• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.112-115
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• 2010

본 논문은 그림 1과 같은 네트워크 환경에서 두 송신단이 LT code를 오류정정 부호로 사용할 때, 두 송신단이 생성하는 인코딩 심볼과 수신단이 수신하는 인코딩 심볼들의 degree distribution의 관계에 대해 다룬다. LT code를 복호하기 위해 belief propagation 방법을 사용했을 때, 수신단이 받은 인코딩 심볼들의 degree distribution은 robust soliton distribution(RSD)을 따를 때, overhead 대비 가장 높은 확률로 복호에 성공한다. 하지만 그림 1과 같은 네트워크 환경에서, 두 송신단 모두 RSD에 따라 인코딩 심볼을 생성하여 송신하면, 수신단에서 수신한 심볼은 RSD를 따르지 않는다. 본 논문은 한 송신단($S_1$) 이 생성하는 인코딩 심볼의 degree distribution을 알 때, 수신단에서의 인코딩 심볼의 분포가 근사적으로 RSD를 따르도록 하는 또 다른 송신단($S_2$)에서의 degree distribution을 구하는 방법을 제시한다.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.433-434
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• 2013

본 논문에서는 절연타입의 Half-bridge 구조를 이용하여 입력단을 구성하고 출력단에 5레벨의 출력전압을 생성할 수 있는 새로운 구조의 멀티레벨 PWM 인버터를 제안한다. 기존의 Cascaded H-bridge 멀티레벨 인버터는 두 대의 H-Bridge 인버터 모듈을 직렬 결합하여 5레벨의 출력전압을 생성하는 방식이며, 제안하는 방식은 기존 멀티레벨 인버터의 기본 모듈인 H-bridge의 전원을 절연타입의 Half-bridge 구조를 이용하여 구성하고 스위칭 소자 1개와 다이오드 1개를 추가한 구조이다. 동일한 5레벨의 출력전압 생성 시 기존 방식은 2차 측에 8개의 스위칭 소자가 사용되는 반면 제안된 방식은 5개의 스위칭 소자와 1개의 다이오드가 사용되기 때문에 스위칭 손실 및 부피를 줄일 수 있으며 입력단과 출력단 사이의 절연으로 인한 시스템의 안정성을 확보할 수 있다. PSIM 기반의 컴퓨터 시뮬레이션을 통해 제안된 멀티레벨 인버터의 타당성을 검증한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.9-16
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• 2003

This paper presents an novel multilevel inverter employing series connected transformers to reduce the harmonics of output voltage. The proposed inverter consists of several full-bridge modules and their corresponding transformers. Continuous output voltage levels can be generated from a suitable selection of turns ratio of transformer. And it appears an integral ratio to input DC source. Because of its series operation of transformers, output filter inductor is not required. The validity of the proposed system is verified through the experimental results using a 1.5 [kW] prototype, which can generate a 220 $[V_ac]$ output voltage from $[V_dc]$ input.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.294-296
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• 2020

코로나(COVID-19)로 인해 언택트(Untact) 방송이 활성화된 현 시점에서 기존 방송의 형태는 나날이 변화하고 있다. 특히 1인 미디어 대한 관심이 급증하게 되면서 1인 방송 체제가 전통적 미디어뿐만 아니라 대중에게까지 많은 영향을 미치며 하나의 트렌드로 자리 매김하게 되었다. 따라서 본 연구는 1인 방송의 특성과 시스템 설계를 바탕으로 최소한의 장비를 사용하여 양질의 스트리밍 서비스를 제공하기 위한 1인 방송 시스템을 구축하고자 한다.

• Journal of Animal Environmental Science
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• v.12 no.3
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• pp.141-150
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• 2006

To optimise the efficient use of nutrients in pig slurry is to cultivate friendly environmental crops. This field survey is to investigate the actual conditions of pig slurry utilization for cultivation of crops in the agricultural farm, based on the survey for 407 selected farms in 9 provinces included 78 counties in Korea. The results obtained in this survey were summarized as follow ; The motive which came to use pig slurry in the agricultural farm were production of friendly environmental crops (29.7%), economy of chemical fertilizer (25.1%), spontaneously (19.2%), inducement of neighboring farmhouse (16.0%), increase of soil fertility (9.3%), and the others (0.7%), respectively. The proportions of pig slurry application land were 56.5% for.ice paddy, 22.6% for dry field, 13.3% for orchard, 4.4% for controlled agriculture and 3.2% for other, respectively. The number of times of pig slurry utilization per year were once (48.9%), twice (31.9%), thrice (14.0%), and the others (5.2%), respectively. The controversial points of pig slurry utilization were malodor (54.1%), insufficiency of spread equipment (22.1%), inconvenience (14.5%), over application (3.4%), over cost (2.9%), heavy metal (1.7%), sanitation (1.0%) and the other (0.2%), respectively. The results indicated that pig slurry could be used as fertilizer source of friendly environmental crops, but further studies are needed to determine the application method and value of the pig slurry for crop cultivation.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.63-71
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• 2023

