• Transactions of the Korean hydrogen and new energy society
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• v.20 no.2
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• pp.87-94
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• 2009

There are several types of compressors which are appropriate for hydrogen gas station. Diaphragm type of compressor is the one of them and it satisfies the requirements for that purpose in terms of maintaining gas purity and making high pressure over 700 bar. The objective of this study is to find an optimal design of oil distribution hole configuration. The number of holes is changed maintaining total cross-sectional area of holes. Five cases(1 hole, 4, 8,16 and 24 holes) were studied through Fluid Structure Interaction(FSI) analysis method. Gas and oil pressure, the deflection and stress of the diaphragm were analysed during compression and suction process respectively. There is no specific difference among the cases during compression. An additional deflection due to the existence of hole was found during suction for all case. But the highest deflection and stress were found in the 1 hole case. It was seen that 60% decrease of stress in magnitude in 24 hole case compare to the 1 hole case.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Journal of Convergence for Information Technology
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• v.11 no.2
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• pp.10-15
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• 2021

In this paper, we formed perovskite (CH3NH3PbI3) thin films on glass with wet coating methods, and used various analytical techniques to discuss film thickness, surface roughness, crystallinity, composition, and optical property. The coated semiconductor material has no defects and is uniform, the surface roughness value is very small, and a high absorption rate has been observed in the visible light area. Next, in order to implement the hole shape in the organic-inorganic layer, Samples in the order of a metal mask with holes at regular intervals, a glass coated with a perovskite material, and a magnet were etched with atmospheric pressure plasma equipment. The shape of the hole formed in the perovskite material was analyzed by changing the time. It can be seen that more etching is performed as the time increases. The sample with the longest processing time was examined in more detail, and it was classified into 7 regions by the difference according to the location of the plasma.

• Journal of Sensor Science and Technology
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• v.32 no.5
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• pp.328-333
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• 2023

This study experimentally verified the etch rate of the SiO₂ sacrificial layer etching process with a single etch hole using vapor-phase hydrogen fluoride (VHF) etching. To fabricate small-sized polysilicon etch holes, both circular and triangular pattern masks were employed. Etch holes were fabricated in the polysilicon thin film on the SiO₂ sacrificial layer, and VHF etching was performed to release the polysilicon thin film. The lateral etch rate was measured for varying etch hole sizes and sacrificial layer thicknesses. Based on the measured results, we obtained an approximate equation for the etch rate as a function of the etch hole size and sacrificial layer thickness. The etch rates obtained in this study can be utilized to minimize structural damage caused by incomplete or excessive etching in sacrificial layer processes. In addition, the results of this study provide insights for optimizing sacrificial layer etching and properly designing the size and spacing of the etch holes. In the future, further research will be conducted to explore the formation of structures using chemical vapor deposition (CVD) processes to simultaneously seal etch hole and prevent adhesion owing to polysilicon film vibration.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.208-214
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• 1995

In order to study on the penetrations of HF solution acording to the geometrical shrinkage of contact-hole pattern size, the wet etch characteristics for oxide in microchannel patterns was investigated. Microchannel patterns of LPCVD oxide surrounded by nitride film, with dimensions of 0.1~1$\mu\textrm{m}$ height and 0.1~20$\mu\textrm{m}$, width, were fabricated. And the etch rates of oxide in HF solution were observed. It was found that oxide etch rate for micro-channel patterns in HF was not affected by pattern sizes and initial aspect ratios up to $0.1 \times 0.1 \mu \textrm{m}^{2} size and 1.2$\mu\textrm{m}$ depth. Finally, it was concluded that there were no special limitations for penetrations of HF solution in wet processes according to the geometrical shrinkage of contact-hole pattern size.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.254-257
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• 2017

As a part of the development of aircraft gas turbines, combustion performance tests have been conducted in the single combustor sector. The effects of change in the amount of air supplied to the main combustion zone to the performance of the combustor, such as a pollutant emission, a liner temperature distribution and an exit temperature patterns, were studied. Emissions of CO and NOx increased with the main air-ratio and exit temperature pattern was improved. When changing the pattern of the dilution holes, it was shown that the temperature patterns on the exit plane of the combustor and the surface of liner changed depending on the main flame structure and mixing with diluent air. These observations will be applied to combustor liner designs to improve combustor durability and emissions reduction performance.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1085-1088
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• 2001

The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.7
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• pp.1004-1014
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• 2000

The purpose of this study was to develop a well-fitting bodice basic pattern for high school irk. Two bodice patterns were first made based on the most recent existing drafting methods and sensory evaluation was done on the patterns by the present researchers Two high school girls possessing standard physical condition tried and evaluated the functionality of the garments made by the two bodice patterns. Based on the results of the evaluation, a new bodice basic pattern was developed. The new bodice basic pattern was drafted by long measurement method. The dimensions of new bodice basic pattern were as follows. Bust circumference=B/2+4cm, Arms hole depth=C.B/2+1.5cm, Back width=B/6+4cm, Front width=B/6+3cm, Back neck width=B/12+0.5cm, Back neck depth=Back neck width/3cm, Front neck width=B/12cm, Front neck depth=B/12+0.5cm. The sensory and functional evaluations were also conducted for the new bodice basic pattern and the two patterns drafted by the existing methods. The new bodice basic pattern showed better fit both visually and functionally than the existing patterns. SPSS package including means, standard deviation and one-sample T-test were used for data analysis.

• Journal of the Korea Fashion and Costume Design Association
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• v.13 no.1
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• pp.59-71
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• 2011

As an exaggerated-shoulder becomes a growing trend women's clothing, the crescent shaped sleeve with parallel style lines in the arm hole is a highly used women's sleeve pattern. This study develops and provides an applicable method for making the crescent shaped power shoulder sleeve. An efficient basic method for making the 2 piece crescent shaped sleeve was developed and the sensory appearance test was carried out with experimental clothes. There are two principles for making the crescent shaped sleeve: having a style line in the sleeve and pasting part of the cut arm hole of the bodice to the sleeve. The latter would be more convenient for a 2 piece sleeve, mostly used for jackets. The crescent shaped sleeve used in power shoulder jackets should set the shoulder angle as you wish to extend and raise the shoulder point of the bodice and sleeve to the same height. For a stronger power shoulder image, a 3 piece sleeve has a better appearance. Also, the height of the shoulder has to be enhanced with a shoulder pad for a more stable sleeve.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.53-61
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• 1993

One of the most interesting and promising steel groups considered for the rocket motor case, aircraft and aerospace component is the maraging(martensitic plus aging) nickel steel, developed by International Nickel Company in 1960. This material attains a very high strength with good fracture toughness by simple heat treatments which do not involve a quenching. Full strength can be obtained by "maraging" at 480.deg. for 3 hours for the 18% Ni maraging steel. The effect of heat treatments was considered on the residual stress field of 18% Ni maraging steel weldments. In experiments, various heat treatments such as stress relieve heat treatment, aging and solution heat treatment were carried out of the GTA weldments and the residual stresses were measured by using the hole drilling method. Whereas the conventional pattern of residual stress shows the stresses to be maximum along the weld centerline with tensile stress extending into the heat affected zone, the pattern in maraging steels shows the centerline stress to be compressive. After welding, a series of aging, solution heat treatment and solution heat treatment plus aging treatment were carried out and the residual stresses were measured to reveal that these heat treatments almost completely remove the welding residual stresses.