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산소부화연소에서 Co<sub>2</sub> 첨가에 대한 연소 특성
김한석,김호근,안국영,김용모,Kim, Han-Seok,Kim, Ho-Keun,Ahn, Kook-Young,Kim, Yong-Mo 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.1
$CO_2$ is a well-known green house gas as well as the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. Because its adiabatic flame temperature is relatively too high, existing facilities must be changed or the flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were investigated experimentally for the various oxygen-enriched ratios(OER) by the addition of $CO_2$, under constant $O_2$ flow rate. Results showed that the reaction zone was quenched and broadened as the addition of $CO_2$ was increased. The emission of NOx in flue gas was decreased as decreasing temperature in reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone was increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0%, but the composition of CO was decreased by quenching effect at OER=50% and 100%.
김한석,김훈용,김대중,이종악,Kim, Han-Suk,Kim, Hoon-Yong,Kim, Dae-Jyung,Lee, Jong-Arc 한국전기전자학회 1999 전기전자학회논문지 Vol.3 No.2
본 논문에서는 CDMA 방식 중계기용 전력증폭기의 선형특성을 향상시키기 위해 기존의 전치왜곡 방식과 전방귀환 방식을 혼합한 전력증폭기를 설계 제작하였다. CDMA방식의 이동통신 시스템은 기존의 아날로그 셀룰라 방식과는 사용 스펙트럼 대역폭이 훨씬 크며 증폭기의 비선형성에 의한 채널사이의 혼변조 왜곡을 충분히 제거하여야만 통신이 가능하기에 선형성이 우수한 전력증특기가 필수적으로 요구된다. 본 논문에서 제작한 전력증폭기는 37dBm, 2-tone 인가시의 IMD 특성이 -50dBc로써 나타났으며, 불요방사 특성도 IS-95 기준을 만족하는 $fc{\pm}\;885kHz$에서 약 -46dBc, $fc{\pm}\;1.98MHz $ 에서는 약 -52dBc로 나타났다. In this paper, a new type of linearization technique proposed, in which the predistortor was added to the feedforward linearizer. As the input power level is applied to HPA, the gain and phase characteristics of the amplifier are also varied. By using of the predistorter the amplitude imbalance and phase imbalance is kept constant. Experimental results are present for Korea PCS frequency band. The center frequency of the feedforward amplifier is 1.843.75 MHz with 1.23 MHz bandwidth. The 2-tone intermodulation distortion at 37dBm output power is about -50dBc, and spurious emission are -46dBc at $fc{\pm}\;885KHz\;and\;-52dBc\;at\;fc\;{\pm}1.98MHz$, respectively.
공기 다단 분무연소기의 NOx 발생특성에 관한 실험적 연구
김한석,안국영,김호근,백승옥,Kim, Han-Seok,An, Guk-Yeong,Kim, Ho-Geun,Baek, Seung-Ok 한국기계연구원 2001 硏究論文集 Vol.31 No.-
An experimental investigation on the reduction of nitrogen oxide emission from swirling, turbulent diffusion flames was conducted using multi air staged combustor, The combustor utilizes swirler to dampen fuel/air mixing, allowing an extended residence time for fuel pyrolysis and fuel-N conversion chemistry in an locally fuel-rich environment prior to burnout. This process also allow to reduce thermal NOx formation to lessen the temperature of reaction zone. The aerodynamic process therefore emulates the conventional staged combustion process, but without the need for the physically separate fuel-rich and -lean stages. Parametric studies on the ratios of each staged air and droplet size were carried out the feasibility of fuel/air mixing for low NOx combustion with diesel and pyridine mixed diesel fuel oil.
동축 공기다단 LPG화염의 NOx 생성특성에 관한 연구
김한석,안국영,김호근,유명종,백승욱,Kim, Han-Seok,Ahn, Kook-Young,Kim, Ho-Keun,Yu, Myung-Jong,Baek, Seung-Wook 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.2
Experimental and numerical studies have been done to examine the effects of excess air ratio and tertiary air swirl number on the formation characteristics of NOx in a pilot scale combustor adopting a multi-air staged burner. In numerical calculation the mathematical models for turbulence, radiation and nitric oxide chemistry were taken into account. The radiative transfer equation was solved using the discrete ordinates method with the weighted sum of gray gases model. In the NOx chemistry model, the chemical reaction rates for thermal and prompt NOx were statistically averaged using a probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-staged air burner has been designed and fabricated. Using the numerical simulation developed here, a variation of thermal and prompt NOx formation was predicted by changing the excess air ratio and tertiary air swirl number. As the excess air ratio increased up to 1.9, the formation of the total as well as thermal NOx at exit increased while the prompt NOx decreased. The formation of thermal NOx was more affected by concentration of $O_2$ and $N_2$ than gas temperature. When the tertiary air swirl number increased, the formation of the total as well as the prompt NOx slightly decreased.
