• Journal of Power System Engineering
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• v.12 no.5
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• pp.48-53
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• 2008

Heat exchangers are commonly used in practice in a wide range of application, from heating and air-conditioning system in a household, to chemical processing and power production in a large plant. Heat transfer in a heat exchanger usually involves convection in each fluid and conduction through the wall separating the two fluids. The heat transfer characteristics of tube banks of in-line arrangements of four circular cylinders in a cross flow are compared for a range of tube locations and Reynolds numbers. The in-line pitch ratio was set up in the range of $1.5\leq L/d\leq4.0$, where L is the center to center distance and d the circular cylinder diameter, and in the Reynolds number of $13,000\leq Re\leq50,000$. The local and mean Nusselt numbers were estimated, and then. Subsequently, the heat transfer characteristics of four circular cylinders were found to exhibit a strong dependency upon the cylinder spacing and separation point of their upstream cylinders.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1135-1141
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• 2006

Air foil bearing supports the rotating journal using hydrodynamic force generated at thin air film. The bearing performance, stiffness, damping coefficient and load capacity, depends on the rotating speed and the performance of the elastic foundation, bump foil. The main focus of this study is to decide the dynamic performance of corrugated bump foil, structural stiffness and Coulomb damping caused by friction between bump foil and top foil/bump foil and housing. Structural stiffness is determined by the bump shape (bump height, pitch and bump thickness), dry-friction, and interacting force filed up to fixed end. So, the change of the characteristics was considered as the parameters change. The air foil bearing specification for analysis follows the general size; diameter 38.1 mm and length 38.1mm (L/D=1.0). The results show that the stiffness at the fixed end is more than the stiffness at the free end, Coulomb damping is more at the fixed end due to the small displacement, and two dynamic characteristics are dependent on each other.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.187-197
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• 1996

Many investigations have been made to determine the pressure drop and heat transfer characteristics for single phase flow in tape generated swirl flow. But few studies have been carried out to investigate the heat transfer in two component, two phase swirl flow with non-boiling. An experimental study has been conducted to determine the effects of tape twist ratios on two phase convective heat transfer coefficients, pressure drop, and void fraction distribution in a non-boiling, air-water, two phase flow. The flow conditions were both swirl and non swirl flows. The internal diameter of the test section is 42.5mm. The tape twist ratios of pitch to diameter ratio varied from 4.0 to 10.6. The heating conditions were isothermal and nonisothermal. The flow patterns identified with experiments were bubbly, bubbly-slug, slug, and slug-annular flow in up-flow. This study has concluded that no significant difference in void fraction distribution were observed both isothermal and nonisothermal conditions, the pressure drop for two phase flow with twisted tape swirler increase as the tape twist ratio decrease, and that values of two phase heat transfer coefficient increase when the tape twist ratio decreases.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2479-2490
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• 2020

We performed experiments to measure a single-phase upward flow in a 5 × 5 rod bundle with spacer grids using a particle image velocimetry, focusing on the crossflow. The Reynolds number based on the hydraulic diameter and the bulk velocity is 10,000. The ratio of pitch between rods and rod diameter is 1.4 and spacer grid is installed periodically. The turbulence in the rod bundle results from the combination of a forced mixing and natural mixing. The forced mixing by the spacer grid persists up to 10D_h from the spacer grid, while the natural mixing is attributed to the crossflow between adjacent subchannels. The combined effects contribute to a sinusoidal distribution of the time-averaged stream-wise velocity along the lateral direction, which is relatively weak right behind the spacer grid as well as in the gap. The streamwise and lateral turbulence intensities are stronger right behind the spacer grid and in the gap. Based on these findings, we newly defined a modified mixing coefficient as the ratio of the lateral turbulence intensity to the time-averaged streamwise velocity, which shows a spatial variation. Finally, we compared the developed model with the measured data, which shows a good agreement with each other.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.396-408
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• 2014

In this study, uncertainty analysis based on ITTC(International Towing Tank Conference) Recommended Procedures is carried out in the towing-tank experiment for motion responses and added resistance. The experiment was conducted for KVLCC2 model in head sea condition. The heave, pitch and added resistance were measured in different wave conditions, and the measurement was repeated up to maximum 15 times in each wave condition in order to observe the uncertainty of measured data. The uncertainty analysis was carried out by adopting the ISO-GUM(International Organization for Standardization, Guide to the Expression of Uncertainty in Measurements) method recommended by ITTC. This paper describes the details about the analysis method, uncertainty and the measured uncertainty for each source. The uncertainty analysis results are summarized as a tabular form. To validate the accuracy of the present measurement, the experimental results are compared with the results of numerical computation and other experiment. From the present uncertainty analysis, the main sources of uncertainty are identified, which can be very useful to improve the accuracy for added resistance experiment.

• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.103-112
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• 2018

In this paper, a high performance underwater vehicle which can be manufactured at low cost is designed and fabricated, and its performance is verified through experiments. To improve efficiency, the Myring equation is used to design the appearance and the duct structure including the thruster is planned to increase the propulsion efficiency while reducing the drag force. Through various methods, it is secured stable waterproof performance, and also is devised to have high speed movement and turning performance. The developed underwater vehicle is equipped with a high output BLDC motor to achieve a linear speed of up to 2 m/s and can change direction rapidly with stability through four rudders. The rudders are driven by coupling a timing belt and a pulley by extending the axis of a servo motor, and are equipped at the end of the body to turn heading. In addition, for stable posture control, the roll keeps its internal center of gravity low and maintains its stability due to restoring force. By controlling the four rudders, pitch and yaw are handled by the PID controller and show stable performance. To investigate the horizontal turning performance, it is confirmed that the yaw rate controller is designed and stable yaw rate control is performed.

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.195-200
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• 1992

This paper deal with the acoustic cues of Pyoung-An Do dialect using linear prediction. Also, this paper descrbes a statistical comparison between standard tone speech data and Pyoung-An Do dia lects. The analysis done mainly focused on the distribution of formants and pitch periods accord to ac- cents variation. For the purpose of objective comparison, the experiments are performed by extracts for- mant LPC spectrum and pithch periods from average magnitude difference function waveforms. Summing up the results, In disyllable words (VCV pattern) , prepositioned vowels have longer phona lion time than postpositioned vowels and the intrin, iii phonation time is whore longer in the low vowels than in the high ones. The africative consonants show the mixed characteristics of the plosive and frlc ative consonants. The remarkable acoustic cues are the low frequency noise-like waves just before the 1st formants in the plosive consonants, the high frequency noise-like waves in the fricative consonants, and phonation time is not affected by the kinds of prepositioned or postpositioned vowels.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.904-913
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8 mm and oblique angle were 80$^{\circ}$. The space from rods to the heating surface was C=1, 2, 4 mm, the pitch between each rods was P=30, 40, 50 mm, and the distance from nozzle exit to flat plate was H=100, 500 mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8 mm, C=1 mm, P=30 mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

• Journal of Magnetics
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• v.14 no.1
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• pp.47-51
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• 2009

The coreless linear synchronous motor (coreless LSM) has been widely used as a driving source of semiconductor production processes for machine speeding up, positioning accuracy and simple maintenance. However, this coreless LSM suffers the disadvantage of decreased thrust force created by the leakage of magnetic flux. With the goal of increasing the generated thrust force and decreasing the cogging force, the slot of the core part was removed and a moving-coil-type slotless LSM (moving-coil-type slotless LSM) is proposed in this paper. Although this moving-coil-type slotless LSM with a back-yoke at the primary side demonstrated an increase in the generated thrust force, it remained capable of generating the cogging force when the primary side was moved due to the position between the permanent magnet and the back-yoke. Therefore, we attempted to decrease the cogging force of the moving-coil-type slotless LSM. We found that the back-yoke length at the primary side needs to be made $0.5{\tau}$ longer than the integral multiple of the magnetic pole pitch in order to decrease the cogging force created by the moving-coil-type slotless LSM.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.10
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• pp.3355-3372
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• 2022

Composing music is an inspired yet challenging task, in that the process involves many considerations such as assigning pitches, determining rhythm, and arranging accompaniment. Algorithmic composition aims to develop algorithms for music composition. Recently, algorithmic composition using artificial intelligence technologies received considerable attention. In particular, computational intelligence is widely used and achieves promising results in the creation of music. This paper attempts to provide a survey on the music generation based on the Monte Carlo (MC) algorithm. First, transform the MIDI music format files to digital data. Among these data, use the logistic fitting method to fit the time series, obtain the time distribution regular pattern. Except for time series, the converted data also includes duration, pitch, and velocity. Second, using MC simulation to deal with them summed up their distribution law respectively. The two main control parameters are the value of discrete sampling and standard deviation. Processing the above parameters and converting the data to MIDI file, then compared with the output generated by LSTM neural network, evaluate the music comprehensively.