• Clean Technology
• /
• v.26 no.1
• /
• pp.72-78
• /
• 2020

The use of fossil fuel and biogas production causes air pollution and climate change problems. Research endeavors continue to focus on converting methane and carbon dioxide, which are the major causes of climate change, into quality energy sources. In this study, a novel plasma-carbon converter was proposed to convert biogas into high quality gas, which is linked to photovoltaic and wind power and which poses a problem on generating electric power continuously. The characteristics of conversion and gas production were investigated to find a possibility for biogas conversion, involving parametric tests according to the change in the main influence variables, such as O₂/C ratio, total gas feed rate, and CO₂/CH₄ ratio. A higher O₂/C ratio gave higher conversions of methane and carbon dioxide. Total gas feed rate showed maximum conversion at a certain specified value. When CO₂/CH₄ feed ratio was decreased, both conversions increased. As a result, the production of solar fuel by plasma oxidation destruction-carbon material gasification conversion, which was newly suggested in this study, could be known as a possibly useful technology. When O₂/C ratio was 0.8 and CO₂/CH₄ was 0.67 while the total gas supply was at 40 L min^-1 (VHSV = 1.37), the maximum conversions of carbon dioxide and methane were achieved. The results gave the highest production for hydrogen and carbon dioxide which were high-quality fuel.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1566-1577
• /
• 2015

A novel high step-up converter is presented herein, which combines the conventional buck-boost converter, the charge pump capacitor and the coupling inductor. By doing so, a quite high voltage conversion ratio due to not only the turns ratio but also the duty cycle, so as to increase design feasibility. It is noted that the denominator of the voltage conversion ratio is the square of one minus duty cycle. Above all, there is no voltage spike across the switch due to the leakage inductance and hence no passive or active snubber is needed, and furthermore, the used switch is driven without isolation and hence the gate driving circuit is relatively simple, thereby upgrading the industrial application capability of this converter. In this paper, the basic operating principles and the associated mathematical deductions are firstly described in detail, and finally some experimental results are provided to demonstrate the effectiveness of the proposed high step-up converter.

• Journal of Hydrogen and New Energy
• /
• v.32 no.6
• /
• pp.534-541
• /
• 2021

In this study, a novel microwave-matrix reformer was proposed to convert CH₄, which is a major component, to a high quality hydrogen energy. And to identify this performance, it was investigated for O₂/C ratio, steam feed amount and reformed gas recirculation which are affected for methane conversion and product gas yield. Through the parametric screening studies, optimal operating conditions were that O₂/C ratio, steam feed amount and recirculation rate were 1.1, 10 mL/min and 30 L/min. In this conditions, CH₄ conversion was 68.1%, H₂ selectivity 77.2 and H₂/CO ratio 2.62 which are possible applying SOFC stack for RPG (residential power generator).

• Journal of Power Electronics
• /
• v.13 no.5
• /
• pp.737-745
• /
• 2013

Offshore wind farms are rapidly growing owing to their comparatively more stable wind conditions than onshore and land-based wind farms. The power capacity of offshore wind turbines has been increased to 5MW in order to capture a larger amount of wind energy, which results in an increase of each component's size. Furthermore, the weight of the marine turbine components installed in the nacelle directly influences the total mechanical design, as well as the operation and maintenance (O&M) costs. A reduction in the weight of the nacelle allows for cost-effective tower and foundation structures. On the other hand, longer transmission distances from an offshore wind turbine to the load leads to higher energy losses. In this regard, DC transmission is more useful than AC transmission in terms of efficiency because no reactive power is generated/consumed by DC transmission cables. This paper describes some of the challenges and difficulties faced in designing high-power-density power conversion systems (HPDPCSs) for offshore wind turbines. A new approach for high gain/high voltage systems is introduced using transformerless power conversion technologies. Finally, the proposed converter is evaluated in terms of step-up conversion ratio, device number, modulation, and costs.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.89-92
• /
• 2007

Partail oxidation(POX) of n-butane was investigated in this research by employing ceria-promoted Ni/calcium hydroxyapatite catalysts ($Ce_xNi_{2.5}Ca_{10}(OH)_2(PO_4)_6$ ; x = $0.1{\sim}0.3$) which had recently been reported to exhibit good catalytic performance in POX of methane and propane. The experiments were carried out with changing ceria content, $O_2/n-C_4H_{10}$ ratio and temperature. As the $O_2/n-C_4H_{10}$ feed ratio increased up to 2.75, n-$C_4H_{10}$ conversion and $H_2$ yield increased and the selectivity of methane and other hydrocarbons decreased. But with $O_2/n-C_4H_{10}$ = 3.0, $n-C_4H_{10}$ conversion and $H_2$ yield decreased. This is considered due to that too much oxygen may inhibit the reduction of Ni or induce the oxidation of Ni, which results in poor catalytic activity. The optimum $O_2/n-C_4H_{10}$ ratio lay between 2.50 and 2.75. $Ce_{0.1}Ni_{2.5}Ca_{10}(OH)_2(PO_4)_6$ showed the highest $n-C_4H_{10}$ conversion and $H-2$ yield on the whole. In durability tests, higher hydrogen yield and better catalyst stability were obtained with the $O_2/n-C_4H_{10}$ ratio of 2.75 than with the ratio of 2.5.

