• 상하수도학회지
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• 제23권5호
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• pp.547-555
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• 2009

The objectives of this research were focused on the effects of various operating parameters on nitrous oxide emission such as C/N ratio, ammonia concentration and HRT in the hybrid and suspension reactors. With the decreasing of C/N ratios, $N_2O$ emission rates in the both processes were increased because organic carbon source for denitrification was depleted. In case of biofilm reactor operated using medium, $N_2O$ release from the nitrification was not affected by the variation of ammonia concentration. But in the suspension reactor, $N_2O$ production from the nitrification was rapidly increased with the increase of ammonia. Nitrite accumulation caused by undesirable nitrification conditions could be a important reason for the increase in the $N_2O$ production from the aerobic reactor. And rapid increase in $N_2O$ production was reflected by the decrease of HRT, similar to the results observed in the results of ammonia loading changes. So it could be said that it is very important to put in consideration both its optimum conditions for wastewater treatment efficiency and suitable conditions for $N_2O$ diminish, simultaneously, in order to development an eco-friendly and advanced wastewater treatment, especially in BNR process.

• 한국대기환경학회지
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• 제13권1호
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• pp.9-18
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• 1997

Precipitation samples were collected by the wet- only event sampling method from Seoul during September 1991 to April 1995. These samples were analyzed for the concentrations of the major ionic components (N $O_3$$^{[-10]}$ , N $O_2$$^{[-10]}$ , S $O_4$$^{2-}$, C $l^{[-10]}$ , $F^{[-10]}$ , N $a^{＋}$, $K^{+}$, $Ca^{2＋}$, $Mg^{2＋}$, and N $H_4$$^{＋}$), pH, and electric conductivity. During the study period, a total of 182 samples were collected, but only 163 samples were used for the data analysis via quality assurance of precipitation chemistry data. The volume-weighted pH was found to be 4.7. The major acidifying species from our precipitation studies were identified to be non-seasalt sulfate (84$\pm$9 $\mu$eq/L) and nitrate (24$\pm$2 $\mu$eq/L) except for chloride. Because the Cl/Na ratio in the precipitation was close to the ratio in seawater. If all of the non-seasalt sulfate and nitrate were in the form of sulfuric and nitric acids, the mean pH in the precipitation could have been as low as 3.7 lower than the computed value. Consequently, the difference between two pH values indicate that the acidity of precipitation was neutralized by alkaline species. The equivalent concentration ratio of sulfate to nitrate was 3.5, indicating that sulfuric and nitric acids can comprise 78％ and 22％ of the precipitation acidity, respectively. Analysis of temporal trend in the measured acidity and ionic components were also performed using the linear regression method. The precipitation acidity generally showed a significantly decreasing trend, which was compatible with the pattern of the ratio (N $H_4$$^{＋}$＋C $a^{2＋}$)/ (nss-S $O_4$$^{2-}$＋N $O_3$$^{[-10]}$ ).).

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1720-1725
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• 2015

The performance of the AlGaN/GaN MSM-2DEG varactor with different dielectric films deposited by the E-beam deposition is investigated in detail. The capacitance swing and the capacitance ratio of the varactor without dielectric film as well as with, SiO₂, Gd₂O₃, and Si₃N₄ films, respectively, are determined by electrodes of varying areas. The maximum capacitance, the minimum capacitance and the capacitance ratios are proportional to the increasing of the electrode areas. The capacitance ratio determined by the maximum and the minimum capacitance is found to be 18.35 (with Si₃N₄ dielectric film) and 149.51 (without dielectric film), respectively. The transition voltages of the fabricated varactors are almost the same for a bias voltage of about ±5 V and leakage current can be lower three orders of magnitude while the varactors with dielectric films. The tunability of the capacitance ratio makes the AlGaN/GaN MSM-2DEG varactor with a dielectric film highly useful in multirange applications of a surge free preamplier.

