• 항공우주시스템공학회지
• /
• 제7권1호
• /
• pp.1-7
• /
• 2013

Launch vehicles cause several shock events during their lift-off. The excessive shock loads in the several thousands of g's level can results in permanent damage to electronics, optics and other sensitive payload components. The shock can be attenuated by mounting a shock absorber. In this paper, we proposed a semi-active control logic to attenuate the shock so that the input acceleration to main instruments does not exceed the allowable maximum acceleration value. For the performance investigation, two elements model of variable damping and spring stiffness has been used and the analysis results indicate that the proposed semi-active control logic attenuates shock level better than an optimal passive and conventional semi-active on-off control system.

• The Plant Pathology Journal
• /
• 제20권4호
• /
• pp.271-276
• /
• 2004

To examine the control effect of damping-off on radish caused by Pythium spp., researchers used the isolates of a fungivorous nematode, Aphelenchus avenae, and antagonistic fungi, Trichoderma spp. These were used as biocontrol agents, either alone, or in combination. Growth rates of the A. avenae isolates and fungal damages by the nematodes varied depending on Trichoderma spp., which contained lower T. koningii and T. virens cultures than other Trichoderma cultures. Phythium spp. were damaged by all five Aphelenchus isolates, but the multiplication rate of nematode isolate Aa-3 was very poor. Antibiotic activity of T. virens and T. harzianum to Pythium spp. was stronger than that of T. koningii. Control efficacy against damping-off of radish was most enhanced under the treatment using the nematode-T. harzianum combination. On the contrary, the combinations of the nematodes and T. virens or T. koningii mostly did not increase or decreased their control effect vis-$\`{a}$-vis that of the nematodes or antagonistic fungi being used alone. The results suggest that the fungivorous nematodes may play a leading role in the disease control, and that the activity of the fungivorous nematodes may be activated by T. harzianum, but inhibited by T. koningii and T.virens.

• Journal of Microbiology and Biotechnology
• /
• 제14권3호
• /
• pp.599-606
• /
• 2004

Gram-positive antagonistic bacilli were isolated from agricultural soils for possible use in biocontrol of plant pathogenic fungi, Fusarium oxysporum, Rhizoctonia solani, and/or Pythium ultimum. Among the 65 antagonistic Gram-positive soil isolates, 22 strains were identified as Bacillus species by 16S rDNA sequence analyses. Four strains, including DF14, especially exhibited multiple antagonistic properties against the three damping-off fungi. Genotypic properties of the Bacillus isolates were characterized by rapid molecular fingerprinting methods using repetitive extragenic palindromic-PCR (REP-PCR), ribosomal intergenic spacer-length polymorphisms (RIS-LP), 16S rDNA PCR-restriction fragment length polymorphisms (PCR-RFLP), and strain-specific PCR assays. The results indicated that the REP-PCR method was more valuable than the RIS-LP and 16S rDNA PCR-RFLP analyses as a rapid and reliable approach for bacilli typing and identification. The use of strain-specific primers designed based on 16S rDNA sequence comparisons enabled it to be possible to selectively detect a strain, DF14, which is being used as a biocontrol agent against damping-off fungi.

• Journal of Ginseng Research
• /
• 제14권3호
• /
• pp.432-436
• /
• 1990

Incidence of damping-off callsed by Rhizoctonia solani was 0.6-10.9% at "Yangjik" seedbed in Pocheon, Korea. The seedbeds where the lengths of etiolated stems (underground portion) of ginseng seedlings were 0.78-1.25 cm showed 0.8-3.2% of the disease, while 6.9-10.9% disease incidence was observed at the seedbeds with the longer etiolated stem (1.89-2.26 cm). The pathogen produced a typical girdle symptom on the etiolated portion of ginseng stems close to the soil surface. The deeper the seeds were sown, the more the disease occurred in pot soil inoculated with the pathogen, AG 2-1, showing 18.4, 27.4 and 32.9% of damping-off at the seeding depth of 1, 2 and 4 cm, respectively. Cuticle layers of colored stems (over ground portion) were well - developed to be 42.8, 58.0, and 55.0 um in thickness compared to the etiolated stems with 8.5, 15.0 and 8.0um for seedling, 2 year-old, and 3 year-old ginsengs, respectively, when the disease occurred. In the seedling and 2 year-old ginseng, the colored stems were more rigid than the etiolated. There was however, no difference in rigidness of the stem of the 3 year-old ginseng where the disease is not severe as in seedlings and 2 year-old ginseng plants.ng plants.

