• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.547-553
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• 1989

Last several stages of high capacity fossil power steam turbine and most stages of nuclear power steam turbine operate on wet steam. As a consequence, the flows in those cascades are accompanied by condensation, and the latent heat caused by condensation affects an oblique shock wave being generated at the vicinity of trailing of the blade. In the case of expanding of moist air through a suction type indraft wind tunnel, the effect of condensation affection the oblique shock wave generated by placing the small wedge into the supersonic part of the nozzle was investigated experimentally. In these connections, the relationship between condensation zone and reflection point of the incident oblique shock wave, angle between wedge bottom wall and oblique shock wave, and the variations of angles of incident and reflected shock waves due to the variation of initial stagnation relative humidity are discussed. Furthermore, the relationship between initial stagnation relative humidity and load working on the nozzle wall, obtained by measuring static pressure at the nozzle centerline, is discussed.

• Journal of radiological science and technology
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• v.45 no.5
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• pp.423-431
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• 2022

The purpose of this study is to present objective information in applying 3D printing technology for PET/CT (Positron Emission Tomography/Computed Tomography) performance evaluation and use it as a basic research that can be applied to various purposes in the future. Phantoms were manufactured with step wedge of ABS(Acrylonitrile Butadiene Styrene) and ACR(Acrylic acid) material. The counts for each ROI(Region of Interest) were analyzed through image acquisition in PET/CT. And the variation rate of counts and CNR(Contrast Noise Ratio) was evaluated. In the counts analysis, the effect of thickness occurred. In addition, in the variation rate analysis, the thickness setting of steps wedge 4 to 5 levels should be considered first. These results minimize quantitative and qualitative changes in the phantom manufactured based on 3D printing, and enable more stable PET/CT performance evaluation. Based on 3D printing in PET/CT, various phantoms are expected to be produced in the future. If the characteristics of each material are considered and applied through the basic research such as this research, the result of the phantom manufactured through 3D printing can be more meaningful and will be used in a wide range.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.289-295
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• 2017

The aim of this study was to evaluate the dose comparison using Radon phantom with 5 mm and 10 mm tissue equivalent materials, FIF, Wedge(15, 30 angle) and IMRT, to reduce the skin dose of the contralateral breast during breast cancer radiation therapy(Total dose: 50.4Gy). The dose was measured for each treatment plan by attaching to the 8 point of the contralateral breast of the treated region using a optical-stimulated luminance dosimeter(OSLD) as a comparative dose evaluation method. Of the OSLD used in the study, 10 were used with reproducibility within 3%. As a result, the average reduction rates of 5 mm and 10 mm in the FIF treatment plan were 37.23 cGy and 41.77 cGy, respectively, and the average reduction rates in the treatment plan using Wedge $15^{\circ}$ were 70.69 cGy and 87.57 cGy, respectively. The IMRT showed a reduction of 67.37 cGy and 83.17 cGy, respectively. The results of using bolus showed that as the thickness of the bolus increased in all treatments, the dose reduction increased. We concluded that mastectomy as well as general radiotherapy for breast cancer would be very effective for patients who are more likely to be exposed to scattered radiation due to a more demanding or complex treatment plan.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.99-105
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• 2001

Flow computations have been conducted to study the impingement flowfield over the KSR-III flume deflector To validate Euler solver for the jet impingement flowfieid, the jet flow over a double wedge deflector have been calculated and showed reasonable agreement with experimental data. The transient flow behavior of flume over deflector have been investigated and the flume from the rocket nozzle proved to be getting out of the deflector safely and the thermal effect on the base region of rocket was not considerable.

• Tribology and Lubricants
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• v.8 no.1
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• pp.30-37
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• 1992

The displacement and pressure field of liquid crystals are analyzed numerically and compared with classical Reynolds theory. A plane slider bearing is employed as a simple example considering elasticity, permeability and splay effect which are the inherent characteristics of layered liquid crystals. Due to the geometric constraint of thin wedge and the strong anchoring behavior of the liquid crystals dislocations are inevitable. A finite element method is used to solve five coupled nonlinear equations. The load characteristics based on the pressure distribution along the gap shows that the liquid crystals can carry large load compared to the conventional lubricants.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.576.2-576
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• 2001

The purpose of this study was to evaluate the effect of dentinal sclerosis and tubular orientation on Class V restoration bonded with three dentin bonding agents using confocal laser scanning microscope(CLSM). Class V cavities were prepared from freshly extracted caries-free human teeth. thirty of these cavities were divided into two groups based upon the status of class V cavities: Group 1, cervical abrasive lesions without preparation; Group 2, artificially-prepared wedge-shaped cavities.(omitted)