In the present study, the effect of pitch amplitude on the unsteady aerodynamics of a NACA 0012 airfoil is numerically investigated. When the frequency ratio is equal to 1.0, airfoil pitching with 20 and 30 degrees of pitch amplitude shows almost small lift generation, but the lift is significantly increased in case of 10-degree pitch amplitude. When the frequency is 0.5, the lift coefficients have large values, and the lift increases with a decrease in pitch amplitude. When the frequency ratio is 1.0, the airfoil generates large thrust. The thrust decreases as the pitch amplitude decreases. When the frequency ratio is 0.5, drag is generated for the 30-degree pitch amplitude, but the thrust is generated for 10-degree pitch amplitude. In future, the effect of heave amplitude on the unsteady aerodynamics of the airfoil will be studied.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.197-204
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• 2007

The reciprocal effects towards the enhanced biological phosphorus removal were performed for anaerobic, aerobic and anoxic phases. The batch experiments showed that the p-absorption in the anoxic phase was 50% lower than aerobic phase. The correlation coefficient between p-back-solution and p-absorption was found to be $R^2=0.557$ however, the coefficient b(b = 8.4049) was relatively higher than the other researchers results. The increase and/or acceptance of the $K^+-,\;Mg^{2+}-$ and $NH_4-N$-concentration was proportional to those of the $PO_4-P$-concentration in the batch test. The relationship between $K^+-,\;Mg^{2+}$ and $PO_4-P$ was determined. The average value of this relation-ship agreed with 0.2 mol $K^+Ion$ / mol $PO_4-P$ ion and 0.21 mol $Mg^{2+}Ion$ / moi $PO_4-P$ ion in the anaerobic phase. The absorbed ratio of $K^+$ to $Mg^{2+}$ over $PO_4-P$ was found to be 1 : 5.

• Journal of Applied Biological Chemistry
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• v.60 no.1
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• pp.19-22
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• 2017

This study was conducted to investigate the effect of acetic acid and citric acid treatments on amount and content ratio of calcium (Ca) and phosphorus (P) which were extracted from beef shank bones. The amount of Ca in shank bone extracts significantly increased with increasing citric acid and acetic acid concentration, whereas the amount of P increased with only adding citric acid to extraction media. In the case of combined treatment with 0.2 % acetic acid and 0.1 % citric acid, the amounts of Ca and P increased to 30 and 400 %, respectively and Ca and P ratio were drastically improved from 7.53 to 1.85 compared with treatment of 0.2 % acetic acid. The sensory score of shank bone extract prepared with 0.2 % acetic acid and 0.1 % citric acid treatment showed the highest values in taste and overall acceptability among the tested shank bone extracts.

• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.213-219
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• 2002

The CellCaSi, a porous silicate material, was tested for the removal of phosphorus (P as phosphate) in water. The effect of the CellCaSi was investigated on the basis of both particle size (under 1,2, and 4 mm) and added amount (0, 1, 2.5, 5, and 10 g/1) of the CellCaSi. The removal efficiency of phosphorus was highest with a particle size of under 1 mm and also increased with an increasing amount of the CellCaSi. The pH change showed little effect on the phosphorus removal of the CellCaSi. The calcium ion was eluted from the CellCaSi into the water, while the aluminium and iron were not. The eluted calcium ion was combined with dissolved phosphorus and then precipitated. The highest removal efficiency of phosphorus was obtained by the combined addition of the CellCaSi, calcium chloride, and ferric chloride. That is, the phosphorus concentrations of 0.10 and 1.0 mg/1 decreased to 0.03 and 0.47 mg/l by the addition of the CellCaSi (1 g/l), calcium ion (30 mg/l), and ferric ion (1 mg/l) at day 8 after treatment. The water qualities at the end of the experiment were as follows: pH was 8.1 and conductivity was 318 ${\mu}$S/cm (a registered maximum conductivity of 500${\mu}$S/cm for raw and potable wafers).

• Korean Journal of Poultry Science
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• v.13 no.1
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• pp.15-21
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• 1986

An experiment was conducted for 14 days using 108 Manina Brown laying hens of 27 weeks of age to study the effects of dietary phosphorus levels on egg production, feed intake, feed efficiency, time of oviposition, specific gravity and weight of eggs. Hens were divided into 12 pens and each was assigned to one of the three treatments with 4 replications. Each hen was housed in individual cage. Birds on treatment 1 were fed a control diet (0.70% P) continuously and served as control. Hens on treatment 2 received a high phosphorus diet (HP: 2.54% P) between 06:00 and 10:00 and a low phosphorus diet(LP;0.33% P) for the rest of the day, Treatment 3 was fed HP diet for four hours immediately following oviposition and LP diet for the rest of the day. All diets contained a constant level of calcium (4.04 %). Results indicated that egg production, feed intake, feed efficiency were not significantly affected by the treatments. Hens in treatment 3 tended to lay earlier than those in treatments 1 (P〈.0.05 ) and 2 (P〈.0.01 ). There were no significant differences in egg weights among treatments. Egg specific gravity, however, was significantly (P〈0.01) improved by feeding HP diet for 4 hours immediately fellowing oviposition (treatment 3). There was no significant difference in the specific gravity between eggs from the control and treatment 2. There were found a linear relationship for egg weight and a quadratic relationship for egg specific gravity (P〈0.01) with time of oviposition. Specific gravity of eggs tended to be low as the egg weight increased.