is produced from the oxide reduction process. It is necessary to scrap and effectively collect uranium dendrites from the surface of the solid cathode for high yield. When a steel electrode is used as the cathode in the electrorefining process, uranium is deposited and regularly stuck to the steel cathode during electrorefining. The sticking coefficient of a steel cathode is very high. In order to decrease the sticking coefficient of the steel cathode effectively, vibration mode was applied to the electrode in this study. Uranium dendrites were scraped and fell apart from the steel cathode by a vibration force. The vibrational scraping of the steel cathode was compared to the self-scraping of the graphite cathode. Effects of the applied current density and the vibration stroke on the scraping of the uranium dendrites were also investigated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.438-441
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• 2003

남해 동부 연안 지역 지하수의 해수 침투 영향을 광역적으로 파악하기 위하여, 202개소의 지하수 시료를 채취하고 수리지구화학적 연구를 수행하였다. 전체 시료 중 14.4%가 500 $\mu\textrm{m}$/cm을 초과하는 높은 EC값을 나타내어 해수 영향을 시사해 주었다. 해수 영향 판단의 또 다른 파라메터로 사용되는 CI/HCO$_3$ 몰비는 전체 시료의 23.3%가 1.3 이상의 값을 나타내었다. 한편, 대표적으로 해수침투 영향 및 인위적 오염의 영향을 각각 반영하는 것으로 알려진 Cl과 NO$_3$의 농도에 관한 누적도수분포도를 작성하여 배경수질군과 오염영향군을 구분짓는 배경치(background concentration)를 구한 결과, 각각 Cl = 22.3 mg/1 및 NO$_3$= 23.1 mg/l로 나타났다. 이 두 파라메터의 농도 분포를 기준으로 하여 채취된 지하수 시료를 크게 4개의 그룹으로 나눌 수 있었다. 그 결과, 자연적 또는 인위적 기원의 오염이 배제된 그룹 1은 전체 시료의 31%, 자연적 오염(해수 영향)을 반영하는 그룹 2는 전체의 24%, 인위적 오염의 영향을 반영하는 그룹 3은 전체의 9%, 해수 영향 및 인위적 오염을 동시에 반영하는 그룹4는 전체의 36%로 나타났다. 또한 그룹2와 그룹4는 대부분 Na-Cl유형으로 진화하는 Ca-Cl유형을 나타내었다. 따라서, 여러 지구화학 방법에 의한 해수 영향 판단 결과는 서로 잘 일치하고 있음을 알 수 있다. 결국, 지구화학적 파라메터를 종합적으로 활용함으로써, 연안 지역 해수침투의 효과적인 파악은 물론 예측 및 방지, 복구에 효과적으로 사용될 수 있을 것으로 판단된다.으로 토양에서 유동 가능성이 있는 중금속만을 추출하였다. 분석실험은 토양의 Cd2+ 와 Pb2+를 대상으로 행하여졌으며, 여러 토양에서 추출 분석한 결과를 EDTA분석결과와 비교하였다. 실험결과, 중금속은 매우 신속하게 고분자 자성체와 결합하였고, 그 후 자성체를 외부 자장으로 모은 후 산으로 용해시키고, 결합된 중금속은 Graphite furnace AAS로 분석함으로써 빠르고 효율적으로 분석실험을 수행할 수 있음을 알 수 있었다. 한편, 실험에서 나타난 수치들을 비교 검토한 결과 토양 분석시 sandy soil에서는 자성체를 이용한 분석이 EDTA에 의한 방법보다 더 높은 추출도를 보인 반면, silt 함량이 많은 토양의 경우에서 EDTA분석에서 더 높은 중금속 추출도를 보였다.s 중에서 490nm와 555nm의 복합밴드를 포함하는 OC2 알고리즘(ocean color chlorophyll 2 algorithm)을 사용하는 것이 OC2 series 및 OC4 알고리즘보다 좋은 추정 값을 도출할 수 있을 것으로 기대된다.환경에서는 5일에서 7월에 주로 이 충체의 유충이 발육되고 전파되는 것으로 추측되었다.러 가지 방법들을 적극 적용하여 금후 검토해볼 필요가 있을 것이다.잡은 전혀 삭과가 형성되지 않았다. 이 결과는 종간 교잡종을 자방친으로 하고 그 자방친의 화분친을 사용할 때만 교잡이 이루어지고 있음을 나타내고 있다. 따라서 여교잡을 통한 종간잡종 품종육성 활용방안을 금후 적극 확대 검토해야 할 것이다하였다.함을 보이고 있다.X> , ZnCl$_{3}$$^{-}$같은 이온과 MgCl$^{+}$, MgCl$_{2}$같은 이온종을 형성하기 때문인것 같다. 한편 어

• The Korean Journal of Nuclear Medicine
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• v.24 no.2
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• pp.237-243
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• 1990

Pulmonary embolism demands rapid and accurate diagnosis. And ventilation imaging has greatly improved the diagnostic accuracy of pulmonary embolism in addition to perfusion imaging. Agents currently used include xenon-133, krypton-81m and technetium-99m radioaerosols. However radioactive gases are compromised by availability and cost for krypton-81m, radiation dose, gamma energy and non?physiologic behaviour for xenon-133. Radioaerosols of technetium-99m componds are rapidly cleared from the lung after inhalation, and their relative low effeciency (specific radioactivity) and wide distribution of particle sizes make them also suboptimum. A new ventilation agent, Technegas is a suspension of structured graphite ellipsoids with diameter below 20nm, labelled with $^{99m}Tc$ in a carrier gas of Argon. This report describes the authors' clinical experience with Technegas. This is the first reported clinical study of this agent in Korea. A comparison of Technegas and $^{99m}Tc-DTPA$ aerosol was performed in 12 patients with various pulmonary diseases such as COPD, pulmonary tuberculosis and pleural effusion. All patients were studied with $^{99m}Tc-DTPA$ aerosol inhalation and Technegas ventilation. In both studies image quality was assessed (1) semiquantitatively by scoring bronchial and gastric activity, (2) subjectively by direct visual comparison of peripheral lung images and (3) quantitatively by computing the peripheral penetration index(PI) for each lungs. The bronchial activites were seen in 7 out of 12 cases with $^{99m}Tc-DTPA$ aerosol and in 5/12 with Technegas. The gastric activities were seen in 5/12 and 1/12 cases respectively. The average values of PI were 61.26% with $^{99m}Tc-DTPA$ aerosol and 69.20% with Technegas (p>0.05). Using $^{99m}Tc-DTPA$ aerosol, COPD patients showed deposition in the central airways with poor visualization of the peripheral areas of the lungs. In Technegas studies these phenomena were less prominent, and the examination is well tolerated by pateients and requires only a minimum of patient cooperation. With superiority of easy availability and handling, better physical characteristics and favorable Image quality, Technegas is a Promising agent for lung ventilation scanning.