• Journal of the Korean Wood Science and Technology
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• 제43권2호
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• pp.196-205
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• 2015

The aim of this study was to evaluate the fuel characteristics of thermally treated wood chips of the Larix kaempferi C. As torrefaction temperature was increased ($200^{\circ}C$ to $300^{\circ}C$), the carbon content, calorific value, and mass loss of torrefied wood chips increased significantly. The torrefied wood chips were shown to have hydrophobic properties even when only treated by mild torrefaction. The energy required to grind torrefied wood chips was reduced by the torrefaction process. Different sizes of wood chips were used in this study; however, this produced almost no difference in the fuel characteristics of processed Larix kaempferi C, except in the distribution of ground wood particles. Similar results were observed when the wood chips were torrefied for different lengths of time (15 min to 60 min) at a constant temperature. Torrefaction was shown to have positive effects on the fuel characteristics of Larix kaempferi C, including improved energy density, storage, and grindability.

• 대한기계학회논문집A
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• 제36권8호
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• pp.829-833
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• 2012

대체천연가스(SNG)는 에너지 안보 차원에서 에너지 수급 안정화 방안의 하나로 많은 관심을 받고 있다. 또한 HCNG (또는 $H_2CNG$)는 배기가스 내의 유해 성분을 현저히 줄이고 열효율도 높일 수 있어서 내연기관이나 가정용 연료로 사용될 것으로 기대되고 있다. 그러나 SNG나 HCNG에 포함되어 있는 수소는 재료에 침투하여 그 재료의 역학적 특성을 크게 저하시키는 것으로 알려져 있다. 따라서 SNG나 HCNG를 안전하고 효율적으로 수송 공급하려면 이를 위해 운용되는 인프라의 안전성과 신뢰성 확보가 선결되어야 한다. 본 연구에서는 중공 시험편을 이용한 인장시험법을 통하여 CNG 저장용기용 저합금강이 나타내는 고압 수소 분위기에서의 인장 특성 변화에 대하여 조사하였다.

• Progress in Superconductivity
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• 제13권1호
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• 한국수소및신에너지학회논문집
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• 제25권1호
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• pp.19-27
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• 2014

Mg hydride has a high hydrogen capacity (7.6%), at high temperature, and is a lightweight and low cost material, thus it a promising hydrogen storage material. However, its high operation temperature and very slow reaction kinetics are obstacles to practical application. In order to overcome these disadvantages of Mg hydride, graphene powder was added to it. The addition of graphene has been shown to reduce the operating temperature of dehydrogenation. Moreover, in this report the environmental aspects of $MgH_x$-Graphene composites are investigated by means of the environmental life cycle assessment (LCA) method. $MgH_x$-Graphene mixture was prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD(X-ray Diffraction). The hydrogenation behaviors were evaluated by using a Sievert's type automatic PCT apparatus. Such evaluation of Materials also conducted in the LCA. From the result of P-C-T(Pressure-Composition-Temperature) curves, the $MgH_x$-3wt.% graphene composite was evaluated as having a 5.86wt.% maximum hydrogen storage capacity, at 523K. From absorption kinetic testing, the $MgH_x$-7wt.% graphene composite was evaluated as having a maximum 6.94wt.%/ms hydrogen absorption rate, at 573K. Environment evaluation results for the $MgH_x$-graphene composites and other materials indicated environmental impact from the electric power used and from the materials themselves.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.156.1-156.1
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• 2016

Nickel sulfide (NiS) is one of the most promising candidates as an electrode material for supercapacitors due to its good capacitive properties, high electrical conductivity and low cost. In addition to the development of the new electrode materials, nanostructuring the electrode surface is one of the main issues in enhancing the capacitive performance of the supercapacitors because the increased surface area can improve the charge transfer and energy storage processes occurring at the electrode surface. However, most nanofabrication techniques require complicated and delicate nanoprocesses, and hence are not suitable for practical use. In this work, we developed a simple method to fabricate nanostructured NiS electrodes by depositing NiS onto $TiO_2$ nanoparticles. First, $TiO_2$ nanoparticles were spin-coated on a fluorine-doped tin oxide (FTO) substrate, and then NiS layers were deposited onto the $TiO_2$ nanoparticles by consecutive dip-coatings in the solutions containing nickel and sulfur precursors. This nanostructured NiS electrode showed significantly improved capacitive properties compared to the electrode of NiS films deposited without $TiO_2$ nanoparticles. The asymmetric full-cell supercapacitor with this nanostructured NiS electrode and activated carbon electrode was also fabricated and investigated.

