• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.348-352
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• 2014

In light of the sure protection function, the most important factors of a varistor are the clamping voltage ratio and degradation characteristics. The degradation characteristics of Pr/Co/Cr/Er co-doped zinc oxide varistors were investigated by impulse currents (0.4~2.1 kA) stress for the specified content of $Er_2O_3$ (0.5 and 2.0 mol%). The varistor doped with 2.0 mol% $Er_2O_3$ exhibited the best clamp characteristics, with the clamp voltage ratio (K) in the range of K = 1.63~1.88 at the impulse currents of 5-50 A. However, the varistor doped with 0.5 mol% exhibited excellent electrical stability, with variation rates for the breakdown field, for the nonlinear coefficient, and for the leakage current density of -6.9%, -12.6%, and -14.3%, respectively, after application of an impulse current of 2.1 kA. In contrast, the varistor doped with 2.0 mol% was destroyed after application of an impulse current of 1.2 kA.

• 대한전기학회논문지:전력기술부문A
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• 제54권8호
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• pp.401-409
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• 2005

This paper describes a feasibility analysis result of STATCOM application for the Jeju-Haenam HVDC system. The Jeju-Haenam HVDC system is one of the typical HVDC system interconnected with the low short-circuit-ratio AC system, which is vulnerable to the commutation failure due to the AC voltage variation. STATCOM has been considered as an effective reactive-power compensator to increase short-circuit-ratio of the interconnected AC system. In this study, a simulation model of Jeju-Hacnam HVDC system with STATCOM was developed using PSCAD/EMTDC. The developed simulation model was utilized to analyze the dynamic performance analysis of Jeju-Haenam HVDC system with STATCOM. The analysis results show that STATCOM can improve the dynamic performance of Jeju-Haenam HVDC system, such as load-change recovery performance and fault recovery performance.

• Journal of Communications and Networks
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• 제9권1호
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• pp.67-74
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• 2007

The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.85-91
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• 2001

LPG has been well known as a clean alternative fuel for vehicles. As a fundamental study on liquid phase LPG injection (hereafter LPLI) system application to heavy-duty engine, engine output and combustion performance were investigated with various operating conditions using a single cylinder engine equipped with the LPLI system. Experimental results revealed that no problems were occurred in application of the LPG fuel to heavy-duty engine, and that volumetric efficiency and engine output, by 10% approximately, were increased with the LPLI system. It was resulted from the decrease of the intake manifold temperature through liquid phase LPG fuel injection. These results provided an advantage in the decrease of the exhaust gas temperature, in the control of knocking phenomena, spark timing and compression ratio. The LPLI engine could normally operated under $\lambda$=1.5 or EGR 30% condition. The optimized swirl ratio for the heavy duty LPG engine was found around R_s$ = 2.0.

• 한국통신학회논문지
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• 제13권1호
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• pp.54-62
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• 1988

본 논문에서는 부호분할다중접근을 위한 주파수도약대역확산통신방식의 통신시스템을 구현하는데 기본적으로 필요한 요소인 주파수합성기에 대하여 각 사용자에게 부여된 번지에 따라 원하는 도약형태로 주파수를 출력시키는데 적합하고 실제 시스템의 구현이 용이하도록 다중루프 PLL 주파수합성기의 모델을 제시하였으며 원하는 주파수를 출력시키는데 필요한 주파수분주정수의 분포와 그 결정방법, 그리고 이 분주정수와 다중도에 따른 대역통과필터의 대역폭의 변화에 대해 분석하였다.

• 한국환경과학회지
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• 제32권11호
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• pp.777-788
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• 2023

Potato common scab disease is caused by pathogens belonging to Streptomyces spp. and results in a serious yield loss worldwide. Despite decades of research aimed at disease management, a definitive control method remains undiscovered. This study aims to explore the correlation between the C/N ratio and urea application with potato common scab pathogen dynamics and disease severity. We applied sawdust with a high C/N ratio and urea into the soil prior to potato cropping, both in pot and field experiments. Disease severity assessments and quantification of the TxtB gene were conducted at the harvest stage. Furthermore, culture experiments were performed to assess the direct impact of urea on the pathogen. Our findings revealed that higher disease severity was correlated with a high C/N ratio application and pathogenic gene quantity. Urea exhibited a direct influence on S. scabiei activity, reducing the disease severity in pot experiments. However, the effects of urea application on disease suppression in the conductive field were inconclusive. Although the results of urea application experiments displayed inconsistencies between pot and field trials, urea worked as the control to suppress S. scabiei activity. Further investigations are needed under various field conditions to confirm these findings.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.359-362
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• 2005

This study was performed to know the properties and estimation of field application of concrete(Bluecon) using fluosilicate salt based admixture made from by-product during phosphoric acid manufacturing process. Mix proportions for experiment were modulated at 0.45 of water-binder ratio and $0.5-2.0\%$ of adding ratio of fluosilicate salt based inorganic compound. Evaluation for Field application of concrete was carried out batch plant test at remicon factory and building construction. According to results. it was found that slump of concrete(Bluecon) using fluosilicate salt based admixture is higher about 10 to 20 mm than plain concrete, and air content is similar to each other. And the water permeability and crack of bluecon is lower than that of plain concrete.

