• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.115-119
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• 2009

I think this will be valuable reference for assuring consistency and homogeneity of clarity and managing dental radiation equipment by experimentation of dental radiation equipment permanent which based on KS C IEC 61223-3-4 standard and KS C IEC 61223-2-7. Put a dental radiation generator and experiment equipment as source and film(sensor) length within 30 em, place the step-wedge above the film(sensor). Tie up tube voltage 60 kVp, tube current 7 mA and then get an each image through CCD sensor and film by changing the exposure time as 0.12sec, 0.25sec, 0.4sec. Repeat the test 5times as a same method. Measure the concentration of each stage of film image, which gained by experiment, using photometer. And the image that gained by CCD sensor, analyze the pixel value's change by using image J, which is analyzing image program provided by NIH(National Institutes of Health). In case of film, while 0.12sec and 0.25sec show regular rising pattern of density gap as exposure time's increase, 0.4sec shows low rather than 0.12sec and 0.25sec. In case of CCD sensor density test, the result shows opposite pattern of film. This makes me think that pixels of CCD's sensor can have 0~255 value but it becomes saturation if the value is over 255. The way that getting clear reception during decreasing human's exposed radiation is one of maintaining an equipment as a best condition. So we should keeping a dental radiation equipment's condition steadily through cyclic permanent test after factor examination. Even digital equipment doesn't maintain a permanent, it can maintain a clarity by post processing of image so that hard to set it as standard of permanent test. Therefore it would be more increase the accuracy that compare a film as standard image. Thus I consider it will be an important measurement to care for dental radiation equipment and warrant homogeneity, consistency of dental image's clarity through comparing pattern which is the result from factor test against cyclic permanent test.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.22-27
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• 2000

Amorphous FeCoSiB films with high saturation magnetostriction and excellent soft magnetic properties have been studied to evaluate their strain sensitivity. Films were subjected to a strain by bending of their substrates, which caused a change in the magnetic anisotropy of films via magnetoelastic coupling. Films were exhibited a figure of merit $F=({\Delta}{\mu}/{\mu})/{\varepsilon}$ (change in film permeability $\mu$ per unit strain $\varepsilon$) of $1.2{\times}10^5$, which is comparable with that of amorphous ribbons. To make a study of application of magnetostrictive films as strain sensor elements, we have prepared a micro-patterned film by means of the photolithography and ion milling processes. Impedance change in the patterned films, when strain was applied, was measured over the frequency range from 1 MHz to 1 GHz. Reflecting a large value of figure of merit F, a variation of 46% impedance of films was shown at 100 MHz frequency when a strain of $300{\times}10^{-6}$ was applied.

• Tuberculosis and Respiratory Diseases
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• v.59 no.4
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• pp.432-435
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• 2005

An 82-year-old female non-smoker with a history of hypertension presented with increasing dyspnea, cough and some purulent sputum without fever. Upon admission, the patient was in a distressed condition. Auscultation revealed diminished breath sounds with no rales over the right lung. An examination of the heart revealed a regular rhythm and a systolic murmur radiating from the apex of the heart. There was no pitting edema in the lower extremities. The blood tests showed mild leukocytosis and an increased C-reactive protein level. The $O_2$ saturation was 98 % whilst breathing room air. The electrocardiogram demonstrated sinus tachycardia. The chest radiograph showed a moderate cardiomegaly, right lobe infiltrates, and blunting of the both costophrenic sulcus suggesting a small pleural effusion. Three days after admission, the symptoms became slightly aggravated despite being treated with empirical antibiotics for presumed community-acquired pneumonia. Transthoracic color Doppler echocardiography indicated an ejection fraction of 48 %, mild left ventricular enlargement, and moderate left atrial enlargement resulting in severe mitral regurgitation. The clinical symptoms and right pulmonary edema resolved quickly with intravenous furosemide treatment.

