• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.114-122
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• 2012

Vertical closed-loop ground source heat pump systems(GSHP) have been installed widely in Korea since it can extract moderate temperature level of geothermal heat in a small area. As a ground heat exchanger, a vertical closed -loop type with brine circulation is mostly preferred since it is simple and less harmful to ground environment. However, it requires a secondary heat exchange loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground is increased, which are important parts of performance degradation. In this paper, annual and seasonal performances of direct expansion(DX) geothermal heat pump were estimated mathematically as an alternative of classical indirect geothermal heat pump based on the annual performance evaluation. As results, DX geothermal heat pump showed 43% higher annual performance than the classical U-tube geothermal heat pump.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.6
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• pp.479-486
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• 2021

In this paper, an ultra small phase locked loop (PLL) with a single capacitor loop filter has been proposed by adding a signal sensing circuit (SSC). In order to extremely reduce the size of the PLL, the passive element loop filter, which occupies the largest area, is designed with a very small single capacitor (2pF). The proposed PLL is designed to operate stably by the output of the internal negative feedback loop including the SSC acting as a negative feedback to the output of the single capacitor loop filter of the external negative feedback loop. The SSC that detects the PLL output signal change reduces the excess phase shift of the PLL output frequency by adjusting the capacitance charge of the loop filter. Although the proposed structure has a capacitor that is 1/78 smaller than that of the existing structure, the jitter size differs by about 10%. The PLL is designed using a 1.8V 180nm CMOS process and the Spice simulation results show that it works stably.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3371-3376
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• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the thermal conductivity of the ground. To evaluate this heat transfer property, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to water over various test lengths. By measuring the water temperatures entering and exiting the loop, water flow rate, and heat load, effective thermal conductivity values of the ground were determined. The effect of increasing thermal conductivity of grouting materials from 0.82 to 1.05 W/m$^{\circ}C$ resulted in overall increases in effective ground thermal conductivity by 25.8% to 69.5%.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.830-835
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• 1998

This paper describes a new digital control method of 3-phase PWM inverter with LC filter for uninterruptible power supply(UPS). The overall control system is based on the dead beat control, which has the minor loop of current control within the voltage control major loop. In this paper, the full-order disturbance observer is proposed to compensate the disturbances generated due to a sudden change of load currents. The proposed disturbance observer is composed of dead beat observer which estimates state values within a finite time, and cancels the disturbances by adding feedforward compensation loop in the control system. In addition, on order to remove a defect of oscillation generated in output of conventional dead beat controller, a modified dead beat algorithm is proposed in this paper.

• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.59-67
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• 2017

This paper proposes an asymmetric split-loop resonator with an outer square loop (ASLR-OSL), which can actively control terahertz wave transmission properties while maintaining a high-Q-factor of the asymmetric split-loop resonator (ASLR). An added outer square loop is designed to play the roles of both a metamaterial and a micro-heater, which can control the temperature through a directly applied bias voltage. A vanadium dioxide ($VO_2$) thin film, which exhibits an insulator-metal phase transition with temperature change, is used to control the transmission properties. The proposed ASLR-OSL shows transmission properties similar to those of the ASLR, and they can be successfully controlled by directly applying bias voltage to the outer square loop. Based on these results, an electrically controllable terahertz high-Q metamaterial could be achieved simply by adding a square loop to the outside of a well-known high-Q metamaterial.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.199-202
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• 2001

In this paper, we proposed and analyzed a new class of irregular fault-tolerant multistage interconnection network named as Extended-QT(Quad Tree) network. E-QT network is extended QT network. A unique path MIN usually is low hardware complexity and control algorithm. So we proposes a class of multipath MIN which are obtained by adding self-loop auxiliary links at the a1l stages in QT(Quad Tree) networks so that they can provide more paths between each source-destination pair. The routing of proposed structure is adaptived and is based by a routing tag. Starting with the routing tag for the minimum path between a given source-destination pair, routing algorithm uses a set of rules to select switches and modify routing tag. Trying the self-loop auxiliary link when both of the output links are unavailable. If the trying is failure, the packet discard. In simulation, an index of performance called reliability and cost are introduced to compare different kinds of MINs. As a result, the prouosed MINs have better capacity than 07 networks.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.229-231
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• 2006

The paper presents a sensorless speed control of interior permanent magnet synchronous motors using an adaptive integral binary observer in view of composition with a main loop regulator and an auxiliary loop regulator. The binary observer has a property of the chattering alleviation in the constant boundary layer; however, the steady state estimation accuracy and robustness are dependent upon with width of the constant boundary. In order to improve the steady state performance of the binary observer, the binary observer is formed by adding extra integral dynamic to the switching hyperplane equation.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.83-85
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• 2003

This paper presents a speed control of permanent magnet synchronous motors (PMSM) using an adaptive integral binary observer without speed and position sensors. In view of composition with a main loop regulator and an auxiliary loop regulator, the binary observer has a property of the chattering alleviation in the constant boundary layer. In order to improve the steady state performance of the binary observer, the proposed adaptive integral binary observer is formed by adding extra integral dynamics to the switching hyperplane equation. The effectiveness of the proposed system is conformed by the experimental results.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.48-53
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• 1999

We demonstrate small-scale high-T$_c$ superconductor RSFQ(Rapid Single Flux Quantum) circuits using multilayer bicrystal technology. An RSFQ balanced comparator is demonstrated with good current resolution, and its operating conditions are discussed in some detail. A single-loop delta-sigma modulator is realized adding a feedback loop to the comparator. The effect of the feedback is confirmed by dc measurement and simulation. A design of an RSFQ toggle flip-flop with the same multilayer bicrystal technology is suggested.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.397-401
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• 1997

In this paper, we propose a neural-network that detects moving objects in an image using a diffusion neural network. The proposed neural network is improved by adding a self loop to diffusion layer to remove the noise in an image and to reduce the detection of phantom edge. Computer simulation with real images show that the proposed neural network can extract edges of moving object efficiently.