• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.990-997
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• 1998

In this work, the $SiO_2$ films on the silicon substrate with different orientations were first prepared by the low temperature process using the ECR plasma diffusion as a function of microwave power and oxidation time. Before and after thermal treatment, the surface morphology, Si/O ratio from physicochemical properties, and the electrical properties of the oxide films were also investigated. The oxidation rate increased with microwave power, while surface morphology showed the nonuniform due to etching. The film quality, therefore, was lowered with increasing the defect by etching and the content of positive oxide ions in the oxide films from bulk by higher self-DC bias. The content of positive oxide ions in the oxide films with different Si orientations showed Si(100) < Si(111) < poly Si. The defects in $Si/SiO_2$ interface of $SiO_2$ film could be decreased by annealing, while $Q_{it}$ and $Q_f$ were independent of thermal treatment and the dependent on concentration of reactive oxide ions and self-DC bias of substrate. At microwave power of 300, and 400 W, the high quality $SiO_2$ film that had lower surface roughness and defect in $Si/SiO_2$ interface was obtained. The value of interface trap density, then, was ${\sim}9{\times}10^{10}cm^{-2}eV^{-1}$.

• Childhood Kidney Diseases
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• v.18 no.2
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• pp.85-91
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• 2014

Purpose: We aimed to investigate the correlation between serum cystatin C and clinical manifestations in pediatric patients with urinary tract infections (UTIs). Methods: We studied 137 patients admitted with UTIs from June 2012 to May 2014. Depending on the presence of renal cortical defects on 99m Tc-dimercaptosuccinic acid scintigraphy, we classified patients into non-renal and renal defect groups. Laboratory and clinical parameters were analyzed, including the levels of serum cystatin C. The correlation between cystatin C and other variables was assessed. Results: Serum cystatin C levels did not differ between the non-renal and renal defect groups. In both groups, serum cystatin C levels increased after 4-5 days of treatment, compared with the level at admission (P<0.001). However, mean levels were within normal ranges. The concentration of serum cystatin C positively correlated with serum creatinine and negatively correlated with age (P <0.05). In contrast, there was no correlation between serum cystatin C and other variables. Conclusion: Serum cystatin C does not appear to be a useful biomarker for renal defects in pediatric patients with UTIs. Further studies are necessary to conclude whether serum cystatin C is helpful in predicting deterioration in renal function in pediatric patients with UTIs.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.347-351
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• 2003

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

• Nuclear Engineering and Technology
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• v.1 no.2
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• pp.91-101
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• 1969

Resistivity changes of n-type float-zone silicon crystals with 6.4$\times$10$^{14}$ to 1.25$\times$10$^{17}$ phosphorus atoms/㎤ due to irradiation by (1) 1 MeV electrons, (2) two types of research reactors, and (3) $Co^{60}$ ${\gamma}$-ray sources were investigated. The results were analyzed on the basis of a simple exponential formula derived by Buehler. While the formula gave a fair fit in the low fluence range in most cases, the deviation was quite appreciable in the case of 1 MeV electron irradiation, and a linear change gave better fit in some cases. The large change in the carrier removal rate in electron-irradiated samples in the high fluence range was analyzed in detail in terms of the Fermi level cross-over of the defect levels. Based on the damage constants evaluated from the initial portion of data where the formula was applicable, the relative effectiveness of various radiation sources in causing the resistivity change in n-type silicon was compared. The TRIGA Mark II reactor neutrons, for example, were found to be about 40 times more effective than 1 MeV electrons. The dependence of the damage constant on the initial carrier concentration was also examined. The physical basis of the exponential law and the effect of the Fermi level cross-over of the defect levels on the resistivity change in the high fluence ranges are discussed.

• Archives of Plastic Surgery
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• v.34 no.5
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• pp.551-556
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• 2007

Purpose: Pseudomonas aeruginosa is an etiologic agent in serious wound infection. Pseudomonas aeruginosa infection is problematic because this organism is resistant to many antimicrobial drugs. The purpose of this study was to compare the bactericidal effect of commonly used topical agents and their effect on wound healing. Methods: Pseudomonas aeruginosa-infected full-thickness skin defect was developed on the mouse to compare 3 commonly used topical agents-Betadine, 2% Gentamicin solution and 0.3% Acetic acid with the control group. Wound size change, bacterial colony counts and histologic findings of each groups were analyzed. Results: The wound size decreased in all treated groups as compared with the control group. However, there was no statistical difference. Gentamicin solution group was showed the lowest bacterial colony count and statistically significant difference compared with the control group(p=0.032). Other treated groups were also effective against Pseudomonas aeruginosa, but not different statistically. Histologic findings revealed that epithelialization, granulation tissue formation and microvessel proliferation were increased and necrosis and inflammation were decreased in all treated groups compared to the control group, but not different statistically. Betadine group significantly increased granulation tissue formation compared to the control group (p= 0.041). Conclusion: There is no universal topical agent that enhances most aspects of wound healing while simultaneously decreasing the bacterial concentration. However, Gentamicin solution may be an optimal topical agent for Pseudomonas aeruginosa infected wound. Further study should experiment on human with Gentamicin solution to confirm a effect on Pseudomonas aeruginosa infected wound for clinical applications.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.128-134
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• 2016

