• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.168-174
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• 2016

A conductive oxide-based sapphire glass indium tin oxide/metal electrode and the optical coating, through patterning process was studied in excellent optical properties and integrated touch panel has a high strength. Indium tin oxide conductive oxides of the sapphire glass to 0.3 A at DC magnetron sputtering method of 10 min, gas flow Ar 10 Sccm Ar, $O_2$ 1.0 Sccm the formation conditions of the thin film after annealing at $550^{\circ}C$ for 30min was achieved through a 86% transmittance. In addition, the coating 130 nm hollow silica sol-gel was to improve the optical transmittance of the indium tin oxide to 91%. For the measurement by the modeling hollow silica sol by Macleod simulation and calculated the average values of silica part to the presence or absence in analogy to actual. Refractive index value and the actual value of the material on the simulation the transmittance difference is it does not completely match the air region similar to the actual value (transmission) could be confirmed that the measurement is set to a value of between 5 nm and 10 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.420-420
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• 2013

We investigated oxygen plasma effect on defect states near the interface of AlGaN/GaN High Electron Mobility Transistor (HEMT) structure grown on a silicon substrate. After the plasma treatment, electrical properties were evaluated using a frequency dependant Capacitance-Voltage (C-V) and a temperature dependant C-V measurements, and a deep level transient spectroscopy (DLTS) method to study the change of defect densities. In the depth profile resulted from the temperature dependant C-V, a sudden decrease in the carrier concentration for two-dimensional electron gas (2DEG) nearby 250 K was observed. In C-V measurement, the interface states were improved in case of the oxygen-plasma treated samples, whereas the interface was degraded in case of the nitrogen-plasma treated sample. In the DLTS measurement, it was observed the two kinds of defects well known in AlGaN/GaN structure grown on sapphire substrate, which have the activation energies of 0.15 eV, 0.25 eV below the conduction band. We speculate that this defect state in AlGaN/GaN on the silicon substrate is caused from the decrease in 2DEG's carrier concentrations. We compared the various DLTS signals with filling pulse times to identify the characteristics of the newly found defect. In the filling pulse time range under the 80 us, the activation energies changed as the potential barrier model. On the other hand, in the filling pulse time range above the 80 us, the activation energies changed as the extended potential model. Therefore, we suggest that the found defect in the AlGaN/GaN/Si structure could be the extended defect related with AlGa/N/GaN interface states.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2
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• pp.89-94
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• 1997

A new type SO$_2$ gas sensor with a particular inorganic thin film on SAW devices was developed. The sensor consisted of twin SAW oscillators of the center frequency of 54 MHz fabricated on the LiTaO$_3$ piezoelectric single crystal. One delay line of the sensor was coated with a CdS thin film that selectively adsorbed and desorbed SO$_2$, while the other was uncoated for use as a stable reference. Deposition of the CdS thin film was carried out by the spray pyrolysis method using an ultrasonic nozzle. The sensor could measure the concentration in air less than 0.25 parts per million of SO$_2$. Stability of the sensor turned out to be as good as less than 20ppm, recovery time after each measurement was as short as 5 minutes. Repeatability of the measurement was confirmed through so many reiterated experiments. Hence, the SAW sensor developed through this work showed promising performance as a microsensing tool of SO$_2$. Further work required to improve the performance of the sensor includes enhancement of the reactivity of the CdS thin film with SO$_2$ through appropriate dopant addition, an increase of the center frequency of the SAW device.

• Environmental Analysis Health and Toxicology
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• v.17 no.3
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• pp.197-205
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• 2002

