• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.449-454
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• 2014

The purpose of this study is(was) to investigate the shielding ratio of 1 mmPb and the off axis ratio outside the field edge at depth of 1 cm from a phantom surface for 6 MV photon beam. A dose of 180 cGy was delivered to a depth of 10 cm for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field in the SAD technique. The off axis ratio was calculated by measuring the dose of optically stimulated luminescent nanoDot dosimeters(OSLnDs) positioned at 2, 4 and 6 cm from the field edge, and the center axis of field. And the shielding ratio of 1 mmPb was calculated by measuring the dose of OSLnDs positioned at 2, 4 and 6 cm from the field edge.. As a result, for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field, the off axis ratios were acquired 0.008-0.023 and 0.011-0.028, respectively. Also the shielding ratios of 1 mmPb were acquired 0.868-0.888 and 0.807-0.842, respectively. These results provide data to protect organs at risk outside the radiation treatment field.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.5
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• pp.542-547
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• 2015

Since the oil price has been significantly jumped for several years, a heavy oil of low quality has been mainly used in the diesel engine of the merchant ship. Thus, a combustion chamber of the engine has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of the combustion chamber has been getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the engine parts such as exhaust valve, piston crown and cylinder head surrounded with combustion chamber are more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these engine parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 625 filler metal were welded with GTAW method in the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected and base metal zones were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. Furthermore, the corrosion current density of the weld metal zone revealed the lowest value, having the highest value of hardness. The corrosive products with red color and local corrosion like as a pitting corrosion were considerably observed at the base metal zone, while these morphologies were not wholly observed in the weld metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogran associated with corrosion resistance property were well in good agreement with each other. Consequently, it is suggested that the mechanical and corrosion characteristics of the piston crown can be predominantly improved by repair welding method using the Inconel 625 electrode.

• The Korean Journal of Food And Nutrition
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• v.22 no.3
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• pp.430-442
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• 2009

This study was designed to investigate the relationship between the dietary intake according to calorie intake from a coffee containing beverage and the bone health status of 189 female collegians. The study was conducted through questionnaires, anthropometric checkup, 3-days food records and ultrasound measurement of calcaneus bone mineral density. Subjects were divided into three groups: students not drinking coffee(non-coffee group, N=56), students consuming <100 kcal daily from coffee(low-calorie coffee group, N=84), and students consuming $\geq100$ kcal of their total daily calories from coffee(high- calorie coffee group, N=49). There were no significant differences in weight, height, body mass index, body fat and calcaneus bone mineral density among the three groups. The low-calorie coffee group usually drank black coffee or instant coffee mix, and the high-calorie coffee group habitually drank coffee with milk or sugar syrup. There were no significant differences in the mean daily energy and food intake among the three groups. However, vitamin $B_2$(p<0.05) and calcium (p<0.01) intake in the high-calorie coffee group were higher than in the non-coffee group. Also, mean intake of sugars, fish and shellfishes, milks and beverages in the high-calorie coffee group were also significantly higher than in non coffee group(p<0.05). There was no significant difference in the Korean Dietary Diversity Score(KDDS) among the three groups. The main calcium source was milk in all three groups, and milk intake(total and included with coffee) was highest in the high-calorie coffee group. Although no significant difference was apparent between the high-calorie and non-coffee groups concerning anthropometric factors and calcaneus bone mineral density, consumption of coffee may have influenced food and nutrient intake. The results suggest that consumption of milk-supplemented coffee may be of nutritional benefit.

• Nuclear Engineering and Technology
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• v.19 no.1
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• pp.22-33
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• 1987

The confirmed integrity of nuclear fuel cladding materials is an important object during steady state and transient operations at nuclear power plant. In this context, the clad material yielding behavior is especially important because of pellet-clad gap expansion. During the steep power excursion, the in-pile irradiation behavior differences between uranium-dioxide fuel pellet and zircaloy clad induce the contact pressure between them. If this pressure reaches the zircaloy clad yield pressure, the zircaloy clad will be plastically deformed. After the reactor power resumed to normal state, this plastic permanent expansion of clad tube give rise to the pellet-clad gap expansion. In this paper, the simple mandrel expansion test method which utilizes thermal expansion difference between copper mandrel and zircaloy tube was adopted to simulate this phenomenon. That is, copper mandrel which has approximately three times of thermal expansion coefficient of zircaloy-4 (PWR fuel cladding material) were used in this experiment at the temperature range from 400C to 700C. The measured plastic expansion of zircaloy outer radius and derived mathematical relations give the yield pressure, yield stress of zircaloy-4 clad at the various clad wall temperatures, the activation energy of zircaloy tube yielding, and pellet-clad gap expansion. The obtained results are in good agreement with previous experimental results. The mathematical analysis and simple test method prove to be a reliable and simple technique to assess the yielding behavior and gap expansion measurement between zircaloy-4 tube and uranium-dioxide fuel pellet under biaxial stress conditions.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.202-211
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• 2001

Luminescence is a physical phenomenon exhibited by many non-conducting, crystalline materials, such as quartz and feldspar. Within the crystals, energy absorbed from ionising radiation frees electrons to move through the crystal lattice and some are trapped at defects in the lattice. Observable luminescence is produced by electrons, released from traps by stimulation by absorption of light, which recombine with lattice defects which act as luminescence centers - optically stimulated luminescence (OSL). In a similar way to thermoluminescence(TL) dating, controlled measurement of the OSL signal can provide a means of determining the time since the last exposure of a layer of sediment to sunlight, the age of the sediment. However, whereas in the thermoluminescence dating of sediment only part of the latent thermoluminescence signal is bleached by sunlight as the sediment is deposited and allowance must be made during the laboratory measurements for the light insensitive component, optically induced luminescence dating has the advantage of working only with light sensitive traps in the crystal. Determination of the time since deposition of Quaternary sediment samples from the OSL of quartz grains using blue light was performed. A series of experiments and recent developments relating OSL dating are described, beginning by identifying the features which make OSL signals suitable for the development of dating method. Additionally, there are suggestions as to future research for obtaining reliable ages and a comment on current best practice on procedures, with the dating results of Quaternary sediment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.272-278
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• 2010