• 한국토양비료학회지
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• 제12권3호
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• pp.153-167
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• 1979

수도(水稻)의 생산능력(生産能力)을 최대(最大)한 발현(發顯)시키는데 필요(必要)한 시비량(施肥量) 결정방법(決定方法)을 시도(試圖)했다. 이 시도(試圖)에서는 양분(養分)의 균형적(均衡的) 공급(供給)을 토양특성(土壤特性)과 품종(品種)의 특성(特性)에 바탕을 두어 공식화(公式化)하고저 했으며, 과거(過去)에 실시(實施)된 시험성적(試驗成績)들을 이용(利用)하여 그 타당성(妥當性)을 검토(檢討)했다. 그 요지(要旨)는 다음과 같다. 1. 다수확(多收穫)을 도모(圖謀)할 경우(境遇), 양분(養分)의 균형적(均衡的) 공급(供給)이 매우 중요(重要)하다. 2. 규산(珪酸)은 시용(施用)된 질소(窒素)를 고수량(高收量)으로 연결(連結)시키는데 중요(重要)한 역할(役割)을 한다. 3. 수량(收量)에 가장 결정적(決定的)인 몫을 하는 질소(窒素)의 시용량(施用量)은 토양중(土壤中) 유기물(有機物) 및 유효규산(有效珪酸)의 비(比) 즉(卽) $SiO_2$/O.M. 비(比)를 참작(參酌)함이 타당하다. 4. $SiO_2$/OM. 비(比)를 근거(根據)로 질소시용량(窒素施用量)을 결정(決定)코저 할 경우(境遇), 수도(水稻)의 품종적(品種的) 특성(特性)이 고려(考慮)돼야한다. 그 까닭은 품종별(品種別)로 토양중(土壤中) 유기물(有機物) 함량(含量)에 영향(影響)받는 정도(程度)가 상이(相異)하기 때문이다. 5. 토양(土壤)에 규산질(珪酸質) 비료(肥料) 혹(或)은 유기물(有機物)의 시용(施用)으로 $SiO_2$/O.M. 비(比)를 변화(變化)시킬 수 있으며 이에 따라 질소량(窒素量)도 변동(變動)시킬 수 있다. 이 때에 수도품종(水稻品種)의 특성(特性)이 고려(考慮)돼야 한다. 6. 질소시용량(窒素施用量)을 이와 같이 결정(決定)한 다음 가리(加里)의 시용량(施用量)은 질소량(窒素量)과 토양중(土壤中) K/Ca+Mg 비(比)를 토대(土台)로 산출(算出)할 수 있다.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.16-21
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• 2004

In order to investigate the characteristics of diamond wheel grinding of ceramic materials, grinding resistance, surface roughness of ground surface and image of grinding wheel were acquired using experimental method. Through the experiments, this makes it possible to observe grinding wheel behavior by grinding resistance, surface roughness and cutting edge ratio. In case of $Al_2O_3$, cutting edge ratio is bigger than that of $ZrO_2$ and $Si_3N_4$. That's because $Al_2O_3$ has a characteristic of low fracture toughness and bending stress.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.308-313
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• 2002

In order to investigate the characteristics of grinding and diamond wheel grinding ceramic materials, grinding resistance, surface roughness of worked surface and image of grinding wheel were acquired using experimental method. Through the experiments, this makes it possible to observe grinding wheel behavior by grinding resistance, surface roughness and cutting edge ratio. In case of A1$_2$O$_3$, cutting edge ratio is begger than that of ZrO$_2$and Si$_3$N$_4$. That's because A1$_2$O$_3$has a characteristics of low fracture toughness and bending stress.

• 대한환경공학회지
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• 제27권1호
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• pp.59-66
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• 2005

