• Sleep Medicine and Psychophysiology
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• v.9 no.1
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• pp.34-40
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• 2002

Objectives: The gold standard for diagnosing obstructive sleep apnea syndrome (OSAS) is nocturnal polysomnography (NPSG). This is rather expensive and somewhat inconvenient, however, and consequently simpler and cheaper alternatives to NPSG have been proposed. Oximetry is appealing because of its widespread availability and ease of application. In this study, we have evaluated whether oximetry alone can be used to diagnose or screen OSAS. The diagnostic performance of an analysis algorithm using arterial oxygen saturation ($SaO_2$) base on 'dip index', mean of $SaO_2$, and CT90 (the percentage of time spent at $SaO_2$<90%) was compared with that of NPSG. Methods: Fifty-six patients referred for NPSG to the Division of Sleep Studies at Seoul National University Hospital, were randomly selected. For each patient, NPSG with oximetry was carried out. We obtained three variables from the oximetry data such as the dip index most linearly correlated with respiratory disturbance index (RDI) from NPSG, mean $SaO_2$, and CT90 with diagnosis from NPSG. In each case, sensitivity, specificity and positive and negative predictive values of oximetry data were calculated. Results: Thirty-nine patients out of fifty-six patients were diagnosed as OSAS with NPSG. Mean RDI was 17.5, mean $SaO_2$ was 94.9%, and mean CT90 was 5.1%. The dip index [4%-4sec] was most linearly correlated with RDI (r=0.861). With dip index [4%-4sec]${\geq}2$ as diagnostic criteria, we obtained sensitivity of 0.95, specificity of 0.71, positive predictive value of 0.88, and negative predictive value of 0.86. Using mean $SaO_2{\leq}97%$, we obtained sensitivity of 0.95, specificity of 0.41, positive predictive value of 0.79, and negative predictive value of 0.78. Using $CT90{\geq}5%$, we obtained sensitivity of 0.28, specificity of 1.00, positive predictive value of 1.00, and negative predictive value of 0.38. Conclusions: The dip index [4%-4sec] and mean $SaO_2{\leq}97%$ obtained from nocturnal oximetry data are helpful in diagnosis of OSAS. CT90${\leq}$5% can be also used in excluding OSAS.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.231-236
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• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• Corrosion Science and Technology
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• v.10 no.6
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• pp.199-204
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• 2011

Hot dip metallic coated steels like as galvanized (GI), zinc-aluminium (GL) and aluminium coated steels are mostly used where corrosion resistance is needed. There are two kinds (type 1 and type 2) of aluminium coated steel being commercially used among them. Type 1 aluminium coated steel is coated with an Al-5~11 wt%Si alloy and Type 2 aluminium coated steel consists of commercially pure aluminium. Type 1 Al coated steel is generally used in automotive components and electrical appliances while type 2 aluminium coated steel is mainly used in construction applications such as building cladding panels, air conditioning and ventilation system. In this study, Type 1 aluminium coated steels have tested by accelerated conditions (salt spray or corrosive gas) and outdoor exposure condition in order to understand their corrosion behaviour. Due to the distinct corrosion mechanism of Al which exposes to the severe chloric condition, Salt Spray Test cannot predict the ordinary atmospheric corrosion of Al based coated materials. In addition, the test results and their corrosion feature of Al coated steel sheets will be discussed comparing with other metallic coated steel sheets of GI and GL.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.211-217
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• 2008

A $ZrO_2$ coating solution containing $ZrO_2$ photo-catalysis, which is transparent in visible light, was prepared by the hydrolysis of alkoxide, and thin films on the $SiO_2$ glass substrate were formed in a dipcoating method. These thin films were heat-treated at temperatures ranging from $250^{\circ}C-800^{\circ}C$ and their characteristics were subjected to thermal analysis, XRD, spectrometry, SEM, EDS, contact angle measurement, and AFM. Tetragonal $ZrO_2$ phase was found in the thin film heat treated at $450^{\circ}C$, and anatase $TiO_2$ phase was detected in the thin film heat-treated at $600^{\circ}C$ and above. The thickness of the films was approximately 300 nm, and the roughness was 0.66 nm. Thus, the film properties are excellent. The films are super hydrophilic with a contact angle of $4.0^{\circ}$; moreover, they have self-cleaning effect due to the photo catalytic property of anatase $TiO_2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.365-370
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• 1998

We studied a electrical properties in GaAs/AlGaAs/InGaAs pseudomorphic high electron mobility transistors(PHEMT s) recessed by electron cyclotron resonance(ECR) plasma and wet etching. Using the $NH_4OH$ solution, a nonvolatile AlF$_3$layer formed on AlGaAs surface after selective gate recess is effectively eliminated. Also, we controlled threshold voltage($V_th$) using $H_3PO_4$ etchant. We have fabricated a device with 540 mS/mm maximum transconductance and -0.2 V threshold voltage by using $NH_4OH$ and $H_3PO_4$dip after ECR gate recessing. In a 2-finger GaAs PHEMT with a gate length of 0.2$\mu m$ and width of 100 $\mu m$, a current gain of 15 dB at 10 GHz and a maximum cutoff frequency of 58.9 GHz have been obtained from the measurement of current gain as a function of frequency at 12mA $I_{dss}$ and 2 V souce-drain voltage.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2001-2003
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• 2005