연소용 공기중 $N_2$의 $CO_2$대체에 대한 연소특성 해석
김한석,안국영,김호근,이윤원,이창언,Kim, Han-Seok,Ahn, Kook-Young,Kim, Ho-Keun,Lee, Yun-Won,Lee, Chang-Eon 한국연소학회 2002 한국연소학회지 Vol.7 No.4
[$CO_2$] is a well-known greenhouse gas, which is the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. The central method of low $CO_2$ emission is Oxygen/CxHy combustion. Theoretically Oxygen/CxHy combustion only produces $CO_2\;and\;H_2O$ and allows convenient recovery of $CO_2$. The combustion characteristics, flame stability, composition in the flame zone and temperature profile were studied experimentally for various compositions of oxidant by substituting $CO_2\;for\;N_2$ with the constant $O_2$ concentration. Results showed that flame became unstable due to the high heat capacity, low transport rate and strong radiation effect of $CO_2$ in comparison with those of $N_2$. The reaction zone was quenched and broadened, as the ratio of $CO_2\;to\;N_2$ was increased. The emission of NOx in flue gas decreased due to the decreased temperature of the reaction zone. As the conversion ratio of $CO_2\;to\;N_2$ was increased, the emission of CO and the higher temperature zone increased due to decrease of reaction rate by the a quenching effect.
조현병 환자에서 불안자극에 대한 선택적 주의 편향과 환청과의 연관성 : 예비 연구
김한석,한진희,홍승절,정종현,임현국,김태원,엄유현,채정호,이경욱,서호준,Kim, Han-Suk,Han, Jin-Hee,Hong, Seung-Chul,Jeong, Jong-Hyun,Lim, Hyun-Kook,Kim, Tae-Won,Um, Yoo-Hyun,Chae, Jeong-Ho,Lee, Kyoung-Uk,Seo, Ho-Jun 대한불안의학회 2016 대한불안의학회지 Vol.12 No.1
Objective : This study was conducted to evaluate the relationships between selective attention bias for fear stimuli and hallucination in patients with schizophrenia Method : A total of 66 patients with schizophrenia admitted to psychiatry clinics were included in the study. Selective attention bias was measured by the dot-probe task. Patient symptoms were measured using the Positive and Negative Symptom Scale, Psychotic Symptom Rating Scale (PSYRATS), Korean version of the Scale to Assess Unawareness of Mental Disorder, and Clinical Global Impression-Severity scale. Results : Selective attention bias was correlated with the hallucination subscale of PSYTATS (r=0.268, p=0.029). No correlation was found between selective attention bias and other clinical measures. There was no significant difference, but a statistical trend was found (p=0.092) in hallucination severities between the biased and non-biased groups. Conclusion : The results suggest that selective attention bias for fear stimuli is associated with auditory hallucination. This preliminary study suggests the possibility of correlation between auditory hallucination in the psychotic domain and anxiety of the affective component.
PIN 다이오드를 이용한 C-Band 위상 변위기의 설계에 관한 연구
김한석,김훈영,이창식,이종악,Kim, Han-Suk,Kim, Hoon-Yong,Lee, Chang-Sik,Lee, Jong-Arc 한국전기전자학회 1999 전기전자학회논문지 Vol.3 No.2
본 논문에서 C-밴드 6-비트 변위기의 설계와 제작을 하였고 각 비트에 대한 설계 기술을 기술하였다. $5.625^{\circ},\;11.25^{\circ},\;22.5^{\circ}$ 그리고 $45^{\circ}$ 위상 비트는 부하선로 방식, $90^{\circ}$ 위상 비트는 하이브리드 결합 방식 그리고 $180^{\circ}$ 위상 비트는 가변선로 방식을 각각 마이크로스트립 구리 기판 위에 적용하였다. In this paper, a C-band 6-bit phase shifter is designed and fabricated and design techniques for each phase bit are represented. We applied the loaded line type to $5.625^{\circ},\;11.25^{\circ},\;22.5^{\circ}\;and\;45^{\circ}$ phase bits and the hybrid coupled type to $90^{\circ}$ phase bit and the switched line type to $180^{\circ}$ phase bit, respectively on a microstrip copper substrate.