• 한국전기전자재료학회논문지
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• 제26권9호
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• pp.707-711
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• 2013

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

• 생태와환경
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• 제40권4호
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• pp.576-580
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• 2007

Phytoplankton community dynamics were studied from 2004 to 2006 with two and four weeks interval at mid to lower part of the Nakdong River (Waegwan: RK 194, Goryeong: RK 157, Jukpo: RK 112, Namji: RK 75 and Hanam: RK 63: RK: distance from the Estuarine Barrage), South Korea. Annual averages of water temperature was about $16^{\circ}C$, and dissolved oxygen was ranged between 10.0 and 11.5 mg $L^{-1}$ (percent saturation, 106.5 to 112.8%). Diatoms were dominant group with over 60% of phytoplankton abundance in all study sites (Waegwan: 64%, Goryeong: 69%, Jukpo: 73%, Namji: 79%, and Hanam: 83%). However, the occasional dominances of other groups such as green algae and blue-green algae were observed from March to October. Stephanodiscus hantzschii was dominant species and the relative abundances were highat all study sites (48-72%). The ratio of S. hantzschiiltotal phytoplankton abundance were showed a clear increasing tendency toward the estuarine barrage: i.e. 0.31 at Waegwan, 0.39: Goryeong, 0.50: Jukpo, 0.56: Namji, 0.60: Hanam. The results of this study provide the information that the phytoplankton community structure in a regulated river system is basically affected by the physical properties such as water velocity and retention time, resulting in single species dominance by the stagnancy of river flow.

• 한국자기학회지
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• 제11권2호
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• pp.45-49
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• 2001

RF 마그네트론 스퍼터링으로 제조한 Fe/CoNbZr 다층박막의 구조 및 열처리 조건에 따르는 고주파 연자기 특성을 연구하였다. Fe층의 두께가 5nm일 때 1.1Oe의 최소보자력을 얻었으며, Fe층의 두께가 15nm일 때 100Mz에서 2300의 최대 투자율을 얻었으며, 약 20 kG의 높은 포화자화를 얻었다. Fe층의 두께가 증가함에 따라 보자력이 증가하는 것은 결정립 크기에 의한 것이며, Fe층의 두께가 얇을 경우 계면에서의 CoFe과 같은 높은 자기변형의 혼합층 형성으로 인해 투자율이 감소한 것으로 판단된다. 300 $^{\circ}C$에서 40분간 일축자장 열처리를 행하여서 보자력 0.35 Oe, 투자율 2500을 얻었다. 또한 250및 30$0^{\circ}C$ 열처리에서만 연자기 특성이 향상되었다. 이는 최적의 Fe의 격자변형과 일측 이방성의 발달로 자기이방성에너지의 감소에 의한 것으로 판단된다.

• 한국자기학회지
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• 제10권2호
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• pp.81-85
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• 2000

Orthoferrite LaFeO$_3$ 화합물에서 Fe 이온의 미량을 Mn 이온으로 치환시킨 시료인 LaFe$_{1-x}$Mn$_{x}$ O$_3$(0.0$\leq$x$\leq$0.4)을 제조하여 Mn 이온의 치환에 따른 결정학적 및 자기적 특성의 변화를 밝히기 위하여 x-선 회절기, M ssbauer 분광기, 진동자력계와 초전도 양자간섭계 등을 이용한 연구를 하였다. 제조한 시료는 모든 조성비 범위에서 단일상의 orthorhombic distorted perovskite 구조를 보였다. M ssbauer 스펙트럼은 상온에서 한 개의 육중선(x=0.0)에서 두 개의 육중선 세트(x=0.1, 0.2, 0.4)로 변했다. 특히 x=0.4에서는 상자성의 이중선과 육중선이 중첩된 모양을 보였다. 본 시료에서 Fe는 모두 Fe$^{3+}$ 상태로 팔면체자리에 위치함을 알았다. 또 LaFe$_{1-x}$Mn$_{x}$ O$_3$에서 Mn의 양이 증가함에 따라 포화자화 값은 증가하지만 보자력은 감소함을 알아냈다.

