• 한국통신학회논문지
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• 제34권12C호
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• pp.1167-1176
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• 2009

본 논문에서는 OFDM(Orthogonal Frequency Division Multiplexing) 송신단에서 IFFT 를 수행한 후 Cyclic Prefix를 첨부하여 OFDM 심볼을 생성하는데 필요한 지연을 감소시킬 수 있는 IFFT(Time shifted DIT IFFT)의 구조를 제안하고, IEEE 802.16e Mobile WiMax OFDMA/TDD규격에 적합한, 1024크기의 FFT에 1/8 cyclic prefix를 가지는 시스템의 송신단 IFFT를 VHDL로 설계한 결과를 제시한다. 본 논문에서 제안하는 IFFT는 OFDM송신단의 지연을 줄이기 위하여 IFFT에 역비트(Bit-Reversed) 순서로 데이터를 입력하고, FFT의 Frequency Translation 특징을 이용해 IFFT의 출력이 cyclic prefix의 길이만큼 시간영역 쉬프트(Time-shift) 되어 나오도록 구현되었다. 이 과정은 cyclic prefix의 길이 특성을 이용하여 부가적인 복소곱셈기(Complex Multiplier)없이 구현되었고, OFDM 송신단의 지연과 함께 IFFT 결과를 저장하는 메모리의 크기도 줄일 수 있다. 송신단의 최종 출력이 통상적인 OFDM 심볼과 완전히 동일하기 때문에 전체 시스템의 성능에도 영향을 미치지 않는다.

• 농업과학연구
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• 제43권1호
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• pp.80-86
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• 2016

An in vitro trial was conducted to examine the effects of total mixed rations (TMR) on fermentation characteristics and effective degradability (ED) by rumen microbes. Three TMR diets were growing period TMR (GR-TMR, 67% TDN), early fattening period TMR (EF-TMR, 75.4% TDN) and late fattening TMR (LF-TMR, 80% TDN). Three TMR diets (3 g of TMRs in each incubation bottles) was added to the mixed culture solution of stained rumen fluid with artificial saliva (1:1, v/v) and incubated anaerobically for 48 hours at $39^{\circ}C$. The pH in all incubation solutions tended to decrease up to 48h, but the opposite results were found in concentration of total gas production, ammonia-N and total VFA in all incubations.The total gas production (p<0.05) in LF-TMR was highest compared with those of other diets. Also, concentration of total VFA was tended to increase in LF-TMR compared with other TMR diets in all incubations. The EDDM in both EF-TMR and LF-TMR was tended to high compared with GR-TMR (p=0.100). In this in vitro trials, concentration of propionate in all incubation solution was not affected by increased concentration of TDN. The results of the present in vitro study indicate that TMR may provide more favorable condition for nutrient digestion both in the rumen.

• 한국재료학회지
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• 제18권11호
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• pp.583-591
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• 2008

In this study, two series of CNT/$TiO_2$ electrodes were prepared. The decrease of surface area compared with that of the pristine carbon nanotubes (CNTs) indicated the blocking of micropores on the surface of the CNTs; was further supported by scanning electron microscopy (SEM) and field emission SEM (FE-SEM) observations. The X-ray diffraction (XRD) results showed that the CNT/$TiO_2$ composites contained a mix of anatase and rutile forms of $TiO_2$ particles when the precursor was $TiO_2$ powder, whereas when the precursor was Ti ($OC_4H_7$) (TNB), the composites contained only the typical single and clear anatase $TiO_2$ particles. The energy dispersive X-ray spectroscopy (EDX) spectra showed the presence of C, O and Ti peaks for all samples. It was found that catalytic decomposition of methylene blue (MB) solution could be attributed to synthetic effects between the $TiO_2$ photocatalysis and electro-assisted CNTs network, and that photoelectrocatalytic oxidation increased with an increase of CNT composition. It was also found that the photoelectrocatalytic oxidation efficiency for MB is higher than that of photocatalytic oxidation. Moreover, the CNT/$TiO_2$ composites catalyst prepared by the impregnation method demonstrates higher photoelectrocatalytic activity than the mechanical mixture with the same CNT content.