Volatile organic compounds (VOCs) are an important public health problem throughout the world. Many important questions remain to be addressed in assessing exposure to these compounds. Because they are ubiquitous and highly volatile, special techniques must be applied in the analytical determination of VOCs. Personal exposure measurements are needed to evaluate the relationship between microenvironmental concentrations and actual exposures. It is also important to investigate exposure frequency, duration, and intensity, as well as personal exposure characteristics. In addition to air monitoring, biological monitoring may contribute significantly to risk assessment by allowing estimation of absorbed doses, rather than just the external exposure concentrations, which are evaluated by environmental and personal monitoring. This study was conducted to establish the analytic procedure of VOCs in air, blood, urine and exhaled breath and to evaluate the relationships among these environmental media. The subjects of this study were selected because they are occupationally exposed to high levels of VOCs. Environmental, personal, blood, urine and exhalation samples were collected. Purge ＆ trap, thermal desorber, gas chromatography and mass selective detector were used to analyze the collected samples. Analytical procedures were validated with the“break through test”, 'quot;recovery test for storage and transportation”,“method detection limit test”and“inter-laboratory QA/QC study”. Assessment of halogenated compounds indicted that they were significantly correlated to each other (p value < 0.01). In a similar manner, aromatic compounds were also correlated, except in urine sample. Linear regression was used to evaluate the relationships between personal exposures and environmental concentrations. These relationships for aromatic and halogenated are as follows: Halogen $s_{personal}$ = 3.875+0.068Halogen $s_{environmet}$, ($R^2$= .930) Aromatic $s_{personal}$ = 34217.757-31.266Aromatic $s_{environmet}$, ($R^2$= .821) Multiple regression was used to evaluate the relationship between exposures and various exposure deter-minants including, gender, duration of employment, and smoking history. The results of the regression model-ins for halogens in blood and aromatics in urine are as follows: Halogen $s_{blood}$ = 8.181+0.246Halogen $s_{personal}$+3.975Gender ($R^2$= .925), Aromatic $s_{urine}$ = 249.565+0.135Aromatic $s_{personal}$ -5.651 D.S ($R^2$ = .735), In conclusion, we have established analytic procedures for VOC measurement in biological and environmental samples and have presented data demonstrating relationships between VOCs levels in biological media and environmental samples. Abbreviation GC/MS, Gas Chromatography/Mass Spectrometer; VOCs, Volatile Organic Compounds; OVM, Organic Vapor Monitor; TO, Toxic Organicsapor Monitor; TO, Toxic Organics.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.674-680
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• 2014

Monitoring systems of informations for ship performance have become important gradually for economical management of existing ship. Monitoring of NOx emission from marine diesel engines is one of them. The measurement of NOx emission, however has been many difficulties due to technical and costly problems. A monitoring by prediction method of NOx on-board ship according to sailing condition of ship could be an useful method. In this paper, it is discussed about modified method of one-zone model which has been utilized usually for analyzing the combustion process. The modified method is able to calculate the temperature of burned region from the result by one-zone model. Influences which excess air ratio during combustion process affected for the gas temperature and NOx emission were investigated. From the results variation of excess air ratio during combustion process could be estimated inversely through the comparison with measurement of NOx emission.

• Preventive Nutrition and Food Science
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• v.10 no.1
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• pp.40-45
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• 2005

Age-related changes in bone metabolism are well established by biochemical markers of bone matrix in serum and urine, but analysis of the residual bone matrix, which is still turning over, has not been investigated. In the present study, we measured in vivo rates of bone protein synthesis using a precursor-product method based on the exchange of ²H from ²H₂O into amino acids. Four percent ²H₂O was administered to mice in drinking water after intraperitonial (i.p) bolus injection of 99.9% ²H₂O. Mice were divided into the two groups: growing young mice were administered 4% ²H₂O for 12 weeks after an i.p bolus injection at 5 week of age, whereas weight stable adult mice started drinking 4% ²H₂O 8 weeks later than the growing group and continued 4% ²H₂O drinking for 8 weeks. Mass isotopomer abundance in alanine from bone protein was analyzed by gas chromatography/mass spectrometry. Body ²H₂O enrichments were in the range of 1.88-2.41% over the labeling period. The fractional synthesis rates (ks) of bone protein were 2.000±0.071%/d for growing mice and 0.243±0.014%/d for adult mice. These results demonstrate that the bone protein synthesis rate decreases with age and present direct evidence of age-related changes in bone protein synthesis.

