• 한국식물병리학회지
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• 제11권1호
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• pp.9-16
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• 1995

Undiluted neoasozin solution (6.5% a.i.), an arsenic fungicide, was sprayed on 169 cankers of apple trees from early March to September in 1987 twice at intervals of one week without scraping off the affected barks. Among the treated cankers, 79.9% ceased to grow within 1∼7 weeks, 13.0% showed partial development, and 7.1% grew continuously to girdle the branches. The partially developed cankers, however, could also be cured by an additional spray after slightly piercing at the edge of cankers to facilitate the penetration of the chemical. When the canker growth was blocked, cankers were encircled by cracks developed at the marginal area of the cankers. If the cracks developed once, very few cankers grew beyond them. The above results suggest that the crack development may be the consequence of the host defense activity to wall off the pathogen. In addition to the curative efficacy, the neoasozin solution inhibited sporulation of the pathogenic fungus almost completely. However, the pathogen survived for more than three months in some cankers that externally appeared to be cured, suggesting that an indirect mode of action of the chemical against apple Valsa canker seems to be still more persuasive than the direct fungicidal effect. In the final examination conducted in the mid April of the next year, 72.7% of the cankers were completely cured by the two successive neoasozin treatments. Moreover the cure rate became 83.1% if that of partially developed cankers which were also completely cured by an additional treatment was also taken into account. Since 1989 when this method was widely applied in apple orchards in Korea, apple Valsa canker has been effectively controlled to reach a tolerable level.

• 한국환경성돌연변이발암원학회지
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• 제25권4호
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• pp.157-160
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• 2005

Biofilm 내부의 항생제 내성 박테리아의 성장형태는 만성감염과 질병을 발생한다. 인위적 형성한 biofilm의 체외실험 모델 시스템 통한 항생제 침투 실험을 수행하였다. 항생제 내성 균주 (E. coli, S. aureus)는 항생제 내성균주 은행으로부터 획득하였다 Ca-alginate bead를 인위적 biofilm으로 사용하였고, 세포 생존률을 향상시키기 위해 공기 압축을 이용한 세포 포획 실험도 측정되었다. biofilm의 항생제 감수성은 항생제의 농도 따라 최저 저해 농도 (MIC)를 이용하여 측정되었다. bead생성에 따른 안정성은 bead를 형성하지 않은 세포와 비교하여 감소하였다. 항생제에 민감한 E. coli의 경우 시간이 지남에 따라 균체수도 감소하였으나, 항생제 내성 E. coli는 일정한 균체수를 유지하였다. bead형성 후 항생제 투여 효과는 항생제 내성이 있고, 낮은 농도의 항생제를 처리할수록 더 높은 생존률을 보였다.

• 전기학회논문지
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• 제65권8호
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• pp.1334-1339
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• 2016

In a power grid that has a high wind power penetration, the fast voltage support of a wind power plant (WPP) during the grid fault is required to stabilize the grid voltage. This paper proposes a voltage control scheme of a doubly-fed induction generator (DFIG)-based WPP that can promptly support the voltage of the point of common coupling (PCC) of a WPP during the grid fault. In the proposed scheme, the WPP and DFIG controllers operate in a voltage control mode. The DFIG controller employs two control loops: a maximum voltage dip-dependent reactive current injection loop and a reactive power to voltage loop. The former injects the reactive power in proportion to the maximum voltage dip; the latter injects the reactive power in proportion to the available reactive power capability of a DFIG. The former improves the performance of the conventional voltage control scheme, which uses the latter only, by increasing the reactive power as a function of the maximum voltage dip. The performance of the proposed scheme was investigated for a 100-MW WPP consisting of 20 units of a 5-MW DFIG under various grid fault scenarios using an EMTP-RV simulator. The simulation results indicate that the proposed scheme promptly supports the PCC voltage during the fault under various fault conditions by increasing the reactive current with the maximum voltage dip.