• 대한한방부인과학회지
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• 제21권1호
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• pp.39-54
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• 2008

Purpose: The purpose of this study was to investigate the anti-inflammatory effects of the water extract of Omisodokeum (OMSDE) on peritoneal macrophages, Methods: To verify the anti-inflammatory mechanism of OMSDE, the activation of nuclear $factor-{\kappa}B$ $(NF-{\kappa}B)$ and the phosphorylation of MAPK were examined. Results: The extract of OMSDE suppressed the production of LPS-induced nitric oxide (NO), tumor necrosis factor $(TNF)-{\alpha}$, interleukin $(IL)-1{\beta}$, IL-6 and IL-12 in the macrophages. OMSDE inhibited the degradation of inhibitory ${\kappa}B-{\alpha}$ $(I{\kappa}B-{\alpha})$ and it suppressed the activation of extracellular signal-regulated kinase (ERK 1/2) but didn't inhibit c-Jun N-terminal kinase (JNK) and p38, indicating that OMSDE may inhibit the pro-inflammatory cytokine production process by inhibiting the activation of $NF-{\kappa}B$ and ERK 1/2. Furthermore, OMSDE inhibited the production of interferon $(IFN)-{\beta}$ but didn't inhibit of $IFN-{\alpha}$ in the LPS-stimulated macrophages through the down-regulation of interferon regulatory factor (IRF)-1 and IRF-7. The Oral administration of OMSDE inhibited LPS-induced endotoxin shock and the production of $TNF-{\alpha}$ in serum but didn't inhibit of $IL-1{\beta}$ and IL-6. Conclusion: These results suggest that OMSDE may be effective in the prevention and treatment of inflammatory diseases.

• The Korean Journal of Physiology and Pharmacology
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• 제20권3호
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• pp.229-236
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• 2016

Resveratrol (RSV) may provide numerous protective effects against chronic inflammatory diseases. Due to local hypoxia and hypertonicity, the renal medulla is subject to extreme oxidative stress, and aldehyde products formed during lipid peroxidation, such as 4-hydroxy-2-hexenal (HHE), might be responsible for tubular injury. This study aimed at investigating the effects of RSV on renal and its signaling mechanisms. While HHE treatment resulted in decreased expression of Sirt1, AQP2, and nuclear factor erythroid 2-related factor 2 (Nrf2), mouse cortical collecting duct cells (M1) cells treated with HHE exhibited increased activation of p38 MAPK, extracellular signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and increased expression of NOX4, $p47^{phox}$, Kelch ECH associating protein 1 (Keap1) and COX2. HHE treatment also induced $NF-{\kappa}B$ activation by promoting $I{\kappa}B-{\alpha}$ degradation. Meanwhile, the observed increases in nuclear $NF-{\kappa}B$, NOX4, $p47^{phox}$, and COX2 expression were attenuated by treatment with Bay 117082, N-acetyl-l-cysteine (NAC), or RSV. Our findings indicate that RSV inhibits the expression of inflammatory proteins and the production of reactive oxygen species in M1 cells by inhibiting $NF-{\kappa}B$ activation.

• Current Photovoltaic Research
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• 제2권4호
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• pp.168-172
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• 2014

Under concentrated illuminations, the solar cells show higher efficiencies mainly due to an increase of the open circuit voltage. In this study, InGaP/InGaAs/Ge triple-junction solar cells have been grown by a low pressure metalorganic chemical vapor deposition. Photovoltaic characteristics of the fabricated solar cells are investigated with a class A solar simulator under concentrated illuminations from 1 to 100 suns. Ideally, the open circuit voltage should increase with the current level when maintained at the same temperature. However, the fabricated solar cells show degraded open circuit voltages under high concentrations around 100 suns. This means that the heat sink design is not optimized to keep the cell temperature at $25^{\circ}C$. To demonstrate the thermal degradation, changes of the device performance are investigated with different bonding conditions and heat sink materials.

