• The Journal of the Convergence on Culture Technology
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• v.5 no.1
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• pp.265-273
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• 2019

This research aims at developing human resources who will serve as flexible mediators in the future national or cultural conflict situations. The primary learning contents approach the class by selecting the upcycling design activities, in which the students recognize the problem of waste that is for all and study representative characteristics and backgrounds of each culture. The classes were held centering around the student members of GunpoYMCA, and the culturally characteristic materials were made through upcycling design. The activities included making giraffes in Africa with plastic bottles, Mongolian tents with wooden posts, snow globes with sauce pots, patchworks and rugs with shirts and textiles, and garlands with banners, which helped students learn the new term upcycling as well as get interested in the environmental problems. Also, they could understand other cultures by creating materials that represent each culture and studying their origins and historical backgrounds. In conclusion, this research offers value by developing abilities to cope with not only conflicts between cultures but confrontations between nations in the larger scope.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.33-39
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• 2021

As the interest and demand in the recycled yarn field has increased rapidly worldwide, domestic companies are also promoting research and development and business on recycled yarn. The chemical and thermal properties of four types of virgin and recycled PET samples from A and B company, which are the leading domestic companies in the recycled polyester yarn business, were confirmed through infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Virgin and recycled PET from two companies were compared. FT-IR spectroscopy revealed the typical spectra of PET for both companies and a different peak at 872 cm-1. DSC confirmed that the melting point and crystallization temperature of recycled PET were lower than those of virgin PET. These results indicate that small amounts of contaminants are an important parameter affecting the thermal properties of recycled PET. In the DSC results after seven repeats of the heating and cooling processes, all four samples showed that a lower melting point, crystallization temperature, and low heat flow intensity increased with increasing number of cycles. The results of melting and crystallization enthalpy also showed similar patterns.

• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.149-157
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• 2008

Since wireless sensor networks consist of nodes with the constrained battery, energy efficient MAC operation is one of the important issues. Low duty cycle operation is critical to conserve energy in wireless sensor network MAC protocol. Some paper proposed a new approach to low power listening, which employs a short preamble to further reduce energy consumption and to reduce latency. But short preamble suffers from unfair channel access problem since there was no consideration for contention between transmission nodes. Preamble counting proposes a solution to each of these problems by employing node selection information. Simulation results show that the preamble counting provides an improved energy efficiency and fairness of packet delivery.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.153-163
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• 2020

Compared to gaeous hydrogen, liquid hydrogen has approximately 1/800 volume, 800 times higher volumetric energy density at the same pressure, and the advantage of lower explosion risk and easier transportation than gaseous hydrogen. However, hydrogen liquefaction requires larger scale facility investment than simple compression storage method. Therefore, the research on energy-saving hydrogen liquefaction processes is highly necessary. In this study, helium/neon (mole ratio 80 : 20) refrigeration cycle was investigated as the main refrigeration process for hydrogen liquefaction. Process simulation for less energy consumption were carried out using PRO/II with PROVISION V10.2 of AVEVA. For hydrogen liquefaction, energy consumption was compared in three cases: Using a helium/neon refrigerant cycle, a SMR+helium/neon refrigerant cycle, and a C3-MR+helium/neon refrigerant cycle. As a result, the total power consumptions of compressors required to liquefy 1 kg of hydrogen are 16.3, 7.03 and 6.64 kWh, respectively. Therefore, it can be deduced that energy usage is greatly reduced in the hydrogen liquefaction process when the pre-cooling is performed using the SMR process or the C3MR process, which have already been commercialized, rather than using only the helium/neon refrigeration cycle for the hydrogen liquefaction process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.707-712
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• 2012

Very high cycle fatigue (VHCF) behavior of aerospace components has emerged much attention due to their long service life. In this study, a piezoelectric ultrasonic fatigue testing (UFT) system has been developed by Mbrosiatec Co., Ltd. to study the high cycle fatigue (HCF) strength of Ti-6Al-4V alloy. Hourglass-shaped specimens have been investigated in the range from $10^6$ to $10^9$ cycles at room temperature under completely reversed R = -1 loading conditions,. Scanning electron microscopy (SEM) analysis revealed that failures occurred in the entire range up to the gigacycle regime, and the fractures have beenfound to be initiated from the surface, unlike in steels. However, it was found from the SEM microgprahs that microcracks transformed into intergranular fractures. Thus, it can be concluded from according to the results that this test method can be applicable to commercialized automotive and railroad parts that require high cycle fatigue strength.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.318-326
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1 MW organic Rankine cycle system was designed and developed. The exhaust gases of 175$^{\circ}C$ at two 100 MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1 MW as designed but only 670 kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• Journal of Energy Engineering
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• v.18 no.3
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• pp.156-162
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• 2009

Cylinder-pressure based combustion analysis provides a mechanism through which a combustion researcher can understand the combustion process. This paper was to identify the most significant sources of cycle-to-cycle combustion variability in a spark ignition engine at idle. To analyse the cyclic variation in the test engine, the burn parameters are determined on a cycle-to-cycle basis through analysis of the engine pressure data. The burn rate analysis program was used in the analysis of the data. Burn parameters were used to determine the variations in the input parameter-i.e., fuel, air, residual mass, and so on.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.10
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• pp.9-15
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• 2009

In this paper, we invented a new structure of fast ATC(Automatic Threshold Control) circuit. Using the structure we made a new burst-mode limiting amplifier with fast ATC function using commercial $0.8{\mu}m$ BiCMOS technology. It's ATC function worked so fast that even the first bit of burst-data could be detected, which confirmed that the new structure was useful for fast ATC. However, in the beginning of a burst, distortions in duty-cycle occurred and increased up to 59% of duty-cycle as amplitude of input signal increased. But we confirmed that after 10 cycles passed, duty-cycles was staying below 52% of duty-cycle for any magnitude of input signal.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.23-32
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• 1992

The objective of this study is to identify the quantitative relationships among the important physical factors associated with failure of steel members under strong seismic excitations through very low-cycle fatigue tests. Very low-cycle fatigue is meant to be structural fatigue causing cracks and rupture in about 5~30 cycle ranges. The angle specimen was subjected to repeated axial Ioad after undergoing inelastic buckling. The test results reveal that the energy absorption capacities vary heavily with the history of loading and the failure mode. The maximum values of residual local strain at the initiation of a visible crack due to the very low-cycle fatigue were of the order of 25~40%, regardless of loading patterns, deflection modes, and width-to-thickness ratios.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.163-167
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• 2009

In this paper, we analyze key agreement algorithms based on co-cyclic Jacket matrices, and propose key agreement algorithms based on co-cyclic Hadamard matrices to fix the problem. The performance of our proposal is better than conventional one's and the construction of the matrices is very simple. Also time complexity of our proposal is proportional to the factor that determinees the size of the matrix, and the length of the key. So our proposal is fast and will be useful for the communcations of two or three users, especially for those have low computing power.