Some recent researches reported that high temperature rising decreases the carbonation depth of concrete, which is contrary to the previous research results. Carbonation has been known as a reaction between calcium hydroxide and carbon dioxide. But a few researches showed that the other cement hydrates as well as calcium hydroxide react with carbon dioxide. This paper investigates the influence of temperature on carbonation and the variation of $Ca(OH)_2$ and $CaCO_3$ by carbonation. In order to estimate the carbonation depth and the quantities of reactant and product of carbonation reaction, phenolphthalein testing and thermagravimetric analyzer test were conducted. The measurement of carbonation depth with temperature showed that the temperature increase from $20^{\circ}C$ to $30^{\circ}C$C in carbonation environment makes the carbonation depth larger, but the increase from $30^{\circ}C$ to $40^{\circ}C$ has a small influence on the carbonation depth. Comparing calcium hydroxide and calcium carbonate with temperature, the quantity of $CaCO_3$ of specimen carbonated at $30^{\circ}C$ is greater than that of specimen carbonated at $40^{\circ}C$ and the quantity of $Ca(OH)_2$ of specimen carbonated at $30^{\circ}C$ is similar to that of specimen carbonated at $40^{\circ}C$. This observation shows that there is the optimum temperature increasing carbonation depth and the optimum temperature is close to $30^{\circ}C$.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.117-126
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• 2005

A stoichiometric mixture of evaporating materials for $AgGaS_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $AgGaS_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $590^{\circ}C\;and\;440^{\circ}C$, respectively The temperature dependence of the energy band gap of the $AgGaS_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.7284 eV-(8.695{\times}10^{-4}eV/K)T^2/T(T+332K)$. After the as-grown $AgGaS_2$, single crystal thin films was annealed in Ag-, S-, and Ga-atmospheres, the origin of point defects of $AgGaS_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10K. The native defects of $V_{Ag},\;V_s,\;Ag_{int},\;and\;S_{int}$, obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted $AgGaS_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $AgGaS_2$ crystal thin films did not form the native defects because Ga in $AgGaS_2$ single crystal thin films existed in the form of stable bonds.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.194-201
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• 2012

Moxibustion is utilized not only to cure disease but also to increase immunity. However, it may lead to undesired effects including severe pains(blisters and burns) because of the difficulty of controlling heat intensity. To overcome these problems we developed the RF heat stimulation system which can control stimulus. Also, we developed the RF stimulation protocol for effective heat transfer in subcutaneous tissue of rabbit. RF stimulator consists of a medical RF capacitive heating device, isolation probe, isolation plate, negative pressure control part and temperature measurement part. For the designed stimulus protocol, we measured the temperature distribution on epidermis and in subcutaneous(5mm, 10mm) area of rabbit during moxibustion. A stimulation protocol was designed by controlling the ON/OFF duty ratio, repeating number, and energy of applied pulse to get the temperature distribution similar with that by moxibustion. In results, the correlation coefficients between temperature distribution by moxibustion and that of stimulator were 95% and 91% from 5mm and 10mm thick respectively. However, temperature distribution on epidermis by stimulator was remarkably lower than that of the moxibustion. Finally, the RF stimulation system showed that it can not only transfer effectively heat similar with moxibustion to the subcutaneous area, but also the influence by unwanted side effects can be minimized.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.5
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• pp.1-7
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• 2007

AZO thin films have been fabricated on quartz substrate with various Al doping concentrations and annealing temperatures by sol-gel method. The bset condition of (002) orientation and smooth surface (rms = 1.082 nm) is obtained for the AZO thin film doped with 1 mol % Al and annealed at 550 $^{\circ}C$. The optical transmittance of AZO thin films is higher than 80 % in the visible region. We observe that the energy band gap extends with increasing the Al doping concentration. This phenomenon is due to the Burstein-Moss effect. Through the measurement of Hall effect, it is observed that the AZO thin film has larger carrier concentration and smaller electrical resistivity than the pure ZnO thin film. However, the AZO thin film shows the decrease of carrier concentration and the increase of resistivity with the increase of Al concentration, that is due to the segregation of Al at grain boundaries. The maximum carrier concentration of $1.80{\times}10^{19}\;cm^{-3}$ and the minimum resistivity of 0.84 ${\Omega}cm$ are obtained for the AZO thin film doped with 1 mol % Al and annealed at 550 $^{\circ}C$.

• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.79-88
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• 2017

In this paper, the wind tunnel test for the measurement of aerodynamic characteristics of transmission conductors with asymmetric sections is described. A single conductor model and bundled conductor models with ice accreted shapes are tested both in steady and turbulent flow, and the aerodynamic coefficients are acquired. Transmission conductor galloping is a kind of wind-induced vibration which is characterized by primarily vertical oscillation with a very low frequency and a high amplitude. It is well known that transmission conductor galloping is generally caused by moderately strong, steady winds when a transmission conductor has an asymmetric cross-section shaped by accreted ice. Galloping should be considered from the design stage of overhead lines because it can cause severe wear and fatigue damage to attachments as well as transmission conductors. It is reported that there have been normally 20 events of galloping per year in Korea, which may be followed by serious consequences in the electric power system. Therefore, this research is performed to measure aerodynamic characteristics of ice accreted transmission conductors to understand and control transmission conductor galloping so that it would help to prevent unexpected failures and reduce the maintenance costs caused by galloping.