• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.245-251
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• 2006

The main idea of this study is to turn attention on the question of good cooling ability of customer substations in large district heating networks. The main reason for that is based on our experience that the optimization of district heating very often is directed toward production, whereas questions of optimal distribution are neglected if only the necessary load can be supplied and the customer's request for comfort is met. Our view is that low return temperature(operational temperature differences, ${\Delta}T$) in district heating systems is an Important feature for efficient net operation and gives both economic and operational benefits to the district heating supplier Furthermore, it is as well a prerequisite for meeting the customers demand for reliable supply of the heat load. However, in many practical cases we have seen that district heating return temperatures are higher than necessary. Hence, the aim of the study is to propose and verify a method for detection of the most critical consumers of the net and to identify the reasons for resulting high return temperature. From the results, temperature control system is presented as one of the most important reason of high return temperature in DH networks.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.265-266
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• 2019

This paper proposed a three-channel transformer-type power regulator to control the heater temperature by adjusting the voltage across the heater for pre-heating and the post-heating procedures of the material welding. The experimental results are carried out to verify the performance of three-channel heater temperature control for the heat treatment.

• Journal of Bio-Environment Control
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• v.8 no.3
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• pp.152-163
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• 1999

It is required to analyze the controlled response of air temperature in greenhouse according to control techniques for precise control. In this study, a mathematical model was established for air heating of greenhouse with hot-water heating system The parameters of the model were decided by regression analysis using reference data measured at the greenhouse being heated In the simulation for the digital control of air temperature in the greenhouse, the mathematical model to evaluate the control performances was used. Tested control methods were ON-OFF contpol, p control, rl control and PID control. The mathematical model represented by inside air temperature ( T$_{i}$), hot-water temperature (T$_{w}$) in heating pipe and outside air temperature (T$_{o}$) was expressed as a following discrete time equation ; T$_{i}$($textsc{k}$＋1)＝ 0.851.T$_{i}$($textsc{k}$)＋0.055.T$_{w}$($textsc{k}$)＋0.094.T$_{o}$($textsc{k}$) Control simulations for various control methods showed the settling time, the overshoot and the steady state nor as follows; infinite time, 3.5$0^{\circ}C$, 3.5$0^{\circ}C$ for ON-OFF control : 30min 2.37$^{\circ}C$, 0.51$^{\circ}C$ for P control; 21min, 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PI control; 18min 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PID control, respectively. PI and PID controls appeared to be optimal control methods. There was no effect of differential gain on the heating process but much effect of integral gain on it.on it.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1254-1256
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• 2000

In this paper, a control scheme for induction heating is proposed. The propose scheme estimates, resonant frequency by PI control subbing a phase of output voltage and resonant capacitor voltage. There are would be two advantages in the proposed system over existing induction heating system. One is the rapid resonant frequency estimation. A other is the just control of temperature. Power Circuit is used a inverter stack and transformer rated on 5.5kw.

• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.11-17
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• 2010

The developed control valves, installed on the hot water distribution manifolds for the floor heating system, consist of the balancing valves and the shut-off valves. The balancing valve was designed to improve the flow control performance and to reduce the noise emitted from the valve by modification of the general V port. The port of the shut-off valve was designed with two ceramic plates, working by rotating upper plate, to improve the duration and to reduce the noise. For the evaluation of the new valves, the flow rate was measured and noise level test was carried out. The test results showed that the error of the flow rate accuracy test for the flow balance of each manifold circuit was less than ${\pm}3%$ and the noise level was less than 35 dB(A).

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.256-264
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• 2022

The frequency power control method (FCM) which has a wide operating frequency range is adopted for induction heating (IH) cooktops. When FCM is applied to the full-bridge series resonant converter (FB-SRC) based IH system, high-frequency switching of the inverter is required compared to the half-bridge SRC (HB-SRC)-based IH system. Therefore, the switching loss of the inverter increases, and applying FCM under the condition that the inverter operating frequency range is limited is difficult. Therefore, this paper proposes a control strategy with the phase shift power control method considering that limited frequency conditions are presented. Loss analysis following the control method is performed through simulation and mathematical analysis. In addition, the validity of the proposed control strategy is verified by analyzing the heating performance following the control method through the test results of the 3,200[W] prototype.

• Journal of the Korean Solar Energy Society
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• v.26 no.4
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• pp.119-126
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• 2006

This study describes thermal performance of heating and cooling demonstration system using ETSC(Evacuated tubular solar collector) installed at Seo-gu art center of Kwangju. For demonstration study, a reading room with about $350m^2$ was heated and cooled using that system. The demonstration system was consisted of ETSCs, storage tank, hot water supply tank, subsidiary boiler, and subsidiary tank. From January to March in 2006, demonstration test were performed with 4 control mode to find the optimum control condition for solar thermal system. After experiments and analysis, this study found that solar thermal system of control mode IV was corresponded to 78% for the hot water supply and 49% for space heating.

• International journal of advanced smart convergence
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• v.7 no.2
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• pp.38-46
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• 2018

This study proceeded an experiment that can increase such physiological properties of heated radish extract. During the extraction of radish, including the byproduct, an increase in antioxidant properties of radish according the heating temperature was performed. Upon the extracts of radish bark and radish green extract(mucheong), the physiological functionalities and antioxidant activity were investigated. As a result, the color of radish ethanol extract in dependence of heating temperature, showed light brown color at low heating temperature and black color from $150^{\circ}C$. The total polyphenol content significantly increased as a result of heat treatment; 6.7 times and 22 times higher than the control at $110^{\circ}C$ and $150^{\circ}C$, respectively. DPPH radical scavenging ability and antioxidant property increased with increasing heating temperature; in comparison to heat-treated radish at $110^{\circ}C$ and $150^{\circ}C$, $IC_{50}$ decreased by 1/22 times. $IC_{50}$ of the control was 23times higher than $150^{\circ}C$ heat treated radish (Control $IC_{50}$:130.305). According to the graph that represents ABTS activity, antioxidant activity increased in dependence of heat treatment likewise to the total polyphenol content and DDPH radical scavenging activity. Upon heat treatment at $150^{\circ}C$, antioxidant activity in consequence of ABTS assay increased 23 times higher than the control.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.832-837
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• 2006

This study describes thermal performance of heating and cooling demonstration system using ETSC(Evacuated tubular solar collector) installed at Seo-gu art center of Kwangju. For demonstration study, a reading room with about $331m^2$ was heated and cooled using that system. The demonstration system was consisted of ETSCs, storage tank, hot water supply tank, subsidiary boiler, and subsidiary tank. From January to March in 2006, demonstration test were performed with 4 control mode to find the optimum control condition for solar thermal system. After experiments and analysis, this study found that solar thermal system of control mode IV was corresponded to 78% for the hot water supply and 49% for space heating.

• Carbon letters
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• v.10 no.3
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• pp.230-233
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• 2009

In this study, a low temperature growth of high-quality carbon nanotubes on glass substrate using a local surface heating without heating damage to substrate was tried and characterized. The local joule heating was induced to only Ni/Ti metal film on glass substrate by applying voltage to the film. It was estimated that local surface joule heating method could heat the metal surface locally up to around $1200^{\circ}C$ by voltage control. We could successfully obtain high-quality carbon nanotubes grown at $300^{\circ}C$ by applying 125 V for joule heating as same as carbon nanotubes grown at $900^{\circ}C$.