• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.1168-1173
• /
• 2006

This research is to verify the cooling effect of the acting surface on the rotary motor using heat pipe and conventional cooling fan. In order to show the cooling performance of the rotary motor and heat pipe with the fin-typed heat sink, the surface temperature of the motor and condenser was measured in real time. The experiments were also conducted as for not only cooling device installed with heat pipe only, but with heat pipe and conventional cooling fan simultaneously.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.3
• /
• pp.230-240
• /
• 2004

An experimental investigation was conducted to study two-phase flow distribution in a T-type distributor of slit fin-and-tube heat exchanger using R22. A comparison was made between the predictions by previously proposed tube-by-tube method and experimental data for the heat transfer rate of evaporator. Experiments were carried out under the conditions of saturation temperature of 5$^{\circ}C$ and mass flow rate varying from 0.6 to 1.2kg/min. The inlet air has dry bulb temperature of 27$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.63 to 1.71㎧. Experiment show that air velocity increased by 85.2% is need for T-type distributor with four outlet branches than that of two outlet branches under the superheat of 5$^{\circ}C$, which resulted in air-side pressure drop increase of 130% for T-type distributor with four outlet branches as compared to two outlet branches.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.4_2
• /
• pp.645-653
• /
• 2022

Recently, deep reinforcement learning has been applied to a variety of industries, such as games, robotics, autonomous vehicles, and data cooling systems. An algorithm called reinforcement learning allows for automated asset allocation without the requirement for ongoing monitoring. It is free to choose its own policies. The purpose of this paper is to carry out an empirical analysis of the performance of asset allocation strategies. Among the strategies considered were the conventional Mean- Variance Optimization (MVO) and the Proximal Policy Optimization (PPO). According to the findings, the PPO outperformed both its benchmark index and the MVO. This paper demonstrates how dynamic asset allocation can benefit from the development of a reinforcement learning algorithm.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.17 no.2
• /
• pp.192-198
• /
• 2017

In this paper, we propose a novel double gate vertical channel tunneling field effect transistor (DVTFET) with a dielectric sidewall and optimization characteristics. The dielectric sidewall is applied to the gate region to reduced ambipolar voltage ($V_{amb}$) and double gate structure is applied to improve on-current ($I_{ON}$) and subthreshold swing (SS). We discussed the fin width ($W_S$), body doping concentration, sidewall width ($W_{side}$), drain and gate underlap distance ($X_d$), source doping distance ($X_S$) and pocket doping length ($X_P$) of DVTFET. Each of device performance is investigated with various device parameter variations. To maximize device performance, we apply the optimum values obtained in the above discussion of a optimization simulation. The optimum results are steep SS of 32.6 mV/dec, high $I_{ON}$ of $1.2{\times}10^{-3}A/{\mu}m$ and low $V_{amb}$ of -2.0 V.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.5
• /
• pp.397-407
• /
• 2004

It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7 $^{\circ}C$ and mass flux varied from 150 to 250 kg/$m^2$s. The condition of air was dry bulb temperature of 27$^{\circ}C$, air Velocity Varied from 0.38 to 1.6 m/s. Experiments Showed that air Velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5$^{\circ}C$, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.

• Journal of Information Technology Applications and Management
• /
• v.27 no.3
• /
• pp.1-18
• /
• 2020

Recently, following the development of FinTech technology that combines finance and information and communication technology, the need and social demands for a block chain technology-based trading system have increased significantly. In this study, a research model was developed and hypothesized through literature research on the concept of block chain technology, the technology acceptance model, and the unified theory of acceptance and use of technology. The research theories were tested by collecting data through surveys and analyzing the collected data. This study conducted empirical research to identify the factors influencing the user acceptance intention and utilization behavior of the block chain technology in introducing the block chain technology. First, factors affecting the acceptance intention of the blockchain user were performance expectation, effort expectation, social impact, and blockchain transparency variables. Second, the facilitation conditions and stakeholder confidence variables were analyzed as factors that did not affect the acceptability of the blockchain users. Third, variables such as blockchain transparency, stakeholder trust and intention of acceptance are factors that affect the usage behavior of the blockchain. Fourth, it was confirmed that the acceptance intention had a very high explanatory power on usage behavior of Blockchain technology.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.8
• /
• pp.1055-1061
• /
• 2002

A numerical and experimental study on the flow fields behind the fan outlet was carried out to improve the performance of a conventional fan-sink(fan and heat sink). Conventional fan-sinks have a heat sink of which fin configurations tend to increase the flow resistance, thus decreasing the performance and the cooling capabilities of a fan-sink. Lifting surface method is used for the prediction of flow fields behind the fan outlet. Oil-dot flow visualization technique is applied for the validation of numerical results. The numerical results and experimental data show agreement each other. A conventional heat sink is modified and redesigned using flow patterns behind the fan outlet. The newly designed heat sink has the configuration of curved fins which minimize flow resistance. It showed improvements in both cooling: capabilities and volumetric flow rate compared to the conventional one.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.4
• /
• pp.499-510
• /
• 1999

A computer program was developed for simulating performance(capacity, power consumption and etc.) of air-conditioners using compressor, fin-tube heat exchanger and capillary tube. The program consists of five modules, condenser, evaporator, compressor, capillary tube simulation modules and properties modules of refrigerant and moist air, The present program is focused on R22 only, however can be easily extended for other refrigerants such as R407C and R410A just by adding property modules. The compressor simulation module utilizes performance maps supplied by manufacturers-map-based model. The condenser and evaporator simulation modules are modeled using tube-by-tube method. Simulation results(capacity and power consumption) were compared with calorimeter test results of actual air-conditioners of window and split types, where more than 82% of the data lied within ${\pm}5$% of the predicted results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.2
• /
• pp.63-68
• /
• 2015

The fin and tube type heat exchangers widely used in air conditioners have been developed to improve on the heat transfer performance and compactness. This study presents the new type of tube for the heat exchanger to improve the heat transfer performance by increasing the heat transfer area per unit volume in the air-conditioner heat exchanger. The new type tube can be used for mechanical expansion facility, due to the two-port copper tube. Numerical calculation shows that the heat exchanger using the two-port copper tube outperforms the conventional heat-exchanger using a circular copper tube, in terms of the increased heat transfer coefficient and higher pressure drop. The calculation results were experimentally validated and are in agreement with the experimental results. Compared to the heat exchanger using a conventional circular tube, the heat exchanger with a two-port tube increased the heat transfer coefficient up to 21%, and the pressure dropped up to 16%.

• Journal of the Semiconductor & Display Technology
• /
• v.15 no.3
• /
• pp.12-17
• /
• 2016

In this study, numerical simulations for the conjugate heat transfer of air with a heat-sink of CPU were conducted. The heat-sink consisted of many fins of cylinder shape and the effect of the number of fins on the cooling performance of the heat sink was investigated. Grid independent solutions were obtained to compare the maximum temperature of the heat-sink for various conditions. It was found that maximum temperature of the heat-sink asymptotically approached 310K as the number of fins went to infinity. The energy exchange of air with the heat-sink was found to be nearly independent on the number of fins.