• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1303-1306
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• 2005

The mechanical properties of bellows, such as the extensibility and the strength can be changed depending on the shape. For the shipbuilding material, it is favorable that the fatigue life is long due to the elastic property and the reduction of thermal stress in piping system. Nowadays, the domestic production and design of bellows are based on the E.J.M.A Code. Therefore, the design standard is in need because of much errors and lack of detailed analysis. In this study, it is attempted to find out the optimal shape of U-type bellows using the finite element method. The effective factors, mountain height, length, thickness, and number of mountains and the length of joint are considered and the proper values are chosen for the simulation. The results shows that if the number of mountains are reduced, the volume decreases while the stress increases. However, the number of mountains are increased, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the volume and stress are decreasing at a certain lower value region.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.53
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• pp.315-336
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• 2012

In year 2011 export volume of South Korea surpassed 500billion USD and overall trade volume has exceeded one trillion USD. South Korea is ranked at 7th in the world by its export volume. Such an expansion of the trade volume leads to growth in customs clearance service demand. However, there are only handfuls of studies on the efficiency of customs clearance service which customs broker provide. If the efficiency in this study is not absolute, it shows relative efficiency to decision making unit. In this research survey was conducted targeting members of Korea Customs Brokers Association. Based on the survey improvement plans to enhance efficiency of customs clearances are as follows. First, rationalize the customs broker fee. Second, setup batch processing system to improve efficiency of the work process. Third, develop new area of task such as FTA and AEO certification. Forth, raise service quality by improving professionalism of customs brokers. Fifth, work efficiency of the office in the capital area will increase. Sixth, when inspecting import export cargo, customs broker should attend at the scene by their choice. Meanwhile, difference analysis on competent customs, type of office, and duration of the business was done but all the aspects were rejected. Such aspects does not influence on its effectiveness.

• Journal of Hydrogen and New Energy
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• v.33 no.6
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• pp.692-698
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• 2022

With the expansion of domestic hydrogen fuelling station infrastructure, it is necessary to secure reliability among hydrogen traders, and for this, technology to accurately measure hydrogen is important. In this study, 4 types of hydrogen trading volume calculation models (model 1-4) were presented to improve the accuracy of the hydrogen trading volume. In order to obtain the reference value of model 4, and experiment was conducted using a flow rate measurement equipment, and the error rate of the calculated value for each model was compared and analyzed. As a result, model 1 had the lowest metering accuracy, model 2 had the second highest metering accuracy and model 3 had the highest metering accuracy until a certain point. But after the point, model 2 had the highest metering accuracy and model 3 had the second metering accuracy.

• Archives of Plastic Surgery
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• v.39 no.2
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• pp.118-123
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• 2012

Background : An area of the skull exposed by burn injury has been covered by various methods including local flap, skin graft, or free flap surgery. Each method has disadvantages, such as postoperative alopecia or donor site morbidities. Due to the risk of osteomyelitis in the injured skull during the expansion period, tissue expansion was excluded from primary reconstruction. However, successful primary reconstruction was possible in burned skull by tissue expansion. Methods : From January 2000 to 2011, tissue expansion surgery was performed on 10 patients who had sustained electrical burn injuries. In the 3 initial cases, removal of the injured part of the skull and a bone graft was performed. In the latter 7 cases, the injured skull tissue was preserved and covered with a scalp flap directly to obtain natural bone healing and bone remodeling. Results : The mean age of patients was $49.9{\pm}12.2$ years, with 8 male and 2 female. The size of the burn wound was an average of $119.6{\pm}36.7cm^2$. The mean expansion duration was $65.5{\pm}5.6$ days, and the inflation volume was an average of $615{\pm}197.6mL$. Mean defect size was $122.2{\pm}34.9cm^2$. The complications including infection, hematoma, and the exposure of the expander were observed in 4 cases. Nonetheless, only 1 case required revision. Conclusions : Successful coverage was performed by tissue expansion surgery in burned skull primarily and no secondary reconstruction was needed. Although the risks of osteomyelitis during the expansion period were present, constant coverage of the injured skull and active wound treatment helped successful primary reconstruction of burned skull by tissue expansion.

• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.437-441
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• 2017

This study was carried out to investigate the volumetric expansion ratio and hardness of expanded graphite after coating with various resins which were used as an additive of fireproof sealant. The coating thickness of the resin, which represents the coating rate, was dependent of the drying speed of the resin and the viscosity of the resin. Therefore the coating thickness was shown as follows: polyvinyl acetate > acrylic resin > urethane resin > water soluble latex. Furthermore, the volumetric expansion ratio was as follows: urethane resin > water soluble latex > acrylic resin > polyinyl acetate and the hardness was as follows: polyvinyl acetate resin > acrylic resin > water soluble latex > urethane resin. This showed that the volume of expansion was reduced by expansion, which was not covered by coating, but significantly increased by increasing hardness and allowed it to be used as a refractory addition. According to the response surface methodology, the optimized addition amount and stirring speed of acrylic resin were 37.6 wt% and 441.4 rpm, respectively.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.309-320
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• 2003

Since the concrete covers most structures in modern architecture and it is composed of aggregates of about 75%, the appropriate selection of aggregates is valuable for the durability of concrete. A major cause of the expansion of mortar-bar measured by ASTM C 227-90 has been accounted by the alkali-aggregate reaction. This study carried out designed experiments on some aggregates including basalt and sandstone, to classify the expansion factors into the alkali-aggregate reaction, the increase of the gel pore volume, and the interstitial water that could expand physically the cracks or foliation developed in aggregates itself. The quantitative analyses of expansion by each factor indicated that the interstitial water and/or the alkali-aggregate reaction had major roles in the concrete expansion. Thus, if the supplied aggregates have deteriorated the structural framework, it is important to investigate the exact causes through this suggested method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2552-2559
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• 2000

Most of ferrous b.c.c weld materials have martensitic transformation during rapid cooling after welding. It is well known that volume expansion due to the phase transformation could influence on the relaxation of welding residual stress. To apply this effect practically, it is necessary to establish a numerical model which is able to estimate the effect of phase transformation on residual stress relaxation quantitatively. For this purpose, the analysis is carried out in two regions, i.e., heating and cooling, because the variation of material properties following a phase transformation in cooling is different in comparison with the case in heating, even at the same temperature. The variation of material properties following phase transformation is considered by the adjustment of specific heat and thermal expansion coefficient, and the distribution of residual stress in analysis is compared with that of experiment by previous study. In this study, simplified numerical procedures considering phase transformation, which based on a commercial finite element package was established through comparing with the experimental data of residual stress distribution by other researcher. To consider the phase transformation effect on residual stress relaxation, the transition of mechanical and thermal property such as thermal expansion coefficient and specific heat capacity was found by try and error method in this analysis. In addition to, since the transformation temperature changes by the kind and control of alloying elements, the steel with many kinds of transformation temperature were selected and the effect of transformation on stress releasement was investigated by the numerical procedures considering phase transformation.

• The Journal of Korean Physical Therapy
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• v.26 no.3
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• pp.169-174
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• 2014

Purpose: This study demonstrated a postural alignment exercise as conservative management strategy for a woman with excessive thoracic kyphosis presenting decreased chest function, and reports its results. Methods: A 21-year-old woman with thoracic kyphosis presenting limited chest function. The exercise program underwent for 30 min in the intervention phase, which consisted of exercises to improve the strength of back extensor and to stretch anterior chest region. Outcome measures comprised the severity of thoracic kyphosis and chest function (vital capacity [VC], forced expiratory volume in a second [FEV1], and chest expansion length). Results: The thoracic kyphotic angle decreased by 23.6% ($9.38^{\circ}$) and 25.4% ($10.58^{\circ}$) in the intervention and follow-up phases respectively. Also, chest function was improved in the intervention (VC: 3.7% [$0.10{\ell}$], FEV1: 17.1% [$0.39{\ell}$], and chest expansion length: 17.1% [0.96 cm]), and the improvement was maintained during the follow-up phase (VC: 4.8% [$0.13{\ell}$], FEV1: 17.1% [$0.39{\ell}$], and chest expansion length: 64.3% [1.81 cm]). Conclusion: These findings suggest that the postural alignment exercise was favorable for improving chest function of a woman with thoracic kyphosis.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.696-698
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• 2001

This paper considers the research of the hybrid interrupter which adopts both rotating arc and thermal expansion technology. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. To develope this type of interrupter, we introduced analytical analysis including electromagnetic and arc fluid simulation and experimental analysis including construction of current source generation facility and arc behavior measurements. In this research, the principle of the interrupting techniques are given and analytical and experimental results of hybrid interrupter which is developed by new technology is introduced.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.568-573
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• 2003

When a safety valve equipped in a nuclear power plant opens in an instant by an accident, a moving shock wave propagates downstream the valve, inducing a complicated unsteady flow field. The moving shock wave may exert severe load to the structure. So, to reduce the load acting on the wall of POSRV, a gradual opening of POSRV is adopted in general. In theses connections, a numerical work is performed to investigate the effect of valve opening time on the unsteady flow fields downstream of the valve. Compressible, two-dimensional Navier-Stokes equations are used with the finite volume method. The obtained results show that sharp pressure rise through moving shock tor the case of instant opening is attenuated by employing the gradual opening of valve. It is turned that the flows for the two cases of gradual valve opening time show the similar to that of highly under-expanded one in jet structure having expansion and compression waves and Mach stem. Also, comparing with the results for the two cases of opening time, the shorter the valve opening is, the pressure gradient at the downstream of the valve becomes softly.