• Corrosion Science and Technology
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• 제12권6호
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• pp.274-279
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• 2013

Flow accelerated corrosion (FAC) of the carbon steel piping in nuclear power plants (NPPs) has been major issue in nuclear industry. During the FAC, a protective oxide layer on carbon steel dissolves into flowing water leading to a thinning of the oxide layer and accelerating corrosion of base material. As a result, severe failures may occur in the piping and equipment of NPPs. Effect of alloying elements on FAC of pipe materials was studied with rotating cylinder FAC test facility at $150^{\circ}C$ and at flow velocity of 4m/s. The facility is equipped with on line monitoring of pH, conductivity, dissolved oxygen(DO) and temperature. Test solution was the demineralized water, and DO concentration was less than 1 ppb. Surface appearance of A 106 Gr. B which is used widely in secondary pipe in NPPs showed orange peel appearance, typical appearance of FAC. The materials with Cr content higher than 0.17wt.% showed pit. The pit is thought to early degradation mode of FAC. The corrosion product within the pit was enriched with Cr, Mo, Cu, Ni and S. But S was not detected in SA336 F22V with 2.25wt.% Cr. The enrichment of Cr and Mo seemed to be related with low, solubility of Cr and Mo compared to Fe. Measured FAC rate was compared with Ducreaux's relationship and showed slightly lower FAC rate than Ducreaux's relationship.

• 한국수소및신에너지학회논문집
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• 제20권4호
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• pp.309-316
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• 2009

The effect of gas diffusion layers (GDLs) on the freeze/thaw condition durability in polymer electrolyte fuel cells (PEFCs) were investigated. For this purpose, three kinds of GDLs, such as, felt, paper and cloth types with different basic properties have been first prepared, then the changes in the properties and performance of cells was observed during the freeze/thaw cycles ranging from -30 to $70^{\circ}C$. The performance evaluations were conducted by using the single cells consisting of different GDLs. The performance degradation and the cell resistance increase could be directly correlated. The physical destruction of electrode was shown by SEM analysis. The mechanically supporting ability on the interface between the cell components can help enhancing the durability of PEFCs in the freeze/thaw condition.

• 한국통신학회논문지
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• 제31권11C호
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• pp.1077-1084
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• 2006

본 논문에서는 H.264/AVC에서 가장 많은 연산량을 차지하는 인터 예측(inter prediction)을 고속으로 수행할 수 있는 방법을 제안하였다. 제안한 방법은 율-왜곡 최적화 기법(Rate-Distortion Optimization, RDO)이 적용된 JM(Joint Model)의 FME(Fast Motion Estimation)를 대상으로 예측된 움직임 벡터의 방향성을 고려하여 탐색영역을 결정한 후 적응적인 후보 나선형 탐색을 수행한다. 동시에 가변 블록 크기에 대하여 비용함수의 임계값(threshold)을 결정한 후 가변 구간 움직임 탐색을 수행함으로써 인터 예측의 부호화 복잡도를 감소시킨다. 다양한 영상들을 대상으로 실험한 결과 기존의 예측 방식에 최대 80%의 연산량을 줄일 수 있음을 확인하였다. 이에 따른 화질 열화는 평균 $0.05dB{\sim}0.19dB$에 불과하며, 압축률은 평균 0.58%의 미미한 감소를 보임으로써, 제안한 방법이 고속 인터 예측 알고리즘으로 매우 효율적인 방법임을 확인하였다.

• 동의생리병리학회지
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• 제23권2호
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• pp.368-373
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• 2009

The purpose of this study was to investigate the anti-inflammatory effects of water extract from Euonymus alatus (Thunb.) Sieb. (EAS) on the RAW 264.7 cells. To evaluate of anti-inflammatory of EAS, we examined the cytokine productions on lipopolysaccharide (LPS)-induced RAW 264.7 cells and also inhibitory mechanisms using Western blot. EAS reduced LPS-induced production of nitric oxide (NO), interleukin (IL)-1b, IL-6, IL-10 and tumor necrosis factor-a (TNF-a) in RAW 264.7 cells. EAS inhibited the activation of mitogen-activated protein kinases (MAPKs) such as p38, extracelluar signal-regulated kinase (ERK 1/2) and c-Jun NH2-terminal kinase (JNK) but not of inhibitory kappa B a (Ik-Ba) degradation in the LPS-stimulated RAW 264.7 cells. In conclusion, EAS down-regulated LPS-induced NO and cytokines production, which could provide a clinical basis.