• Journal of Ship and Ocean Technology
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• v.6 no.4
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• pp.1-12
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• 2002

A control system for an automated line heating process is developed by use of object-oriented methodology. The main function of the control system is to provide real-time heating information to technicians or automated machines. The information includes heating location, torch speed, heating order, and others. The system development is achieved by following the five steps in the object-oriented procedure. First, requirements are specified and corresponding objects are determined. Then, the analysis, design, and implementation of the proposed system are sequentially carried out. The system consists of six subsystems, or modules. These are (1) the inference module with an artificial neural network algorithm, (2) the analysis module with the Finite Element Method and kinematics analysis, (3) the data access module to store and retrieve the forming information, (4) the communication module, (5) the display module, and (6) the measurement module. The system is useful, irrespective of the heating sources, i.e. flame/gas, laser, or high frequency induction heating. A newly developed automated line heating machine is connected to the proposed system. Experiments and discussions follow.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.114.1-114.1
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• 2010

A highly performed Pd-based hydrogen membrane has prepared successfully on a modified porous nickel support. The porous nickel support modified by impregnation method of $Al(NO_3)_3{\cdot}9H_2O$ (Aldrich Co.) over the nickel powder showed a strong resistance to hydrogen embrittlement and thermal stability. Plasma surface modification treatment was introduced as a pre-treatment process instead of conventional HCl wet activation. Ceramic barrier was coated on the external surface of the prepared nickel supports to prevent intermetallic diffusion and to enhance the affinity between the support and membrane. Palladium and copper were deposited at thicknesses of $4\mu}m$ and $0.5{\mu}m$, respectively, on a barrier-coated support by DC sputtering process. The permeation measurement was performed in pure hydrogen at $400^{\circ}C$. The single gas permeation of our membrane was two times higher than that of the previous membrane which do not have ceramic barrier.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.1
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• pp.13-25
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• 2014

In the current study, a drug-eluting stent coated with biodegradable polymers and sirolimus was developed by using an ultrasonic nanocoater and characterized in aspects of surface smoothness and coating thickness. In addition, in vitro release profiles of sirolimus by changing top coating layer with different biodegradable polymers were investigated. Smooth surfaces with variable thickness could be fabricated by optimizing polymer concentration, flow rate, nozzle-tip distance, gas pressure, various solvents and ultrasonic power. Smooth surface could be generated by using volatile solvents (acetone, chloroform, and methylene chloride) or post-treating with solvent vapor. Coating thickness could be controlled by varying injection volume or polymer concentration, and higher concentration could reduce the coating time while obtaining the same thickness. The thickness measurement was the most effectively performed by a conventional cutting method among three different methods that were investigated in this study. Release profiles of sirolimus were effectively controlled by changing polymers for top layer. PLGA made the release rate 3 times faster than PDLLA and PLLA and all top layers prevented burst release at the initial phase of profiles. Our results will provide useful and informative knowledge for developing drug-eluting stents, especially coated with biodegradable polymers.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.181.2-181.2
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• 2015

Sputtering is one of the most popular physical deposition methods due to their versatility and reproducibility. Synthesis of Cr thin films by DC magnetron sputtering using glancing angle deposition (GLAD) has been reported. Chromium thin films have been prepared at two different working pressure($2.0{\times}10-2$, 30, $3.3{\times}10-3torr$) on Si-wafer substrate using magnetron sputtering with glancing angle deposition (GLAD) technique. The thickness of Cr thin films on the substrate was adjusted about 1 mm. The electrical property was measured by four-point probe method. For the measurement of density in the films, an X-ray reflectivity (XRR) was carried out. The sheet resistance and column angle increased with the increase of glancing angle. However, nanohardness and density of Cr thin films decreased as the glancing angle increased. The measured density for the Cr thin films decreased from 6.1 to 3.8 g/cc as the glancing angle increased from $0^{\circ}$ to $90^{\circ}$ degree. The low density of Cr thin films is resulted from the isolated columnar structure of samples. The evolution of the isolated columnar structure was enhanced at the conditions of low sputter pressure and high glancing angle. This GLAD technique can be potentially applied to the synthesis of thin films requiring porous and uniform coating such as thin film catalysts or gas sensors.