• Tribology and Lubricants
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• v.21 no.3
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• pp.122-129
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• 2005

The floating ring seal has the ability of minimizing clearance without rubbing phenomenon. However, the seal ring can be unstable due to extremely high lock-up eccentricity ratio arisen from the poor design of height and surface finish of the ring. The exact prediction of the lock-up position of the floating ring is necessary to design the floating ring properly. The governing equations are developed and solved numerically. The test facility for the measurement of the boundary-lubrication-friction coefficient of the ring‘s surface has been established. Based on the results of analysis, the geometric conditions of the floating ring seal are suggested for operating at a low lock-up eccentricity ratio.

• Journal of Conservation Science
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• v.33 no.1
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• pp.43-49
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• 2017

The ancient paper document we chose as a case study for our research is "One Hundred Poets of the Tang Dynasty", which is housed in the Ryukoku University Library. The purpose of this research is to introduce a method to analyze the surface roughness and microstructure at a high resolution. In addition, we attempt to quantitatively measure the surface unevenness of the types and curve structure. We used a tridimensional digital microscopy as a non-contact and a non-destructive method to study ancient cultural paper. The information contained in the paper may be lost in the process of applying strong pressure to clean and lining or press. However, this microscopic measurement method can non-destructively analyze a large amount of data in old printed books. Moreover, it enables observing them directly with reflected light. Therefore, this method may be useful for collecting printed information remaining on the surface of the paper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.546-551
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• 2020

Generally, surface vessels have many compartments for operation and living quarters, and each compartment is an important space for the ship's survivability. During ship construction, a compartment leak test is necessary and is carried out on each vessel. However, the current test method is in doubt when looking at the actual test results. The reason is that only one pressure gauge is used for the measurement to check the air, so an uncomprehended phenomenon is detected during group compartment leak tests. From this point of view, an improved test device and method are needed. In this study, a multi-channel data acquisition device with multiple pressure sensors is proposed to detect each compartment's pressure variation or pressure drop. This test is a more confidential compartment leak test than the current method, and the test device can show real-time pressure detection values of each of the pressure sensors, which are installed in each compartment, including unmanned space.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1049-1058
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• 2023

The flow passing through river-crossing structures such as weirs and low-fall dams is dominated by rapidly varied flow including hydraulic jump. The intense unsteadiness of flow velocity and free surface profile affects the stability of such hydraulic structures. In particular, the steady hydraulic jump generated at high Froude number conditions includes remarkably air entrainment, making the flow characteristics more complicated. In this study, a large-eddy simulation was performed for turbulence effect and the hybrid VoF technique to simulate the steady hydraulic jump at the Froude number of 7.3 and the Reynolds number of 15,700. The results of the numerical simulation showed that the instantaneous maximum pressure and time-average pressure distribution calculated on the bottom surface downstream of the structure could be reasonably well reproduced being in good agreement with the experimental values. However, the instantaneous minimum pressure distribution in the direct downstream of the structure shows the opposite pattern to the target experimental measurement value. However, the numerical simulation performed in this study is considered to reasonably predict the minimum pressure distributions observed in various experiments conducted at similar conditions. The vertical distributions of flow velocity and air concentration computed in the center of the hydraulic jump were found to be in good agreement with the experimental results measured under similar conditions, showing self-similarity. These results show that the large eddy simulation and hybrid VoF techniques applied in this study can reproduce the hydraulic jump with strong air entrainment and the resulting intense free surface and pressure fluctuations at high Froude number conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.950-967
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• 1995

Acoustic holography makes it possible to reconstruct the acoustic field based on the measurement of the pressure distribution on the hologram surface. Because of the merit that one can obtain an entire three-dimensional wave field from the data recorded on a two-dimensional surface, the holographic method has been widely studied. Being an experimental method, holography has an unavoidable error which is generate by sampling in space and frequency domain and finite aperture size. Its magnitude is dependent on the space and frequency domain and finite aperture size. Its magnitude is dependent on the shape of hologram surface, acoustic holography may be classified into four types of holography : rectangular type planeholography, circular type plane holography, cylindrical holography and spherical holography. In this paper, four types of holography are studied by modal summation method. Numerical simulation is performed using a monopole source with varying parameters to find out effects to the estimation error in each holography. Experiments of circular type plane holography and cylindrical holography explain strong relation between the shape of hologram surface and the acoustic field.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.29-37
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• 2000