An analysis of the main factors and its degree of impact on power production is performed against the landfill gas power plant in S landfill site. The number of normal operation (50 MWh & 24 hr) days was 70.9% to the total number of operation days from 2007 to 2014, and the percentage of the actual power production was 79.3% of 3,428,400 MW which is the theoretical maximum estimation. The ratio of factors that accounted for the efficiency of power production are: 44.0% of repairing of the defect and regular servicing, 37.4% of cut-down operation due to hydrogen sulfide, and 18.6% of air pre-heater washing, respectively. Yet, considering that the cut-down operation due to hydrogen sulfide was carried out for only two years, the high concentration of hydrogen sulfide was the most influential factors on landfill gas power production. The long-term power production was analyzed as 35.9 MWh in 2018, and the constant drop is anticipated, resulting in 16.6 MWh by 2028, and under 8.4 MWh in 2038.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.292-299
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• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.2
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• pp.101-105
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• 2010

Silicon electrode and ring in a plasma etcher those are in contact with harsh plasma suffer from periodic heating and cooling during their lifetime. This causes the silicon components failure due to thermal stress remaining the persistent slip bands (PSBs) on their surfaces. The factors that determine the lifetime of silicon electrode and ring were discussed with respect to silicon ingot. The impurity level and the average defect concentration measured with glow discharge mass spectrometer (GDMS) and microwave photo-conductance decay (${\mu}$-PCD) were compared with the grade of silicon ingots those are divided to slip-free and slip-allowed ingot. Some silp-allowed samples showed planar defects along <110> direction on {001} surface. The role of these defects was suggested from the viewpoint of the lifetime of silicon components.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.13-17
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• 2004

We have investigated the effect of Hf insertion in the Al oxide tunnel barrier on the properties of magnetic tunnel junctions (MTJs). MTJs with Hf inserted barrier show the higher tunnel magnetoresistance (TMR) ratio and less temperature and bias voltage dependence of TMR than MTJs with a conventional Al$_2$O$_3$ barrier. The enhancement of TMR ratio and the reduction of the temperature and bias voltage dependence might be due to the reduction of defects in the barrier. Al-Hf oxide was formed by depositing Al and Hf simultaneously, and oxidizing the compound films. The TMR ratio of 36% was almost the same value as that with Hf inserted barrier. This implies that the inserted Hf layers mixed with Al layers during deposition or oxidation, and they might form Al Hf oxide barriers. This compound Al Hf oxide formation may be responsible to reduction of defect concentration which enhanced the TMR ratio and reduced temperature and bias-voltage dependence.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.1
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• pp.130-139
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• 2016

The purpose of this paper is to analyze the problems and the sources of defective products and draw improvement plans in a small plastic boat manufacturing process using TOC (Theory Of Constraints) and statistical analysis. TOC is a methodology to present a scheme for optimization of production process by finding the CCR (Capacity Constraints Resource) in the organization or the all production process through the concentration improvement activity. In this paper, we found and reformed constraints and bottlenecks in plastic boat manufacturing process in the target company for less defect ratio and production cost by applying DBR (Drum, Buffer, Rope) scheduling. And we set the threshold values for the critical process variables using statistical analysis. The result can be summarized as follows. First, CCRs in inventory control, material mix, and oven setting were found and solutions were suggested by applying DBR method. Second, the logical thinking process was utilized to find core conflict factors and draw solutions. Third, to specify the solution plan, experiment data were statistically analyzed. Data were collected from the daily journal addressing the details of 96 products such as temperature, humidity, duration and temperature of heating process, rotation speed, duration time of cooling, and the temperature of removal process. Basic statistics and logistic regression analysis were conducted with the defection as the dependent variable. Finally, critical values for major processes were proposed based on the analysis. This paper has a practical importance in contribution to the quality level of the target company through theoretical approach, TOC, and statistical analysis. However, limited number of data might depreciate the significance of the analysis and therefore it will be interesting further research direction to specify the significant manufacturing conditions across different products and processes.