• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.695-701
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• 2018

Research into exhaust heat recovery has been actively carried out to improve the thermal efficiency of internal combustion engines. In this study, the performance of thermoelectric generation from exhaust heat recovery for motorcycle engines was analyzed by 1-D thermo-fluid simulation. GT-SUITE, which was developed by Gamma Tech., was used for the simulation of the internal combustion engine and thermoelectric generation system. The basic performance of the engine was analyzed in the range of engine speed of 1000~7000 rpm and engine load of 0~100%. The ratio of exhaust heat energy to fuel chemical energy was found to be about 40~60%. A combined simulation of the engine model and thermoelectric generation model was carried out to analyze the voltage, current and power generated by the thermoelectric material. The generation characteristics of the thermoelectric material was dominantly affected by the exhaust gas temperature. The maximum generated power of the current thermoelectric generation system was found to be about 2.2% of the total exhaust heat energy. The design optimization of the thermoelectric generation system will be carried out to maximize its power generation and economic feasibility.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.446-452
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• 2016

The aircraft has to be considered for safety very importantly because of peculiarity of flight in the air, so it should be retained through proper inspection and maintenance not only in production phase but also in operating phase. Recently, it is using the latest technology as engineering approach not depending on human factor to determine on maintenance needs, and domestic production rotary aircraft also has the health & usage monitoring system to measure and to monitor major components. However, continued vibration exceedance phenomenon occurred in production and operation phase because of inappropriate thresholds, and it confirmed as false alarm which is not necessary to repair. In this paper, it is described that operational concept of HUMS, and especially it contains a study result for efficiency of aircraft operation and ultimately the improvement of flight safety by optimizing HUMS thresholds to determine efficiently necessity of maintenance under limited conditions and by establishing inspection/maintenance procedures when the re-designated thresholds exceedance occurred.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.195-215
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• 2017

This paper proposes gob-side entry retaining by roof break and filling in thick-layer soft rock conditions based on the thick-layer soft rock roof strata migration law and the demand for non-pillar gob-side entry retaining projects. The functional expressions of main roof subsidence are derived for three break roof direction conditions: lateral deflection toward the roadway, lateral deflection toward the gob and vertically to the roof. These are derived according to the load-bearing boundary conditions of the main roadway roof stratum. It is concluded that the break roof angle is an important factor influencing the stability of gob-side entry retaining surrounding rock. This paper studies the stress distribution characteristics and plastic damage scope of gob-side entry retaining integrated coal seams, as well as the roof strata migration law and the supporting stability of caving structure filled on the break roof layer at the break roof angles of $-5^{\circ}$, $0^{\circ}$, $5^{\circ}$, $10^{\circ}$ and $15^{\circ}$ are studied. The simulation results of numerical analysis indicate that, the stress concentration and plastic damage scope to the sides of gob-side entry retaining integrated coal at the break roof angle of $5^{\circ}$ are reduced and shearing stress concentration of the caving filling body has been eliminated. The disturbance of coal mining to the roadway roof and loss of carrying capacity are mitigated. Field tests have been carried out on air-return roadway 5203 with the break roof angle of $5^{\circ}$. The monitoring indicates that the break roof filling section and compaction section are located at 0-45 m and 45-75 m behind the working face, respectively. The section from 75-100 m tends to be stable.

• Steel and Composite Structures
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• v.34 no.5
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• pp.743-767
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• 2020

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R² = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R² = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

• Microbiology and Biotechnology Letters
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• v.30 no.3
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• pp.223-229
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• 2002

For the research of the natural marine antioxidant, several bacteria were isolated from the coast of jin-Hae in Korea. Among the marine bacteria studied, strain HJ-14, a gram-negative, motile, strait rod, aerobic, and $Na^{+}$ required bacterium showed high activity of 1,1-diphenyl-2-picrylhydrazyl radical scav- enging. The morphological, physiological, and biochemical characteristics of the strain HJ-14 were similar to those of the Alteromonas macleodii ATCC $27126^{T}$ . Thus, it was tentatively identified as Alteromonas sp. HJ-14. The compositions of major fatty acids in cell membrane of Alteromonas sp. HJ-14 were $C_{ 14:0}$ , $ C_{15:0}$ , $C_{16:0}$ and $C_{17:1}$ $_{w8c}$ , which also suggest that it is affiliated with Alteromonas sp. The optimum culture conditions for production of antioxidant materials with Alteromonas sp. HJ-14 were at $25$~$37^{\circ}C$ and pH 6~8. The optimum conditions for the production of antioxidant for carbon, inorganic nitrogen, and sodium chloride sources were 2.5%(w/v) dextrin, 0.5%(w/v) ammonium sulfate, and 2~6%(w/v) sodium chloride, respectively. The hydroxyl radical scavenging ability of Alteromonas sp. HJ-14 broth was 90.03%, which is higher than ascor-bic acid(83.28%) and lower than butylated hydroxyanisole(95.46%) and $\alpha$-tocopherol(97.17%).

