• Membrane Journal
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• v.20 no.1
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• pp.62-68
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• 2010

The powder mixture for fabricating the cermet membranes was prepared by mechanically mixing 60 vol.% vanadium with $Y_2O_3$-stabilized $ZrO_2$ (YSZ). The powder mixture was pressed into disks, which were then sintered in vacuum at $1600^{\circ}C$ for 2 h. As-sintered membrane was dense and mounted to a stainless steel ring with brazing filler. Hydrogen fluxes of V/YSZ membrane have been measured in the range of $200{\sim}350^{\circ}C$ with 100% $H_2$. The crack was formed in the both sides of membrane at $350^{\circ}C$ and pressure of 0.5 bar. During permeation experiment, vanadium of V/YSZ membrane reacted with hydrogen to form $V_2H$ which was the origin of crack formation.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.499-503
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• 2016

Dual fuel engines are suitable for stricter regulations as they significantly decrease exhaust gas output. Hence, research and development of double wall bellows for dual fuel engines is important. In this study, optimum forming methods and welding conditions were derived to develop double wall bellows made of austenite stainless steel. The reliability of the prototypes was ensured by various performance evaluations. In this study, the buckling load and bellows stress were obtained by structural design, buckling, and stress analysis to design optimum bellows. As a result, the buckling load in the embossing shape of bellows increased by approximately 1.6 times, and no buckling and squirming occurred at 30.0 bar, which was twice that of the maximum design pressure.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.331-336
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• 2004

Dissimilar friction welding were produced using 10mm and 11mm diameter solid bar in Inconel ally(IN X-750) to Stainless steel(STS316L) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Virkers hardness surveys of the bond of area and HAZ and macro-structure investigations. The specimens were tested as welded, not heat-treated. The tensile strength of the friction welded steel bars was increased up to $95\%$ of the STS316L base metal under the condition of all heating time. Optimal welding conditions were n=2,000(rpm), $P_1=220(MPa),\;P_2=260(MPa),\;t_1=4(s),\;t_2=4(s)$ when the total upset length is 7(mm).

• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.32-38
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• 2015

PURPOSE. The aim of this study was to compare the durability and retention of 4 types of attachments placed over computer aided design/computer aided manufacturing (CAD/CAM) titanium bars when subjected to different pH conditions. MATERIALS AND METHODS. Four commercially available attachments were investigated: Hader Yellow, Hader Red, Ackerman Gold and Ackerman Stainless Steel. These attachments and Ackerman CAD/CAM titanium bars were placed in 2 vessels containing different artificial saliva solutions (pH 7/pH 4) at $37^{\circ}C$ for one month to simulate corrosion conditions, and they were then subjected to mechanical testing (5400 cycles of insertion and removal). RESULTS. The results revealed that there were significant differences in the average values of insertion/removal force due to the pH (F (1, 24)=9.207, P<.05) and the type of attachment (F (3, 24)=11.742, P<.05). CONCLUSION. More acidic pH values were found to have a negative influence on the retention capacity of the attachments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.903-909
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• 2007

A fatigue capsule is one of the special capsules to investigate the fatigue characteristics of the nuclear materials during an irradiation test in a research reactor, HANARO. In this study, the performance test and the preliminary fatigue test results by using a cyclic load device newly developed for a fatigue capsule are described. In order to obtain the characteristics such as a realization and a controllability of the periodic wave shape and the relationship between the pressure and the load, a spring and rigid bar specimens are used. The fatigue test for the 316L stainless steel specimen with 1.8mm in diameter and 12.5mm in gage length is also performed under the same conditions as the temperature($550^{\circ}C$) of the specimen during irradiation tests. As a result of the test, the fracture of the specimen occurs at a total of 70,120 cycles(about 12 days), and the displacement in this case is 2.02 mm. It is expected that these results will be used for determining test conditions and a comparison of the in-pile fatigue test results.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.336-343
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• 1998

An iteration method has been developed for determining crack growth and fracture resistance cure (J-R curve) from the load versus load-line displacement record only. In this method, the hardening curve, the load versus displacement curve at a given crack length, is assumed to be a power-law function, where the exponent varies with the crack length. The exponent is determined by an iterative calculation method with the assumption that the exponent varies linearly with the load-line displacement. The proposed method was applied to the static J-R tests using compact tension(CT) specimens, a three-point bend (TPB) specimen, and a cracked round bar (CRB) specimen as well as it was applied to the quasi-dynamic J-R tests using CT specimens. The J-R curves determined by the proposed method were compared with those obtained by the conventional testing methodologies. The results showed that the J-R curves could be determined directly by the proposed iteration method with sufficient accuracy in the specimens from SA508, SA533, and SA516 pressure vessel steels and SA312 Type 347 stainless steel.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.296-301
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• 2003

