• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.701-706
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• 2006

Groundwater heat pump systems are the oldest of the ground-souce systems and it has various type. Standing column well type are must be located in hard rock geology site and produce sufficient water for the conventional open loop system. These system are indirect type(the building circulating loop and ground water are intercept). Existence of the exchanger the foundation protect water quality to use of open loop. The design of open loop system are concern on the power requirements. An experimental study was analysis the extremely heating operation COP of ground water heat pump system. Operation efficiency of the 50RT systems shows that, COP $2.9{\sim}5.0$ in heating operation. And generally it shows 3.4.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.55-61
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• 2019

Motor pumps cannot be used in those areas where electricity is not accessible such as remote rural areas in many African countries. Hydraulic ram pump is one of the solutions for supplying water for irrigation or domestic uses. The hydraulic ram pumps are working based on the water hammer effect for pumping without external power or electricity. This study was conducted to investigate the effect of air chamber volume and operation parameters on the performance of the hydraulic ram pump which was assembled with common plumbing parts. The experimental results showed the volume of the air chamber did not affect the performance such as discharge rate and head. When drive heights were 1.7 and 2.35 m, the maximum discharge heads were up to 7 m and 10 m, respectively. When the air chamber volume was 1 L, discharge rates were 0.23 and 2.12 L/min under the drive heights of 1.7 and 2.35 m, respectively. The average energy efficiency of the hydraulic ram pump assembled in this study was about 60% for all the experimental conditions.

• Advances in Computational Design
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• v.6 no.1
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• pp.31-42
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• 2021

This research aims to demonstrate the optimal geometrical design of splayed multiple cross-sectional pin fin heat sinks (SMCSPFHS), which are a type of side-inlet-side-outlet heat sink (SISOHS). The optimiser strength Pareto evolutionary algorithm2 (SPEA2)is employed to explore a set of Pareto optimalsolutions. Objective functions are the fan pumping power and junction temperature. Function evaluations can be accomplished using computational fluid dynamics(CFD) analysis. Design variablesinclude pin cross-sectional areas, the number of fins, fin pitch, thickness of heatsink base, inlet air speed, fin heights, and fin orientations with respect to the base. Design constraints are defined in such a way as to make a heat sink usable and easy to manufacture. The optimum results obtained from SPEA2 are compared with the straight pin fin design results obtained from hybrid population-based incremental learning and differential evolution (PBIL-DE), SPEA2, and an unrestricted population size evolutionary multiobjective optimisation algorithm (UPSEMOA). The results indicate that the splayed pin-fin design using SPEA2 issuperiorto those reported in the literature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.191-192
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• 2023

In recent years, the use of high-strength grout has gained popularity in offshore wind power generation complexes for facility foundations and bridges. These marine wind farms require support for horizontal loads from wind and waves. To ensure the strength of the grout produced in environments similar to the actual placing site, this study investigated the curing of high-strength grout discharged through pump pressure in various environments, and examined the difference in strength according to different variables. Compressive strength measurements revealed that the core specimen collected from the bottom (3cm) and uppermost (50cm) of the specimen exhibited lower strength compared to other height specimens, while the core specimen obtained from the corner exhibited lower strength compared to the center. These findings suggest that the strength difference between the center and the corner is more pronounced when curing at low temperatures. This effect is greater than the strength reduction that typically occurs during low-temperature curing, and thus, necessitates careful attention in similar construction environments.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.79-84
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• 2024

As microchips' degree of integration is getting higher, its cooling problem becomes important more than ever. One of the promising methods is using fractal microchannel heat sink by mimicking nature's Murray networks. However, most of the related works have been progressed only by numerical analysis. Perhaps such lack of direct experimental studies is due to the technical difficulty of the temperature and heat flux measurement in complex geometric channels. Here, we demonstrate the direct visualization of in situ temperature profile in a fractal microchannel heat sink. By using the temperature-sensitive fluorescent dye and a transparent Polydimethylsiloxane window, we can map temperature profiles in silicon-based fractal heat sinks with various fractal scale factors (a=1.5-3.5). Then, heat transfer rates and pressure drops under a fixed flow rate were estimated to optimize hydrodynamic and thermal characteristics. Through this experiment, we found out that the optimal factor is a=1.75, given that the differences in heat transfer among the devices are marginal when compared to the variances in pumping power. This work is expected to contribute to the development of high-performance, high-efficiency thermal management systems required in various industrial fields.

