• The Journal of Engineering Research
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• v.1 no.1
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• pp.5-14
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• 1997

The purpose of thesis is to analyze the radiation characteristics of an offset gregorian antenna in order to design the satellite-loaded antenna. In order to compute the radiation pattern of the sub-reflector, the reflected wave is obtained by GO(Geometric Optics) at an arbitrary shaped sub-reflector. Then the total radiation EM wave is obtained by summing the diffracted fields obtained by UTD(Uniform Geometrical Theory of Diffraction) and the GO fields. In order to calculate the far field radiation pattern of the main reflector, the radiation integral equation is derived from the induced current density on reflector surface using PO(Physical Optics). The kernel is expanded in terms of Jacobi-Bessel series for increasing the computational efficiency, then the modified radiation integral is represented as the double integral equation independent of observation points. When the incident fields are assumed to be x-or y-polarized field, the characteristics of radiation patterns in the gregorian antenna is analyzed in case of the main reflector having the focal length of 62.4$\lambda$, diameter of 100$\lambda$, and offset height of 75$\lambda$, and the sub-reflector having the eccentricity of 0.501, the inter focal length og 32.8$\lambda$, the horn axis angle of $9^{\circ}$ and the half aperture angle of $15.89^{\circ}$. The cross-polarized level and side lobe level in the offset geogorian reflector are reduced by 30dB and 10dB, respectively, in comparison with those of the offset parabolic antenna.

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.124-132
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• 2008

effect of some furfural hydrazone derivatives (I -V) as corrosion inhibitors for C-steel in 3M H3PO4 solution in which M indicates mol/l has been studied using weight-loss and galvanostatic polarization techniques. A significant decrease in the corrosion rate of C-steel was observed in the presence of the investigated compounds. This study revealed that, the inhibition efficiency increases with increasing the inhibitor concentration, and the addition of iodide and thiocynate ions enhances it to a considerable extent. The effect of temperature on the corrosion behavior of C-steel was studied in the range from 30-60oC with and without 510-6 M investigated compounds using weight-loss method. Apparent activation corrosion energy (Ea*) and other thermodynamic parameters for the corrosion process were calculated and discussed. The polarization measurements show that the investigated compounds act as mixed-type inhibitors, but the cathode is more polarized when an external current was applied. The adsorption of these compounds on the surface of C-steel in 3M H3PO4 obeys Frumkins adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the investigated compounds.

• Safety and Health at Work
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• v.8 no.3
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• pp.318-321
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• 2017

This commentary presents the regulatory backgrounds and development of the national proficiency testing (PT) scheme on asbestos analysis in the Republic of Korea. Since 2009, under the amended Occupational Safety and Health Act, the survey of asbestos in buildings and clearance test of asbestos removal works have been mandated to be carried out by the laboratories designated by the Ministry of Employment and Labor (MOEL) in the Republic of Korea. To assess the performance of asbestos laboratories, a PT scheme on asbestos analysis was launched by the Korea Occupational Safety and Health Agency (KOSHA) on behalf of the MOEL in 2007. Participating laboratories are evaluated once a year for fiber counting and bulk asbestos analysis by phase contrast microscopy and polarized light microscopy, respectively. Currently, the number of laboratory enrollments is > 200, and the percentage of passed laboratories is > 90. The current status and several significant changes in operation, sample preparations, and statistics of assigning the reference values of the KOSHA PT scheme on asbestos analysis are presented. Critical retrospect based on the experiences of operating the KOSHA PT scheme suggests considerations for developing a new national PT scheme for asbestos analysis.

• Journal of Korean Public Health Nursing
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• v.28 no.3
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• pp.522-535
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• 2014

Purpose: This study was constructed in order to examine factors that influence work-related musculoskeletal disease (WMSD) approvals and current status according to the company size. Method: This is a descriptive study that utilized Industrial Accident Compensation Claim Data. Workplaces with over 35,811 workers derived from the 2012 claim data, which comprised approximately 91.5%, were selected for this study. Then workplaces were divided into three groups according to the number of workers: less than 5, 5~299, and 300 and over. Results: Since 2008, the number of small sized workplaces has increased. The 2012 data showed that 32.5% of workers at small sized workplace had WMSD. However, workplaces with 5~299 workers showed WMSD approval rate of 60%. Of note most WMSD approved workers were employed by manufacturing and construction companies, regardless of the workplace size. Most of them were engaged in elementary tasks. The days of medical treatment at OPD and IPD were most prevalent among workers at the largest workplaces. Conclusions: It is certain from this study that WMSD has been polarized by the company size. More policy attention should be paid to the WMSD status of workers at small sized workplaces which usually do not have their own health office.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.590-593
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• 2010

The processes of supplying propellants into propellant tanks play important roles during launch preparation of satellite launch vehicle. The total weight of launch vehicle greatly depends on the accuracy of filling quantity of propellant during launch preparation. Among propellants used for launch vehicles a cryogenic propellant such as liquid oxygen is widely adapted as an oxidizer for launch vehicles. Such cryogenic propellant usually resides in a propellant tank as two-phase fluid with liquid and gas, which needs an accurate level measurement system to detect the position of propellant surface precisely. In this paper the fabricating process of a level measurement system using capacitance type with three electrodes is analyzed. In addition, the change of electric signal according to the height of liquid is verified by testing the level measurement system under consideration. The results of tests shows as expected the linear trend of voltage according to the change of water height in a tank.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.862-865
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• 2008

