• Transactions of the Korean hydrogen and new energy society
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• v.24 no.4
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• pp.302-310
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• 2013

As an initial step to develop a liquid hydrogen pump of piston type operated under cryogenic and high pressure, leakage and piston head shape for the piston pump were discussed with temperature and pressure. As the results, the leakage depended on correlation among density, viscosity, clearance area by the low temperature. In order to reduce the leakage, it was found that the air-tightness can be improved by minimizing contact surface between piston and cylinder, and also increasing pressure in-cylinder can reduce piston clearance. Among the proposed piston shapes, D type piston shape had the most air-tightness. D type piston had smaller contact surface than other piston shape and easier expansion of cup shape by pressure. The leakage of D type piston shape was found about 7%, compared with A type piston shape. But it was required that analyze about vapor lock by friction and wear resistance.

• Journal of the Korean Society of Costume
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• v.57 no.6 s.115
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• pp.112-121
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• 2007

Gamtu was a name recorded in Korean in respect of 'Mo(帽), Moja(帽子), Somoja(小帽子), Jeongmoja(頂帽子), Jeonmo(氈帽), Yangmomo(羊毛帽), Tangjeon(宕巾)' from the beginning to the end of Joseon dynasty which includes various shapes and uses according to wordbook. Also, Gamtu has various phonetic transcriptions, however Manchu pronunciation of 'Moja(帽子)' is indicated as 'Kamtoo' in $\ulcorner$Dongmunyuhae(同文類解)$\lrcorner$ so the origin of the word Gamtu should be discussed. Accordingly, I want to clearly define the concept of Gamtu in this research by studying the history and shape of Gamtu, and Chinese entries annotated in Korean as Gamtu. Even though we can assume that the etymology of Gamtu is Manchu language as Manchu pronunciation of 'Moja(帽子)' is indicated as 'Kamtu' in $\ulcorner$Dongmunyuhae(同文類解)$\lrcorner$, I think the Korean pronunciation of Gamtu already existed because there already was a Chinese transcription of 'Gamtu' in the Goryeosa(高麗史). So, we can conjecture that Gamtu could be originated from Yeojin language which is the same lineage of Manchu. As a conclusion, Somoja(小帽子), Jeongmoja(頂帽子), Moja(帽子), Jeonmo(氈帽), Yangmomo(羊毛帽), Tangjeon(宕巾) had a common feature that they were produced to fit head without visor, and were annotated as Gamtu per woolen cloth was used as Jeonmo(氈帽), Yangmomo(羊毛帽), and Gamtu was just a Korean transcription that includes these names.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.46-50
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• 2012

A high-speed centrifugal pump requires more attention to the control of its axial thrust due to the high discharge pressure than a conventional industrial pump. Vanes employed toward the rear cavity of the impeller can be an effective device to control the axial thrust of the pump. The vanes disturb circumferential flow of the cavity and it can modify the axial force acting on the impeller. In this paper, three types of vanes are installed in the high-speed centrifugal pump for liquid rocket engines and the thrust of the pump is measured with an additional thrust measurement unit. According to the results, shapes of cavity vanes have effects on the axial thrust of the pump. As the height of vanes increases, the outlet pressure of the rear floating ring seal decreases which results in a decrease of the thrust. On the other hand, head of the pump is almost same regardless of cavity vanes. Also, the pressure drop of the bypass pipeline increases when vanes are removed.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.280-283
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• 1997

Human cervical spine has to protect the neural components and vascular structures. Also, it must have the flexibility afforded by an extensive range of motion to integrate the head with the body and environment. Because of these two-sided features, human cervical spine has very complicated shapes and their injury mechanisms are not fully understood yet. We have developed analytical model of human CS by using the finite element method. The model has been verified with in vivo and in vitro experimental results. From the qualitative analysis of simulation results, we were able to explain some of the fundamental mechanisms of neck pain. Further more, this FE model of human CS can be used as an analytical tool or biomechanical design of the clinical device and safety restraints.

• Korean Journal of Bronchoesophagology
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• v.17 no.1
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• pp.40-45
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• 2011

Background and Objectives Detailed information about the impacted esophageal foreign body is essential for safe extraction. Three dimensional reconstruction technique was applied to know shape, size and location of the simulative foreign bodies of stone, hyoid bone and endotracheal tube. Materials and Methods Submandibular gland stone, hyoid bone and endotracheal tube were used to simulate impacted foreign bodies. Axial CT, multi-planar reconstruction, volume of interest and virtual camera of Rapidia software were used to get information about the simulative foreign bodies from CT data. Shape and size were compared with the real materials. Exact locations were measured in appropriate modes of Rapidia. Results Shapes of the simulative foreign bodies matched well with the real materials. Size and location could be measured in various modes with some variable results. Conclusion 3D technique can be applied to get information about the simulative foreign bodies. This technique could be applied to the impacted esophageal foreign body.

