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RISS 인기검색어
- 검색키워드
- 저자 : Ecker, Horst (검색결과 5 건)
- 무료
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- 유료
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Electrically-induced actuation for open-loop control to cancel self-excitation vibration
Makihara, Kanjuro,Ecker, Horst Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.9 No.2
This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variable-stiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electrically-induced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.
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Electrically-induced actuation for open-loop control to cancel self-excitation vibration
Kanjuro Makihara,Horst Ecker 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.9 No.2
This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variablestiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electricallyinduced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.
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INSIGHT INTO THE GROWTH MECHANISM OF WS2 NANOTUBES IN THE SCALED-UP FLUIDIZED-BED REACTOR
R. TENNE,A. ZAK,L. SALLACAN-ECKER,A. MARGOLIN,M. GENUT 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2009 NANO Vol.4 No.2
The growth mechanism of WS2 nanotubes in the large-scale fluidized-bed reactor is studied in greater detail. This study and careful parameterization of the conditions within the reactor lead to the synthesis of large amounts (50–100 g/batch) of pure nanotubes, which appear as a fluffy powder, and (400–500 g/batch) of nanotubes/nanoplatelets mixture (50:50), where nanotubes usually coming in bundles. The two products are obtained simultaneously in the same reaction but are collected in different zones of the reactor, in a reproducible fashion. The characterization of the nanotubes, which grow catalyst-free, by a number of analytical techniques is reported. The majority of the nanotubes range from 10 to 50 micron in length and 20–180 nm in diameter. The nanotubes reveal highly crystalline order, suggesting very good mechanical behavior with numerous applications.
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Li, Hong,He, Zengyong,Lu, Guihua,Lee, Sung Chul,Alonso, Jose,Ecker, Joseph R,Luan, Sheng American Society of Plant Physiologists 2007 The Plant cell Vol.19 No.8
<P>Chromatin-based silencing provides a crucial mechanism for the regulation of gene expression. We have identified a WD40 domain cyclophilin, CYCLOPHILIN71 (CYP71), which functions in gene repression and organogenesis in Arabidopsis thaliana. Disruption of CYP71 resulted in ectopic activation of homeotic genes that regulate meristem development. The cyp71 mutant plants displayed dramatic defects, including reduced apical meristem activity, delayed and abnormal lateral organ formation, and arrested root growth. CYP71 was associated with the chromatin of target gene loci and physically interacted with histone H3. The cyp71 mutant showed reduced methylation of H3K27 at target loci, consistent with the derepression of these genes in the mutant. As CYP71 has close homologs in eukaryotes ranging from fission yeast to human, we propose that it serves as a highly conserved histone remodeling factor involved in chromatin-based gene silencing in eukaryotic organisms.</P>
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Ryu, Jong Sang,Kim, Jeong-Il,Kunkel, Tim,Kim, Byung Chul,Cho, Dae Shik,Hong, Sung Hyun,Kim, Seong-Hee,Ferná,ndez, Aurora Piñ,as,Kim, Yumi,Alonso, Jose M.,Ecker, Joseph R.,Nagy, Ferenc,Lim, Elsevier 2005 Cell Vol.120 No.3
<P><B>Summary</B></P><P>Environmental light information such as quality, intensity, and duration in red (∼660 nm) and far-red (∼730 nm) wavelengths is perceived by phytochrome photoreceptors in plants, critically influencing almost all developmental strategies from germination to flowering. Phytochromes interconvert between red light-absorbing Pr and biologically functional far-red light-absorbing Pfr forms. To ensure optimal photoresponses in plants, the flux of light signal from Pfr-phytochromes should be tightly controlled. Phytochromes are phosphorylated at specific serine residues. We found that a type 5 protein phosphatase (PAPP5) specifically dephosphorylates biologically active Pfr-phytochromes and enhances phytochrome-mediated photoresponses. Depending on the specific serine residues dephosphorylated by PAPP5, phytochrome stability and affinity for a downstream signal transducer, NDPK2, were enhanced. Thus, phytochrome photoreceptors have developed an elaborate biochemical tuning mechanism for modulating the flux of light signal, employing variable phosphorylation states controlled by phosphorylation and PAPP5-mediated dephosphorylation as a mean to control phytochrome stability and affinity for downstream transducers.</P>
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