• 식물병연구
• /
• 제8권4호
• /
• pp.234-238
• /
• 2002

Bacillus stearothermophilus YC4l94는 in vitro 와 in vivo 에서 병원균 Pythium aphanidermatum에 대한 억제 효과를 보였다 in vitro 실험에서 P. aphanidermatum의 유주포자낭 형성과 피낭포자 발아를 억제하였을 뿐 아니라 식물체에 적접 길항균 제제 처리 시 50% 이상의 방제가를 보였다. 그리고 다른 화학 살균제와 비슷한 방제효과를 보여 미생물 제제로서의 개발 가능성을 보여주었다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2011년도 추계학술대회 논문집
• /
• pp.59-63
• /
• 2011

Friction damping is one of the attractive vibration control technique for space structures due to its simplicity and large damping capacity. However, passive approaches for friction damping have a limitation because energy is no longer dissipated at sticking. In order to overcome this problem, semi-active control methods to adjust normal force at frictional interface have been studied in previous researches. In this paper, two semi-active friction control method is compared by simulating SDOF model of truss structure. The first approach is on-off control to maximize rate of energy dissipation, whereas the second concept is variable friction force control to minimize amplitude ratio for each half period. The maximum friction force, control variable in on-off control method, is obtained to minimize 1% settling time, and is different from optimal friction force in passive control. Simulation results show that performance of on-off control is better than that of variable friction force control in terms of settling time and controlled friction force.

• Ocean Systems Engineering
• /
• 제7권2호
• /
• pp.89-106
• /
• 2017

The study explores a novel design of wave energy converter (WEC) that utilizes the interaction between an inside heaving vertical cylinder with an outside fixed hollow cylinder. This design originates from the oscillating water column (OWC) type WEC but replaces the pneumatic power take off (PTO) through the Wells turbine with the hydrodynamic PTO through the inside heaving cylinder. To effectively evaluate the maximum power output, the system has been modeled in the hydrodynamic software AQWA (developed by ANSYS Inc) that has accumulated extensive offshore industry users. Ranges of the PTO parameters have been examined to make sure that proper linear damping can be implemented to simulate the PTO force. Comparing the efficiency of the pneumatic PTO with the hydrodynamic PTO, it appears that the hydrodynamic PTO is more promising than the traditional Wells turbine for an OWC system.

• 한국소음진동공학회논문집
• /
• 제21권5호
• /
• pp.447-454
• /
• 2011

This paper reports a filtered velocity feedback(FVF) controller, which is an alternative to direct velocity feedback(DVFB) controller. The instability problems due to high frequency response under DVFB can be alleviated by the suggested FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The FVF controller and the dynamics of clamped beams under forces and moments are first formulated. The effects of the design parameters(cut-off frequency, gain, and damping ratio) on the stability and the performance are then investigated. The cut-off frequency should be selected not to affect the system stability. The magnitude of the open loop transfer function(OLTF) at the cut-off frequency should be small. As increasing the gain of the FVF controller, the magnitude of the OLTF is increased, so that the closed loop response can be reduced more. The enhancement of the OLTF at the cut-off frequency is reduced but the phase behavior around the cut-off frequency is distorted, as the damping ratio is increased. The control performance is finally estimated for the clamped beam. More than 10 dB reductions in velocity response can be achieved at the modal frequencies from the first to eighth modes.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2011년도 춘계학술대회 논문집
• /
• pp.264-270
• /
• 2011

This paper reports a filtered velocity feedback (FVF) controller, which is an alternative to direct velocity feedback (DVFB) controller. The instability problems due to high frequency response under DVFB can be alleviated by the suggested FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The FVF controller and the dynamics of clamped beams under forces and moments are first formulated The effects of the design parameters (cut-off frequency, gain, and damping ratio) on the stability and the performance are then investigated. The cut-off frequency should be selected not to affect the system stability. The magnitude of the open loop transfer function (OLTF) at the cut-off frequency should be small. As increasing the gain of the FVF controller, the magnitude of the OLTF is increased, so that the closed loop response can be reduced more. The enhancement of the OLTF at the cut-off frequency is reduced but the phase behavior around the cut-off frequency is distorted, as the damping ratio is increased The control performance is finally estimated for the clamped beam. More than 10dB reductions in velocity response can be achieved at the modal frequencies from the first to eighth modes.

• 농약과학회지
• /
• 제11권1호
• /
• pp.8-17
• /
• 2007

N-phenylbenzenesulfonamide 및 N-phenyl-2-thienylsulfonamide 유도체(1-34)들의 phenyl 및 theinyl 고리상치환기(R1-R5) 변화에 따른 모잘록병균(Pythium ultimum)의 살균활성에 관한 3차원적인 정량적 구조와 활성과의 관계(3D-QSARs)들을 비교 분자장 분석(CoMFA)과 비교분자 유사성 지수분석(CoMSIA) 방법으로 각각 검토하였다. 전반적으로 CoMSIA 모델들의 통계값은 atom based fit 정렬보다는 field fit 정렬시에 높은 값을 나타내었으나 CoMFA모델의 경우에는 차이가 없었다. 그리고 CoMSIA (FF1) 모델($r_{cv.}^2\;(q^2)=0.674$ 및 $r_{ncv.}^2=0.964$)이 CoMFA (AF5) 모델($r_{cv.}^2\;(q^2)=0.616$ 및 $r_{ncv.}^2=0.930$)보다 상관성과 예측성이 양호하였다. CoMSIA (FF1) 모델의 정보에 따라 살균활성은 분자의 정전기장과 소수성장에 의존적이었다. 또한, CoMSIA (FF3) 모델의 등고도 분석 결과로부터 N-phenyl 고리상 R4-치환기의 친수성과 수소결합 받게로서의 성질인 모잘록병균의 살균활성에 기여할 것으로 예상되었다.