• Journal of Korean Society on Water Environment
• /
• v.30 no.2
• /
• pp.128-137
• /
• 2014

The land use of the unit watersheds should be maintained appropriately in order to keep the load allotment stable for the management of Total Maximum Daily Loads (TMDLs). This study classified the land area in four types and analyzed the use of each land type and its changing pattern by calculating the occupation and conversion ratios for the unit watersheds in three river basins. The forest land showed the greatest occupation ratio with 63.0%, followed by the farm land with 23%, the other area with 8.0% and the site area with 6.0% in 2003. The occupation ratio of the site and the other area increased by 0.4% and 0.2% respectively, and that of the farm and the forest land decreased by 0.4% and 0.2% respectively in 2007. The conversion ratio for the site area ranged from 1.65% to 1.97%, for the farm land from -0.47% to -0.33%, for the forest land from -0.10% to -0.04% and for the other area from 0.17% to 1.97%. It can be inferred that the decrease in the farm and the forest land contributed to the increase in the site area and that the increase in the other area was mainly made by the decrease in the forest land. It could be more effective to take into account the changes in the site area and in the forest land in the process of developing the TMDL plans.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.19 no.1
• /
• pp.77-84
• /
• 2024

This paper introduces a study on an electromagnet magnetic gear designed for gear ratio conversion. In comparison to magnetic gears using permanent magnets, this electromagnet magnetic gear exhibits lower torque density, highlighting the need for torque density improvement. To address this, the research focuses on enhancing torque density by examining the consistent orientation of each rotor's magnetization during gear ratio conversion and attaching permanent magnets accordingly. However, an issue arises due to the uneven magnetic flux density caused by the non-uniform attachment of permanent magnets, leading to an increase in torque ripple. Therefore, building upon previous studies aimed at reducing torque ripple in electromagnet magnetic gears, this research explores the optimal methods, such as pole piece bridges and fillet configurations, to mitigate torque ripple even during gear ratio conversion.

• Restorative Dentistry and Endodontics
• /
• v.37 no.2
• /
• pp.96-103
• /
• 2012

Objectives: This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems. Materials and Methods: Two monomer mixtures (37.5 Bis-GMA/37.5 Bis- EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/ 0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance. Results: DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A ($14.63{\pm}10.42$, $25.23{\pm}6.32$, $51.62{\pm}2.69$, $68.52{\pm}2.77$); Group B ($4.04{\pm}6.23$, $16.56{\pm}3.38$, $37.95{\pm}2.79$, $64.48{\pm}1.21$); Group C ($16.87{\pm}5.72$, $55.47{\pm}2.75$, $60.83{\pm}2.07$, $68.32{\pm}3.31$); Group D ($23.77{\pm}1.64$, $61.05{\pm}1.82$, $65.13{\pm}2.09$, $71.87{\pm}1.17$); Group E ($28.66{\pm}2.92$, $56.68{\pm}1.33$, $60.66{\pm}1.17$, $68.78{\pm}1.30$); Group F ($39.74{\pm}6.31$, $61.07{\pm}2.58$, $64.22{\pm}2.29$, $69.94{\pm}2.15$). Conclusion: All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.6 no.1
• /
• pp.31-42
• /
• 1998

A fundamental study on methane conversion for the collection organic wastes of agriculture, forestry and fishers was performed in a laboratory scale. As a result, selected Run B sample were obtained 18.41 C/N Ratio and 168.96 mg/L TCOD; Under the biochemical methane potential test, theoretical and actual methane generation was 313.6 mg/L VS added and 234.2 mg/L VS added, respectively; However, methane conversion from Run B were occurred 74% by anaerobic digestion. By the first order reaction kinetics, kinetic constant were $0.2476d^{-1}$ for Run B. Three steps fill-up filter reactor was evaluated methane content 16% up to promote than blank reactor; TCOD and SCOD have reduced 44.7% and 44.2%, respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.11
• /
• pp.1977-1983
• /
• 2000

SCR(selective catalytic reduction) pilot plant for reduction of the nitrogen oxides using diesel oil as a reductant was installed at the NG(natural gas) fired combined cycle and the activity of Pt(0.3%)/Zeolite catalyst was studied in real flue gas condition according to the amount of reductant. reaction temperature and space velocity. NOx conversion gradually increased with increasing the diesel oil concentration up to C/N ratio 5.5(C/N ratio: the ratio of the number of carbon atom to the number of NOx molecules included in the flue gas). Increasing the reaction temperature. NOx conversion increased and reached a maximum conversion of 50% at $190^{\circ}C$. NOx conversion did not changed with increasing the space velocity up to 18,500/hr and then gradually decreased. These results reveal the potential for diesel oil as a reductant for de-NOx SCR process.