• Bulletin of the Korean Chemical Society
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• 제13권6호
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• pp.613-620
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• 1992

The solvent-dependent photophysical properties of 2-biphenylcarboxylic acid (2BPCA) and 4-biphenylcarboxylic acid(4BPCA), which have a pre-twisted conformation in the ground state, have been investigated. The fluorescence spectra of 4BPCA show vibrational structure with a non-mirror image to the absorption spectra in nonpolar solvent while those of 2BPCA show no structure even in nonpolar solvents. As the solvent polarity increases, the fluorescence spectra become diffuse and broad with a strong red shift resulting in the large Stokes shift. The large fluorescence Stokes shift of BPCA's in polar solvent is also partially due to an intramolecular charge transfer (ICT) interaction in the excited state, as demonstrated by the large dipole moment in the excited state (7.6-10.6 D). The fluorescence decay behaviors of BPCA's (decay-times and their pre-exponential factors) also depend on solvent polarity in agreement with the solvent-dependent properties of the steady-state fluorecence. The data have been discussed in terms of change in the excited-state potential energy surface with respect to change of the dihedral angle of biphenyl moiety.

• 한국대기환경학회지
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• 제29권5호
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• pp.615-624
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• 2013

In this study, the emission patterns of reduced sulfur compounds (RSC) were investigated using four different types of food samples (boiled egg, milk, canned meat and strawberry) between fresh and decaying stages. To this end, the concentrations of RSCs were measured at storage days of 0, 1, 3, 6, and 9 under room temperature. Four sulfur compounds ($H_2S$, $CH_3SH$, DMS and DMDS) were selected as target compounds along with two reference compounds ($CS_2$ and $SO_2$). Their concentrations were quantified using GC-PFPD equipped with thermal desorption (TD) system. The boiled egg showed the highest concentration of $H_2S$ (3,655 ppb) at D-1, while $CH_3SH$ reached its maximum value of 64.4~78.5 ppb after 3 days. In milk samples, concentration of $CH_3SH$, DMS, and DMDS went up to 487, 16.3, and 578 ppb, respectively with the progress of decay (D-9). In case of canned meat, concentration of $H_2S$ and $CH_3SH$ peaked in the beginning (D-0) such as 345 and 66.6 ppb. In case of strawberry, $CH_3SH$ and DMDS showed the maximum concentrations 135 and 50.5 ppb at D-1, respectively. The olfactometry dilution-to-threshold (D/T) ratio by air dilution sensory (ADS) test showed similar patterns when sum of odor intensity (SOI) was derived via conversion of odorant concentration data. The results of this study confirm that the time of strong RSC emissions is distinguished for each food type between fresh (e.g., strawberries) and decaying conditions (e.g., milk).

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.367-373
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• 2008

Spinning detonations propagating in a circular tube were numerically investigated with a one-step irreversible reaction model governed by Arrhenius kinetics. Activation energy is used as parameter as 10, 20, 27 and 35, and the specific heat ratio and the heat release are fixed as 1.2 and 50. The time evolution of the simulation results was utilized to reveal the propagation mechanism of single-headed spinning detonation. The track angle of soot record on the tube wall was numerically reproduced with various levels of activation energy, and the simulated unique angle was the same as that of the previous reports. The maximum pressure histories of the shock front on the tube wall showed stable pitch at Ea=10, periodical unstable pitch at Ea=20 and 27 and unstable pitch consisting of stable, periodical unstable and weak modes at Ea=35, respectively. In the weak mode, there is no Mach leg on the shock front, where the pressure level is much lower than the other modes. The shock front shapes and the pressure profiles on the tube wall clarified the mechanisms of these stable and unstable modes. In the stable pitch at Ea=10, the maximum pressure history on the tube wall remained nearly constant, and the steady single Mach leg on the shock front rotated at a constant speed. The high and low frequency pressure oscillations appeared in the periodical unstable pitch at Ea=20 and 27 of the maximum pressure history. The high frequency was one cycle of a self-induced oscillation by generation and decay in complex Mach interaction due to the variation in intensity of the transverse wave behind the shock front. Eventually, sequential high frequency oscillations formed the low frequency behavior because the frequency behavior was not always the same for each cycle. In unstable pitch at Ea=35, there are stable, periodical unstable and weak modes in one cycle of the low frequency oscillation in the maximum pressure history, and the pressure amplitude of low frequency was much larger than the others. The pressure peak appeared after weak mode, and the stable, periodical unstable and weak modes were sequentially observed with pressure decay. A series of simulations of spinning detonations clarified that the unsteady mechanism behind the shock front depending on the activation energy.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.367-373
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• 2008