• 한국자기학회지
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• 제3권2호
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• pp.143-148
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• 1993

열 분해법으로 $Bi_{x}Dy_{3-x}Al_{1}Fe_{4}O_{12}$(x=1, 1.2, 1.5) 자기 가넷 박막을 유리기판 위에 제조하였다. Bi 치환량을 증가시켰을 때 $M_{s}$ 값은 5 emu/cc에서 12 emu/cc로 증가하였고, 제조된 모든 박막이 수직 자기 이방성을 나타내었다. Bi 양의 증가에 따라 파장 780 nm의 광원을 사용했을 때 패러디 회전각이 $0.11^{\circ}/\mu\textrm{m}$에서 $0.20^{\circ}/\mu\textrm{m}$로 증가 하였으며 가넷 결정화 온도는 $660^{\circ}C$에서 $630^{\circ}C$로 감소하였다. 또한 보자력은 1200 Oe에서 600 Oe로 감소하였으며 결정립의 크기가 증가하였다. 박막의 두께를 $2000\;{\AA}$에서 $4000\;{\AA}$으로 증가시킴에 따라 $H_{c}$가 1750 Oe에서 1200 Oe로 감소했으며 ${\theta}_F$는 반사광의 간섭 효과에 의해 증가하였다.

• 한국자원식물학회지
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• 제9권3호
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• pp.274-278
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• 1996

본 실험은 포장과 포트재배에서 토양시비수준(土壤施肥水準), 온도(溫度) 및 광조건(光條件下)에서 건물생산량과 광합성(光合成) 속도의 차이를 측정분석하여 야콘의 적정생장(滴定生長) 조건(條件)을 밝히고자 실시하였다. 1. 포장에서의 시비수준별 건물생장율은 무처리구 보다 퇴비구에서 높게 나타났으며, 구근의 건물중은 무처리구와 질소처리구와는 큰 차이를 보이지 않았다. 2. 최대 엽광합성 속도는 퇴비구(S-1)에서 17.3mg $CO_2gdm^{-2}s^{-1}$로 다른 질소 처리구 보다 높았으au, 무처리구의 엽광합성 속도가 가장 낮았다. 3. 광환경(光環境) 조건(條件)에 따른 퇴비구와 무처리구의 엽광합성 속도차이는 뚜렷하게 차이가 났으며 광포화점은 $1200{\pm}50{\mu}molm^{-2s^{-1}$이었다. 4. 광합성속도는 $34{\pm}3^{\circ}C$ 정도에서 높은 반면 $28^{\circ}C$ 정도 이하에서는 기공저항에 의하여 엽광합성 속도가 낮았다.

• 공업화학
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• 제5권3호
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• pp.509-516
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• 1994

에탄올의 제조시 불순물로서 미량 생성되는 크로톤 알데히드를 수소와 반응시켜 n-부틸알콜로 전환하여 불포화 탄화수소를 제거하는 공정에 액상수소 첨가반응을 이용하고자 하며, 기존의 기상 수소첨가반응보다 월등한 에너지 절약 효과가 있다. 반응촉매는 내구성 및 가격 등 경제적인 측면을 고려하여 니켈촉매를 선택하였으며, 반응전화율의 측정은 PMT(permanganate time) test 방법을 적용하였다. PMT는 에탄올에 미량으로 함유되어 있는 크로톤알데히드의 초기농도 증가에 따라 급격히 감소하였으며, 크로톤 알데히드로부터 n-부틸알콜로의 수첨반응은 탄소-탄소 이중결합의 환원 후, 알데히드의 환원 과정이 연속적으로 일어나고, 각 반응단계는 0차 반응속도 상수를 가진다. 실험조건 범위 내에서는 반응 온도가 높을수록, LHSV가 느릴수록 PMT는 길어지고, 반응압력은 PMT와 거의 무관함을 보였다.

