• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.383-388
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• 1995

Two-phase transient phenomena in the noncondensable gas-filled closed loop was investigated numerically using the RELAP5/MOD3 version 3.1 computer code. The condensation heat transfer correlation for noncondensable gases was studied in detail. Two modes of the reflux condensation which can be characterized by countercurrent flow of steam and its condensed water and the oscillatory between reflux condensation and natural circulation were predicted well. However, the natural circulation mode which the condensed water carried over the U-bend concurrently with steam was failed to predict.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.28-31
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• 1988

This paper proposes a new linear adaptive position controller of DC servo motor. The proposed method can improve the drive performance and rapidly reject the state error caused by both parameter variations and force disturbance. The structure of this adaptive control method is based multiloop feedback control and model reference control. Simulation results are presented to verify the improved response when parameter variations and load disturbance give relatively significant effects to the servo system.

• Journal of Microbiology
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• v.45 no.1
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• pp.79-82
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• 2007

The 58 rRNA gene from Sphingobium chungbukense DJ77 was identified. The secondary structure of the 199-base-long RNA was proposed. The two-base-long D loop was the shortest among all of the known 5S rRNAs. The U19-U64 non-canonical pair in the helix II region was uniquely found in strain DJ77 among all of the sphingomonads.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.45-51
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• 2009

A ground-loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. The size and performance of this heat exchanger is highly dependent on ground thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U-tube configurations on ground effective thermal conductivity. In this study, thermal response tests were conducted using a testing device with 9-different ground-loop heat exchangers. From the experimental results, the length of ground-loop heat exchanger affects to the effective thermal conductivity. Among the various grouting materials, the bentonite-based grout with silica sand shows the largest thermal conductivity value.

• Journal of Korea Multimedia Society
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• v.14 no.3
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• pp.414-422
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• 2011

The paper is for top and bottom symmetrical phase controlled loop antenna using for multi-media devices. We developed a top and bottom phase control loop pattern arrangement methods for loop antenna in mobile devices like as a cell phone and PCS, WCDMA. In the loop antenna pattern, arrange close adhesive the loop antenna pattern $180^{\circ}$ cycle in wave length, the radiated electro-magnetic wave from close adhesive loop pattern in $180^{\circ}$ become to coherent wave than the phase controlled loop antenna has high efficiency and high radiation gain. To acquire a wide band width on phase controlled loop antenna, we arrange a top and bottom symmetrical architecture loop pattern that bas a $180^{\circ}$ wave length in each layer. Top and bottom each layer bas a U form pattern separated $90^{\circ}$ wave length each other. This architecture cause a well balanced electro-magnetic flow control that acquired wide bandwidth resonance response in loop pattern antenna. In experiment, we designed a WCDMA mobile multi-media antenna in $40mm{\times}6mm$ area thickness 0.2mm, in that passive experiment the radiation efficiency is over 50% and over 0dBi radiation average gain was acquired, in the active experiment in real multi-media device we acquired -4dBi average gain and 43% transmit/receive efficiency.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1955-1962
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• 2020

In a sudden shutdown of primary pump or coolant loss accident in a marine nuclear power plant, the primary flow decreases rapidly in a transition process from forced circulation (FC) to natural circulation (NC), and the lower flow enters the steam generator (SG) causing reverse flow in the U-tube. This can significantly compromise the safety of nuclear power plants. Based on the marine natural circulation steam generator (NCSG), an experimental loop is constructed to study the characteristics of reverse flow under middle-temperature and middle-pressure conditions. The transition from FC to NC is simulated experimentally, and the characteristics of SG reverse flow are studied. On this basis, the experimental loop is numerically modeled using RELAP5/MOD3.3 code for system analysis, and the accuracy of the model is verified according to the experimental data. The influence of the flow variation rate on the reverse flow phenomenon and flow distribution is investigated. The experimental and numerical results show that in comparison with the case of adjusting the mass flow discontinuously, the number of reverse flow tubes increases significantly during the transition from FC to NC, and the reverse flow has a more severe impact on the operating characteristics of the SG. With the increase of flow variation rate, the reverse flow is less likely to occur. The mass flow in the reverse flow U-tubes increases at first and then decreases. When the system is approximately stable, the reverse flow is slightly lower than obverse flow in the same U-tube, while the flow in the obverse flow U-tube increases.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.165-168
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• 2008

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.327-328
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• 2008

• Journal of the Korean Society of Radiology
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• v.84 no.2
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• pp.418-426
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• 2023

Purpose Practical challenges are encountered in percutaneous intravascular procedures when applied to markedly angulated branching vessels. Herein, we introduced a folded-loop guidewire remodeling technique-the guidewire-shaping technique-to overcome difficult catheterization. Materials and Methods First, the tip of a 0.014-inch micro-guidewire was manually shaped like a pigtail loop. Second, the shaped guidewire was introduced into the microcatheter and was preloaded into the hollow metal introducer for suitability with the microcatheter hub. Gentle rotation of the guidewire after release from the microcatheter can create the preshaped pigtail loop configuration. On pulling back, the loop loosened, the configuration was changed to a small U-shaped tip, and the guidewire tip was easily introduced into the target artery. Results Between December 2019 and January 2022, the described technique was used in 64 patients (male/female, 49/15; mean age, 66.8 ± 9.5 years) for selective arterial embolization, after failed attempts with the conventional selection technique. The technique was successful in 63/64 patients (98%). The indications of embolization include transcatheter arterial chemoembolization, gastrointestinal bleeding, hemoptysis, trauma-induced bleeding, and tumor bleeding. Conclusion The folded-loop guidewire remodeling technique facilitates the catheterization of markedly angulated branching arteries; when usual catheterization method fails.

• ETRI Journal
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• v.37 no.2
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• pp.204-211
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• 2015

For this study, we designed an implantable rectangular spiral antenna for medical biotelemetry in the Medical Implant Communications Service band (402 MHz to 405 MHz). The designed antenna has a U-shaped loop for impedance matching. The antenna impedance is easily adjusted by controlling the shape and length of the U-shaped loop. Significant design parameters were studied to understand their effects on the antenna performance. To verify the potential of the antenna for the desired applications, we fabricated a prototype and measured its performance in terms of the resonant characteristics and gain radiation patterns of the antenna. In the testing phase, the prototype antenna was embedded in human skin tissue-emulating gel, which was developed to simulate a real operation environment. The measured resonant characteristics show good agreement with the simulations, and the -10 dB frequency band is within the range of 398 MHz to 420 MHz. The antenna exhibits a maximum gain of -22.26 dBi and an antenna efficiency of 0.215%.