• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.9
• /
• pp.845-852
• /
• 2001

The phenomena of energy separation in vortex tubes was investigated experimentally to see the effects of the conductivity of a tube and convective heat transfer on the outer surface of a tube. The experiment was carried out with different conductivity (pyrex, stainless steel and copper) of a tube and three kinds of convective heat transfer modes (adiabatic condition, natural convection (air) and forced convection (water) on the outer surface of a tube. the results were obtained that hot exit fluid temperature was highly affected by a change of conductivity of a tube when the outer surface was cooled by the forced convection of water. However, the cold exit temperature was little affected by heat transfer modes on the outer surface in vortex tubes.

• Journal of the Korean Society of Safety
• /
• v.13 no.3
• /
• pp.51-59
• /
• 1998

The vortex tube is a simple device for separating a compressed fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air conditioner for special purpose. The phenomena of energy separation through the vortex tube were investigated to see the effects of cold flow inlet-outlet ratios and partial admission rates on the energy separation experimentally. The experiment was carried out with various cold flow inlet-outlet ratios from 0.28 to 10.56 and partial admission rates from 0.176 to 0.956 by varying input pressure and cold air flow ratio. To find best use in a given cold flow inlet-outlet ratio and partial admission rate, the maximum temperature difference of cold air was presented. The experimental results were indicated that there are an optimum range of cold flow inlet-outlet ratio for each partial admission rate and available partial admission rate.

• Nuclear Engineering and Technology
• /
• v.53 no.10
• /
• pp.3352-3358
• /
• 2021

Aiming at selective adsorption and separation of Y(III) from the Y(III)-Sr(II) group in acid solution, a silica-based TODGA impregnated adsorbent [(TODGA+1-dodecanol)/SiO₂-P-F600] has been prepared. Batch adsorption experiments were conducted under the effect of contact time, acid concentration, solution temperature, and adsorption capacity etc. Chromatography recovery of more than 90% Y(III) was successfully achieved under elution with 0.01 M DTPA solution in nitric acid adsorption system, and 0.1 M HCl solution in hydrochloride adsorption system, respectively.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2019.05a
• /
• pp.297-298
• /
• 2019

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2018.11a
• /
• pp.606-607
• /
• 2018

• Korean Chemical Engineering Research
• /
• v.46 no.3
• /
• pp.633-638
• /
• 2008

The bunsen reaction, part of IS(Iodine-sulfur) cycle that one of the hydrogen production by the thermochemical water splitting, was investigated. It was observed that $H_2SO_4$ was uniformly generated and generation of $H_2SO_4$ was independent of iodine input. However, generation of HI was decreased with increasing iodine input. It was thought that HI and unreacted iodine were formed complex compound such as $HI_3$ $HI_5$ or $HI_7$. The complex compound accelerated liquid-liquid separation properties in the product. It was also revealed that reaction kinetics was increased with increasing iodine input. Liquid-liquid separation properties were improved with increasing iodine input and reaction temperature. Moreover, no side reaction was occurred at all reaction conditions.

• Wind and Structures
• /
• v.37 no.6
• /
• pp.445-460
• /
• 2023

Accurate estimation of modal parameters (i.e., natural frequency, damping ratio) of tall buildings is of great importance to their structural design, structural health monitoring, vibration control, and state assessment. Based on the combination of variational mode decomposition, smoothed discrete energy separation algorithm-1, and Half-cycle energy operator (VMD-SH), this paper presents a method for structural modal parameter estimation. The variational mode decomposition is proved to be effective and reliable for decomposing the mixed-signal with low frequencies and damping ratios, and the validity of both smoothed discrete energy separation algorithm-1 and Half-cycle energy operator in the modal identification of a single modal system is verified. By incorporating these techniques, the VMD-SH method is able to accurately identify and extract the various modes present in a signal, providing improved insights into its underlying structure and behavior. Subsequently, a numerical study of a four-story frame structure is conducted using the Newmark-β method, and it is found that the relative errors of natural frequency and damping ratio estimated by the presented method are much smaller than those by traditional methods, validating the effectiveness and accuracy of the combined method for the modal identification of the multi-modal system. Furthermore, the presented method is employed to estimate modal parameters of a full-scale tall building utilizing acceleration responses. The identified results verify the applicability and accuracy of the presented VMD-SH method in field measurements. The study demonstrates the effectiveness and robustness of the proposed VMD-SH method in accurately estimating modal parameters of tall buildings from acceleration response data.

• Fibers and Polymers
• /
• v.2 no.2
• /
• pp.81-85
• /
• 2001

The effects of rate of phase separation to ester interchange reactions and the repulsive pair interaction energy on the phase behavior in a phase-separated immiscible polyester blend are investigated using a Monte Carlo simulation method. The time evolution of structure factor and the degree of randomness are monitored as a function of homogenization time. When the phase separation is dominant over ester interchange reactions, the domain size slowly increases with homogenization time. However, when the pair interaction becomes less repulsive, the domain size does not significantly change with homogenization time. On the other hand, when ester interchange reactions are dominant over the phase separation, the homogenization proceeds without a change in the domain size. The higher the extent of phase separation, the lower the increasing rate of the DR. However, when the phase separation is sufficiently dominant, the effect of the extent of phase separation on the increasing rate of the degree of randomness become less significant.

• Journal of Electrochemical Science and Technology
• /
• v.8 no.3
• /
• pp.250-256
• /
• 2017

A graphene electrode with a novel in-plane structure is proposed and successfully adopted for use in supercapacitor applications. The in-plane structure allows electrolyte ions to interact with all the graphene layers in the electrode, thereby maximizing the utilization of the electrochemical surface area. This novel structure contrasts with the conventional out-of-plane stacked structure of such supercapacitors. We herein compare the volumetric capacitances of in-plane- and out-of-plane-structured devices with reduced multi-layer graphene oxide films as electrodes. The in-plane-structured device exhibits a capacitance 2.5 times higher (i.e., $327F\;cm^{-3}$) than that of the out-of-plane-structured device, in addition to an energy density of $11.4mWh\;cm^{-3}$, which is higher than that of lithium-ion thin-film batteries and is the highest among in-plane-structured ultra-small graphene-based supercapacitors reported to date. Therefore, this study demonstrates the potential of in-plane-structured supercapacitors with high volumetric performances as ultra-small energy storage devices.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.4
• /
• pp.1210-1216
• /
• 2014

This paper deals with an application of Teager Energy Operator (TEO) and Energy Separation Algorithm(ESA) to detect and determine various voltage waveform distortions like harmonics, inter-harmonics and frequency variation. Because the TEO and DESA algorithm was initially proposed for speech or communication analysis, its applications are limited to some types of waveform in the power quality analysis area. For example, an undistorted voltage signal is similar with a pure sinusoid. A voltage fluctuation is very similar with an amplitude-modulated signal, from the viewpoint of signal theory. And a continuous frequency variation is similar with a frequency-modulated signal, which is also known as a chirp signal. This paper is written to show that the TEO and DESA algorithm can be used for detecting occurrences of the representative waveform distortions and determining their instantaneous information of amplitude and frequency.