• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.139-140
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• 2013

Ground source heat pump systems can achieve the energy saving of building and reduce CO₂ emission by utilizing stable ground temperature. However, they have many barriers such as high cost of installation, incompletion of design tool, lack of recognition as heating and cooling systems. In order to solve the problems, the building integrated geothermal system (BIGS) developed by several researches which use building foundation as a heat exchanger. In order to establish the optimum design tool of BIGS with the horizontal heat exchanger, the prediction method of ground heat exchange rate developed with numerical simulation model. In this study, the economic analysis for BIGS was conducted based on simulation results and the optimal design method was suggested. As a result, it was found that the case of 32 A, piping space 0.3 m, piping deep 0.5 m and flow rate 9.52 L/min was the best case as 50.1 W/m2 of heat exchange rate. In this case the initial cost was reduced to 115 million won.

• KIEAE Journal
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• v.10 no.5
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• pp.23-30
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• 2010

The residence means a given place. It is repeated that process of overcome, protection, assimilation and adaptation has applied to environmental condition. Architecture is part of environment and various. Thus there are lots of types. We need the place with uniqueness, and it is suitable for biological and humanistic environment. The living space turned to be meaningful place with design, and people start to live with nature together. Therefore design restructures whole environment and makes people to be closed with nature. We have to understand nature of environment to connect one place with the other place, and people start to put down roots certain place. Coping with social needs, we have to develop the architectural alternative which can be applied to natural condition. This study suggest sound high-density urban residential model as it function social mix.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.69-72
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• 2004

In recent, there have been several developments in lamp technology that promise savings in electrical power consumption and improved quality of the lighting space. Above all, the advantage of ring-shaped electrodeless fluorescent lamp is the removal of internal electrodes and heating filaments that are a light-limiting factor of conventional fluorescent lamps. The ring-shaped electrodeless lamp is intended as a high efficacy replacement for the incandescent reflector lamp in many applications. Therefore, the life time of ring-shaped electrodeless fluorescent lamps is substantially higher than that of conventional fluorescent lamps and last up to 60,000 hours. In this paper, we present measurement results of electrical characteristics of a ring-shaped electrodeless fluorescent lamp as a function of frequency and number of coil turns using a highly permeable Mn-Zn ferrite. It is found that the impedance are increased while the quality factor decreases as frequency increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.521-524
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• 2003

In recent, there have been several developments in lamp technology that promise savings in electrical power consumption and improved quality of the lighting space. Above all, the advantage of ring-shaped electrodeless fluorescent lamp is the removal of internal electrodes and heating filaments that are a light-limiting factor of conventional fluorescent lamps. The ring-shaped electrodeless lamp is intended as a high efficacy replacement for the incandescent reflector lamp in many applications. Therefore, the life time of ring-shaped electrodeless fluorescent lamps is substantially higher than that of conventional fluorescent lamps and last up to 60,000 hours. In this paper, maxwell 3D finite element analysis program (Ansoft) was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 250kHz and some specific conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.850-854
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• 2011

Nano-fibers of the $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ electrode were synthesized from a metal oxide precursor using the electrospun method. The XRD patterns of all prepared powders showed a hexagonal ${\alpha}$ - $NaFeO_2$ structure (space group: R-3 m, 166). Scanning electron microscopy showed that all the synthesized samples were comprised of nanofibers with a size of 100~800 nm. Among the samples tested, the calcined $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ nanowires in oxygen heating atmosphere showed a high charge and discharge capacity of 239.22 and 172.81 $mAhg^{-1}$ at the $1^{st}$ cycle, respectively. In addition, the charge transfer resistance was also improved significantly compared to the other samples.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.864-873
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• 2006

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.212-218
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• 2013

Tuff specimens were thermally treated with predetermined temperatures of 200, 400 and $600^{\circ}C$ to construct specimens simulating weathered tuff rocks. Specific gravity, absorption ratio, elastic wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio and slake-durability index were measured for pre-heated specimens. Heating of rock specimens entailed the degradation of material properties except for slake-durability index. It was found that correlations among P-wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio are high. Regression equations which use the P-wave velocity as an independent variable were presented to evaluate uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.4
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• pp.37-46
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• 2001

This study numerically investigates thermal comfort of a space cooled by a floor-supply air-conditioning system, in which three different combinations of supply and return locations, one floor-supply/ceiling-return and two floor-supply/floor-return, are treated. A complementary experiment is performed to validate the present numerical analysis, and the prediction agrees favorably with the measured data. In the numerical procedure, a simplified model mimicking the inlet flow through a diffuser is developed for efficient simulations. The calculated results show that the ceiling-return type is far better in terms of thermal comfort than the floor-return ones within the extent of this study, which seems to be caused by effective vertical penetration of the supply air against natural convection. It is also revealed that the arrangement of port locations in the floor-supply/floor-return system has insignificant effect on the cooling performance. For selecting a proper system, other characteristics including the heating performance should be accounted for simultaneously with the present considerations.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.4
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• pp.53-60
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• 2018

This study was conducted for analysis of a heat pump system using waste heat in an enclosed space such as a green house. The model was developed with mathematical equations in literature and Engineering Equation Solver (EES) was used to get the solution of the developed equations. The simulation results have 5% of reliability comparing the results with actual test data of heat pump system's dynamic operation. The operating performance of the system was calculated with variation of working fluid temperature in the thermal storage tank such as $25^{\circ}C$, $35^{\circ}C$, $45^{\circ}C$ and $55^{\circ}C$. As a result, the system's the highest total heating capacity shows 280 kWh and the storage tank's operating time decreased as the starting storage tank's temperature was high.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3277-3290
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• 2023

Nuclear power plant (NPP) operations with multiple objectives and devices are still performed manually by operators despite the potential for human error. These operations could be automated to reduce the burden on operators; however, classical approaches may not be suitable for these multi-objective tasks. An alternative approach is deep reinforcement learning (DRL), which has been successful in automating various complex tasks and has been applied in automation of certain operations in NPPs. But despite the recent progress, previous studies using DRL for NPP operations have limitations to handle complex multi-objective operations with multiple devices efficiently. This study proposes a novel DRL-based approach that addresses these limitations by employing a continuous action space and straightforward binary rewards supported by the adoption of a soft actor-critic and hindsight experience replay. The feasibility of the proposed approach was evaluated for controlling the pressure and volume of the reactor coolant while heating the coolant during NPP startup. The results show that the proposed approach can train the agent with a proper strategy for effectively achieving multiple objectives through the control of multiple devices. Moreover, hands-on testing results demonstrate that the trained agent is capable of handling untrained objectives, such as cooldown, with substantial success.