• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.6
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• pp.397-404
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• 1991

The steady state and decay characteristics of primary fluorescenece of phytoplanktons including Cyanophyceae and Cryptophyceae were investigated in vivo. At 580-640 nm region, fluorescence emission spectra were obtained from all algae examined. The observed fluorescence emission maxima were similiar$(\pm3\;nm)$ except Synechocorcus sp. (SYN). Considered $\lambda_{max}$ of emission spectra of phycobiliproteins and the excitation spectra with $\lambda_{max}=540-560nm$, it seems to be originated from biliproteins. Fluorescence lifetimes $(\tau)$ and decay curves were compared with standard solution of candidate organic compounds, b-phycoerythrin. The $\tau$ values obtained for phytoplankton with $\lambda_{max}=580nm$ were different depending upon the species of algae. The observed $\tau$ values were ranged from 1.39 ns to 1.95 ns. These are considerably shorter than $\tau(3.23\;us)$ for standard solution of b-phycoerythrin. The reduction of $\tau$ for phycoerythrin in vivo seems to be originated from effective energy transfer system between Chl. a and phycobiliprotein in intact cell. There are subtantial differences in fluorsecence spectra and lifetimes at the class level. At the species level, differences seems to be much smaller. The result of experiment suggests that measurement of fluorescence lifetimes may be helpful in the rapid characterization of algae. Direct application will likely be found in combination with the measurement of other luminescence parameters.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.310-314
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• 1999

A prototype of Flywheel Energy Storage System with high Tc superconducting bearings was fabricated and tested to verify its applicability for the energy industry. The moment of inertia of assembled wheel with rotor magnets is about 1.072${\times}$10$^{-1}$ Kg-m$^2$. The wheel was designed to withstand its integrity up to the rotation speed of 20,000 rpm. YBCO bulk superconductors prepared by seed growth method were used as bearing to levitate and stabilize the rotating wheel. High speed rotation of the flywheel without mechanical contact was achieved by using specially designed Halbach type motor. The flywheel system showed very high stability during test operation performed up to the speed of about 10,000rpm. The energy loss measured by free decay test performed between 9,300 rpm and 7,000 rpm was calculated as about 45 W.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.165-169
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• 2018

An assessment for determining N-16 activity concentrations during the operation condition of Bangladesh Atomic Energy Commission TRIGA Research Reactor was performed employing several governing equations. The radionuclide N-16 is a high energy (6.13 MeV) gamma emitter which is predominately created by the fast neutron interaction with O-16 present in the reactor core water. During reactor operation at different power level, the concentration of N-16 at the reactor bay region may increase causing radiation risk to the reactor operating personnel or the general public. Concerning the safety of the research reactor, the present study deals with the estimation of N-16 activity concentrations in the regions of reactor core, reactor tank, and reactor bay at different reactor power levels under natural convection cooling mode. The estimated N-16 activity concentration values with 500 kW reactor power at the reactor core region was $7.40{\times}10^5Bq/cm^3$ and at the bay region was $3.39{\times}10^5Bq/cm^3$. At 3 MW reactor power with active forced convection cooling mode, the N-16 activity concentration in the decay tank exit water was also determined, and the value was $4.14{\times}10^{-1}Bq/cm^3$.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.179-190
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• 2013

A station blackout experiment called SBO-01 was performed at the ATLAS facility. From the SBO-01 test, the station blackout scenario can be characterized into two typical phases: A first phase characterized by decay heat removal through secondary safety valves until the SG dryouts, and a second phase characterized by an energy release through a blowdown of the primary system after the SG dryouts. During the second phase, some physical phenomena of the change over a pressurizer function, i.e., the pressurizer being full before the POSRV $1^{st}$ opening and then its function being taken by the RV, and the termination of normal natural circulation flow were identified. Finally, a core heatup occurred at a low core water level, although under a significant amount of PZR inventory, whose drainage seemed to be hindered owing to the pressurizer function by the RV. The transient of SBO-01 is well reproduced in the calculation using the MARS code.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.96-104
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• 2015