• 한국분말재료학회지
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• 제26권3호
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• pp.231-236
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• 2019

Ni hydroxides ($Ni(OH)_2$) are synthesized on Ni foam by varying the hexamethylenetetramine (HMT) concentration using an electrodeposition process for pseudocapacitor (PC) applications. In addition, the effects of HMT concentration on the $Ni(OH)_2$ structure and the electrochemical properties of the PCs are investigated. HMT is the source of amine-based $OH^-$ in the solution; thus, the growth rate and morphological structure of $Ni(OH)_2$ are influenced by HMT concentration. When $Ni(OH)_2$ is electrodeposited at a constant voltage mode of -0.85 V vs. Ag/AgCl, the cathodic current and the number of nucleations are significantly reduced with increasing concentration of HMT from 0 to 10 mM. Therefore, $Ni(OH)_2$ is sparsely formed on the Ni foam with increasing HMT concentration, showing a layered double-hydroxide structure. However, loosely packed $Ni(OH)_2$ grains that are spread on Ni foam maintain a much greater surface area for reaction and result in the effective utilization of the electrode material due to the steric hindrance effect. It is suggested that the $Ni(OH)_2$ electrodes with HMT concentration of 7.5 mM have the maximum specific capacitance (1023 F/g), which is attributed to the facile electrolyte penetration and fast proton exchange via optimized surface areas.

• 한국분무공학회지
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• 제23권4호
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• pp.192-204
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• 2018

In this study, a 3D CFD analysis method for the combustion process was established for a low calorific value syngas-diesel dual-fuel engine operating under very lean fuel-air mixture condition. Also, the accuracy of computational analysis was evaluated by comparing the experimental results with the computed ones. To simulate the combustion for the dual-fuel engine, a new dual-fuel chemical kinetics set was used that was constituted by merging two verified chemical kinetic sets: n-heptane (173 species) for diesel and Gri-mech 3.0 (53 species) for syngas. For dual-fuel mode operations, the early stage of combustion was dominated by the fuel burning inside or near the spray plume. After which, the flame propagated into the syngas in the piston bowl and then proceeded toward the syngas in the squish zone. With the baseline injection system and piston shape, a significant amount of unburned syngas was discharged. To solve this problem, effects of the injection parameters and piston shape on combustion characteristics were analyzed by calculation. The change in injection variables toward increasing the spray plume volume or the penetration length were effective to cause fast burning in the vicinity of TDC by widening the spatial distribution of diesel acting as a seed of auto-ignition. As a result, the unburned syngas fraction was reduced. Changing the piston shape with the shallow depth of the piston bowl and 20% squish area ratio had a significant effect on the combustion pattern and lessened the unburned syngas fraction by half.

• Restorative Dentistry and Endodontics
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• 제46권2호
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• pp.22.1-22.12
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• 2021

Objectives: This study evaluated and compared the effects of radiation therapy on the dislocation resistance of AH Plus and BioRoot RCS applied to dentin and the sealer-dentin interface. Materials and Methods: Thirty single-rooted teeth were randomly assigned to 2 groups (n = 15 each): AH Plus (Dentsply DeTrey) and BioRoot RCS (Septodont). Each group was subdivided into control and experimental groups. The experimental group was subjected to a total radiation dose of 60 Gy. The root canals of all samples were cleaned, shaped, and obturated using the single-cone technique. Dentin slices (1 mm) were sectioned from each root third for the push-out test and scanning electron microscopy (SEM) was done to examine the sealer-dentin interface. The failure mode was determined using stereomicroscopy. Bond strength data were analyzed by the independent t-test, 1-way analysis of variance, and the Tukey post hoc test (α = 0.05). Results: Significantly lower bond strength was observed in irradiated teeth than non-irradiated teeth in the AH Plus group (p < 0.05). The BioRoot RCS group showed no significant reduction in bond strength after irradiation (p > 0.05) and showed a higher post-irradiation bond strength (209.92 ± 172.26 MPa) than the AH Plus group. SEM revealed slightly larger gap-containing regions in irradiated specimens from both groups. Conclusions: The dislocation resistance of BioRoot RCS was not significantly changed by irradiation and was higher than that of AH Plus. BioRoot RCS may be the sealer of choice for root canal treatment in patients undergoing radiation therapy.