• Journal of Biosystems Engineering
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• 제31권4호
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• pp.369-375
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• 2006

Mechanical properties of potato and sweet potato were measured under impact and compression loading. The test apparatus consisted of disgital storage oscilloscope and simple mechanisms which can apply compression and impact forces to potatoes and sweet potatoes. The mechanical properties could be measured while the tissues were ruptured in a very short period time less than 10 ms by impact loading. Rupture force, energy, and deformation were measured as mechanical properties of potatoes and sweet potatoes under impact and compression loading. Rupture forces under impact and compression loading were in the range of 84.1 to 93.7N and 128.9 to 132.2N for external tissues and 60.1 to 64.8N and 158.9 to 171.1N for internal tissues of potato and sweet potato, respectively. Compression speeds and drop heights for each test were in the range of 1.25 to 62.5mm/min and 8 to 24cm.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2007년도 추계학술발표논문집
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• pp.93-102
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• 2007

Biocomposite was organized with biodegradable polymer and natural fiber that has potential to be used as replacement for glass fiber reinforced polymer composite with the benefits of low cost, low density, acceptable specific strength, biodegradability, etc. Until now, non-wood fibers have been used as reinforcements of biocomposite which are all plant-based fibers. The present study focused on investigating the fabrication and characterization of biocomposite reinforced with red algae fiber. The bleached red algae fiber(BRAF) showed very similar crystallinity to the cellulose. It has high stability against thermal degradation (maximum thermal decomposition temperature of 359.3$^{\circ}C$) and thermal expansion. Biocomposites reinforced with BRAF have been fabricated by a compression molding method and their mechanical and thermal properties have been studied. The storage modulus and the thermomechanical stability of PBS matrix are markedly improved with reinforcing the BRAF. These results support that the red algae fiber can be used as an excellent reinforcement of biocomposites as "green-composite" or "eco-composite".

• 접착 및 계면
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• 제6권4호
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• pp.12-17
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• 2005

Natural fiber/phenolic biocomposites with chopped henequen fibers treated at various levels of electron beam irradiation (EBI) were made by means of a matched-die compression molding method. The interfacial property was explored in terms of interfacial shear strength measured by a single fiber microbonding test. The thermal properties were studied in terms of storage modulus, tan ${\delta}$, thermal expansion and thermal stability measured by dynamic mechanical analysis, thermomechanical analysis and thermogravimetric analysis, respectively. The result showed that the interfacial and thermal properties depend on the treatment level of EBI done to the henequen fiber surfaces. The present result also demonstrates that 10 kGy EBI is most preferable to physically modify the henequen fiber surfaces and then to improve the interfacial property of the biocomposite, supporting earlier results studied with henequen/poly (butylene succinate) and henequen/unsaturated polyester biocomposites.

• 펄프종이기술
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• 제40권1호
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• pp.62-67
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• 2008

Biocomposite was fabricated with biodegradable polymer and natural fiber that has potential to be used as replacement for glass fiber reinforced polymer composite with the benefits of low cost, low density, acceptable specific strength, biodegradability, etc. Until now, mostly natural cellulosic fibers on land have been used as reinforcement for biocomposite. The present study focused on investigating the fabrication and the characterization of biocomposite reinforced with red algae fibers from the sea. The bleached red algae fiber (BRAF) showed very similar crystallinity to the wood cellulose. It has high stability against thermal degradation (maximum thermal decomposition temperature of 359.3$^{\circ}C$) and thermal expansion. Biocomposites reinforced with BRAF have been fabricated by a compression molding method and their mechanical and thermal properties have been studied. The storage modulus and the thermomechanical stability of PBS (polybuthylenesuccinate) matrix are markedly improved by reinforcing with the BRAF. These results indicate that red algae fiber can be used as an excellent reinforcement of biocomposites, which are sometimes called as "green-composites" or "eco-composites".

• Journal of Advanced Marine Engineering and Technology
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• 제38권5호
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• pp.533-540
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• 2014

Recently, latent heat thermal energy storage system (LHTES) has gained attention in order to utilize middle temperature (373~573 K) waste heat from biomass gasification. This paper has investigated thermo-physical properties of erythritol [$CH_2OHCHOH$ $CHOHCH_2OH$], mannitol [$CH_2OH$ $(CHOH)_4CH_2OH$] and their compounds as phase change materials (PCMs). The differential scanning calorimetry (DSC) was applied to measure the melting point and latent heat of these PCMs. Also the melting and solidification characteristics of these PCMs were observed in a glass tube with a digital camera. In the DSC measurement, when the amount of mannitol content was more than 40 mass%, the melting point of these compounds show two melting points. The experimental results showed that the velocity of melting and solidification were different for every mixture ratio of compounds. These compounds had the super-cooling phenomenon during the solidification process.