• Transactions of Materials Processing
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• v.11 no.8
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• pp.668-675
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• 2002

The circles deform into various shape during deformation, the major and minor axes of which indicate the direction of the major and minor principal strains. Likewise, the measured dimensions are used to determine the major and minor principal strain magnitudes. This circular grid technique of measuring strains can be used to diagnose the causes of necking and fracture in industrial practice and to investigate whether these defects were caused by material property variation, changes in lubrication, of incorrect press settings. In non-axisymmetric deep drawing, three modes of forming regimes are found: draw, stretch, plane strain. The stretch mode for non-axisymmetric deep drawing could be defined when the major and minor strains are positive. The draw mode could be defined when the major strain is positive and minor strain is negative, and plane strain mode could be defined when the major strain is positive and minor strain is zero. Through experiments the draw mode was shown on the wall and flange are one of a drawn cup, while the plane strain and the stretch mode were on the punch head and the punch corner area respectively, We observed that the punch load of elliptical deep drawing was decreased according to increase of die corner radius and the thickness deformation of minor side was more large than major side.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.15-22
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• 2014

As the risk of the various external risk was increased, a study on the integrity assessment of the nuclear transport cask was needed. In this paper, an integrity assessment of the nuclear transport cask under the ballistic impact was studied. The projectile with L/D = 5 was used in simulation. The applied head shapes of the projectile were five types such as flat shape, conical shape, hemispherical shape, truncated conical and sliced flat shape, respectively. The range on the velocity of the projectile was 85 m/s to 680 m/s. The cask body of the nuclear transport cask was not penetrated by the projectile speed up to Vprojectile = 510 m/s. As the cask body was penetrated by the all types projectile with Vprojectile = 680 m/s and the cask lead in the nuclear transport cask was collided with the projectile. As the projectile moved to 31.3 mm in the cask lead, the cask lead was not penetrated by the projectile with Vprojectile = 680 m/s. The integrity assessment on the nuclear transport cask under ballistic impact up to Vprojectile = 680 m/s was obtained.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.32-37
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• 2006

The recording density of a hard disk drive(HDD) has been increased so rapidly that the storage capacity of a commercial HDD for the personal computer already reaches several hundred giga-bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize higher recording density. Especially, airflow inside the HDD cavity has been concerned as the rotational speed of the disk increases. Typical problem due to the airflow is the off-track vibration of a head stack assembly(HSA) as the airflow collides with the E-block, suspensions, and sliders, i.e., the flow induced vibration(FIV). This problem is one of the most significant sources of the track mis-registration(TMR) so that it must be resolved. In this study, disk damper shape is modified to minimize the influence of airflow on the HSA. Modified disk dampers, which change the flow field of the inside cavity of a HDD, show good effects not only on the disk vibration but also on the off-track vibration of a HSA. Vibrations of E-block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed with commercial CFD program to verify these effects.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.5
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• pp.246-254
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• 2013

Some characteristics of nitrogen-water slug flow were optically measured, in vertical acrylic tubes of 2, 5 and 8 mm diameter. Bubble velocity, bubble and unit cell lengths were measured, by analyzing the light intensity signals from two sets of dot laser-infrared sensor modules mounted along the transparent tubes. Optical images of the bubbles were also taken and analyzed, to measure bubble shapes and liquid film thickness. It was found that the measured bubble velocities were in good agreement with the empirical models in the literature, except for those measured under high superficial velocity condition in the 2 mm tube. Bubble length was found to be the longest in the 2 mm tube, being 4 to 5 times those of the other tubes. Liquid film was found to have developed early in the 2 mm tube, which made the blunt shape of the bubble head. Liquid film thickness in the 8 mm tube was measured at almost twice those of the other tubes.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.649-655
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• 2006

Waves progressing into the coastal area can be amplified, swashed and overtopped by a wave overtopping control structure, and it converts the kinetic energy of the waves to the potential energy with a hydraulic head above the mean sea level by conserving the overflow in a reservoir. Then the potential energy in the form of hydraulic head can be converted to electric power utilizing extremely low-head hydraulic turbine. This study aims to find the most optimal shape of wave overtopping structure which maximizes overtopping volume rate of sea water. Laboratory experiments for the performance evaluation of wave overtopping control structures were carried out in three dimensional wave tank, and the three dimensional structure models with planar wave concentration shapes(B/b) were manufactured into five classes, which were optimized by cross sectional parameters of the structure, ie, length of ramp(l), gradient of inclined ramp($cot{\phi}$) and freeboard height of the wave overtopping structure($h_e$) proposed by Shin and Hong(2005). The wave overtopping discharges were investigated with 20 incident wave conditions and wave directions of $0^{\circ},\;15^{\circ},\;30^{\circ}$.