• Progress in Medical Physics
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• v.31 no.2
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• pp.9-19
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• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.6
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• pp.499-506
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• 2004

The copper foil surface inspection system is necessary for the factory automation and product quality. The developed system is composed of the high speed line scan camera, the image capture board and the processing computer. For the system resource utilization and real-time processing, multi-threaded architecture is introduced. There are one image capture thread, 2 or more defect detection threads, and one defect communication thread. To process the high-speed input image data, the I/O overlap is used through the double buffering. The defect is first detected by the predetermined threshold. To cope with the light irregularity, the compensation process is applied. After defect detection, defect type is classified with the defect width, eigenvalue ratio of the defect covariance matrix and gray level of defect. In experiment, for high-speed input image data, real-time processing is possible with multi -threaded architecture, and the 89.4% of the total 141 defects correctly classified.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.2923-2943
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• 2021

The double helix structure of DNA makes it diverse, stable and can store information with high density, and these characteristics are consistent with the requirements of molecular communication for transport carriers. In this paper, a specific structure of molecular communication system based on DNA length coding is proposed. Transmitter (Tx) adopts the multi-layer golden foil design to control the release of DNA molecules of different lengths accurately, and receiver (Rx) adopts an effective and sensitive design of nanopore, and the biological information can be converted to the electric signal at Rx. The effect of some key factors, e.g., the length of time slot, transmission distance, the number of releasing molecules, the priori probability, on channel capacity is demonstrated exhaustively. Moreover, we also compare the transmission capacity of DNA-based molecular communication (DNA-MC) system and concentration-based molecular communication (MC) system under the same parameter setting, and the peak value of capacity of DNA-MC system can achieve 0.08 bps, while the capacity of MC system remains 0.025 bps. The simulation results show that DNA-MC system has obvious advantages over MC system in saving molecular resources and improving transmission stability.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.24-29
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• 2012

In this study, the numerical simulation has been performed to investigate the hydrodynamic evaluation between double plate steel rudder and newly designed foil type rudder for small fishing boat. The simulations are carried out in 2 speed ranges with 7 variations of flow's angle of attack which is at intervals of about 5 degree respectively. As the well-known commercial code, FLUENT and CATIA are used as the solver. The simulation results show that new designed foil type rudder is better than conventional double plate rudder in terms of Lift and Drag of running boat in the water.

• Tribology and Lubricants
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• v.23 no.4
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• pp.162-169
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• 2007

This paper deals with friction effects on the performance of double-bumped AFBs. The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. The double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. A static and dynamic performance analysis is carried out by using the finite difference method and the perturbation technique. The results of the performance analysis for a double-bumped AFB are compared with those obtained for a single-bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single-bumped AFB in a heavily loaded condition.

• Journal of Ocean Engineering and Technology
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• v.33 no.2
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• pp.189-195
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• 2019

In this study, experiments with a floater using flapping foils were performed to develop a new station keeping system that can maintain its position in waves without mooring lines. The foils applied to this system generate thrust using wave energy. In this experiment, the motion of the floater was analyzed in three different wave periods. Sixteen foils were attached to the cylindrical floater. The thrust of each foil was controlled by changing its azimuth angle, and three cases were compared. Based on the previous data, we made more precise measurements and found an optimal model for stationkeeping under each wave condition. We verified the potential of this new stationkeeping system using flapping foils, and conclusions were drawn from the results.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.371-371
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• 1999

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.7
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• pp.842-851
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• 2007

Oscillating foil propulsion, the engineering application of fish-like movement of a hydrofoil, has received in recent decades as a possible competitor for propellers. The oscillating foil produces an effective angle of attack, resulting in a normal force vector with thrust and lift components, and it can be expected to be a new highly effective propulsion system. We have explored propulsion hydrodynamics as a concept in wake flow pattern. The present study has been examined various conditions such as oscillating frequencies and amplitudes in NACA0010 profile. Flow visualizations showed that high thrust was associated with the generation of moderately strong vortices, which subsequently combine with trailing-edge vorticity leading to the formation of a reverse $K\acute{a}rm\acute{a}n$ vortex street. Vortex generation was inherent to jet production and playeda fundamental role in the wake dynamics. And it was shown that the strong thrust coefficient obtained as the Strouhal number was larger.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.231-238
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• 2001

Electrocatalytic activity of palladium for hydrogen oxidation and reduction was studied using AC impedance method. The system under study was arranged in electrolytic mode consisting of Pd electrode under study, Pt counter electrode and Nafion electrolyte between them. Two types of Pd electrodes were used - carbon-supported Pd (Pd/C) and Pd foil electrode. Pd/C anode contacting pure hydrogen showed a steady decrease of charge transfer resistance with the increase of anodic overpotential, which is an opposite trend to that found with Pd foil anode. But Pd foil cathode also exhibited a decrease of the resistance with the increase of cathodic overpotential. The relationship between imposition of overpotential and subsequent change of the charge transfer resistance is determined by the ratio of the rate of faradaic process to the rate of mass transportation; if mass transfer limitation holds, increase of overpotential accompanies the increase of charge transfer resistance. Regardless of the physical type of Pd electrode, the anode contacting hydrogen/oxygen gas mixture did not reveal any independent arc originated from local anodic oxygen reduction.

• International Journal of Fluid Machinery and Systems
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• v.8 no.1
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• pp.23-35
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• 2015

This paper presents the rotordynamic performance measurement of oil-free turbocharger (TC) supported on gas foil bearings (GFBs) for 2 liter class diesel vehicles and comparison to floating ring bearings (FRBs). Oil-free TC was designed and developed via the rotordynamic analyses using dynamic force coefficients from GFB analyses. The rotordynamics and performance of the oil-free TC was measured up to 85 krpm while being driven by a diesel vehicle engine, and compared to a commercial oil-lubricated TC supported on FRBs. The test results showed that the GFBs increased the rotor speed by ~ 20% at engine speeds of 1,500 rpm and 1,750 rpm, yielding the reduction of turbine input energy by more than 400 W. Incidentally, an external shock test on the oil-free TC casing was conducted at the rotor speed of 60 krpm, and showed a good capability of vibration damping due to the well-known dry friction mechanism of the GFBs.