• Journal of the Semiconductor & Display Technology
• /
• v.15 no.2
• /
• pp.49-54
• /
• 2016

$SrAl_{12}O_{19}:Ce_x{^{3+}}$,$Eu_{0.01}{^{2+}}$ phosphors were synthesized through a combustion process and their optical properties were investigated using time-resolved photoluminescence. A PL spectrum showed two dominant peaks which appeared at 300 and 410 nm. It is seen that, as the $Ce^{3+}$ concentration increases, the intensity of 300 nm decreases and the intensity of 410 nm increases. This behavior has been explained by two independent energy transfer mechanism. The first energy transfer occurs from $Ce^{3+}$ ion to $Eu^{3+}$ ion. The second energy transfer takes place from $Ce^{3+}$ ion to $Ce^{3+}-O_{ME}$ complex created in the magnetoplumbite structural host materials. The blue emitting 410 nm peak has been explained by both energy transfer mechanisms.

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.5
• /
• pp.469-476
• /
• 2015

The purpose of this work is to investigate main factors to design a solid-state hydrogen stroage system with magnesium hydride with 10 wt% graphite using numerical simulation tools. The heat transfer characteristic of this material was measured in order to perform the highly reliable simulation for this system. Based on the measured effective thermal conductivity, a transient heat and mass transfer simulation revealed that the total performance of hydrogen storage system is prone to depend on heat and mass transfer behaviors of hydrogen storage medium instead of its inherent kinetic rate for hydrogen adsorption. Furthermore, we demonstrate that the thermodynamic aspect between equlibrium presssure and temperature is one of key factor to design the hydrogen storage system with high performance using magnesium hydride.

• Transactions of the Korean hydrogen and new energy society
• /
• v.12 no.3
• /
• pp.191-199
• /
• 2001

In this paper molecular dynamics simulations have been carried out to investigate energy and momentum transfer of hydrogen ions impacted on the Ni (100) surface with $45^{\circ}$ and $90^{\circ}$ incident angles. The initial kinetic energies of the hydrogen ion were ranged from 100 eV to 1,600 eV to study the layer-by-layer energy variation as a dependence of incident energies and angles. At low incident energies, the scattering energy transfer is dominated by the normal motion of surface layers due to thermal vibrations and multiple collision effects. For higher incident energies, the scattering energy transfer in a normal direction is greater than that in a parallel direction. In the case of penetration, the amount of transferred energies do not affect much on Ni layers at low incident energy. It was found channeling effects through Ni layers with increasing incident energies.

• Analytical Science and Technology
• /
• v.6 no.3
• /
• pp.319-328
• /
• 1993

Energy transfer process between $Tb^{3+}$ and $Ce^{3+}$ has been studied in LaOCl host. The energy absorbed by $Ce^{3+}$ transfers to $Tb^{3+}$ which has levels emitting strong fluorescence. The probability of energy transfer depends strongly on the concentration or the distance of activator ions. While the energy transferred on $Tb^{3+}$ emits from $^5D_3$ level at low concentration of $Ce^{3+}$, the energy goes back to $Ce^{3+}$(Back Transfer) and then emits from low levels of $Ce^{3+}$ and $Tb^{3+}$ at the high concentration. The Back Transfer process has been identified by the experiment with varying the concentration of the activator, $Ce^{3+}$. The relaxation is more effective if $Ce^{3+}$ intermediates than if not.

• Analytical Science and Technology
• /
• v.8 no.2
• /
• pp.125-129
• /
• 1995

The energy transfer is observed in double-activator-doped LaOCl:Pr, Tb and LaOCl:Pr, Eu system. From laser excitation and fluorescence spectra, a peculiar process for energy transfer between the activators is found. The energy absorbed by $Tb^{3+}$ is directly transferred to $Pr^{3+}$ ion. A cascade relaxation of an excited $Pr^{3+}$ level to lower level, $^1D_2$ is induced by $Eu^{3+}$, $Tb^{3+}$, which has $^7F_J$ ground levels like $Eu^{3+}$ ion, does not affect the cascade relaxation. The result represents that the quantum state of ion is not absolute condition for the energy transfer and that the energy transfer is competitive between levels of activator when the activator ions are closely located.