• International Journal of Computer Science & Network Security
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• v.24 no.4
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• pp.197-205
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• 2024

This paper presents a fully automated stand-alone irrigation system with GSM (Global System for Mobile Communication) module. Solar energy is utilized to power the system and it is aimed to conserve water by reducing water losses. The system is based on a DC water pump that draws energy from solar panels along with automated water flow control using a moisture sensor. It is also fitted with alert and protection system that consists of an ultrasonic sensor and GSM messages sender that transmits signals showing the levels of the water in the reservoir and the battery charge. The control system is designed to stop the water pump from pumping water either when the battery level drops to equal or less than 10% of its full charge, or when the water level becomes less than 10 cm high in the reservoir. The experimental results revealed that the system is appropriate to use in remote areas with water scarcity and away from the national grid.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.314-324
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• 2006

The vacuum characteristics of the KSTAR ICRF antenna were experimentally investigated. The fabricated antenna was installed in the RF Test Chamber(RFTC) which has a vacuum system with an effective pumping speed of 1015 l/s. The time variations of RFTC pressure, total gas load and ultimate pressure were measured before the RF test. RF conditioning effect was studied by repeating RF pulses at low power level. A time variation of the RFTC pressure was measured during a RF power was applied to the antenna. Threshold pressure at which a RF breakdown occurs was investigated. Whenever the pressure was higher than $10^{-4}$ mbar, the RF breakdown occurred. During a long pulse testing, the temperature of the antenna and RFTC pressure were measured to investigate long pulse limitation of the maximum available voltage without any cooling, which were compared with testing results with a water cooling of the antenna.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.17-21
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• 2004

We demonstrate an S/S＋band discretely tunable thulium doped fiber laser (TTDFL), anchored on a 50-㎓ ITU-T grid. Investigating the inversion analysis of the thulium doped fiber (TDF) in applying a dual wavelength (1.4 m and 1.5 m) pumping scheme, a laser whose tuning range covers most of the S/S＋band has been obtained. Within the wide 3-㏈ bandwidth of 65.1 nm, the output power of the tunable laser exceeds 6.1 ㏈m with very flat spectral profile and the number of DWDM channels generated is as large as 178. If we increase the subsidiary pump power to 22 ㎽, the bandwidth is expanded up to 66.2 nm. By controlling the temperature of the fine grid filter, we have also shown that the frequency locking capability of the laser can be improved. The laser developed in this work is expected to be utilized as a practical optical source providing reference wavelengths in the S/S＋band.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.208-213
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• 2009

Artificial lightweight aggregates were produced by using bottom ashes and dredged soils from coal power plant. The amount of glassy phases on the aggregate surfaces, specific gravities, absorption rates, and observations of cross-sectional surfaces were compared according to the compositions, sintering temperatures, and the amount of coating. It is concluded that surface modification by 10 % $CaCO_3$ coating on the aggregate surfaces enhances the properties of aggregates as follows: Specific gravities were controlled by depressing formation of large pores in the aggregates. Sticking phenomena among aggregates during the sintering process was drastically decreased by reducing glassy phases on the aggregate surfaces. Pumping problems during the application of ready-mix concretes containing lightweight aggregates having high value of absorption rates could be solved by reducing the absorption rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.941-947
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• 2017

This paper reports a fractional-N phase-locked-loop(PLL) frequency synthesizer that is implemented in a $0.35-{\mu}m$ standard CMOS process and generates a quadrature signal for an FRS terminal. The synthesizer consists of a voltage-controlled oscillator(VCO), a charge pump(CP), loop filter(LF), a phase frequency detector(PFD), and a frequency divider. The VCO has been designed with an LC resonant circuit to provide better phase noise and power characteristics, and the CP is designed to be able to adjust the pumping current according to the PFD output. The frequency divider has been designed by a 16-divider pre-scaler and fractional-N divider based on the third delta-sigma modulator($3^{rd}$ DSM). The LF is a third-order RC filter. The measured results show that the proposed device has a dynamic frequency range of 460~510 MHz and -3.86 dBm radio-frequency output power. The phase noise of the output signal is -94.8 dBc/Hz, and the lock-in time is $300{\mu}s$.