• 한국습지학회지
• /
• 제10권3호
• /
• pp.27-35
• /
• 2008

Sediment cores were obtained from Upo and Mokpo in Upo Wetland and core samples were divided by depth into 20 ~ 21 subsamples. The heavy metal concentrations of Fe, Mn, Zn, AS, Cu, Cd, Ni, Pb, and Cr in the sediments of each depth were determined by ICP-MS. The texture of sediemnts from Upo Wetland appeared to be clayey silt with average grain size of $7.52{\sim}11.15{\mu}m$ for physical properties. It was found to have a clear tendency of depth profile with respect to TOC and ignition loss. Organics were stabilized in the range of 0.5 ~ 0.7 % TOC and 8 ~ 9 % ignition loss in 30 years, whereas, the surficial sediments have the highest concentrations of about 3.0 % of TOC and 13 ~ 15 % ignition loss. Those are much higher than the values of the main stream, the Nakdong River, which reflects the deposit of biodegradable organics from plants and other lifes. The vertical distribution of heavy metals in two sediment cores was investigated to elucidate historical trends of heavy metals deposited into Upo wetland. The depth profile concentrations of each heavy metal were compared and discussed with the Concensus-Based Sediment Quality Guidelines for freshwater ecosystems. All the Cd data for the vertical distribution in the sediments were detected above PEC value for Cd, which predict harmful effects on sediment-dwelling organisms expected to occur frequently. The concentrations of Zn, Cu, and Cr in all sediment samples for depth profile were detected below the TEC values, which provided a basis predicting the absence of toxicity by Zn, Cu, and Cr.

• 한국자기학회지
• /
• 제4권3호
• /
• pp.233-238
• /
• 1994

건식 기계적 분쇄법을 이용하여 $Nd_{16}Fe_{84-x}B_{x}(x\;=\;5,\;6,\;7,\;8)$ 합금에서 다이업셋과 열처리가 자기적 특성에 미치는 영향을 연구하였다. 기계적 분쇄 이후에 다이업셋하면 시편 전체적으로 압축방향과 평행한 stripe형 자구가 많이 나타나지만 자화용이축인 c축으로 완전하게 정렬되지 않고 있어 잔류자속밀도가 낮다. 다이업셋한 시편을 $1000^{\circ}C$, 5시간 열처리하면 결정립이 약 $20\mu\textrm{m}$으로 성장하여 잔류자속밀도와 보자력이 감소한다. 13시간 동안 기계적 분쇄하여 제조한 분말을 다이업셋$(T:750^{\circ}C,\;\dot{\varepsilon}:0.001/sec,\;{\varepsilon}:60%)$한 시편에서 가장 높은 자기적 특성$(_{i}H_{c}=14\;kOe,\;B_{r}=7.8\;kG)$을 얻을 수 있었다.

• 천문학회지
• /
• 제24권1호
• /
• pp.55-70
• /
• 1991

Infrared emission maps are constructed at 12.5, 25, 60, and $100{\mu}m$ for dark globules B5, B34, B133, B134, B361, L134 and L1523 by using Infrared Astronomical Satellite data base. These clouds are selected on the basis of their appearance in Palomar print as dark obscuring objects with angular sizes in the range of 3 to 30 arcminutes. The short wavelength(12.5 and $25{\mu}m$) maps show the embedded infrared sources. We found many such sources only in B5, B361 and B34 regions, Diffuse component at 12.5 and $25{\mu}m$, possibly arising from the stochastically heated very small dust grains(a < $0.01{\mu}m$) by interstellar radiation field, is found in B361 and L1523 regions. Such emission is characterized by the limb brightening, and it is confirmed in L1523 and in B361. Infrared emissions at the long wavelengths(60 and $100{\mu}m$) are due to colder dusts with temperature less than 20 K. The distribution of color index determined by the ratio 60 to $100{\mu}m$ intensities shows monotonic decrease of dust temperature toward the center. The black body temperature determined from these ratios is found to lie between 16 and 23 K. Such temperature is possible for small(i.e., $a\;{\lesssim}\;0.01{\mu}m$) graphite grains if the grains are mainly heated by interstellar radiation field. Thus IRAS 100 and $60{\mu}m$ emissions are arising mainly from small grains in the colud. The distribution of such dust grains implied from the emissivity distributions at 100 and $60{\mu}m$ resembles that of isothermal sphere. This contrasts to earlier findings of much steeper distribution of dusts contributing visible extinction. These dust grains are mainly larger ones(i.e., $a{\simeq}0.1{\mu}m$). Therefore we conclude that the average grain size increase, toward the cloud center.

