• Transactions of the Korean hydrogen and new energy society
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• v.28 no.4
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• pp.407-418
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• 2017

Battery heat management is essential for high power and high energy battery system because it affects its performance, longevity, and safety. In this paper, we investigated the temperature of the 18650 Lithium Ion Battery Module used in a Energy Storage System (ESS) and the cooling method to minimize cell-to-cell temperature variation of battery module. For uniform temperature distribution within a battery module, the flow direction of the coolant in a battery module has been changed according to the time interval, and studied the effect of the cooling method on the temperature uniformity in a battery module which includes a number of battery cells. The experimental results show that bi-directional battery cooling method can effectively reduce the cell-to-cell temperature variation compared with the one-directional battery cooling. Furthermore, it is also found that bi-directional battery cooling can reduce the maximum temperature in a battery module.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.346-353
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• 2012

The purpose of this study is to verify the energy efficiency of the integrated system combining human and a lower extremity exoskeleton robot when it is applied to the proposed gait pattern. Energy efficient gait pattern of the lower limb was proposed through leg function distribution during stance phase and the dynamic-manipulability ellipsoid (DME). To verify the feasibility and effect of the redefined gait trajectory, simulations and experiments were conducted under the conditions of walking on level ground and ascending and descending from a staircase. Experiments to calculate the metabolic cost of the human body with or without the assistance of the exoskeleton were conducted. The energy consumption of the lower extremity exoskeleton was assessed, with the aim of improving the efficiency of the integrated system.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.131-135
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• 2011

In this study, we fabricated the HDPE and ${\alpha}-Al_2O_3$ composites with PE-g-MA as a function of the ${\alpha}-Al_2O_3$ nanopowder weight ratios. The electron beam irradiations on HDPE/${\alpha}-Al_2O_3$ composites were carried out over a range of absorbed doses from 20 to 200 kGy to make three-dimensional network structures. The mechanical properties were characterized using UTM for confirming the changes of the flexural strength and tensile strength. It was observed that the mechanical properties of HDPE were enhanced by the addition of ${\alpha}-Al_2O_3$. However, the strength of the 5 wt% ${\alpha}-Al_2O_3$ added composites decreased due to the nano-powder aggregation. The mechanical properties of composites were increased as increasing the electron beam irradiation up to 150 kGy. We believed that the electron beam irradiated HDPE/${\alpha}-Al_2O_3$ composites can be a good candidate for a variety of industrial applications.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.137-143
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• 2011

Epoxy resins are widely used as high performance thermosets in many industrial applications, such as coatings, adhesives and composites. Recently, a lot of research has been carried out in order to improve their mechanical properties and thermal stability in various fields. Carbon nanotubes possess high physical and mechanical properties that are considered to be ideal reinforcing materials in composites. CNT-reinforced epoxy system hold the promise of delivering superior composite materials with their high strength, light weight and multi functional features. Therefore, this study used multi-walled carbon nanotubes (MWNT) and gamma rays to improve the mechanical and thermal properties of epoxy. The diglycidyl ether of bisphenol A (DGEBA) as epoxy resins were cured by gamma ray irradiation with well-dispersed MWNTs as a reinforcing agent and triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. The flexural modulus was measured by UTM (universal testing machine). At this point, the flexural modulus factor exhibits an upper limit at 0.1 wt% MWNT. The thermal properties had improved by increasing the content of MWNT in the result of TGA (thermogravimetric analysis). However, they were decreased with increasing the radiation dose. The change of glass transition temperature by the radiation dose was characterized by DMA (dynamic mechanical analysis).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.6
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• pp.242-247
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• 2016

This study analyzed the energy consumption of a building pump system that was originally equipped with a primary-secondary zone pump system. Using the HYSYS program the energy consumption of the primary pump system was compared with the primary-secondary zone pump system. The primary-secondary zone pump system consumes less energy than the originally designed primary pump system. When the distance between the machine room and each building is assumed to be equal, the primary pump system can be more efficient than the primary-secondary zone pump system with decreasing the distance. When the distance is 120 m, the primary system consumes less total annual energy than the primary-secondary zone pump system and saves 2,773 kWh. The suggested energy evaluation program can be useful if the designer seeks a more efficient pump system.

• Journal of the KSME
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• v.18 no.3
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• pp.33-45
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• 1978

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2019.05a
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• pp.153-154
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• 2019

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3365-3370
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• 2007

We developed micro power generation system using piezoelectric materials. In our system, the ambient vibrating energy is converting to electric energy by deflection of piezoelectric beams. The system consists of energy generating parts, converting enhancement parts, electric regulation and charging parts, and interface with small-energy-consuming mobile devices. The geometry of piezoelectric beams, the source of vibrating energy, and the electric load of target application determine the characteristics of generating electric power, such as impedance, voltage, current and power density. Therefore, we made a model for analysis of generating power with given information such as piezoelectric materials, geometry, vibration type, and mass. With this model, we can calculate capacitance of piezoelectric beams, generating voltage, current, and power. To obtain maximum energy transfer efficiency, we approached this study in the view of material, electrical, and mechanical engineering

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1132-1138
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• 2005

Fatigue life of metal material can be predicted by the use of fracture theory and experimental database. Although prediction of fatigue life of rubber material uses the same way as metal, there are many reasons to make it almost impossible. One of the reasons is that there is not currently used fracture criteria for rubber material beacuse of non-standardization, various way of composition process of rubber and so on. Tearing energy is one of the fracture criteria which can be applied to a rubber. Even if tearing energy relaxes the restriction of rubber composition, it is also not currently used because of complication to apply in. Research material about failure process of rubber and tearing energy was reviewed to define the process of fatigue failure and the applicability of tearing energy in estimation of fatigue life for rubber. Also, 1file element formulation of tearing energy which can be used in FE analysis was developed.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.51-54
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• 2015

The mesoporous metal organic framework structure of Ni-BTC was successfully synthesized in a low temperature and short operation time via hydrothermal synthesis process. Such operational route virtuously consumed less electrical and thermal energy. It proved time saving along with acceptable product yield (38%). The product was characterized through FESEM, FT-IR, XRD and $N_2$ gas adsorption measurement. Hightemperature stability of synthesized MOF was gauged by diffraction indexing of XRD patterns of as synthesized and heat treated samples of MOFs. The mathematically calculated particle size of Ni-BTC was found to be 42nm.