Spinning detonations propagating in a circular tube were numerically investigated with a one-step irreversible reaction model governed by Arrhenius kinetics. Activation energy is used as parameter as 10, 20, 27 and 35, and the specific heat ratio and the heat release are fixed as 1.2 and 50. The time evolution of the simulation results was utilized to reveal the propagation mechanism of single-headed spinning detonation. The track angle of soot record on the tube wall was numerically reproduced with various levels of activation energy, and the simulated unique angle was the same as that of the previous reports. The maximum pressure histories of the shock front on the tube wall showed stable pitch at Ea=10, periodical unstable pitch at Ea=20 and 27 and unstable pitch consisting of stable, periodical unstable and weak modes at Ea=35, respectively. In the weak mode, there is no Mach leg on the shock front, where the pressure level is much lower than the other modes. The shock front shapes and the pressure profiles on the tube wall clarified the mechanisms of these stable and unstable modes. In the stable pitch at Ea=10, the maximum pressure history on the tube wall remained nearly constant, and the steady single Mach leg on the shock front rotated at a constant speed. The high and low frequency pressure oscillations appeared in the periodical unstable pitch at Ea=20 and 27 of the maximum pressure history. The high frequency was one cycle of a self-induced oscillation by generation and decay in complex Mach interaction due to the variation in intensity of the transverse wave behind the shock front. Eventually, sequential high frequency oscillations formed the low frequency behavior because the frequency behavior was not always the same for each cycle. In unstable pitch at Ea=35, there are stable, periodical unstable and weak modes in one cycle of the low frequency oscillation in the maximum pressure history, and the pressure amplitude of low frequency was much larger than the others. The pressure peak appeared after weak mode, and the stable, periodical unstable and weak modes were sequentially observed with pressure decay. A series of simulations of spinning detonations clarified that the unsteady mechanism behind the shock front depending on the activation energy.

• 자원리싸이클링
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• 제25권5호
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• pp.28-35
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• 2016

본 연구에서는 매립 처리시설를 대상으로 1996 IPCC G/L에 제시된 Tier 1 방법과 GPG 2000의 Tier 2 방법, 2006 IPCC G/L의 Tier 2 방법을 이용하여 매립시설에서 발생되는 온실가스 배출량을 산정하였으며 각 방법론 별로 적용상의 장단점 및 배출결과에 영향을 주는 요인과 산정된 배출량의 특성을 고찰하였다. 온실가스 배출량을 산정한 결과 1996 IPCC G/L Tier 1의 배출량은 2000 ~ 2013년 기간 동안 평균 약 2,760 ton/yr로 산정되었고, GPG 2000 Tier 2의 배출량은 평균 약 1,500 ton/yr, 2006 IPCC G/L Tier 2의 배출량은 평균 약 880ton/yr로 가장 낮게 산정되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.73-77
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• 1991

200hrs operational characteristics of the single cell in phosphoric acid fuel cell was studied. The initial performance of single cells was examined as a function of PTFE content of electrode in the range of 30 to 60 wt.%. The cell with the electrode of 40wt.% PTFE was chosen for the 200hrs operation. The cell voltage decay was found to be about 0.5mV/hr for 200hrs operation. These results of cell performance were discussed as related to the internal resistance and the exchange current density of the cell.

• Nuclear Engineering and Technology
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• 제34권2호
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• pp.154-164
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• 2002

Neutron cross section data on Dy-160, Dy-161, Dy-162, Dy-163 and Dy-164 were calculated and evaluated in the energy range of 1 keV to 20 MeV using a spherical optical model, statistical model and pre-equilibrium model. The energy dependent optical model potential parameters were obtained based on the recent experimental data. The width fluctuation correction in Hauser-Feshbach particle decay and the quantum mechanical approach in pre-equilibrium analysis were introduced and gave a better cross section calculation in EMPIRE-II. The total, elastic scattering and threshold reaction cross sections were evaluated and compared with the evaluated files. The model calculated (n, tot), (n, ${\gamma}$) and (n, p) cross sections were in good agreement with the experimental data in the measured energy range. The results will be applied to ENDF/B-VI for data improvement.