• KIEAE Journal
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• 제7권4호
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• pp.119-126
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• 2007

In this study, we processed two procedures of application test of filler for fire-resistance utility that are new application methods of aerated concrete and properties test of aerated concrete according to mixing ratio because we investigated the better use of aerated concrete as filler for fireproof safety and we proposed basic data about standardization of mixing of aerated concrete. We measured flow and volume change of aerated concrete. And if its volume doesn't change, we added measuring unit weight and compressive strength. To test application of aerated concrete as filler for fireproof safety, we filled up aerated concrete to fireproof safety according to suitable mixing ratio. Then we measured maximum temperature of inner part of fireproof safety in accordance with the standard test of fireproof. According to the results, aerated concrete as filler for fireproof safety could be possibly used. So when we make aerated concrete, we should consider using an adding agent as well as a foaming agent.

• Journal of Ginseng Research
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• 제14권1호
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• pp.44-49
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• 1990

Effect of liming material application on the prevention or cure of Mn toxicity symptoms including marginal leaf chlorosis in 3-year-old ginseng plants grown in acidic soils were investigated. It was found that the ratio of Fe to Mn was above about 0.5 and the ratio of Mn to Fe was below about 2.00 in 4-year old ginseng leaves when liming materials were applied in field experiments. It was apparent that the occurrence of marginal leaf chlorosis was decreasing affected by application of Ca, Mg and Fe. The appearance of marginal leaf chlorosis was decreased to about 78 percent in 4-year-old ginseng and to about 69 percent in 5-year-old ginseng, and then the fresh root weight was increased up to 66 percent in 4-year ginseng plants.

• 한국토양비료학회지
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• 제3권1호
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• pp.1-10
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• 1970

수도(水稻)에 있어서 가리(加里)의 시용(施用)이 규회석(珪灰石)의 효과에 미치는 영향(影響)을 밝히기 위(爲)하여 Pot시험(試驗)을 실시(實施)하고 정조수량(精租收量)을 증가(增加)시킨 원인(原因)을 수량(收量) 및 수량구성요소(收量構成要素)와 수도(水稻)의 생육시기별(生育時期別) 토양(土壤) 및 식물체분석성적면(植物體分析成績面)에서 검토(檢討)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 가리(加里)의 효과는 규회석(珪灰石)이 시용(施用)되었을 때에 더 커지며 규회석(珪灰石)의 시용량(施用量)이 많을수록 가리(加里)의 요구량(要求量)도 많아진다. 2. 가리(加里)와 규회석(珪灰石)의 시용(施用)은 토양(土壤) 및 고중(藁中)의 가리(加里), 석회(石灰) 및 규산(珪酸)의 농도(濃度)를 증가(增加)시키며 $SiO_2/N$ 및 $K_2O/N$의 비율(比率)을 높여 정조수량(精租收量)을 증가(增加)시켰다. 3. 규회석(珪灰石)을 300kg/10a 이하(以下) 시용(施用)하였을 때에는 가리(加里)는 8kg/10a 에서 수량(收量)이 제일 높았으나 규회석(珪灰石)이 600kg/10a 시용(施用)되었을 때에는 가리(加里) 16kg/10a에서 수량(收量)이 제일 높았다. 4. 규회석(珪灰石)의 시용(施用)은 주당수수(株當穗數)와 수당립수(穗當粒數)는 감소(減少)시키고 등숙율(登熟率)과 천립중(千粒重)은 증가(增加)시키는 경향(傾向)이며 규회석(珪灰石) 시용(施用)으로 증가(增加)된 고중(藁中)의 CaO와 $SiO_2$는 주당수수(株當穗數)와 수당립수간(穗當粒數間)에는 부(負)의 상관(相關)이었으나 등숙율(登熟率)과 천립중(千粒重)과는 정(正)의 상관(相關)이 있었다. 5. 가리(加里)의 시용(施用)은 주당수수(株當穗數)와 수당립수(穗當粒數)를 증가(增加)시키는 경향(傾向)이며 가리시용(加里施用)으로 증가(增加)된 고중(藁中)의 $K_2O$와 수당립수(穗當粒數)와는 정(正)의 상관(相關)이 있었다. 6. 질소(窒素)의 흡수량(吸收量)은 가리(加里)와 규회석(珪灰石)의 시용(施用)이 증가(增加)함에 따라 감소(減少)하는 경향(傾向)이며 $SiO_2/N$ 비율(比率)은 가리(加里)와 규회석(珪灰石) 시용량(施用量)이 증가(增加)할수록 증가(增加)한다. 7. $K_2O/N$ 비율(比率)은 가리(加里)를 시용(施用)할수록 증가(增加)되며 가리무시용구(加里無施用區)에서는 규회석(珪灰石) 시용량(施用量)에 따라 감소(減少)하였다.