A study on the engineering design and numerical thermo-hydraulic analysis for KSTAR TF coil structure cooling system has been conducted. The numerical analyses have been done to verify the engineering design of cooling using the commercial code, FLUENT and in-house code for calculating helium properties which varies with cooling tube's heat transfer. Through the engineering design process based on the steady heat balance concepts, the circular stainless steel tube with inner diameter of 4 mm for TF coil has been selected as cooling tube. From normal operation mode analysis results, total 28 cooling tubes were finally chosen. Also, three dimensional cool down analysis for TF coil with designed cooling tube was satisfied with next three design criteria. First is cooling work termination within a month, second is maximum temperature difference within 50 K in TF coil structure and third is exit helium pressure above 2 bar. Consequently, these cool down scenario results can afford to adopt as operating scenario data when KSTAR facilities operate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.60-63
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• 2009

Manufacturing technologies of micro spur gear and micro mold by micro PIM were studied with stainless steel feedstock. For molding of gears, micro mold with gear cavity of 1.2 mm in diameter was produced by wire EDM. The proper injection pressure was selected to 70bar by observation and measuring of shapes and shrinkage of gears before/after sintering. For fabrication of micro mold, a tiny polymer gear was produced by injection into the mold. Then, 316L feedstock was again injected/compressed on the polymer gear and debinded together with polymer gear followed by sintering. As a result, another metal mold with gear cavity reduced to about 20% was fabricated and through repetition of this process chain, micro gear mold with cavity about below 800 um was finally obtained. In reduction of size by injection/compression molding, height of gear tooth was shrunk more and the effort for decrease of roughness of micro cavity were carried out ultrasonic polishing and as a result, the roughness in cavity decreased from 3-4 um to about 200 nm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.6
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• pp.67-76
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• 2005

This paper proposes a compact-sized surface myoelectric sensor for the myoelectric hand prosthesis. To fit the surface myoelectric sensor in the socket for the myoelectric hand prosthesis, the sensor should be a compact size. The surface myoelectric sensor is. composed of a skin interface and a single processing circuit that are mounted on a single package. The skin interface has one reference and two input electrodes, and the reference electrode is located in the center of two input electrodes. In this paper we propose two types of sensors with the circle- and bar-shaped reference electrode, but all input electrodes are the bar-shaped. The metal material of the electrodes is the stainless steel (SUS440) that endures sweat and wet conditions. Considering the conduction velocity and the median frequency of the myoelectric signal, we select the inter-electrode distance (IED) between two input electrodes as 18mm, 20mm, and 22 mm. The signal processing circuit consists of a differential amplifier with a band pass filter, a band rejection filter for rejecting 60Hz power-line noise, amplifiers, and a mean absolute value circuit. We evaluate the proposed sensor from the output characteristics according to the IED and the shape of the reference electrode. From the experimental results we show the surface myoelectric sensor with the 18mm IED and the bar-shaped reference electrode is suitable for the myoelectric hand prosthesis.

• Progress in Medical Physics
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• v.13 no.3
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• pp.114-119
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• 2002

A immobilizing device that is essential for correct lung and lens shielding with homogenous dose distribution in fractionated total body irradiation was developed and it's efficiency was evaluated. The main frame was made of stainless steel bar (5 cm in diameter) to withstand up to 230 cm in height and 100 kg in weight to prevent any injury even in unconsciousness condition. The saddle was designed to adjust the body weight and hight of standing patients. Chest and back supporter were made of 1 cm acryl which could fix the lung block and cassette holder. Leather and sponge pedding were used for head rest to keep patients comfortable. The device was strongly fixed by specially designed bolts on the bottom panel which was made of 1 cm stainless steel and 10 cm thick wooden board. Precise manipulation ($\pm$2 mm) was possible by upper two pulleys and side handles. Average four minutes twenty five seconds were needed for exact setting in fractionated TBI. No significant difference of lung block location on repeated verification films was confirmed and relatively homogeneous dose distribution was measured in rando phantom experiments and patient treatments ($\pm$5%). This immobilizing device was very efficient to keep correct position of patients, which is essential for better result and less complication in fractionated TBI.