• Journal of Aquaculture
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• v.16 no.1
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• pp.15-23
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• 2003

We have investigated water quality of the coastal saline groundwaters utilized for fish farms in Jeju Island. The water quality investigation included the spatial observations for 75 fish farms during March-May, 1994 and the hi-monthly observations for both coastal saline groundwaters and seawaters at four fish farms from August 1994 to December 1995. Water temperature of the saline groundwaters ranged from 16 to 18$^{\circ}C$ over the study period. Salinity of the saline groundwaters varied between 20.60 ppt and 34.02 ppt, slightly lower than that of the coastal seawaters(26.47~34.53 ppt). This salinity variation must be associated with local precipitation conditions in Jeju Island. The oxygen saturation for most saline groundwater samples was lower than 80%, ranging from 24.7 to 89.8%. The COD and pH values for the saline groundwaters were similar to those for the coastal seawaters. The concentrations of DIP for the saline groundwaters varied between 0.021 mg/L and 0.121 mg/ L, and seasonal variation of DIP in the saline groundwater ranged from 0.014 to 0.077 mg/L, which were higher than that of the coastal seawaters(0.000~0.015 mg/L). Nitrate in the saline groundwaters accounted for more than 90% of the DIM. The maximum concentrations of ammonia, nitrite, nitrate and DIN in the saline groundwaters were 0.085, 0.012, 2.294 and 2.309 mg/L, respectively. These concentrations of the saline groundwaters were considerably lower than those affected culture organisms. Overall, the saline groundwaters utilized for fish farms in Jeju Island appear to maintain good waterquality for fish farms.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.1
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• pp.96-103
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• 2014

A liquefied natural gas(LNG) in cryogenic liquid is converted back into gaseous form for distribution to residential and industrial consumers. In this re-gasification process, LNG supplies a plenty of cold thermal energy about $83.7{\times}10^4kJ/kg$. The LNG cold thermal energy is utilized for the re-liquefaction process of cryogenic fluids such as Nitrogen, Hydrogen and Helium, and ice manufacturing process and air-conditioning system in some advanced countries. Therefore, it is also necessary to establish the recovery systems of the LNG cold thermal energy around Incheon, Pyungtaek and Tongyung LNG import terminals in our country. Methane is used as working fluid in this paper, which is the major component of LNG over 85 % by volume, in order to investigate the flow behavior characteristics of LNG with phase change at low heat flux. This paper presents the effects of pipe diameters, pipe inclinations and saturation pressures on the flow boundaries of methane flowing in a cryogenic heat exchanger tube, together with those of nitrogen, propane, R11 and R134a. The outcomes obtained from this theoretical researches are also compared with previous experimental data. It was also found that the effect of pipe inclination on the methane flow boundaries was significant.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1777-1783
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• 2014

In this paper, we designed and fabricated a high-speed semiconductor sensor for use in power control devices and analyzed the characteristics with pulsed radiation tests. At first, radiation sensitive circular Si PIN diodes with various diameters(0.1 mm ~5.0 mm) were designed and fabricated using Si epitaxial wafer, which has a $42{\mu}m$ thick intrinsic layer. The reverse leakage current of the diode with a radius of 2 mm at a reverse bias of 30 V was about 20.4 nA. To investigate the characteristic responses of the developed diodes, the pulsed gamma-radiation tests were performed with the intensity of 4.88E8 rad(Si)/sec. From the test results showing that the output currents and the rising speeds have a linear relationship with the area of the sensors, we decided that the optimal condition took place at a 2 mm diameter. Next, for the selected 2 mm diodes, dose rate tests with a range of 2.47E8 rad(Si)/sec to 6.21E8 rad(Si)/sec were performed. From the results, which showed linear characteristics with the radiation intensity, a large amount of photocurrent over 60mA, and a high speed response under 350ns without saturation, we can conclude that the our developed PIN diode can be a good candidate for the sensor of power control devices.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.300-304
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• 2006