• 방송공학회논문지
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• 제18권4호
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• pp.572-588
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• 2013

본 논문에서는 지상파방송 무선전송 환경에서 4K-UHDTV 혹은 8K-UHDTV 및 UHD-3DTV 등 차세대방송 구현 및 효과적인 수신환경 구축 가능성을 현재 상용화된 전송방식 중 DVB-T2 기술을 중심으로 제안하였다. 특히, 2012년 완료된 지상파방송 디지털전환에 이어 또다시 UHDTV방송을 위한 차세대방송 투자와 전환의 성공조건으로 초고화질 영상 전송 외에도 TV뿐만 아니라 개인형 멀티미디어 단말기에서도 수신이 가능한 직접수신과 실내수신 및 언제 어디서나 자유로운 수신환경 제공도 매우 중요함을 강조하고 있다. 본 논문에서는 UHDTV방송 구현 시 효율적인 주파수 활용과 효과적인 수신환경 구축방안을 찾는데 목적을 두고 있다. 아울러 DVB-T2 전송방식이 가지고 있는 SFN 기능 및 강력한 수신오류정정 능력을 이용하여 VHF대역과 UHF대역 등 2개의 서로 다른 주파수에 의한 SFN 송출망 구성 방법을 제시하고, SFN 소출력중계기 및 가정용 Gap Filler를 활용한 자유로운 무선수신환경 구축 방안을 제안하고 있다. 그 외 10MHz 폭 채널을 이용한 UHDTV방송 효과와 주파수 소요량을 제시한다.

• 한국지반환경공학회 논문집
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• 제13권1호
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• pp.63-74
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• 2012

국내에서 그라우팅은 대부분 전문성 있는 지식이나 이론적인 연구에 의한 방법이 아닌 경험적인 방법에 의해 설계되고 있다. 따라서, 본 연구에서는 그라우팅이 적용되는 건설현장에서 자동화 그라우팅 기법의 품질관리기술과 방법에 대한 것을 논의하고자 한다. 연구결과, 제한적인 물주입시험에 의한 최적주입압 결정과 관련된 방법은 그라우팅 전.후에 대한 평가만이 가능한 것으로 나타났으며, 그라우팅재료가 지반내에서 확산하는 동안 주입압력(p)~주입속도(q)~침투시간(t) 차트 분석을 통해 주입압, 주입속도, 침투시간의 특성을 평가할 경우 그라우트 압력에 의한 지반의 파쇄를 방지할 수 있을 것으로 나타났다. 주입압력(p), 주입속도(q)와 침투시간(t) 곡선을 분석하여 적합한 값을 도출하면 효과적인 설계를 수행할 수 있다. 본 차트분석기법은 기존의 종이롤에 기록되어 지는 주입압력(p)과 주입속도(q)를 정리하여 관리할 수 있으며, 통합유량계는 정확한 수량을 기록할 수 있으나 기록된 주입압력은 초기, 중급 및 최종 지점에 따라 다르게 나타나므로, 통합유량계 및 그라우팅 대상 지반의 특성의 상관관계가 규명되는 것이 바람직한 것으로 사료된다, 본 연구에서 제안된 자동화 그라우팅 기법은 주입압력과 그라우팅 대상 지반의 특성간의 신뢰성 있는 상관관계를 설명할 수 있으며, 이를 활용한 그라우팅 품질관리 기술을 발전시킬 것으로 기대된다.

