• Elastomers and Composites
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• v.47 no.3
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• pp.231-237
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• 2012

This study measured the mechanical and damping properties of EPDM compounds including fillers. Semi-reinforcing furnace black (SRF), high abrasion furnace black (HAF) and acetylene black were used as fillers. Dicumyl peroxide (DCP) were used as curing agents. The measurements were conducted using a moving die rheometer (MDR), durometer, universal testing machine (UTM), compression set and dynamic mechanical analysis (DMA). The tensile strength and elongation at break increased with increasing SRF contents in EPDM compounds. However, they decreased with increasing the amount of acetylene black. In the inspecting temperature range, EPDM compound filled acetylene black had stable storage modulus. Furthermore, the tan ${\delta}$ of the EPDM compounds obtained was enhanced by compounding with acetylene black.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.833-839
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• 2013

Cardiopulmonary resuscitation (CPR) is performed by thoracic compression and artificial ventilation for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are facing the whole area perpendicular to the flow axis. The present study developed a new air flow transducer conveniently applicable to CPR. Specially designed "sensing rod" samples the air velocity at 3 different locations of the flow cross-section, then transforms into average dynamic pressure by the Bernoulli's law. The symmetric structure of the sensing holes of the sensing rod enables bi-directional measurement simply by taking the difference in pressure by a commercial differential pressure transducer. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1%. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.456-464
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• 2014

Commercial vehicle drivers typically feel more fatigued compared to general-public drivers. because they spend longer periods of time driving and experience more rough road conditions. This study showed that the application of a magnet, a linear spring, and a seat suspension with nonlinear characteristics was the optimal design to increase comfort while driving. The resonant frequency for the optimal design suspension was 2.8 Hz, and the stiffness was analyzed through displacement-load experiments. Vibration transmissibility was analyzed by suspension stiffness and the existing dynamic compression. The magnetic spring type was at 0.875. As a result, the X-type magnetic spring performed better than the existing spring at 0.729.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.6
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• pp.63-72
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• 2005

In this paper, we propose the bit-rate control algorithm for the block based image compression like H.263, H.263+ or MPEG-4. The proposed algorithm is designed to identify the quantization parameter set through the Lagrangian optimization technique based on the well-known linear source model. We set the Lagrangian cost function with the rates and distortion calculated from the linear source model. We calculate the quantization parameter set using the Vitervi algorithm to solve the Lagrangian optimization problem considering the Dquant method of H.263 and MPEG-4. The proposed algorithm improves the video quality by up to 1.5 dB compared with the TMN8 scheme, and is more effective in the video sources with dynamic activities than the consistent quality approaches.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.6
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• pp.515-522
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• 2019

Since Liquefied Natural Gas (LNG) is normally carried at 1.1 bar pressure and at -163℃, special Cargo Containment System (CCS) are used. As LNG carrier is becoming larger, typical LNG insulation systems adopt a method to increase the thickness of insulation panel to reduce sloshing load and Boil-off Rate (BOR). However, this will decrease LNG cargo volume and increase insulation material costs. In this paper, silica aerogel, glass bubble were synthesized in polyurethane foam to increase volumetric efficiency by improving mechanical and thermal performance of insulation. In order to increase dispersibility of particles, ultrasonic dispersion was used. Dynamic impact test, quasi-static compression test at room temperature (20℃) and cryogenic temperature (-163℃) was evaluated. To evaluate the thermal performance, the thermal conductivity at room temperature (20℃) was measured. As a result, specimens without ultrasonic dispersion have a little effect on strength under the compressive load, although they show high mechanical performance under the impact load. In contrast, specimens with ultrasonic dispersion have significantly increased impact strength and compressive strength. Recently, as the density of Polyurethane foam (PUF) has been increasing, these results can be a method for improving the mechanical and thermal performance of insulation panel.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.19 no.1
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• pp.51-56
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• 2013

From the time the product is manufactured until it is carried and ultimately used, the product is subjected to some form of handling and transportations. During this process, the product can be subjected to many potential hazards. One of them is the damage caused by shocks. In order to design a product-package system to protect the product, the peak acceleration or G force to the product that causes damage needs to be determined. When a corrugated fiberboard box loaded with products is dropped onto the ground, part of the energy acquired due to the action of the gravitational acceleration during the free fall is dissipated in the product and the package in various ways. The shock absorbing characteristics of the packaging cushion materials are presented as a family of cushion curves in which curves showing peak accelerations during impacts for a range of static loads are shown for several drop heights. The new method for determining the shock absorbing characteristics of cushioning materials for protective packaging has been described and demonstrated. It has been shown that cushion curves can be produced by combining the static compression and impact characteristics of the material. The dynamic factor was determined by the iterative least mean squares (ILMS) optimization technique in which the discrepancies between peak acceleration data predicted from the theoretical model and obtained from the impact tests are minimized. The approach enabled an efficient determination of cushion curves from a small number of experimental impact data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.9
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• pp.1682-1688
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• 2008

