• 설비공학논문집
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• 제17권2호
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• pp.191-199
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• 2005

Double pane window system, in which an air layer with a finite width is filled between glasses, is used in order to increase the insulation efficiency. In the present study, a conjugate heat transfer problem of a double pane window system has been studied numerically in order to investigate the effect of an air layer on the heat transmittance of the double pane window system using a finite element method based on P2P1 basis function. In this study on the conjugate heat transfer of a double pane window system, numerically predicted Nusselt numbers with or without conjugate heat transfer effect have been compared with an available existing empirical formula. It has been found that a Nusselt number from an existing formula for an enclosed space is different from that obtained from the present conjugate heat transfer analysis mainly due to the effects of a very high aspect ratio and conjugate heat transfer mechanism. Furthermore, it has been shown that the numerically estimated optimal air thickness of the double pane window system with conjugate heat transfer effect is a little bit longer than that obtained without considering conjugate heat transfer effect.

• 정보저장시스템학회논문집
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• 제11권1호
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• pp.6-10
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• 2015

Optical library system consists of disc magazines, cabinets, transfer robot and drive. Transfer robot delivers desired disc or magazine in cabinet to drive which reads data of disc. Conventional archive system stores discs in a line and transfer robot moves in one dimension. However, to store more discs, new optical archive system, optical library system, is developed which stores discs in two dimension like bookcase. Transfer robot should know the position and stored data of desired magazine to get correct data. In this paper, addressing algorithm using optical character recognition is proposed. Proposed algorithm is evaluated by experiments with implemented system.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2297-2310
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• 2022

A condensation heat transfer model is essential to accurately predict the performance of the passive containment cooling system (PCCS) during an accident in an advanced light water reactor. However, most of existing models tend to predict condensation heat transfer very well for a specific range of thermal-hydraulic conditions. In this study, a new correlation for condensation heat transfer coefficient (HTC) is presented using machine learning technique. To secure sufficient training data, a large number of pseudo data were produced by using ten existing condensation models. Then, a neural network model was developed, consisting of a fully connected layer and a convolutional neural network (CNN) algorithm, DenseNet. Based on the hold-out cross-validation, the neural network was trained and validated against the pseudo data. Thereafter, it was evaluated using the experimental data, which were not used for training. The machine learning model predicted better results than the existing models. It was also confirmed through a parametric study that the machine learning model presents continuous and physical HTCs for various thermal-hydraulic conditions. By reflecting the effects of individual variables obtained from the parametric analysis, a new correlation was proposed. It yielded better results for almost all experimental conditions than the ten existing models.

• 대한기계학회논문집A
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• 제30권6호
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• pp.631-636
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• 2006

In this study, a model of pneumatic cylinder position control system considering dynamic characteristics of transmission line is proposed. The transfer characteristics of transmission line are assumed to be second order transfer function because the effect of resonance characteristics of transmission line under high frequency range can be neglected by the friction force and low pass characteristics of the pneumatic cylinder driving system. Therefore, the position control system including transmission line can be modeled by using a model of pneumatic cylinder driving system and the model of transmission line. The effectiveness of the proposed model is proved by comparison of simulation results using proposed model with experimental results.

• 설비공학논문집
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• 제17권11호
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• pp.1022-1027
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• 2005

An experimental study is conducted to investigate the characteristics of the ion wind generated by the electric field between a needle electrode and the parallel plate electrodes. The ion wind enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement makes no noise or vibration. This study is conducted to develop the electronic cooling device. The measured gas velocities and heat transfer coefficients are proportional to the applied voltage. The heat transfer coefficient can be increased as compared with a natural convection. The maximum enhancement of heat transfer obtained in this system is $47\%$ for 3 W in heat transfer rate.

• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.354-362
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• 2002

In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe.

• 대한산업공학회지
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• 제41권6호
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• pp.551-558
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• 2015

The purpose of this paper is to investigate the development of mechanical projectile transfer system to prevent musculoskeletal problems in the firing test range. Prior to 2010, the projectile has been transferred from the worktable to the loading device of 155mm K9 fixed-type artillery by manual. Because the amount of firing test has been increased drastically since 2010, two types of mechanical projectile transfer system were developed to prevent musculoskeletal problems. The NIOSH lift equation and the working posture assessment system such as OWAS, RULA and REBA were used to evaluate the appropriacy of working weight and posture by manual transfer of projectile. The configuration and operation procedure of projectile transfer systems which were developed to improve work efficacy and to reduce the burden of manual transferring were described. The improvements were assessed by the number of processes, the tact time and the working posture assessment for operation of this system by comparing to the manual transfer of projectile.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.129-133
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• 2005

Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time. Today any data storage system cannot satisfy these conditions, however holographic data storage system can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System can be constructed without mechanical actuating part therefore fast data transfer rate and high storage capacity about $1Tb/cm^3$ can be realized. In this paper, to reduce errors of binary data stored in holographic data storage system, a new method for bit error reduction is suggested. First, find cluster centers using subtractive clustering algorithm then reduce intensities of pixels around cluster centers and fuzzy rules. Therefore, By using this error reduction method following results are obtained ; the effect of Inter Pixel Interference noise is decreased and the intensity profile of data page becomes uniform therefore the better data storage system can be constructed.

• 대한기계학회논문집B
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• 제20권1호
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• pp.346-358
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• 1996

A finite volume radiation solution method was applied to a non- orthogonal coordinate system for the analysis of radiative-convective heat transfer about a circular cylinder in crossflow. The crossflow Reynolds number based on the cylinder radius was 20, and the fluid Prandtl number was 0.7. The radiative heat transfer coupled with convection was reasonably predicted by the finite volume radiation solution method. The investigation includes the effects of conduction- to-radiation parameter, optical thickness, scattering albedo and cylinder wall-emissivity on heat transfer about the cylinder. As the conduction- to-radiation parameter decreases, the radiative heat transfer rate increases and conduction rate as well due to the increase in temperature gradient on the cylinder wall which is caused by radiation enhancement. With an increase in the optical thickness, the Nusselt number increases significantly and the temperature gradient shows similar behavior. Though the radiative heat transfer increases with the scattering albedo, the total heat transfer decreases. This is because the decrease in the conduction heat transfer exceeds the increase in the radiation heat transfer. As the wall- emissivity increases, the radiation absorbed in the vicinity of the cylinder wall increases and thereby the total heat transfer increases, even though the conduction heat transfer decreases.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.581-589
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• 2003

Film absorption involves simultaneous heat and mass transfer in the gas-liquid system. While the non-absorbable gas does not participate directly In the absorption process. its pretence does affect the overall heat and mass transfer. An experimental study was performed to investigate the heat and mass transfer characteristics of LiBr-H$_2$O solution flow ing over 6-row horizontal tubes with the water vapor absorption in the pretence of non-absorbable gases. The volumetric concentration of non-absorbable gas, air, was varied from 0.17 to 10.0%. The combined effects of the solution flow rate and its concentration on the heat and mass transfer coefficients were also examined. The presence of 2％ volumetric concentration of air resulted in a 25% reduction in the Nusselt number and 41% reduction in the Sherwood number Optimum film Reynolds number was found to exist at which the heat and mass transfer reach their maximum value independent of air contents. Reduced Nusselt and Sherwood numbers. defined as the ratio of Nusselt and Sherwood numbers at given non-absorbable gas content to that with pure water vapor, were correlated to account for the reduction in the heat and mass transfer due to non-absorbable gases in a falling film absorption process.