• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.583-587
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• 2009

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of the thickness of HDPE pipe and grout thermal properties, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.34.2-34.2
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• 2011

In this talk we explain U-loop emergence, in which U-shaped field lines emerge into the solar surface against gravitational force. In principle, they hardly emerge because mass tends to accumulate at the bottom of U-loops, thereby decreasing buoyancy. A key is found to be the shape of U-loops, that is, if U-loops have a shallow dip whose depth is of the order of the photospheric gravitational scale height, then a diverging flow is generated via a siphon-like mechanism by which the mass accumulated at the dip of the loops is drained out to enhance buoyancy. This successfully makes U-part of the loops emerge against gravity. We also discuss the relation between U-loop emergence and the so-called flux cancellation observed on the Sun in which opposite polarity regions apparently approach together and disappear.

• Bulletin of the Korean Mathematical Society
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• v.36 no.4
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• pp.747-754
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• 1999

We compute the mod p homology of the double loop space of Sp(n)/U(n) by the Serre spectral sequence and the Eilenberg-Moore spectral sequence with the homology operations.

• Bulletin of the Korean Mathematical Society
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• v.40 no.2
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• pp.281-288
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• 2003

We compute the mod p homology of the double loop space of 50(2n)/U(n) by the Serre spectral sequence of Hopf algebras. We also obtain the torsion information of the integral homology.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1638-1646
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• 2008

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 2-D finite element analysis, ANSYS, was employed to evaluate the temperature distribution on the borehole cross section involving HDPE pipe/grout/soil formation to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system which is equipped with a thermally insulating latice in order to reduce thermal interference between the inflow and outflow pipes. In addition, a 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of grout's thermal properties, rate of circulation pump, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.

• Current Optics and Photonics
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• v.8 no.2
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• pp.183-191
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• 2024

High-resolution retinal imaging based on adaptive optics (AO) is important for early diagnosis related to retinal diseases. However, in practical applications, closed-loop AO correction takes a relatively long time, and traditional open-loop correction methods have low accuracy in correction, leading to unsatisfactory imaging results. In this paper, a SH-U-net-based open-loop AO wavefront correction method is presented for a retinal AO imaging system. The SH-U-net builds a mathematical model of the entire AO system through data training, and the Root mean square (RMS) of the distorted wavefront is 0.08λ after correction in the simulation. Furthermore, it has been validated in experiments. The method improves the accuracy of wavefront correction and shortens the correction time.

• The korean journal of orthodontics
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• v.16 no.1
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• pp.133-144
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• 1986

This study was conducted to evaluate the effects of loop formation and heat treatment upon the elastic properties of orthodontic wires. The specimens selected were .016', .018', .016x.022', and .018x.022' sized stainless steel (standard) and cobalt-chromium-nickel wires, and were divided into 7 groups as; 1. straight non-heat treated 2. U looped non-heat treated 3. L looped non-heat treated 4. Circle looped non-heat treated 5. U looped heat treated 6. L looped heat treated 7. Circle looped heat treated Heat treatment was performed in Big Jane furnace at 850' F for 3 minutes. The elastic limit and the elastic range of each specimen were determined by bending test, and load deflection rate was computed from those values. The findings were as follows; 1. The formation of loop resulted in increased load-deflection rate for both stainless steel and cobalt-chromium-nickel wires. 2. The heat treated group showed higher load-deflection rate than non-heat treated group, which was more apparent in cobalt-chromiumnickel wire than in stainless steel wire. 3. L loop had the highest load-deflection rate among 3 types of loops, followed by U loop and circle loop. 4. The specimens with greater diameter displayed the more increase in load-deflection rate by looping and heat treatment.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.385-395
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• 2009

In this study, a series of numerical analysis has been accomplished on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) in a geothermal heat pump system (GHP) considering the circulating fluid, pipe, grout and soil formation. A finite element analysis program, ABAQUS, was employed to evaluate the temperature distribution on the cross section of the U-loop system involving HDPE pipe/grout/formation and to compare sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system. Especially, the latticed pipe is equipped with a thermal insulation zone in order to reduce thermal interference between the inflow pipe and the outflow pipe. Also, a thermal stress analysis was performed with the aid of ABAQUS. 3-D finite volume analysis program, FLUENT, was adapted to analyze a coupled system between fluid circulation in the pipe and heat transfer and simulate an operating process of the closed-loop vertical ground heat exchanger. In this analysis, the effect of the thermal properties of grout, rate of circulation pump, distance between the inflow pipe and the outflow pipe, and the effectiveness of the latticed HDPE pipe system are taken into account.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.58-63
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• 2009

A ground-loop heat exchanger for the ground source heat pump system is the core equipment determining the thermal performance and initial cost of the system. The size and performance of the heat exchanger is highly dependent on the ground thermal properties - the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. Nowadays, precast concrete piles using steel reinforced precast concrete piles - energy piles - are used to reduce the installing cost of the ground-loop heat exchanger. We were carried out some tests to investigate the effects of some parameters such as borehole length, grouting materials and U-tube configuration of the energy piles. 4 concrete piles, each measuring $250mm{\sim}400mm$ in diameter and approx. 10m in length, and rigged with single spiral and 3 U-tube loop of $16mm{\times}2.3mm$ PB piping. The thermal response tests were conducted using a testing device for 4-different ground-loop heat exchangers. During the heating period, the energy piles absorb the heat of 0.89kW to 1.37kW.

• Journal of the Korean Chemical Society
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• v.38 no.10
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• pp.769-773
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• 1994

Higher order structure of 5S rRNA isolated from Xanthomonas celebensis was examined using angiogenic extracted from milk. Angiogenin cleaved exclusively 3' P-O bonds on the far sides of pyrimidines in the single-stranded sequences of 5S rRNA. Whereas angiogenin acted only on the loop d of 5S rRNA at pH 7.0 in the presence of 10 mM $Mg^{2+}$, it acted on all the loops (a, b, c and d) except loop e in the absence of $Mg^{2+}$. In the absence of $Mg^{2+}$, bonds $U_{74}$-$G_{75}$, $U_{77}$-$A_{78}$ and $U_{103}$-$A_{104}$ were highly susceptible to the action of angiogenin both at pH 7.0 and at pH 3.5. On the other hand, at pH 3.5 in the absence of $Mg^{2+}$ angiogenin strongly cleaved the bond $C_{17}$-$G_{18}$ of loop a and the bond $U_{55}$-$G_{56}$ of loop b. The results lead us to the following conclusion. First, angiogenin can be used as one of the probes for the tertiary structure analysis of 5S rRNA. Second, the structure of loop d of 5S rRNA is variable depending on the concentrations of $Mg^{2+}$ and $H^{1+}$.