The Counterpropagation algorithm(CP) is a combination of Kohonen competition network as a hidden layer and the outstar structure of Grossberg as an output layer. CP has been used in many real applications for pattern matching, classification, data compression and statistical analysis since its learning speed is faster than other network models. However, due to the Kohonen layer's winner-takes-all strategy, it often causes instable learning and/or incorrect pattern classification when patterns are relatively diverse. Also, it is often criticized by the sensitivity of performance on the learning rate. In this paper, we propose an enhanced CP that has multiple Kohonen layers and dynamic controlling facility of learning rate using the frequency of winner neurons and the difference between input vector and the representative of winner neurons for stable learning and momentum learning for controlling weights of output links. A real world application experiment - pattern recognition from passport information - is designed for the performance evaluation of this enhanced CP and it shows that our proposed algorithm improves the conventional CP in learning and recognition performance.

• Transactions of Materials Processing
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• v.31 no.6
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• pp.344-350
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• 2022

Extruded Mg-Bi binary alloys are known to have an undesirable bimodal grain structure containing a large amount of coarse unrecrystallized grains. Accordingly, to improve the microstructural homogeneity of extruded Mg-Bi alloys, it is necessary to promote the dynamic recrystallization (DRX) behavior during hot extrusion. An effective way to promote DRX is an increase in nucleation sites for DRX through a pre-deformation process before extrusion, such as cold pre-forging and hot pre-compression. However, the application of these pre-deformation processes increases the cost of final extruded Mg products because of an increase in energy consumption and decrease in productivity. Therefore, a low-cost new continuous process with high productivity is required to improve the microstructural homogeneity and mechanical properties of extruded Mg alloys without a drastic increase in the entire process cost. This study proposes a new extrusion method using an extrusion billet with a truncated cone shape (i.e., tapered billet) instead of a conventional extrusion billet with a cylindrical shape. When the hot extrusion of a Mg-5Bi alloy is conducted using the tapered billet, the DRX behavior during extrusion is considerably promoted. The DRX fraction and average grain size of the extruded alloy significantly increase and decrease from 65% to 91% and from 225 ㎛ to 49 ㎛, respectively. Consequently, the extruded Mg-5Bi alloy fabricated using the tapered billet has a finer homogeneous grain structure and higher tensile elongation than the extruded counterpart fabricated using the cylindrical billet.

• Elastomers and Composites
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• v.56 no.4
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• pp.209-216
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• 2021

In this study, we observed the mechanical properties, thermal stability, and low temperature sealing performance of fluorosilicone elastic composites. When the blend ratio of Phenyl vinyl methyl silicone (PVMQ) was increased, the tensile strength, modulus at 100%, and compression set were decreased. The thermal stability of fluorosilicone elastic composites showed a similar tendency. These were caused by poorer green strength of PVMQ than Fluorosilicone rubber (FVMQ). The change in the tensile strength and elongation at -40℃ showed a decreasing tendency with increasing PVMQ blend ratio. By increasing the PVMQ blend ratio, low-temperature performance was improved. The Dynamic mechanical analysis (DMA) results showed that T_g was decreased and low-temperature performance was improved with increasing PVMQ blend ratio. However tanδ was decreased becaused of the poor green strength and elasticity of PVMQ. From a hysteresis loss at -40℃, the hysteresis loss value was increased and fluorosilicone elastic composites showed the decreasing tendency of elasticity with increasing PVMQ blend ratio. From the TR test, TR10 was decreased with increasing PVMQ blend ratio. FS-4 (45% PVMQ blended composites) showed a TR10 of -68.0℃ that was 5℃ lower than that of FS-1 (100% FVMQ). The gas leakage temperature was decreased with increasing PVMQ blend ratio. The gas leakage temperature of FS-4 was -69.2℃ that was 5℃ lower than that of FS-1. Caused by the polymer chain started to transfer from a glassy state to a rubbery state and had a mobility of chain under T_g, the gas leakage temperature showed a lower value than T_g. The sealing performance at low temperature was dominated by T_g that directly affected the mobility of the polymer chain.

• Composites Research
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• v.32 no.5
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• pp.290-295
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• 2019

In the present study, composite insulation mat was reinforced over polyurethane foam (PUF) to improve the thermal performance and impact resistance of the PUF applied to the liquefied natural gas carrier insulation system. The composite insulation mat used Kevlar, aerogel, and cryogel composite mat that can be applied in a cryogenic environment. The thermal conductivity was measured at $20^{\circ}C$ to investigate the thermal performance, and the drop impact test was carried out under impact energy of 30 J at $20^{\circ}C$, $-163^{\circ}C$ to investigate the impact resistance. The measured thermal performance was compared with neat PUF through effective thermal conductivity theoretical value. The shock resistance was evaluated of contact force, contact time, and absorb energy. In experimental results, cryogel composite mat was the best performance in terms of thermal performance, and aerogel composite mat was the best performance in terms of impact resistance.