• 대한의용생체공학회:의공학회지
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• 제19권5호
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• pp.511-518
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• 1998

세기관지의 구조와 이상유무의 신속 정확한 측정을 위해 세계적으로 활발히 연구되고 있는 에어로졸볼러스기법을 확립하기 위하여, 호흡과정 중 흡기에 공급된 입자펄스가 호흡의 진행에 따라 인체기관지내에서 대류분산된 결과로 호기중 입자농도의 증가된 분포폭을 측정하는 장치를 개발하고 이를 이용한 검증실험을 수행하였다. 개발된 장치는 인체에 무해한 sebacic acid를 이용하여 평균입경이 1 $\mu$m이고 기하표준편차가 1.2정도인 임자를 $10^{9}$개/cc 정도의 고농도로 발생하고, 솔레노이드밸브를 이용하여 호흡중의 원하는 시점에 정확히 짧은 펄스형태로 입자를 공급하며, 레이저광산란을 이용하여 흡기와 호기중의 입자농도의 시간변화를 측정한다. 흡기중의 농도분포는 매우 매끈한 분포를 보임으로써 발생장치와 측정장치의 정강작동은 잘 검증되었다. 농도의 시간변화 측정치로부터 계산된 분산도를 1차원 대류확산방정식 이론치 및 외국에서 보고된 실험결과와 비교한 격과, 입자도달깊이에 따른 분산도의 변화에 대한 정성적인 실험결과는 이론치와 상당히 잘 일치하고 기존의 결과보다도 견과의 산포가 개선되었다. 다만 아직도 산포가 상당히 남아있어 개선의 여지를 가지고 있으며, 외국 결과와의 분산도의 타이는 신체조건의 타이 등으로 파악되었다. 산포도의 개선을 위해서는 호흡시에, 특히 최고농도점 부근에서, 호흡유량이 일정하게 유지되어야만 불규칙 이차파형의 형성을 방지하여 측정결과의 해석에 오차를 줄일 수 있음을 확인하였다.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2016년도 춘계학술대회 및 임시총회
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• pp.13-13
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• 2016

Insects constitute the largest and most diverse group of animals in the world. They also serve as the hosts or nutrient sources for an immense assemblage of pathogens, parasites, and predators. More than 700 fungal species from 100 genera have adopted an entomopathogenic lifestyle. Although entomopathogenic fungi were studied as only biocontrol agents against a variety of pests in various countries, it has been recently focused their additional roles in nature. They are antagonists to/against plant pathogens, endophytes, and possibly even plant growth promoting agents. The potential antimicrobial effect against fungal plant pathogens by an isolate of entomopathogenic fungi including Beauveria bassiana, Lecanicillium spp., and Isaria fumosorosea have been reported since late 1990s, but wasn't reported pathogenicity of the isolate against pests. Later, a Canadian Lecanicillium sp. isolate and L. longisporium isolated from Vertalec$^{(R)}$ showed simultaneous control effect against both aphid and cucumber powder mildew. Therefore, the antimicrobial activities of 342 fungi isolates collected from various regions and conditions in Korea were evaluated against plant pathogenic fungus Botrytis cinerea using dual culture technique on agar plate. As a result, 186 isolates (54.4%) shown the antifungal activity against B. cinerea. The culture filtrates of selected fungi completely suppressed the growth of the microorganisms, indicating that suppression was due to the presence of antimicrobial substances in the culture filtrate. Mode of action of these fungi against insect involves the attachment of conidia to the insect cuticle, followed by germination, cuticle penetration, and internal dissemination throughout the insect. During infection process, secreted enzymes, proteinous toxins, and/or secondary metabolites secreted by entomopathogenic fungi can be used to overcome the host immune system, modify host behavior, and defend host resources. Recently, secondary metabolites isolated from entomopathogenic fungi have been reported as potential bioactive substances. Generally, most of bioactive substances produced by entomopathogenic fungi have reported low molecular weight (lower than 1,000 g/mol) as peptide and, in contrast the high molecular weight fungal bioactive substances are rare. Most substances based on entomopathogenic fungi were shown antimicrobial activity with narrow control ranges. In our study we analyzed the antimicrobial substances having antagonistic effects to B. cinerea. Antimicrobial substances in our fungal culture filtrates showed high thermostability, high stability to proteolytic enzymes, and hydrophilicity and their molecular weights were differed from substance. In conclusion, entomopathogenic fungi showed pathogenicity against insect pests and culture filtrate of the fungi also shown to antimicrobial activity. In the future, we can use the entomopathogenic fungi and its secondary metabolites to control both insect pest control and plant pathogenic fungi simultaneously.