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1467-1470
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• 2008

An upper tibial opening wedge osteotomy is an operation to cure a malalignment and a degenerate arthritis. To prevent the postoperative malalignment caused by the upper tibial opening wedge osteotomy, the research to define the relationship between a Hinge Axis Angle and a Posterior Slope Angle is needed. The effect of the relationship between the hinge axis angle and the gap angle on the posterior slope angle is studied. After 3-D Compute Tomography (CT) scanning image is reconstructed, the virtual surgery is performed by the reconstructed 3-D tibia model. It was proved that the relationship between the hinge axis angle and the gap angle were constant and the simple mathematical model could be derived. To verify the suggested mathematical model, it compared with the measured data from the virtual surgery. In conclusion, while the deviation between the data from the virtual surgery and ones of the mathematical model under the gap angle<$10^{\circ}$ was less than 1%.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.304-304
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• 2011

We investigated the effect of different spin direction of anti-ferromagnetic layer on the magnetic properties of ferromagnetic layer in Fe-NiO and Fe-CoO bi-layer systems. For Fe-NiO system, we prepared the clean MgO(001) surface half-covered with 20 nm Ag films as a substrate for magnetic layers. Then we grew NiO wedge layers on the substrate, and added 8 monolayer(ML) Fe layers on the wedge layer. We examined magnetic properties of the bi-layer system using the surface magnetic optical Kerr effect(SMOKE) and X-ray magnetic linear dichroism(XMLD). From SMOKE measurement we observed the coercivity enhancement due to the set-up of anti-ferromagnetic order of NiO films in both of the Fe/NiO/MgO(001) and Fe/NiO/Ag/MgO(001) system. The most remarkable results in our observation is that the coercivity enhancement of Fe/NiO/Ag/MgO(001) is much larger than that of Fe/NiO/MgO(001). XMLD experiments confirmed the out-of-plane spin direction of NiO layers in Fe/NiO/MgO(001) and in-plane spin-direction of NiO layers in Fe/NiO/Ag/MgO(001), and we concluded that the origin of large enhancement of coercivity is due to the strong parallel coupling between Fe layers and NiO layers. We also confirmed that this strong parallel coupling maintained across the thin Ag layer inserted between Fe and NiO layers. For Fe-CoO system, we prepared Fe/CoO/Ag(001) and Fe/CoO/MnO(001) systems and observed much larger coercivity enhancement in Fe/CoO/Ag(001).

• Tribology and Lubricants
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• v.39 no.3
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• pp.87-93
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• 2023

Nanofluids are dispersions of particles smaller than 100 nm (nanoparticles) in base fluids. They exhibit high thermal conductivity and are mainly applied in cooling applications. Nanolubricants use nanoparticles in base oils as lubricant additives, and have recently started gathering increased attention owing to their potential to improve the tribological and thermal performances of various machinery. Nanolubricants reduce friction and wear, mainly by the action of nanoparticles; however, only a few studies have considered the rheological properties of lubricants. In this study, we adopt a parallel slider bearing model that does not generate geometrical wedge effects, and conduct thermohydrodynamic (THD) analyses to evaluate the effect of higher thermal conductivity and viscosity, which are the main rheological properties of nanolubricants, on the lubrication performances. We use a commercial computational fluid dynamics code, FLUENT, to numerically analyze the continuity, Navier-Stokes, energy equations with temperature-viscosity-density relations, and thermal conductivity and viscosity models of the nanolubricant. The results show the temperature and pressure distributions, load-carrying capacity (LCC), and friction force for three film-temperature boundary conditions (FTBCs). The effects of the higher thermal conductivity and viscosity of the nanolubricant on the LCC and friction force differ significantly, according to the FTBC. The thermal conductivity increases with temperature, improving the cooling performance, reducing LCC, and slightly increasing the friction. The increase in viscosity increases both the LCC and friction. The analysis method in this study can be applied to develop nanolubricants that can improve the tribological and cooling performances of various equipment; however, additional research is required on this topic.

• Korea-Australia Rheology Journal
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• v.18 no.3
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• pp.121-126
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• 2006

A carbonyl iron-based magneto-rheological suspension was compressed in the direction of the applied magnetic field and the change in rheological properties was measured. It was found that the compression did not have a large effect on the magneto-rheological response, which is in contrast to recent reports in the literature describing an almost order of magnitude increase in the shear yield stress. The difference can be attributed to the latter test's use of a sliding wedge apparatus which imparts considerable shearing to the sample during the compression.