• Journal of the Korean Solar Energy Society
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• v.25 no.4
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• pp.133-139
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• 2005

In this paper, the ventilation performance of suspended particulates in indoor side was investigated by step-down method. Experiments were performed in function of mechanical ventilation types and locations of supply and extract air. The type 2 ventilation system shows the highest removal characteristics rather than other 2 types. It means that the displacement ventilation has also good decay rates of concentration compared to mixing ventilation.

• The Korean Journal of Ecology
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• v.4 no.1_2
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• pp.38-51
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• 1981

The present investigation was estimated the effect of temperature, precipitatiion, and time on the decomposition of litters with litter bags of Pinus densiffora and Quercus mongolica at Gure where elevation in 50m, and at Nogodan where elevation in 1300m on Mt. Jiri. As the above results, decomposition model was proposed to relation of the environmental conditions. And was investigated the production and decomposition of litters from the stands of various forest communities in Kwangneung, Mt. Jiri and Mt. Halla. The results are as follows; The models for the decay of organic carbon (C) was as follows: $C=Coe^{-Kt}$ (limiting factor;time) $C=Coe^{-K'te}$ (limiting factor;tempedrature) $C=Coe^{-KnP}$ (limiting factor:precipitation) As observed in litter bag method, the decomposition rate of litter in Pinus densiflora was slower than that of Quercus mongolica. The higher elevation, the slower decomposition rate. The decomposition of litters at Gure where elevation in 50m was equally influenced by temperature and precipitation. But at Nogodan where elevation in 1300m was much inflenced by precipitation. The decay constant of litters was larger in hardwood forest than in coniferous forest. In the same species, the more elevatiion, the less decomposition constant. The time required for the decay of 50%, 95^, 99% of the accumulated litters in the forest floor were faster in hardwood forest than in coniferous forest. In the same species, the higher elevatiion, the longer time required.

• Korean Journal of Food Science and Technology
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• v.18 no.1
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• pp.1-5
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• 1986

Putrefactive microorganisms from infected onion bulbs collected at several areas were isolated and identified. The infecting microorganisms were mostly the species of Botrytis, Fusarium, Penicillium, Ericinia and Pseudomonas, among which the last was not pathogenic to onion bulbs. Fumigation of onion bulbs with Tetrachloroisophthalonitrile cut down decay rate by half of the control and the onion bulbs stored at 80% RH showed slow decay rate than those stored at 90% RH. The decay of onion bulbs was mainly caused by molds and the portions of them were 78-85% of Botrytis, 11-17% of Fusarium and 3-5% of Penicillium.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.654-664
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• 2019

The geometrical and electromagnetic variables of a rectangular-type magnetohydrodynamic (MHD) circulation system are optimized to solve MHD equations for the active decay heat removal system of a prototype Gen-IV sodium fast reactor. Decay heat must be actively removed from the reactor coolant to prevent the reactor system from exceeding its temperature limit. A rectangular-type MHD circulation system is adopted to remove this heat via an active system that produces developed pressure through the Lorentz force of the circulating sodium. Thus, the rectangular-type MHD circulation system for a circulating loop is modeled with the following specifications: a developed pressure of 2 kPa and flow rate of $0.02m^3/s$ at a temperature of 499 K. The MHD equations, which consist of momentum and Maxwell's equations, are solved to find the minimum input current satisfying the nominal developed pressure and flow rate according to the change of variables including the magnetic flux density and geometrical variables. The optimization shows that the rectangular-type MHD circulation system requires a current of 3976 A and a magnetic flux density of 0.037 T under the conditions of the active decay heat removal system.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.1-4
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• 1999

A confocal microscope system was used to study the bursts of fluorescence photons from single dye molecules excited at 638 nm by a short-pulsed diode laser with a repetition rate of 17 MHz. A red dye, JA22, in ethylene glycol solution was used as a sample. The fluorescence decay curves of single molecules were acquired using a time-correlated single photon counting and analyzed by a maximum likelihood estimator. It was possible to measure the fluorescence decay times with an error probability of 21% at photon number of more than 40 per dye molecule.

• Agricultural and Biosystems Engineering
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• v.1 no.1
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• pp.38-42
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• 2000

Though the freshness for agricultural products is an important factor related to their quality management, this terminology is being used restrictedly because it is very subjective. In this study, a dimensionless index which had the span of the maximum of 1 through the minimum of 0 was proposed to describe freshness of the product with time-variant quality and was applied to Tsugaru and Fuji apples. First, the compressive properties having the linearity in their change regarding time elapsed after harvest were selected. For Tsugaru apple, bio-yield and rupture forces had high correlation with time while for Fuji, bio-yield and rupture deformations had high correlations. When the slope, or ratio of force to deformation, was considered, the effect of cultivar could be neglected. When the linearly time-variant compressive properties for Tsugaru and Fuji apples were involved in the freshness indices, they described well freshness of apples. Also, the freshness decay constant depicted a characteristic which related to freshness decay rate. Therefore, the freshness index can be utilized to manage the quality during storage and distribution of apples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.791-796
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• 2011

In order to understand long range wave propagation in railway tracks, it is required to identify how far vibrations can travel along a rail. To answer this question, the attenuation characteristics of the main propagating waves are required as a function of distance. In this work, it is identified which wave types predominantly propagate on various regions of the rail cross-section. Then decay rates of propagating waves in railway tracks are investigated for frequencies up to 80 kHz. A numerical method called the Wavenumber Finite Element (WFE) method is utilized to predict dispersion curves and decay rates for a rail on a continuous foundation. In order to validate the simulated results, measurements have been performed on a test track and an operational railway track. The measured results are compared with the output of the simulations and good agreements are found between them.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.47.1-47.1
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• 2013

Supersonic turbulence is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to investigate the role of global magnetic fields and structures. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in warm neutral medium. Early evolution is consistent with previous studies characterized rapid decay of turbulence with the decaying time shorter than a flow crossing time and power-law temporal decay of turbulent kinetic energy with slope of -1. If initial magnetic fields are strong and perpendicular to the sheet, however long term evolutions of kinetic energy shows that a significant amount of turbulent energy still remains even after ten flow crossing times, and decaying rate is reduced as field strengths increase. We analyse power spectra of remaining turbulence to show that incompressible, in-plane motions dominate.

• Bulletin of the Korean Mathematical Society
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• v.57 no.6
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• pp.1393-1408
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• 2020

In this paper we mainly study existence and regularity of mild solutions to the parabolic-elliptic system of drift-diffusion type with small initial data in Fourier-Besov spaces. To be more detailed, we will explain that global-in-time mild solutions are well-posed and Gevrey regular by means of multilinear singular integrals and Fourier localization argument. Furthermore, we can get time decay rate estimate of mild solutions in Fourier-Besov spaces.