• Journal of Radiation Protection and Research
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• 제22권2호
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• pp.111-117
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• 1997

최근 포괄적 핵실험금지조약 (Comprehensive Test Ban Traety : CTBT)의 체결은 전세계적으로 핵활동 감시 네트워크를 구축하는 것이다. 핵실험금지 위원회의 전문가들은 대기 방사성핵종의 측정을 핵실험 감시에 필수적인 요소로 제안하였으며, 이에 따른 기술적 요구사항을 제시하였다. 본 연구는 이를 근거로 핵활동으로부터 생성된 핵분열생성물을 검출하기 위하여 고성능 공기채집장치(High Volume Air Sampler: HVAS)와 여과지 압축기 그리고 고순도 게르마늄 반도체검출기(HPGe)로 대기 입자 방사성핵종 측정시스템을 구성하였다. 조속한 시일 내에 탐지와 최적의 측정 조건으로 본 시스템을 운영하기 위하여 CTBT 감시 전략에서 주요 핵종들에 대한 최소검출 방사능 농도(Minimum Detectable Concentration : MDC)를 decay time, counting time 그리고 sampler volumetric flow rate 등을 고려하여 결정하였다. 그 결과 각각 $10{\pm}$2h, $20{\pm}$2h, $850{\pm}50m^3$//h 정도로 선정하였다. 감마선 스펙트럼 분석에서 $^{212}Pb$ 방사능 농도의 변화는 Compton continuum의 baseline에 영향을 미치게 되므로 이에 기인한 MDC 관계식을 도출하였다. 이들 결과는 CTBT 감시 전략에 실제적인 도구로 사용될 수 있을 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.19-31
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• 1994

기사용 핵연료 저장조에 대한 열수력 해석과 관련된 인자들이 열수력 해석에 미치는 영향에 대한 분석을 수행하였다. 기사용 핵연료에서 발생하는 붕괴열(decay heat)을 제거하기 위해 일어나는 자연 순환(natural circulation)현상을 모사하기 위해 단순화된 유동망(simplified flow network)해석 모델을 사용하였다. 기사용 핵연료 저장조의 각 셀에 저장되는 연료 집합체에서 발생하는 붕괴열을 제거하기 위해 흐르는 유량의 압력 손실량이 자연순환을 일으키는 밀도차이에 의해 생성되는 구동력(driving force)과 평형을 이루는 관계를 이용하여 지배 방정식을 유도하였다. 그러나 유량, 저항 계수, 붕괴열, 밀도 등의 변수들이 서로 종속 관계를 갖기 때문에 반복 계산을 통해 해를 얻게 된다. 본 해석을 적용한 영광 3, 4호기의 경우, 12채널을 고려하였고 사용되는 입력 (저항 계수, 붕괴열)을 보수적으로 결정하였다. 본 연구를 통해 영광 3, 4호기 기사용 핵연료 저장조의 열수력 특성을 구하였다. 또한 유동로를 따라 형성되는 유동 저항중에 기하학적 요인에 의한 압력 손실은, 기사용 핵연료 저장조의 경우 압력 용기내의 유동과 달리 천이 영역(transition region)이 존재하게 되므로 Reynolds수에 민감한 것을 알 수 있다. 간극 유동은 조밀화된 연료 집합체 (consolidated fuel assembly)가 아닌 경우 무시할 수 있었다.

• 방사성폐기물학회지
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• 제17권4호
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• pp.405-418
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• 2019

국내 원자력발전소에서 발생하는 사용후핵연료의 제원 및 방출시점 등 특성과 현재의 고준위 방사성폐기물 기본계획에 근거한 처분시나리오를 도출하여 기존 심층 처분시스템을 바탕으로 처분효율과 경제성을 향상시킨 개선된 처분시스템을 제안하였다. 이를 위하여 국내 원자력발전소에서 발생하는 사용후핵연료의 길이에 따라 2종류의 처분용기 개념을 도출하고, 사용후핵연료 발생 년도와 현재의 기본계획에 근거한 처분 시나리오 설정에 따른 처분시점에서의 냉각기간을 고려하여 처분용기내 수용 가능한 붕괴열 량을 결정하였다. 그리고 2종류의 처분용기에 대한 처분시스템과 결정된 붕괴열을 바탕으로 열적 안정성 분석을 통하여 제안된 처분시스템의 설계요건에 대한 적합성 여부를 확인하고, 처분효율을 평가하였다. 개선된 처분시스템은 기존 처분시스템에 비하여 처분면적은 약 20% 감소되고 처분밀도는 약 20% 향상됨을 확인하였고, 처분용기와 완충재 재료도 상당량 절감됨을 확인하였다. 본 연구의 결과는 향후 사용후핵연료 관리정책 수립 및 실제 사업을 위한 처분시스템 설계를 위한 자료로 활용될 수 있다.