• Archives of Plastic Surgery
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• 제39권5호
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• pp.546-550
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• 2012

Background This study was designed to introduce the feasibility of toe tissue transfer without venous outflow for fingertip reconstruction. Methods Five cases of fingertip defects were treated successfully with this method. Four cases were traumatic fingertip defects, and one case was a hook-nail deformity. The lateral pulp of a great toe or medioinferior portion of a second toe was used as the donor site. An arterial pedicle was dissected only within the digit and anastomosis was performed within 2 cm around the defect margin. The digital nerve was repaired simultaneously. No additional dissection of the dorsal or volar pulp vein was performed in either the donor or recipient sites. Other surgical procedures were performed following conventional techniques. Postoperative venous congestion was monitored with pulp temperature, color, and degree of tissue oxygen saturation. Venous congestion was decompressed with a needle-puncture method intermittently, but did not require continuous external bleeding for salvage. Results Venous congestion was observed in all the flaps, but improved within 3 or 4 days postoperatively. The flap size was from $1.5{\times}1.5cm^2$ to $2.0{\times}3.0cm^2$. The mean surgical time was 2 hours and 20 minutes. A needle puncture was carried out every 2 hours during the first postoperative day, and then every 4 hours thereafter. The amount of blood loss during each puncture procedure was less than 0.2 mL. In the long-term follow-up, no flap atrophy was observed. Conclusions When used properly, the free toe tissue transfer without venous anastomosis method can be a treatment option for small defects on the fingertip area.

• 한국환경과학회지
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• 제9권1호
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• pp.1-11
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• 2000

A study on the variational characteristics of water quality and phytoplankton biomass by principal component analysis(PCA) was carried out in Kogum-sudo from February to October in 1993. We analyzed PCA on biological factors such as chlorophyll a and phytoplankton cell numbers for centric and pennate diatoms, phytoflagellates, and total phytoplankton as well as physico-chemical factors as water temperature, salinity, transparency, dissolved oxygen(DO), saturation of DO, apparent oxygen utilization (AOU), chemical oxygen demand(COD), nutrient (ammonia, nitrite, nitrate, phosphate and silicate), N/P ratio and suspended solid(SS). The source of nutrients supply depended on the mineralization of organic matters and inputs of seawater from outside rather than runoff of freshwater. The phytoplankton biomass was changed within short interval period by nutrients change. And it was controlled by the combination of several environmental factors, especially of light intensity, ammonia and phosphate. The marine environmental characteristics were determined by the mineralization of organic matters in winter, by runoff of freshwater including high nutrients concentration in spring, by ammonia uptake and high phytoplankton productivity in summer, and phosphate supplied input seawater from outside of Kogeum-sudo in autumn. And Kogum-sudo was separated with 2 regions by score distributions of PCA. That is to say, one region was middle parts of straits which was characterized by the mixing seawater and the accumulated organic matters, other one region was Pungnam Bay and the water around Kogum Island which was done by high phytoplankyon biomass and productivity year-round.

• 한국전산유체공학회지
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• 제18권3호
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• pp.1-7
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• 2013

A pure oxygen combustion technology is crucial in Carbon Capture and Storage (CCS) technology especially in capturing of $CO_2$, where CCS will reduce 9 $GtCO_2$ by 2050, which is 19% of the total $CO_2$ reduction amount. To make pure oxygen combustion feasible, a regenerative system is required to enhance the efficiency of pure oxygen combustion system. However, an existing air combustion technology is not directly applicable due to the absence of nitrogen that occupies the 78% of air. This study, therefore, investigates the heat and fluid flow in a regenerative system for pure oxygen combustion by using commercial CFD software, FLUENT. Our regenerative system is composed of aluminium packed spheres. The effect of the amount of packed spheres in regenerator and the effect of presence or absence of a bypass of exhaust gas are investigated. The more thermal mass in regenerator makes the steady-state time longer and temperature variation between heating and regenerating cycle smaller. In the case of absence of bypass, the regenerator saturates because of enthalpy imbalance between exhaust gas and oxygen. We find that 40% of exhaust gas is to be bypassed to prevent the saturation of regenerator.