• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1347-1348
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• 2006

기존 반도체공정들이 갖는 리소그래피와 식각 등의 공정단계를 배제하는 direct-write 공정을 이용하여 친환경적인 이점을 가질 수 있는 나선형 인덕터의 구조를 제안하고 주파수 특성을 확인하였다. 인덕터의 구조는 Si를 $300{\mu}m$, $SiO_2$를 $3{\mu}m$으로 하였으며, CU 코일의 폭과 선간의 간격은 LAM 공정과 direct-write 공정을 이용할 수 있도록 각각 $100{\mu}m$으로 설정하여 3회 권선하였다. 인덕터는 200-500MHz 범위에서 3.5nH의 인덕턴스, 4GHz에서 최대 29 정도의 품질계수를 가지며, SRF는 2.6GHz로 시뮬레이션 결과를 얻을 수 있었다.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.543-547
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• 2001

A protection scheme for Unified Power Quality Conditioner (UPQC) is presented and analyzed in this paper. The proposed UPQC has the series active power filter operated as a high impedance k($\Omega$) to the fundamentals when short-circuit faults occur in the power distribution system, and three control strategies are proposed in this paper. The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF) and the third is the method by detecting the input voltage. When the short-circuit fault occur in the power distribution system, the proposed scheme protects the UPQC without additional protection circuits. The validity of proposed protection scheme is investigated through simulation results.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.281-282
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• 2014

본 논문은 FPGA 기반의 DSC-PLL(Delayed Signal Cancellation - Phase Locked Loop)을 설계하고, 왜곡된 3상전압 조건에서 위상추종결과를 비교실험 하였다. FPGA 구현 알고리즘은 Matlab/Simulink와 연동된 System Generator를 이용하여 DSC-PLL 모델을 설계하고, Verilog HDL 코드로 변환 하였다. 불평형 및 고조파를 포함한 왜곡된 3상 전압 조건에서 FPGA에 구현된 DSC-PLL과 SRF-PLL (Synchronous Reference Frame - Phase Locked Loop)의 d-q축 고조파 감쇠특성 및 위상추종능력을 실험을 통해 비교하였다. DSC-PLL은 약 5.44ms 이내에 d-q축 고조파 성분을 제거함으로써 정상분 기본파 전압의 위상을 빠르게 추종하는 것을 검증하였다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.494-495
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• 2012

본 논문은 LVRT 제어를 위한 계통 사고 상황에서도 정확한 위상각을 검출하기 위하여 일반화된 2차 적분기(Second Order Generalized Integrator)를 이용한 정상분 전압 검출을 기반으로 하며, 주파수 변동에도 강인성 제어가 가능한 DSOGI (Double Second Order Generalized Integrator) FLL(Frequency locked loop)을 제안한다. 실험을 통해 종래의 SRF(Synchronous reference frame) PLL, DSOGI PLL 제어와 비교, 분석을 통해 본 논문의 타당성을 입증한다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.77-78
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• 2023

This paper experimentally examined the recycling of combustion by-products emitted from a combined heat and power plant using lignocellulosic biomass fuel. Physical and chemical analyzes were performed on Bio-SRF and three types of wood pellet combustion by-product samples (fly-ash, FA). As a result of the experiment, the compressive strength of mortar substituted with 5, 10, and 20% of FA compared to the cement weight was found to be excellent, and its recyclability was confirmed as a substitute for existing admixtures.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.355-361
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• 2013

In this work, torrefaction of the sewage sludge was investigated the characteristics of torrefied products and the value of as energy resource to improve energy density and to maintain consistent quality of SRF. Torrefaction was performed two important torrefaction operational parameter, temperature($150-230^{\circ}C$) and reaction time(10-60min). As raising the torrefaction temperature at long reaction times, the moisture content of torrefied products was decreased, while the heating value was increased. Moreover, increasing of the torrefaction temperature led to a increase of the content of the carbon up to 60% compare to the initial the sample, and a decrease of the content hydrogen and oxygen. Especially, Average heating value was 4,818 kcal/kg regardless of the reaction time when torrefaction was performed over $210^{\circ}C$. In addition, the fuel ration and coal band were improved after torrefaction because the O/C and the H/C ratio were decreased.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.69-89
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• 2019