• Journal of Energy Engineering
• /
• v.24 no.1
• /
• pp.42-50
• /
• 2015

To evaluate the heat removal capability of a condenser tube in the PCCS of an advanced nuclear power plant, a steam condensation experiment in the presence of noncondensable gas on a vertical tube is performed. The average heat transfer coefficient is measured on a vertical tube of 40 mm in O.D. and 1.0 m in length. The experiments covers the pressures of 2-4 bar, and the mass fraction of air ranges from 0.1 up to 0.7. From the experimental results, the effects of the total pressure and the concentration of air on the condensation heat transfer coefficient are investigated. The measured data are compared with the predictions by Uchida's and Tagami's correlations, and it is revealed that these models underestimate the condensation heat transfer coefficient of the steam-air mixture.

• Smart Structures and Systems
• /
• v.17 no.4
• /
• pp.631-646
• /
• 2016

Although the deployment of wireless sensors for structural sensing and monitoring is becoming popular, supplying power to these sensors remains as a daunting task. To address this issue, there have been large volume of ongoing energy harvesting studies that aimed to find a way to scavenge energy from surrounding ambient energy sources such as vibration, light and heat. In this study, a magnetic resonance based wireless power transfer (MR-WPT) system is proposed so that sensors inside a concrete structure can be wirelessly powered by an external power source. MR-WPT system offers need-based active power transfer using an external power source, and allows wireless power transfer through 300-mm thick reinforced concrete with 21.34% and 17.29% transfer efficiency at distances of 450 mm and 500 mm, respectively. Because enough power to operate a typical wireless sensor can be instantaneously transferred using the proposed MR-WPT system, no additional energy storage devices such as rechargeable batteries or supercapacitors are required inside the wireless sensor, extending the expected life-span of the sensor.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.161-167
• /
• 2009

The liquid solar air conditioning system is introduced as an alternative solution to control air condition and to save electrical energy consumption. The heat and mass transfer performances of dehumidifier/regenerator in liquid solar air conditioning system are influenced by air and desiccant condition. The application of this system, the thermal energy from the sun and inlet air are unable to control, but operation parameter of other components such as pump, fan and sensible cooling unit are able to control. The equilibrium point of heat and mass transfer are the liquid desiccant and inlet air conditions, where, the heat and mass are not transferred between the liquid desiccant and vapor air. By knowing equilibrium point of heat and mass transfer, the suitable optimal desiccant conditions for certain air condition are funded. This present experiment study is investigated the equilibrium point heat and mass transfer in various air and desiccant temperature. The benefit of equilibrium point heat and mass transfer will be helpful in choose and design proper component to optimize electrical energy consumption.

• Nuclear Engineering and Technology
• /
• v.56 no.2
• /
• pp.536-545
• /
• 2024

Radioactive iodine is a representative fission product to be quantified for the safety assessment of nuclear facilities. In integral severe accident analysis codes, the iodine behavior is usually described by a multi-physical model of iodine chemistry in aqueous phase under radiation field and mass transfer through gas-liquid interface. The focus of studies on iodine source term evaluations using the combination approach is usually put on the chemical aspect, but each contribution to the iodine amount released to the environment has not been decomposed so far. In this study, we attempted the decomposition by revising the two-film theory of molecular-iodine mass transfer. The model involves an effective overall mass transfer coefficient to consider the iodine chemistry. The decomposition was performed by regarding the coefficient as a product of two functions of pH and the overall mass transfer coefficient for molecular iodine. The procedure was applied to the EPICUR experiment and suppression chamber in BWR.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.505-508
• /
• 2000

A coreless printed circuit board(PCB) transformer is employed in a contactless energy transfer circuit that achieves an efficient power conversion at the presence of a considerable airgap between the source and the load side. A half-bridge series resonant converter is selected as the contactless energy transfer circuit in order to minimize the detrimental effects of large leakage inductance small magnetizing inductance and poor coupling coefficient of the coreless PCB transformer. The operation and performance of the proposed contactless power converter are verified on a 7 W experimental circuit that provides an 18V/0.4A output from a 210-370 V input source.