Reactivity of commercial WGS catalyst and four new catalysts(RMC-3, PC-73, PC-67SU, PC-59) manufactured with various compositions by Korea Electric Power Research Institute(KEPCO RI) were compared to select suitable WGS catalyst for SEWGS system. Steam/CO ratio, gas velocity, flow rates of syngas, and temperature were considered as operating variables. As a result, commercial catalyst showed the highest CO conversion and RMC-3 catalyst showed also high CO conversion. Therefore, commercial and RMC-3 catalysts were selected as applicable catalysts. However, PC-73 catalyst showed low CO conversion at low temperature($200^{\circ}C$) but showed good reactivity at high temperature($225{\sim}250^{\circ}C$), and therefore, PC-73 catalyst was selected as applicable catalyst for high temperature operation. Continuous operations up to 24 hours for those three catalysts(commercial, RMC-3, PC-73) were conducted to check reactivity decay of catalysts. All three catalysts maintained their original reactivity.

• Journal of Photoscience
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• v.9 no.2
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• pp.78-81
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• 2002

Fluorescence rise and decay curves of carotenoids were measured in solutions and in pigment protein complexes with a femtosecond time-resolved fluorescence spectroscopy. For linear carotenoids, the S$_2$ lifetimes showed the maximum value around n = 9-10. The conjugation of a keto-carbonyl group shortened the S$_2$lifetime and prolonged the S$_1$lifetime. The excitation relaxation dynamics within carotenoids and the excitation energy transfer kinetics from carotenoids to chlorophylls are discussed as a function of molecular structure of carotenoids.

• Journal of the Semiconductor & Display Technology
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• v.6 no.4
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• pp.29-32
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• 2007

Zinc gallate, $ZnGa_2O_4:Mn^{2+}$ co-doped with different concentrations of $Mg^{2+}$ (0.001- 0.5 mol%) was prepared by solid state synthesis method. These compositions were investigated for their photoluminescence and cathodoluminescence properties. The optimized composition $Zn_{0.990}Mg_{0.005}Ga_2O_4:Mn_{0.005}$ shows higher luminescence intensity compared to the parent phosphor. The intense green emission peak was found at 504 nm. The $Mg^{2+}$ doping does not affect much the decay time. It remains <10 ms for these compositions which make them potential candidate for application in TV screens.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.230-234
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• 1995

The loss of offsite power test was successfully performed on YGN 4 to demonstrate that the reactor can be shutdown and the RCS can be maintained in a hot standby condition following a loss of all offsite Alternating Current (AC) power. Following the loss of main generator and all offsite AC power, the ensile emergency diesel generators were automatically started and the plant was stabilized via natural circulation. Plant conditions were maintained in hot standby for at least 30 minutes before offsite power was restored. Thus, the capability of equipment, controls and instrumentation necessary to remove decay heat from the core using only ensile emergency power was demonstrated, thereby satisfying all objectives and acceptance criteria of the test.

• Nuclear Engineering and Technology
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• v.2 no.4
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• pp.263-268
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• 1970

The spectrum of continuous transfer operator arising in a time-energy dependent neutron transport equation is analyzed. Four theorems concerning on the spectrum are proved. A convolution theorem of the generalized Mellin energy transform is given. Also the completeness theorem necessary for a final solution is proved. A unique time decay constant 1 - c is found, which is dominant asymptotically.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.389-394
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• 1996

The conceptual design of Korea Next Generation Reactor (KNGR), which is 3914 MWt PWR, includes the safety depressurization system (SDS) to comply with U.S. NRC's severe accident policy. In this analysis, it is assumed that three Monobloc Sebim valves are adopted for the SDS bleed valves of KNGR. The characteristic of Monobloc Sebim are modeled in the CE-FLASH-4AS/REM code for this analysis. The various feed and bleed (F&B) procedures with Sebim valves are investigated for total loss of feedwater (TLOFW) event. It is found that if operators open two out of three Sebim valves in conjunction with four HPSI pumps before hot leg temperature reaches saturation condition, the decay heat removal and core inventory make-up function can be successfully accomplished. Therefore, this F&B procedure can be used for mitigating the TLOFW event of the KNGR. This result also demonstrates the feasibility of adopting the Monobloc Sebim valves for the SDS of KNGR.