• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.539-542
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• 2002

The role of disk clamp is to fasten disks to motor and to prevent the slip of disks during operation. This paper examined the effects of the design parameters of disk clamp - thickness, contact radius and cross-sectional shape -on the clamping force and circumferential stress distribution of disk. The large stress variation in circumferential direction results in large disk waveness and will increase repeatable run-out (RRO) finally. The disk clamp-disk-disk spacer system is modeled and the FE analysis is performed by ANSYS. The disk clamp with large contact radius shows more uniform stress distribution than the one with small contact radius and the stiffness variation around circumferential direct ion or the addition of the bending sect ion can make stress distribution uniform.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.4
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• pp.397-405
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• 2008

The position accuracy is primarily dependent on the satellite position and signal delay caused by several elements. To know the effect of the delay on the estimated positions, we simulated GPS raw data (RINEX) with GPS errors using Bernese ver5.0. GPS errors used in this paper are Ionospheric delay, Cycle slip, Troposphere, DOP and Random error. If the baseline is short, the position error according to TEC is not large, since the ionospheric delay effect can be removed by ion-free combination. However, if the baseline is long, 3 dimensional position error up to 10cm is occurred. The 3D position error of coordinates with cycle slip is hardly ever changed up to 60% of cycle slip. Because the simulated cycle slips are equally distributed on satellites, the positioning was not seriously affected by the cycle slip. Also, if percentage of cycle slip is 60%, three dimensional error is sharply increased over 1m. The position error is calculated by using the observation data (2 hours) which was selected by DOP less than 3. And its accuracy is more improved about $3{\sim}4cm$.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2053-2060
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• 2005

The unsteady Couette flow of an electrically conducting, V1SCOUS, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.355-363
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• 1998

The oxygen flux of SDC ($Sm_2O_3\;doped\;CeO_2$) solid electrolyte membranes with electronic and oxygen ion-ic conductivities has been investigated as a basic research in order to develop the conversion process of na-tural gas to syngas using the ceramic membrane reactor. Tube type membranes(1 mm thickness) were fa-bricated by slip casting of SDC powders prepared by the oxalate coprecipitaion method. Dense oxygen per-meation membranes(0.1 mm thickness) could be synthesized via sintering at $1450^{\circ}C$ for 2h and their re-lative density was over 95% The oxygen flux through SDC membranes doped 20mol% $Sm_15$ was about $1.13{\times}10^{-5}\;mol/m_2{\cdot}sec$ at low temperature around $800^{\circ}C$. In addition the SDC membranes showed a good thermaal stability for a long period of service.

• Journal of Powder Materials
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• v.16 no.2
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• pp.138-145
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• 2009

The combination of focused ion beam (FIB) and 4 point probe nanomanipulator could make various nano manufacturing and electrical measurements possible. In this study, we manufactured individual ZnO nanowire devices and measured those electrical properties. In addition, tensile experiments of metallic Au and Pd nanowires was performed by the same directional alignment of two nanomanipulators and a nanowire. It was confirmed from I-V curves that Ohmic contact is formed between electrodes and nanomanipulators, which is able to directly measure the electrical properties of a nanowire itself. In the mechanical tensile test, Au and Pd nanowires showed a totally different fracture behavior except the realignment from <110> to <002>. The deformation until the fracture was governed by twin for Au and by slip for Pd nanowires, respectively. The crystallographic relationship and fracture mechanism was discussed by TEM observations.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.853-859
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• 2001

The dispersion stability of nano $Y_2O_3-CeO_2$ system was investigated using colloid surface chemistry. Green body of $Y_2O_3$ doped $CeO_2$ was prepared by slip casting in and aqueous system. The dispersion stability of suspension between powders and organic additive was accomplished through electrokinetic behavior of suspension, which was done by ESA apparatus. The dynamic mobility of particles was enhanced when the anionic dispersant of the amount of 1wt% was added. The dissolution of $Y^{3+}$ ion in suspension occurred in the acidic region so that pH value in slurries did not move to below 7.0. In the $CeO_2-Y_2O_3$ system, optimal preparation of suspension was made after adding the anionic dispersant as the amount of 1wt% and pH value of 11.0, and then slip-cast and sintered at 1400$^{\circ}$C, 2 hrs. It appeared relative density of >98% and homogeneous distribution of Y element in depth direction as well as in the microstructure of surface.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.437-445
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• 2016

This paper discussed the effect of ammonia concentration adsorbed on fly ash for the ammonia emission as AAFA (Ammonia Adsorbed Fly Ash) produced from coal fired plants due to operation of NOx reduction technologies was landfilled with distilled or sea water at closed and open systems, respectively. Ammonia bisulfate and sulfates adsorbed on fly ash is highly water soluble. The pH of ammonium bisulfate and sulfate solution had significant effect on ammonia odor emission. The effect of temperature on ammonia odor emission from mixture was less than pH, the rate of ammonia emission increased with increased temperature when the pH conditions were kept at constant. Since AAFA increases the pH of solution substantially, $NH_3$ in the ash can release the ammonia order unless it is present at low concentration. $NH_4{^+}$ ion is unstable in fly ash and water mixtures of high pH at open system, which is changed to nitrite or nitrate and then released as ammonia gas. The proper conditions for < 20 ppm of ammonia concentration released from the AAFAs landfilled in ash pond were explored using an open system with sea water. It was therefore proposed that optimal operation to collect AAFA of less than 168 ppm ammonia at the electrostatic precipitator were controlled to ammonia slip with less than 5 ppm at SCR/SNCR installations, and, ammonia odor released from mixture of fly ash of 168 ppm ammonia with sea water under open system has about 20 ppm.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.703-712
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• 2004

