• The Korean Journal of Ecology
• /
• v.9 no.1
• /
• pp.79-90
• /
• 1986

The production and decomposition of litters and nutrient cycling of forests were studied at the pine forests such as Pinus densiflora, Pinus koraiensis, Pinus rigida, Pinus thunbergii, Abies holophylla and Larix kaempfer. The annual litter production of the P. densiflora forest was the most on Mt. Mudeung which was 620.75g/$m^2$ and the least on Mt. Halla which was 155.00g/$m^2$. The decay rate of litters was the highest at the P. densiflora forest on Mt. Mudeung which was k=0.256 and the lowest at the P. densiflora forest on Mt. Halla and A. holophylla on Mt. Jiri which were k=0.099. The half time of decomposition of litters was shortest at the P. densiflora forest on Mt. Mudeung and the longest at the P. densiflora on Mt. Halla and A. holophylla forests on Mt. Jiri. The average decay rate of the L. kaempferi forests which was k=0.204 was the highest and that of the A. holophylla forests which was k=0.122 was the lowest. The decay rate tended to decrease against increasing the altitude. The annual production of litterr, the contents of mineral nutrients and the amounts of mineral nutrients inputted into the forest soil tended to increase in proportion to the decay rate, k.

• Journal of Ecology and Environment
• /
• v.37 no.1
• /
• pp.13-19
• /
• 2014

The effect of different turnover time of water on the decomposition of emergent macrophyte litter (Zizania latifolia Griseb.) was investigated using a microcosm experiment. Microcosm treatment represented different turnover time of water; 1, 2, 4 and 8 weeks. The litterbags from each treatment were retrieved every 2 weeks until the 8th week and the water simultaneously sampled with the litterbag. The dry weight and the content of major cations in the litter, and the content of available N, P, and major cations in the water were analyzed. Dry weight loss after 8 weeks indicated the lower decay rates under the condition of short turnover time of water. Major cations from the litter and the water showed that the leached amounts of K and Mg from the litter were highest in the 2nd week and dramatically decreased from the 4th week. The dynamics of available nitrogen and phosphorus in the water showed that as the water turnover time was getting longer, the amounts of available nitrogen and phosphorus remained higher. These results suggest that wetlands with longer turnover time of water could maintain the increased nitrogen and phosphorus and no outflow of the nutrients could cause eutrophication problem.

• Journal of Astronomy and Space Sciences
• /
• v.23 no.2
• /
• pp.127-134
• /
• 2006

Variation of the Local Time of Ascending Node (LTAN) has been analysed according to initial inclinations when the altitude of Sun-synchronous satellite is continuously decreased due to the atmospheric drag. Orbit predictions of 3 years have been performed with the satellite of 500 km altitude when the initial LTAN were set to 06:00, 09:00, 12:00, 15:00, and 18:00. Different profiles of the inclination and LTAN have been obtained according to the satellite altitude decay and initial LTAN value. Using the profiles of the inclination and LTAN, initial orbital elements can be derived for minimizing the LTAN variations during the mission life time of the sun-synchronous satellite without any on-board thrusters for orbit maneuvers.

• Journal of Sensor Science and Technology
• /
• v.12 no.1
• /
• pp.1-9
• /
• 2003

CsI single crystals doped with lithium, potassium or rubidium were grown by using Czochralski method at Ar gas atmosphere. The energy resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 14.5%, 15.9% and 17.0% for $^{137}Cs$(0.662 MeV), respectively. The energy calibration curves of CsI(Li), CsI(K) and CsI(Rb) scintillators were linear for $\gamma$-ray energy. The time resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators measured by CFT(constant-fraction timing method) were 9.0 ns, 14.7 ns and 9.7 ns, respectively. The fluorescence decay times of CsI(Li:0.2 mole%) scintillator had a fast component and slow one of ${\tau}_1=41.2\;ns$ and ${\tau}_2=483\;ns$, respectively. The fluorescence decay times of CsI(K:0.5 mole%) scintillator were ${\tau}_1=47.2\;ns$ and ${\tau}_2=417\;ns$. And the fluorescence decay times of CsI(Rb:1.5 mole%) scintillator were ${\tau}_1=41.3\;ns$ and ${\tau}_2=553\;ns$. The phosphorescence decay times of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 0.51 s, 0.57 s and 0.56 s, respectively.