• 한국결정성장학회지
• /
• 제6권3호
• /
• pp.318-326
• /
• 1996

본 연구는 초고집적회로의 금속 배선으로써 보다 유용할 것으로 기대되는 구리박막의 화학적인 증착기술에 관한 것으로 precursor 물질로는 (hfac)Cu(I)VTMS ; (hevaflouoroacetylacetonate trimethyvinylsilane copper)로 명명된 금속 유기 물질을 사용하였다. 실험시스템의 초기 압력은 $10^{-6}$ Torr를 유지하고, 시스템의 챔버압력과 기판온도가 조정 가능하도록 설계, 제작되었다. 공정 조건에 따른 구리 박막 결정의 성장속도, Grain size, 전기적 성질을 측정하였다. 구리 박막을 증착하기 전에 W(tungsten) 또는 TiN(titanium nitride)이 증착되어 있는 실리콘 웨이퍼를 사용하였다. 본 연구에서는 $250^{\circ}C$이하의 상대적으로 낮은 실리콘 웨이퍼 온도에서의 실험이 가능하였으며 헬륨을 carrier gas로 사용하였는데 연구 결과 구리 박막 증착율이 $220^{\circ}C$에서 최대 $1,800\;{\AA}/분$으로 증가한 반면 표면 거칠기는 $200\;{\AA}$를 갖는 다결정 구리 박막을 관찰하게 되었다. 기판 온도가 $250^{\circ}C$이하일 때의 W(또는 TiN)과 $SiO_{2}$ 기판사이에서 구리 증착 선택성이 관찰되었으며, 최적의 기판 증착 온도는 약 $180^{\circ}C$와 반응용기 압력 0.8 Torr로 나타났다.

• 한국전기전자재료학회논문지
• /
• 제15권8호
• /
• pp.664-670
• /
• 2002

The electrical characteristics of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-Y_2O_3$(ZPCCY)-based varistors were investigated with $Y_2O_3$ content in the range of 0.0~4.0 mol%. As $Y_2O_3$ content is increased, the average grain size was markedly decreased in the range of 18.6~3.2 $\mu m$ and the density of the ceramic was decreased in the range of 5.53 ~3.74 $g/\textrm{cm}^3$. While, the varistor voltage was increased in the range of 39.4~748.1 V/mm and the nonlinear exponent was in the range of 4.5~51.2 with increasing $Y_2O_3$ content. The addition of $Y_2O_3$ greatly enhanced the nonlinear properties of varistors, compared with the varistor without $Y_2O_3$. In particular, the varistors with $Y_2O_3$content of 0.5 mol% exhibited the highest nonlinearity, in which the nonlinear exponent is 51.2 and the leakage current is 1.3 $\mu A$. The donor concentration and the density of interface states were decreased in the range of (4.19~0.14) $\times$10$^{18}$ /㎤ and (5.38~1.15)${\times}10^{18}/\textrm{cm}^3$, respectively, with increasing $Y_2O_3$ content.

• 한국세라믹학회지
• /
• 제53권2호
• /
• pp.145-149
• /
• 2016

$(Bi_{1/2}Na_{1/2})_{0.94}Ba_{0.06}(Ti_{1-x}Nb_x)O_3$ (BNBTxNb) ceramics were investigated in terms of the crystal structure as well as the ferroelectric, dielectric, and piezoelectric properties. While little change was observed in the microstructure except for a slight decrease in the average grain size, a significant change was noticed in the temperature dependence of dielectric and piezoelectric properties. It was shown that the property changes are closely related to the downward shift in the position of the ferroelectric-to-relaxor transition temperature with increasing amount of Nb doping. A special emphasis is put on the fact that Nb doping is so effective at decreasing the ferroelectric-to-relaxor transition temperature that even at no more than 2 at.% Nb addition, the transition temperature was already brought down slightly below room temperature, resulting in the birth of a large strain at 0.46 %, equivalent to $S_{max}/E_{max}=767pm/V$.