A variant of the magnetoplasma jet engine (magjet) is here proposed for airbreathing flight in the hypersonic regime. As shown in Figure 1, the engine consists of two distinct ducts: the high-speed duct, in which power is added electromagnetically to the incoming air by a momentum addition device, and the fuel cell duct in which the flow stagnation temperature is reduced by extracting energy through the use of a magnetoplas-madynamic (MPD) generator. The power generated is then used to accelerate the flow exiting the fuel cells with a fraction bypassed to the high-speed duct. The analysis is performed using a quasi one-dimensional model neglecting the Hall and ion slip effects, and fix-ing the fuel cell efficiency to 0.6. Results obtained show that the specific impulse of the magjet is at least equal to and up to 3 times the one of a turbojet, ram-jet, or scramjet in their respective flight Mach number range. Should the air stagnation temperature in the fuel cell compartment not exceed 5 times the incoming air static temperature, the maximal flight Mach number possible would vary between 6.5 and 15 for a magnitude of the ratio between the Joule heating and the work interaction in the MPD generator varied between 0.25 and 0.01, respectively. Increasing the mass flow rate ratio between the high speed and fuel cell ducts from 0.2 to 20 increases the engine efficiency by as much as 3 times in the lower supersonic range, while resulting in a less than 10% increase for a flight Mach number exceeding 8.

• Membrane Journal
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• v.27 no.2
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• pp.199-204
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• 2017

In this study, a study was carried out for the separation of metal ions in lignin extract discharged from the pulp process. alumina powders were mixed with DMAc (N, N-dimethylacetamide) solvent and PESf (Polyethersulfone) polymer, PVP (polyvinylpyrrolidone) dispersant was added and slip casting method was used to prepare the membrane. The membrane was measured for pore size through a CFP (Capillary Flow Porometer) device and the surface and cross-section of the membrane were observed through a FE-SEM (Field Emission Scanning Electron Microscope). The flux was calculated by measuring the filtered weight per hour using a separation experiment device. Pore size measurements were performed under increasing pressure from 0 psi to 30 psi. The pore size of the membrane was $0.4{\mu}m$ and the flux decreased from the initial flux value of $6.36kg{\cdot}m^{-2}{\cdot}h^{-1}$ to $1.98kg{\cdot}m^{-2}{\cdot}h^{-1}$ due to the fouling of the membrane. After the permeation experiment, membrane contaminants were removed by simple washing. Separation experiments showed that Na contained in the initial lignin extract was reduced by 69%, Fe was removed by 87%, K by 95%, Ca by 93% and Mg by 96%.

• Journal of Korean Neurosurgical Society
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• v.51 no.4
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• pp.215-218
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• 2012

Objective: Traumatic epidural hematomas (EDHs) in children are a relatively unusual occurrence. The cause and outcome vary depending on period and reg ion of study. The aims of this analysis were to review the cause and outcome of pediatric EDHs nowadays and to discuss outcome-related variables in a large consecutive series of surgically treated EDH in children. Methods: This is a retrospective review of 29 patients with surgically treated EDHs between Jan 2000 and February 2010. Patients' medical records, computed tomographic (Cl) scans, and, if performed, magnetic resonance imaging (MRI) were reviewed to define variables associated with outcome. Variables included in the analysis were age, associated severe intracranial injury, abnormal pupillary response, hematoma thickness, severity of head injury (Glasgow Coma Scale score), parenchymal brain injury, and diffuse axonal injury. Results: The mean (SO) age of the patients was 109 months (0-185 months). Most of the injuries with EDHs occurred in traffic accident (14 cases, 48.2%) and followed by slip down in 6 cases and falls in 6 cases. There were one birth injury and one unknown cause. EDHs in traffic accidents occurred in pedestrians hit by a motor vehicle, 9 cases; motorbike and car accidents, 5 cases and bicycle accidents, 1 case. The locations of hematoma were almost same in both sides (left side in 15 cases). Temporal lobe is the most common site of hematomas (13 cases, 44%). The mean size of the EDHs was 18 mm (range, 5-40 mm). Heterogeneous hematomas in CT scans were 20 cases (67%). Two patients were referred with unilateral or bilateral dilated pupil(s). There was enlargement of EDH in 5 patients (17%). All of them were heterogeneous hematomas in CT scans. Except for 4 patients, all EDHs were associated with skull fracture(s) (87%). There was no case of patient with major organ injury. CT or MRI revealed brain contusion in 5 patients, and diffuse axonal injury in one patient The mortality was zero, and the outcomes were excellent in 26 and good in 2 patients. None of the tested variables were found to have a prognostic relevance. Conclusion: Regardless of the EDH size, the clinical status of the patients, the abnormal pupillary findings, or the cause of injury, the outcome and prognosis of the patients with EDH were excellent.