• Nuclear Engineering and Technology
• /
• v.25 no.4
• /
• pp.539-547
• /
• 1993

A stochastic approach using continuous time Markov process is presented to model the one-dimensional nuclide transport in fractured rock media as a further extension for previous works［1-3］. Nuclide transport of decay chain of arbitrary length in the single planar fractured rock media in the vicinity of the radioactive waste repository is modeled using a continuous time Markov process. While most of analytical solutions for nuclide transport of decay chain deal with the limited length of decay chain, do not consider the case of having rock matrix diffusion, and have very complicated solution form, the present model offers rather a simplified solution in the form of expectance and its variance resulted from a stochastic modeling. As another deterministic way, even numerical models of decay chain transport, in most cases, show very complicated procedure to get the solution and large discrepancy for the exact solution as opposed to the stochastic model developed in this study. To demonstrate the use of the present model and to verify the model by comparing with the deterministic model, a specific illustration was made for the transport of a chain of three member in single fractured rock medium with constant groundwater flow rate in the fracture, which ignores the rock matrix diffusion and shows good capability to model the fractured media around the repository.

• Journal of the Korean Institute of Gas
• /
• v.25 no.3
• /
• pp.53-58
• /
• 2021

The number of patients with cardiovascular diseases who experience an out-of-hospital cardiac arrest (OHCA) are increasing among young adults as well as the aged population. An automated external defibrillator (AED) is vital in improving survival rates of OHCA victims. Survival rates of OHCA were shown to decline exponentially in time to defibrillation, yet studies in Korea are uncommon that captures the properties of their survival rates in examining optimal locations of AEDs. In this study, we worked on the maximal gradual coverage location problem (MGCLP) with exponential decay coverage function to decide on their optimal locations. The exponential decay coverage function mitigates the drawback of over-estimating survival rates of OHCA patients. It is expected that a more sophisticated facility location problem will be developed to identify the "emergent" characteristics of pedestrians who responds to the OHCA occurrence by incorporating random pedestrian locations and movement through simulation.

• Korean Journal of Optics and Photonics
• /
• v.8 no.3
• /
• pp.213-217
• /
• 1997

We have measured photoluminescence (PL) and time-resolved PL in doped-GaAs. As increasing doping concentration, the PL spectra of n-type GaAs shift to higher energies while the PL spectra of p-type GaAs shift to lower energies than the bandgap of the undoped GaAs. The contribution of the Burstein-Moss effect overrules the band-gap narrowing in n-type GaAs, contrary to p-type GaAs. The PL rise time and decay time become shorter as increasing doping concentration. The PL rise and decay time in doped-GaAs depend on the type of majority carriers and their concentrations, which imply that the carrier-carrier interaction plays an important role in the energy relaxation processes.

• Journal of Information Display
• /
• v.2 no.3
• /
• pp.13-17
• /
• 2001

The manganese-doped magnesium tin oxide with spinel structure was selected as a green phosphor for FED application and was synthesized by the solid state reaction. Its luminescence properties were investigated under low-voltage electron excitation. The $Mg_2SnO_4$:Mn phosphor showed green emission with the spectrum centered at 500 nm due to energy transfer from $^4T_1$ to $^6A_1$ of $Mn^{2+}$ ion. Optimum Mn concentration was 0.6 mole % and the decay time was shorter than 10 ms.

• Architectural research
• /
• v.7 no.1
• /
• pp.19-26
• /
• 2005

Unlike other countries, Korea uses various kinds of wall-paper as finishing material. Conventional wall-paper consists of paper and vinyl, and petrochemical ink is used for the decoration of the surface. Adhesive is used to paste the wall with the wall-paper, which emit substantial amounts of VOCs and formaldehyde. In this study, VOCs characteristics emitted from specimens made of concrete, mortar, gypsum board and wall-paper were investigated using small chamber method. Moreover, concentration and emission factor of BTEX(Benzene, Toluene, Ethylbenzene, m,p,o-Xylene) and TVOC were investigated, and concentration and emission factor decay were estimated. As a result of the prediction, both time-dependent concentration decay and cumulative concentration can be converted into the logarithmic scale. Furthermore, prediction equations were developed from the experimental results under accurately controlled experimental conditions. Therefore, there may be difference if the estimated equations are directly applied to real buildings. Further research should be done on the generalization of the developed prediction equations.

• Journal of the Korean Ceramic Society
• /
• v.32 no.1
• /
• pp.131-139
• /
• 1995

In order to improve transmittance and response properties, various compositions of light controllable films were prepared by phase separation method. The optical and response properties were measured with the variation of PMMA/suspension ratio and block copolymer/light polarizing particles. According to the increase of the PMMA/suspension ratio, the separated droplets of suspension were interconnected in the film. Decay time was 2.6 sec when PMMA/suspension ratio was 0.5 : 1 and ΔT(difference of the transmittance at OFF/ON states) was reduced with increasing of the ratio of PMMA/suspension. On block copolymer/light polarizing particles ratio variation, the highest transmittance of the film was 67.4% when its ratio was 0.6 : 1 and decay time was varied from 2.15 to 46.6 sec as block copolymer content increased 0.2 : 1 to 1 : 1.