• 한국전기전자재료학회논문지
• /
• 제25권7호
• /
• pp.506-510
• /
• 2012

In this study, lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics were fabricated by conventional mixed oxide method. Structural and electrical properties of lead-free $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ ceramics with the variation of sintering temperature were investigated. As results of x-ray diffraction analysis, all specimens showed a typical polycrystalline perovskite structure without presence of the second phase. Sintered density increased with an increases of sintering temperature and the specimen sintered at $1,020^{\circ}C$ showed the maximum value of 4.5 $g/cm^3$. The average grain size of the $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimen sintered at $1,020^{\circ}C$ is about 0.83 ${\mu}m$. Electromechanical coupling factor, relative dielectric constant and dielectric loss of $(Na_{0.465}K_{0.465}Bi_{0.07})(Nb_{0.93}Ti_{0.07})O_3-0.08MnO_2$ specimens sintered at $1,020^{\circ}C$ were 0.252, 741 and 0.043% respectively.

• 한국작물학회:학술대회논문집
• /
• 한국작물학회 2017년도 9th Asian Crop Science Association conference
• /
• pp.258-258
• /
• 2017

We received 73 wheat resources from CIMMYT for analysis of agricultural characteristics and qualities of them. We sowed 73 lines and 4 Korean varieties in fall and spring to compare differences of wheat traits between fall and spring seeding. The heading and maturity date of fall seeding lines has coming faster average 18 days than spring seeding lines. Fall seeding lines have more number of spike per $m^2$ and grain number of spike. Spike and awn length of spring seeding lines were shorter than fall seeding lines and stem length was variable to varieties in both condition. Protein contents of five of 73 lines, Jokyoung and Jopoom varieties decreased but the others increased. The sedimentation values of 34 lines include Jokyoung and falling number (F/N) of 44 lines include two varieties, Keumkang and Jokyoung, decreased but the others increased, respectively. Particle size was presented that most spring seeding lines were bigger. However, when it sowed in fall, the lightness (L) of wheat flour was lighter. Consequently, we confirmed when it was sowed in spring, agricultural traits and qualities of wheat got weak.

• Journal of the korean society of oceanography
• /
• 제33권4호
• /
• pp.178-184
• /
• 1998

To elucidate contamination levels and distribution of methyl mercury (Me-Hg) in Korean coastal areas, 126 sediment samples were collected from Kyeonggi Bay, Namyang Bay, Chinhae Bay, and Lake Shihwa during 1995-1996, and the Me-Hg concentrations were determined by cold vapor atomic fluorescence spectrometry (CVAFS). Contamination levels of Me-Hg in sediments from Kyeonggi Bay, Namyang Bay, Chinhae Bay, and Lake Shihwa were 274 ${\pm}$ 990, 108 ${\pm}$ 24, 294 ${\pm}$ 342, and 1080 ${\pm}$ 760 pg/g, respectively. Concentrations of Me-Hg in sediments were significantly correlated with total organic carbon and sulfur contents, but were independent of mud contents and mean grain size. The highest concentration of Me-Hg (7100 pg/g) was observed at Incheon North Harbor (Site Kl9) in Kyeonggi Bay. This Me-Hg concentration was one or two orders of magnitude higher than those in other Kyeonggi Bay sediments were. The average concentration of Me-Hg in sediments from Lake Shihwa was higher than in those from other study areas. The three peaks of Me-Hg concentrations were observed on three sites (55, 56,and 510) in Lake Shihwa and gradually decreased in distance-dependent manner around these sites. High concentrations of Me-Hg at surface and 10-cm sediment depth in Chinhae Bay maybe due to higher rates of methylation process by active sulfate-reducing bacteria or higher concentrations of total mercury available to sulfate-reducing bacteria.

• Transactions on Electrical and Electronic Materials
• /
• 제18권5호
• /
• pp.261-264
• /
• 2017

$Ni_{0.79}Co_{0.15-x}Cu_xMn_{2.06}O_4$ ($0{\leq}x{\leq}0.09$) thick films were fabricated using the conventional solid-state reaction method and screen-printing method. Structural and electrical properties of specimens based on the amount of Cu were observed in order to investigate their applicability in the infrared detector. All specimens showed a single spinel phase with a homogeneous cubic structure. As the amount of Cu increased, the average grain size increased and was found to be approximately $5.01{\mu}m$ for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen. The thickness of all specimens was approximately $55{\sim}56{\mu}m$. As Cu content increased, the resistivity and TCR properties at room temperature decreased, and these values for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen were $502{\Omega}-cm$ and $-3.32%/^{\circ}C$, respectively. The responsivity and noise properties decreased with an increase in Cu content, with the specimen with a Cu content of x=0.09 showing 0.0183 V/W and $5.21{\times}10^{-5}V$, respectively.