• Journal of Microbiology and Biotechnology
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• v.23 no.9
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• pp.1308-1321
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• 2013

The emergence of microcarrier technology has brought a renewed interest in anchorage-dependent cell culture for high-yield processes. Well-known in vaccine production, microcarrier culture also has potential for application in other fields. In this work, two types of microcarriers were evaluated for small-scale monoclonal antibody (mAb) production by CHO-K1 cells. Cultures (5 ml) of microporous Cytodex 3 and macroporous CultiSpher-S carriers were performed in vented conical tubes and subsequently scaled-up (20 ml) to shake-flasks, testing combinations of different culture conditions (cell concentration, microcarrier concentration, rocking methodology, rocking speed, and initial culture volume). Culture performance was evaluated by considering the mAb production and cell growth at the phases of initial adhesion and proliferation. The best culture performances were obtained with Cytodex 3, regarding cell proliferation (average $1.85{\pm}0.11{\times}10^6$ cells/ml against $0.60{\pm}0.08{\times}10^6$ cells/ml for CultiSpher-S), mAb production ($2.04{\pm}0.41{\mu}g/ml$ against $0.99{\pm}0.35{\mu}g/ml$ for CultiSpher-S), and culture longevity (30 days against 10-15 days for CultiSpher-S), probably due to the collagen-coated dextran matrix that potentiates adhesion and prevents detachment. The culture conditions of greater influence were rocking mechanism (Cytodex 3, pulse followed by continuous) and initial cell concentration (CultiSpher-S, $4{\times}10^5$ cells/ml). Microcarriers proved to be a viable and favorable alternative to standard adherent and suspended cultures for mAb production by CHO-K1 cells, with simple operation, easy scale-up, and significantly higher levels of mAb production. However, variations of microcarrier culture performance in different vessels reiterate the need for optimization at each step of the scale-up process.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.495-504
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• 2000

This study discussed the optimal use of bentonite and cement for the compacted soil liner of landfill. Techniques employed in this optimization included permeability(by KSF 2322) and compressive strength(by KSF 2314). The optimal amount of these materials to the compacted soil liner was determined in accordance with a regulatory guideline of the government: that is, $k=1{\times}10^{-7}cm/sec$. The testing sods were CL(Clayey Soil) and SM(Sandy Soil), which were classified according to LSCS(Unifed Soil Classify System), The results showed that the optimal amounts of bentonite and cement to mix with the compacted CL soil liner were 5% of bentonite and 5% of cement : namely, $k=9.98{\times}10^{-8}cm/sec$ and ${\sigma}_{28}=1275kg/cm^2$. For the compacted SM soil liner. the optimal amount of bentonite was 15%, in conjunction with 5% of cement : namely, $k=9.86{\times}10^{-8}cm/sec$ and ${\sigma}_{28}=18.72kg/cm^2$. It was concluded that the compacted CL or SM soil liner, with containing the optimal amounts of bentonite and cement showed the acceptable permeability and the compressive strength, referring to a regulatory guideline of the government for construction of the landfill.

• Microbiology and Biotechnology Letters
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• v.45 no.2
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• pp.149-154
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• 2017

To increase the efficiency of esterase production by Bacillus, high cell-density culture of recombinant Escherichia coli through fed batch fermentation was tested. Cells were cultured to $OD_{600}$ of 76 (35.8 g/l DCW) with dissolved oxygen level controlled to least above 30% air saturation by supplying pure oxygen. Cells were cultured to an $OD_{600}$ of 90 (42.4 g/l DCW) with glucose feeding controlled to at least 1 g/l. However, the cells reached stationary phase at the late stage of culture, despite glucose being supplied. Cells were cultured to an $OD_{600}$ of 185 (87.3 g/l DCW) by supplying additional medium with fortified yeast extract. To increase the productivity of the recombinant protein, cell growth and esterase productivity based on induction time were evaluated. Late exponential phase induction for esterase production in fed batch fermentation resulted in maximum optical density $OD_{600}$ of 190 (89 g/l DCW) and maximum esterase activity of 1745 U/l, corresponding to a 5.8-fold enhancement in esterase production, compared to the early exponential phase induction. In this study, we established fermentation methods for achieving maximum production of Bacillus-derived esterase by optimizing IPTG induction time in high-cell density culture by supplying pure oxygen and a nitrogen source.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.521-527
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• 2016

Nanoscale zero valent iron (nZVI) has been intensively studied for the treatment of a plethora of pollutants through reductive reaction, however, the nano size should be of concern when nZVI is considered for water treatment, due to difficulties in recovery. The loss of nZVI causes not only economical loss, but also potential risk to human health and environment. Thus, the immobilization onto coarse or structured support is essential. In this study, two representative processes for nZVI immobilization on granular activated carbon (GAC) were evaluated, and optimized conditions for synthesizing Fe/GAC composite were suggested. Both total iron content and $Fe_0$ content can be significantly affected by preparation processes, therefore, it was important to avoid oxidation during preparation to achieve higher reduction capacity. Synthesis conditions such as reduction time and existence of intermediate drying step were investigated to improve $Fe_0$ content of Fe/GAC composites. The optimal condition was two hours of $NaBH_4$ reduction without intermediate drying process. The prepared Fe/GAC composite showed synergistic effect of the adsorption capability of the GAC and the degradation capability of the nZVI, which make this composite a very effective material for environmental remediation.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.2
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• pp.47-52
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• 2015

A microbial fuel cell (MFC) is a device that can be obtained electricity from a variety of organic through the catalytic reaction of the microorganism. The MFC can be applied to various fields, and research is required to promote the performance of the microbial fuel cell for commercialization. The lower performance of an MFC is due to oxygen reduction at the cathode and the longer time of microbial degradation at anode. The MFC amount of power is sufficient but, in consideration of many factors, as a renewable energy, now commonly power density as compared to Nafion117 it is an ion exchange membrane used is PP (Poly Propylene) from 80 to about 11 fold higher, while reducing the cost to process wastewater is changed to a microporous non-woven fabric of a low cost, it may be energy-friendly environment to generate electricity. All waste, in that it can act as a bait for microorganisms, sustainability of the microbial fuel cell is limitless. The latest research on the optimization and performance of the operating parameters are surveyed and through the SSaM-GG(Smart, Shared, and Mutual- Green Growth) or GG-SSaM(Green Growth - Smart, Shared, and Mutual) as the concept of sustainable development in MFC, the middle indices are developed in this study.