Wireless energy supply for an MAV propulsion system using microwave was developed. This system consists of three sub system; the transmitter system, the rectenna system, and the tracking system. In the transmitter system five horn antennas were used as the antenna elements for the phased array system and both the beam divergence and steering angle was about 9deg. Eight rectennas were arrayed in parallel to obtain enough power to drive the electric motor on the MAV(the voltage was 250mV and the current was 6.8mA) in rectenna system. In tracking system two units of antenna system with leaf pattern which received the linearly-polarized wave despite the MAV yaw angle were set in each axis(x, y) for tracking an MAV in a 2-Dimentional space. And three output voltages $V_{com},\;V_1$ and $V_2$ were loaded in the PC to detect if the distance between transmitter and receiver was not constant. Finally when the microwave beam was steered by the phased array system the output voltage from rectenna was measured at 62cm while the MAV circled around above the transmitter system.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3344-3351
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• 2021

The Rare Isotope Science Project was launched in 2011 in Korea toward constructing the Rare isotope Accelerator complex for ON line experiments (RAON). RAON will house several experimental systems, including the Muon Spin Rotation/Relaxation/Resonance (μSR) facility in High Energy Experimental Building B. This facility will use 600-MeV protons with a maximum current of 660 pμA and beam power of 400 kW. The key μSR features will facilitate projects related to condensed-matter and nuclear physics. Typical experiments require a few million surface muons fully spin-polarized opposite to their momentum for application to small samples. Here, we describe the design of a muon transport beam line for delivering the requisite muon numbers and the electromagnetic-component specifications in the μSR facility. We determine the beam-line configuration via beam-optics calculations and the transmission efficiency via single-particle tracking simulations. The electromagnet properties, including fringe field effects, are applied for each component in the calculations. The designed surface-muon beamline is 17.3 m long, consisting of 2 solenoids, 2 dipoles affording 70° deflection, 9 quadrupoles, and a Wien filter to eliminate contaminant positrons. The average incident-muon flux and spin rotation angle are estimated as 5.2 × 10⁶ μ⁺/s and 45°, respectively.

• Food Engineering Progress
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• v.22 no.4
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• pp.353-357
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• 2018

Previous studies have suggested that rice bran oil (RBO), an edible oil from the byproducts of rice milling, has anti-inflammatory effects in inflammation inducing macrophages, known as M1 subsets. Yet the effects of RBO on the counterpart M2 subsets, the "healing" macrophages, were poorly investigated to date. In this regard, recent studies on the molecular/cellular anti-inflammatory mechanisms of dietary components have demonstrated that mitochondrial respiration contributes to macrophage functioning. Therefore, the current study examined whether RBO regulates cytokine secretion by modulating mitochondrial metabolism in wound healing M2 subsets. Palm oil (PO), enriched with medium-chain fatty acids, served as a positive control. C57BL/6 mice were fed a diet containing either corn oil (CO), PO or RBO for 4 weeks, followed by purification of bone marrow-derived macrophages (BMDM) from their tibias and femurs. Cells were further polarized to M2-BMDM, and the expression of M2 marker (CD206) on cellular surfaces were not affected by dietary intervention. In addition, the secretion of anti-inflammatory cytokine (IL-10) in the culture supernatant was not affected by dietary lipids. Oxygen consumption rate, the indicator of mitochondrial respiration in M2-BMDM was not regulated by RBO intervention and PO treatment. Taken together, this study imply that RBO did not intervene both the regulation of inflammatory responses and mitochondrial respiration in M2 macrophages.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.641-646
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• 2023

In this paper, TM(transverse magnetic) scattering problems by a resistive strip grating between a double dielectric layer are analyzed by using the FGMM(fourier galerkin moment method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the resistive boundary condition is applied to analysis of the resistive strip. Overall, as the uniform resistivity of the resistive strip increased, the size of the current density induced in the resistance band decreased, the reflected power decreased, and the transmitted power increased. In addition, As the thickness of the dielectric layer increased, the reflected power increased and the transmitted power relatively decreased. The numerical results of the structure proposed in this paper are shown in good agreement compared to the results of PMM, a numerical analysis method of the existing paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.975-983
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• 2006

This study analyzed bidding data for construction projects ordered by the Public Procurement Service under the lowest bidding system since 2001 by using statistical technique in terms of construction types, company sizes, bidding prices. This study brings out construction company's bidding practices and problems caused by the current lowest bidding system and suggests the way to mitigate the problems and to improve the lowest bidding system. The analysis shows the problem of winning a bid in abnormally low price under the lowest bidding system, feared at the start, was realized. As bidding practice has polarized with low and high price, the analysis shows that the lowest bid system's market has a high possibility to be distorted by construction companies' bid strategies. To complement the lowest bidding system's problem, the analysis shows that introduction of the bidding system using particulars where bidders estimate construction quantities and unit prices by themselves is needed.