Design chart solution and table solution were proposed by Choi et al. (2019a), which conducted a parametric numerical study for the bored PHC piles socketed into weathered rocks through sandy soil layers. Based on the Choi et al. (2019a), the new prediction formulae for mobilized capacity components such as total capacity, total skin friction and skin friction of sand at the settlement of 5% pile diameter were proposed in this study. The proposed prediction formulae (EQ-G1) considers pile diameter, relative embedment length and ${\bar{N}}$ (i.e, corrected N) value and their verification results are as follows. The SRF calculated from the new proposed design method was 71~94%, which are greatly improved compared with results by the existing design method. The design efficiency of bearing capacity was in the range of reasonable design except 4 cases, and the design efficiency of the PHC pile was evaluated as 85%. Therefore, it is possible that allowable compressive load (P_all) of PHC pile can be utilized in the resonable design by means of the new proposed method using EQ-G1 equations. And the other new proposed equations of EQ-G2-3 can be utilized approximately in calculation of axial compressive bearing capacity components for prebored PHC pile.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.361-368
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• 2006

The purpose of this study is to invent the preparation technique of the foam-floater used as a level gauge of liquefied petroleum gas (LPG) tank under high pressure, which has not only closed pores but also has under 5 wt% changingrate in case of depositing 72 h in room-temperature LPG. In pressure-resistance and deposition experiment, the prepared foam-floaters with different sulfur (325 Mesh and 400 Mesh) and foaming agent (dinitrosopentamethylenetetramin; DPT and azodicarbonamide; AC) had a marginal difference in its weight changing-rate. However, the prepared floater with sulfur 400 Mesh and the foaming agent AC had smaller pores and higher closed pore-rate. Under $50kg_f/cm^3$ hydraulic pressure, the floater with medium thermal (MT) carbon showed a lower weight changing-rate than semi reinforcing furnace (SRF) carbon. Providing a post-treatment to the prepared floater, the hardness and the pressure-resistance of the inner pore-wall of floater were increased. Prepared floaters having a specific gravity below 0.30 were distorted and broken, and other floaters with a specific gravity above 0.35 were not useful as a floater because of the low buoyancy. Therefore, it was considered that the floaters with a specific gravity between 0.3~0.35 are the most useful as a floater under $50kg_f/cm^3$ pressure-resistance.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.301-310
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• 2010

Bacillus subtilis strains produce a broad spectrum of bioactive peptides. The lipopeptide surfactin belongs to one well-known class, which includes amphiphilic membrane-active biosurfactants and peptide antibiotics. Both the srfA promoter and the ComP-ComA signal transduction system are an important part of the factor that results in the production of surfactin. Bs-M49, obtained by means of low-energy ion implantation in wild-type Bs-916, produced significantly lower levels of surfactin, and had no obvious effects against R. solani. Occasionally, we found strain Bs-M49 decreased spore formation and the development of competence. Blast comparison of the sequences from Bs-916 and M49 indicate that there is no difference in the srfA operon promoter PsrfA, but there are differences in the coding sequence of the comA gene. These differences result in three missense mutations within the M49 ComA protein. RT-PCR analyses results showed that the expression levels of selected genes involved in competence and sporulation in both the wild-type Bs-916 and mutant M49 strains were significantly different. When we integrated the comA ORF into the chromosome of M49 at the amyE locus, M49 restored hemolytic activity and antifungal activity. Then, HPLC analyses results also showed the comA-complemented strain had a similar ability to produce surf actin with wild-type strain Bs-916. These data suggested that the mutation of three key amino acids in ComA greatly affected the biological activity of Bacillus subtilis. ComA protein 3D structure prediction and motif search prediction indicated that ComA has two obvious motifs common to response regulator proteins, which are the N-terminal response regulator receiver motif and the C-terminal helix-turn-helix motif. The three residues in the ComA N-terminal portion may be involved in phosphorylation activation mechanism. These structural prediction results implicate that three mutated residues in the ComA protein may play an important role in the formation of a salt-bridge to the phosphoryl group keeping active conformation to subsequent regulation of the expression of downstream genes.

• Journal of IKEEE
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• v.11 no.4
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• pp.145-151
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• 2007

In this work, small-size, high-performance solenoid-type RF chip inductors utilizing a low-loss ${Al_2}{O_3}$ core material were investigated. The size of the chip inductors fabricated in this work were $0.86{\times}0.46{\times}0.45m^3$, $1.5{\times}1.0{\times}0.7m^3$, $2.1{\times}1.5{\times}1.0m^3$, and $2.4{\times}2.0{\times}1.4m^3$ and copper (Cu) wire with $27{\sim}40{\mu}m$ diameter was used as the coils. High frequency characteristics of the inductance, quality factor, and impedance of developed inductors were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 7 have the inductance of 13 to 100nH and exhibit the self-resonant frequency (SRF) of 6.4 to 1.1GHz. The SRF of inductors decreases with increasing the inductance and the inductors have the quality factor of 50 to 80 in the frequency range of 300MHz to 1.3GHz. In this study, small-size solenoid-type RF chip inductors with high inductance and high quality factor were fabricated successfully.