[ $TiO_2$ ]박막은 DC 마그네트론 스퍼터링법을 이용하여 다양한 스퍼터링 파라미터(전력 $0.6{\sim}5.2\;kw$, 기판온도 실온${\sim}350^{\circ}C$, 산소량 $0{\sim}50\;sccm$($O_2+Ar$ 90 sccm, 압력은 약 1 mtorr))를 통하여 증착되었다. TiO-N박막도 가스의 유량비를 제외하고는 $TiO_2$박막과 같은 스퍼터링 조건하에서 증착되었다. 이러한 스퍼터링 파라미터에서 증착된 박막의 전기적 특성을 분석하기 위하여 시트저항을 측정하였고, 박막의 두께(${\alpha}$-step), 표면 거칠기(AFM), 형성 조직(FE-SEM, XRD)을 분석하여 최적 스퍼터링 파라미터를 도출하였다. 최적 스퍼터링 파라미터에서 제조된($TiO_2$, TiO-N)박막을 이용하여 광활성도를 평가하기 위하여 VOCs물질 중 toluene, 반응성 염료인 Suncion Yellow를 대상 물질로 선정하여 적용성 연구를 수행하였다. 실험에서 광촉매 박막은 적용물질에 대해서 광활성을 양호하게 보였으며, 특히 TiO-N광촉매 박막은 가시광 영역에서도 최대 33%의 톨루엔(5 ppm) 제거 효율을 나타내었다.

• 한국분무공학회지
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• 제2권4호
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• pp.7-14
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• 1997

Laser Raman scattering method has been applied to measure equivalence ratio of methane/air mixture in injected spray. We used high power KrF excimer laser$(\lambda=248nm)$ and a high gain ICCD camera to capture low intensity signal. Raman shifts and Raman scattering cross -sections of $H_2,\;O_2,\;N_2,\;CO_2,\;CH_4\;and\;C_3H_8$ are measured precisely. Our results show an excellent agreement with those of other groups. Mole fraction measurement of $O_2\;and\;N_2$ from air shows that $O_2:N_2=0.206:0.794$. We used gas injector which was operated at 1 bar. Methane is used as a fuel. Spray region is $10mm\times37mm$ and this region is divided into 80 points. In Raman signals are obtained and ensemble averaged for each point. 3-d and contour plot of distribution of equuivalence ratio is presented. Our measured results show that the equivalence ratio of methane/air mixture in methane-rich region is reasonable. However, more study is necessary for methane-lean region because background noise level is almost same as Raman intensity of methane.

• 한국대기환경학회지
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• 제20권6호
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• pp.749-758
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• 2004

Nitrous oxide ($N_2$O) has been known as an important trace gas due to the greenhouse gas and the major source of stratospheric oxide of nitrogen (NO). Soil is the major source of $N_2$O in nature. The physicochemical characteristics of soils affect the emission of $N_2$O from soil. These physicochemical parameters are soil moisture, soil temperature, and soil N content. Since these parameters are correlated to the flux of $N_2$O from soil individually and compositely, there still remain many unknowns in the mechanism to produce $N_2$O in soil and the roles of such physicochemical parameters which affect the soil $N_2$O emission. Soil $N_2$O fluxes were measured at different levels in water filled pore space (WFPS), soil temperature and soil N contents from the same amounts of soils which were sampled from agriculturally managed upland field in a depth of ～30 cm at Kunsan. The soil $N_2$O flux measurements were conducted in a laboratory with a closed flux chamber system. The optimum soil moisture and soil temperature were observed at 60% of WFPS and ～13$^{\circ}C$. The soil $N_2$O flux increased as soil N contents increases during the whole experimental hours (up to 48 hours). However, average $N_2$O flux decreased after ～30 hours when organic carbon was mixed with nitrogen in the sample soils. It is suggested that organic carbon could be important for the emission of $N_2$O, and that the ratio of N to C needs to be identified in the process of $N_2$O soil emission.

• 한국패류학회지
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• 제24권3호
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• pp.261-267
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• 2008

수온 및 염분에 따른 굴의 일반적인 대사경향을 알아보기 위하여 수온과 개체크기에 따른 산소소비율과 암모니아 질소 배설률을 측정하였으며, O:N원자비를 산출하였다. 산소소비율과 암모니아 질소배설률은 개체의 크기가 작을수록 높았으며, 수온증가에 따라 증가하였다. O:N 원자비는 일반해수에서 8-40의 범위에 있었으며, 수온 $25^{\circ}C$에서 O:N 원자비는 8로 감소하였는데, 이는 산란기에 주요 대사기질로서 단백질을 이용하며, 단백질의 요구가 큰 것으로 추정된다. 이 결과는 굴양식장의 지속적인 관리 및 적정 수용력 산정을 위한 기초자료로 활용이 가능하다.