At present there are many theories as to how various lubricants used in forging perform the role of reducing friction. Little work has been carried out to determine the validity of these theories for solid lubricants. This paper covers the development and preliminary results of the experiments devised to illustrate the movement of graphite at the workpiece/tool interface in the work forging temperature range. The paper describes the results obtained from upsetting of rings between two flat dies for measurement of lubricant thickness and compaction of graphite for density-pressure relationship. These allowed the lubricant to be exposed to forging conditions and by applying the principles of Male's ring test the simple generation of a value fur friction factor could also be determined. The experiments have been undertaken to examine the behavior of lubricant for shot blasted surface and change of surface roughness. A simple computer model of the interface has been constructed characterizing the graphite layer in an attempt to simulate the boundary mechanics.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3805-3810
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• 2013

The surface modification of silica particles (SPs) was systemically conducted by the treatment of 0.1-10 wt % phenylsilanetriol (PST) on the basis of SPs used through two step processes: 1) the PST coating of SPs via evaporation under reduced pressure and 2) their thermal condensation leading to Si-O-Si bond formation via heating at $130^{\circ}C$. The evaluation of the modified SPs was conducted by the simple floating test on water and the measurement of the contact angle (CA) of water droplet on the 2-dimensional layer of modified SPs on slide glass. When PST was used about 2 wt % or above on the basis of SPs (about average size: 50 nm) used, the modified SPs were fully floated on the water and all dispersed into upper organic solvent layer after a shaking with the mixture of the water and benzene, indicating that the modified SPs have hydrophobic properties. The modified SPs were characterized by $^{29}Si$ MAS NMR and physicochemical properties including SEM, TEM, BET, adsorption/desorption isotherms, etc. were measured and compared each other in details. This research demonstrates that the organosilanetriol is a good modifier applicable for the surface modification of inorganic oxide particles using a low amount of modifier on the basis of oxide particles used.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.905-907
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• 2014

The plasma and microwave surface treatments of carbon nanotubes that loaded on plastic substrates were carried out with expecting a change of carbon nanotube dispersion by increasing treatment time. The microwave treatment process was undergone by commercial microwave oven (800 W). The electrical property was measured by hall measurement and resistance was increased by increasing $O_2$ flow rate of plasma, suggesting an improvement of carbon nanotube dispersion and a possibility of controlling the resistances of carbon nanotubes by plasma surface treatment. The resistance was increased in both polyethylene terephthalate and polyimide substrates by increasing $O_2$ flow rate. Resistance changes only slightly with different $O_2$ flow treatment in measure rho for all polyimide samples. Sheet resistance is lowest in polyimide substrate not due to high carbon nanotube loading but due to tendency to remain in elongated structure. $O_2$ or $N_2$ plasma treatments on both polyethylene terephthalate and polyimide substrates lead to increase in sheet resistance.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.339-344
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics in wavy ducts of primary surface heat exchanger. Experiments using a naphthalene technique are carried out to determine the local transfer characteristics for flow in the corrugated wall duct. The aspect ratios of the rectangular duct cross-section are 7.3, 4.7 and 1.8 with a corrugation angle of $145^{\circ}$. The Reynolds numbers, based on the duct hydraulic diameter, are ranged from 1000 to 5000. The local heat/mass transfer measurement is conducted in the spanwise directions. The results show that Tayler-Gortler vortices exist on the pressure surface. Flow separation on the suction surface appears at a high Reynolds number resulting in a sharp decrease in the local transfer rates, but relatively high transfer rates are obtained in the reattachment region.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1352-1353
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• 2008

In this study, aluminium - doped zinc oxide (ZnO:Al) transparent conducting film was deposited on PET(polyethylen terephthalate) substrate by r.f. magnetron sputtering method. PET substrate was surface-treated in an atmospheric pressure DBD(dielectric barrier discharge) plasma to increase deposition rate and to improve electrical propesties. Morphological changes by DBD plasma were obsered using contact angle measurement. The contact angle of water on PET was reduced from 62$^{\circ}$ to 42$^{\circ}$ by DBD plasma surface treatment. The plasma treatment also increased deposition rate and electrical propesties. The electrical resistivity as low as $4.97{\times}10^{-3}[{\Omega}-cm]$ and the deposition rate of 234[${\AA}$-m/min] were obtained in ZnO:Al film with surface treatment time of 5min, and 20min., respectively.