Various organic acid were used in order to prepare new metalorganic deposition solution for high quality $REBa_2Cu_3O_{7-{\delta}}$ (RE=Y, Eu, Gd) films. Prepared fluorine free MO precursor solution was coated on single crystal (001) $LaAlO_3$ (LAO) by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature etc havebeen controlled in order to make high $J_c$ films with a good epitaxial relationship with substrate. 0.5 micron-thick film was obtained by single coating and no crack appeared after calcination. Oxygen partial pressure was varied in the range of $100{\sim}1,000 ppm$ and conversion heat treatment was carried out at the temperature of $725{\sim}765^{\circ}C$. A critical transition temperature $(T_{c0})$ of 90K and a critical transport current density $(J_c)$ of $>0.5MA/cm^2$ (77K and self-field) were demonstrated for the YBCO film on (001) oriented LAO substrates with a thickness of 0.5 micron. $I_c$ was determined by utilizing a transport measurement. SEM and XRD investigations confirmed that films were grown epitaxially onto the LAO single crystal substrate. It is thought that fluorine free new MOD solutionis promising for high quality REBCO films.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.118-123
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• 2015

This work has performed to examine the operation status of regeneration and scrubber system of cold rolling mill plant and established the DIWS(Dip Injection Wet Scrubber) system for the removal of hydrochloric acid with micro bubble. When the initial 22.3 ppm of HCl gas was injected into the system, the average exhaust HCl gas was 0.59 ppm with the removal efficiency of 97.3%. Hydrochloric acid was effectively removed by DIWS system. In the long term monitoring for 10 hours by 5 minutes through TMS(Tele Monitoring System), the average exhaust HCl gas was stably kept 0.69 ppm, which was also verified by manual measurement.

• Korean Journal of Remote Sensing
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• v.37 no.1
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• pp.139-151
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• 2021

By the end of December 2020, an earthquake with Mw about 6.4 hit Sisak-Moslavina County, Croatia. The town of Petrinja was the most affected region with major power outage and many buildings collapsed. The damage also affected neighbor countries such as Bosnia and Herzegovina and Slovenia. As a light of this devastating event, a deformation map due to this earthquake could be generated by using remote sensing imagery from Sentinel-1 SAR data. InSAR could be used as deformation map but still affected with noise factor that could problematize the exact deformation value for further research. Thus in this study, 17 SAR data from Sentinel-1 satellite is used in order to generate the multi-temporal interferometry utilize Stanford Method for Persistent Scatterers (StaMPS). Mean deformation map that has been compensated from error factors such as atmospheric, topographic, temporal, and baseline errors are generated. Okada model then applied to the mean deformation result to generate the modeled earthquake, resulting the deformation is mostly dominated by strike-slip with 3 meter deformation as right lateral strike-slip. The Okada sources are having 11.63 km in length, 2.45 km in width, and 5.46 km in depth with the dip angle are about 84.47° and strike angle are about 142.88° from the north direction. The results from this modeling can be used as learning material to understand the seismic activity in the latest 2020 Petrinja, Croatia Earthquake.

• Corrosion Science and Technology
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• v.21 no.2
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• pp.111-120
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• 2022

To solve the corrosion problem of industrial equipment and other constructions containing metals, corrosion protection can be performed by using coating which provides a barrier between the metal and its environment. Coatings play a significant role in protecting irons and steels in harsh marine and acid environments. This study was conducted to identify an anti-corrosive epoxy coating for carbon steel composite with 0.1, 0.3, and 0.5 wt% concentrations of nanoparticles of SiO₂ using the dip-coating method. The electrochemical behavior was analyzed with open circuit potential (OCP) technics and polarization curves (Tafle) in 3.5 wt% NaCl and 5 vol% H₂SO₄ media. The structure, composition, and morphology were characterized using different analytical techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared spectrum (FT-IR), and Scanning Electron Microscopy (SEM). Results revealed that epoxynano SiO₂ coating demonstrated a lower corrosion rate of 2.51 × 10^-4 mm/year and the efficiency of corrosion protection was as high as 99.77%. The electrochemical measurement showed that the nano-SiO₂ / epoxy coating enhanced the anti-corrosive performance in both NaCl and H₂SO₄ media.

• Corrosion Science and Technology
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• v.23 no.3
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• pp.228-234
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• 2024

Zinc wiping is a phenomenon used to control zinc-coating thickness on steel substrate during hot dip galvanizing by equipment called air knife. Uniformity of zinc coating weight in length and width profile along with surface quality are most critical quality parameters of galvanized steel. Deviation from tolerance level of coating thickness causes issues like overcoating (excess consumption of costly zinc) or undercoating leading to rejections due to non-compliance of customer requirement. Main contributor of deviation from target coating weight is dynamic change in air knives equipment setup when thickness, width, and type of substrate changes. Additionally, cold coating measurement gauge measure coating weight after solidification but are installed down the line from air knife resulting in delayed feedback. This study presents a coating weight control model (Galvantage) predicting critical air knife parameters air pressure, knife distance from strip and line speed for coating control. A reverse engineering approach is adopted to design a predictive, prescriptive, and descriptive model recommending air knife setups that estimate air knife distance and expected coating weight in real time. Implementation of this model eliminates feedback lag experienced due to location of coating gauge and achieving setup without trial-error by operator.