The varied heating temperatures were used for magnetic core materials, which nano sized ${\alpha}-Fe$ crystalline was created in nanocrystalline Fe-Si-B-Nb-Cu materials, with hish permeability and low power loss. The highest permeability and lowest power loss were obtained to the specimen heat-treated at $510^{\circ}C$. The signal transmission characteristics of inductive coupler, which was manufactured by using the magnetic core materials prepared in this study, at low frequency range, was influenced strongly by magnetic property of magnetic core materials as this result is corresponding to the permeability as a function of heat treatment temperature, as well, it was improved by impedance matching at high frequency range. Over $500{\mu}m$ of air gap in coupler is required to maintain the magnetic properties without magnetic saturation on the subterranean line transferred hish current of 300 A. The inductive coupler for PLC, which has an attenuation characteristics of less than 5dB, was manufactured using nano-crystalline magnetic core materials through the above mentioned research results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.19-26
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• 2017

Concrete is a construction material with porous media and corroded steel inside affects negatively to durability and structural safety. This study aims a derivation of quantitative relationship between measured HCP (Half Cell Potential) and corrosion amount considering cover depth and W/C (water to cement) ratio. For the work, cement mortar specimens with 3 different W/C ratios and 4 different cover depths are prepared, HCPs are measured with 3 different corrosion level. HCP measurement significantly increases in the saturated condition and linear relationship is observed between corrosion level and acceleration period. With increasing corrosion level and W/C ratio, and decreasing cover depth, HCP measurement increases. Considering total corrosion level and HCP measurements, relatively low COV(Coefficient of Variation) of 0.67 is evaluated through multi-linear regression analysis, however higher COVs over 0.90 can be obtained considering level of HCP measurement. In the room condition, corrosion level can be evaluated through measured HCP in the given conditions of cover depth, W/C ratio. diameter of steel inside.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.39-43
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• 1994

Polycrystalline nonstoichiometric bismuth-substituted yttrium iron garnet films with cation ratios of Bi:Y:Fe=1.5+u:1.5:5 and Bi:Y:Fe=1.5:1.5+v:5, where $-0.7{\leq}u{\leq}1.0$ and $-0.7{\leq}v{\leq}1.3$, have been prepared by pyrolysis. The crystal phases formed in these films at various temperatures have been analyzed by high power x-ray diffractometry (XRD). The saturation ma- gnetization, the Curie temperatures, and the Faraday rotation at the wavelength of 633 nm have been measured as a function of u and v. The XRD studies indicated that the bismuth and yttrium depleted (u < 0 and v < 0) films consisted of the mixed phases of garnet and impunity. While in the bismuth and ytrium overdosed films, no impurity lines were observed over a wide composition range of $0{\leq}u{\leq}0.5$ and $0{\leq}v{\leq}0.7$. The observed magnetic and magneto-optic data of these overdosed films, however, could only be reasonably explained by assuming the presence of samll amount of spurious phases, not detectable by the XRD.

• Resources Recycling
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• v.28 no.3
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• pp.45-52
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• 2019

$TiO_2$ as a raw material for producing titanium can be produced by carbon reduction of natural ilmenite ores over 1823 K and acid leaching of the obtained titanium-rich slag. However, the conventional process can cause very high energy consumption and a large amount of leaching residues. In the present study, we proposed the sulfurization of $FeTiO_3$ with $Na_2SO_4$ at temperatures below 1573 K, which can separate Fe in $FeTiO_3$ as the FeS based sulfide phase and Ti as the $TiO_2-Na_2O$ based oxide phase. This study is a fundamental study for sulfurization of $FeTiO_3$ to investigate the influence of reducing atmosphere, reaction temperature and the sulfur/Fe ratio on the separability and distribution behaviors of of Fe, Ti, and Na between the oxide phase and the sulfurized phase. At 1573 K and carbon saturation condition, the Fe can be separated from $FeTiO_3$ as Fe-C-S metal and a part of FeS, and the concentration of Fe in oxide decreased to 4 mass% after sulfurization.