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RISS 인기검색어
- 검색키워드
- 저자 : Tomasik, Piotr (검색결과 4 건)
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Sheberla, Dennis,Tumanskii, Boris,Tomasik, Adam C.,Mitra, Amitabha,Hill, Nicholas J.,West, Robert,Apeloig, Yitzhak Royal Society of Chemistry 2010 Chemical Science Vol.1 No.2
<P>Stable <I>N</I>-heterocyclic carbenes and germylenes were allowed to react with a phosphonyl radical, (<I>i</I>-PrO)<SUB>2</SUB>(O)P&z.rad; (<B>7</B>), generated by photolysis of [(<I>i</I>-PrO)<SUB>2</SUB>(O)P]<SUB>2</SUB>Hg. The products were identified by EPR spectroscopy. An unsaturated carbene (<B>1</B>) and germylene (<B>3</B>) react with <B>7</B> at the divalent atom to give unstable radical products (<I>τ</I><SUB>½</SUB> = 0.2 s). A benzo-annulated carbene (<B>4</B>) and a saturated germylene (<B>6</B>) react with <B>7</B> to give more active radicals. An unsaturated (<B>2</B>) and a saturated silylene (<B>5</B>) undergo rapid reaction (in the dark) with [(<I>i</I>-PrO)<SUB>2</SUB>(O)P]<SUB>2</SUB>Hg to yield unusual silyl phosphites. In these cases only secondary radicals were observed. DFT (PBE0/TZVP//B3LYP/6-31+G(d)) calculations of the radical adducts of the different (C, Si, Ge) unsaturated <I>N</I>-heterocyclic divalent species with the phosphonyl radical show that the unpaired electron is delocalized over the five-membered ring; the spin density on the central atoms decreases in the order C, 39% > Si, 14% > Ge, 2%. These trends can be understood in terms of a zwitterionic structure of the radical adducts. The calculations of the radical adducts of <B>4</B>, <B>5</B> and <B>6</B> with <B>7</B> indicate larger spin density on the central atom, 47%, 58% and 42% on C, Si, Ge, respectively.</P> <P>Graphic Abstract</P><P>The geometry, spin density distribution and reactivity of radical adducts of stable <I>N</I>-heterocyclic carbenes, silylenes and germylenes demonstrate a strong dependence on the nature of the heterocycle and on the central atom. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sc00143k'> </P>
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Autonomous variable speed power generating system with five level cascaded converter
Lech M. Grzesiak,Jacek G. Tomasik 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
The paper presents a novel autonomous power generating system with a three-phase five-level cascaded inverter (5LCI) topology fed from a diesel engine with multiple-winding permanent magnet synchronous generator set (DE/PMSG) for UPS application. The power electronics system consists of six isolated windings which supply six full-bridge diode rectifiers with boost converters stabilizing the DC link voltages for a particular cell of the 5LCI. The five-level current mode control algorithm provides the high quality PWM waves which mitigate the high harmonic content and satisfy a robust output voltage regulation even under the unbalanced load conditions. The interfaced battery energy storage (BES), which constitutes an integral part of the entire “gen-set” system, it supplies the DC link capacitor voltages to particular cells of the 5LCI in a standby emergency mode, when the DE/PMSG are off-line. The topology under discussion can be applied to medium or high power UPS systems.
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Novel DC link balancing scheme in generic n-level back-to-back converter system
Lech M. Grzesiak,Jacek G. Tomasik 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
Paper presents a novel DC link balancing scheme for a generic n-level back-to-back system with multi-level diode clamped topologies. The proposed algorithm is generalization of the control strategy formerly introduced with the five-level back-to-back system and it relays on measurement of adjacent capacitor voltages which provide information about the potential variation in consecutive nodes of the n-level DC link network. Subsequently the adequate control signals are used to modify the multi-carrier PWM modulators on the rectifier side as well as on the inverter side respectively. In result, the voltages across all the capacitors in DC link network are effectively maintained balanced. The new balancing scheme has been demonstrated in simulations with 5-level, 7-level and 9-level single phase back-to-back systems and it can be extended to any n-level back-to-back system.
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Non-covalent functionalization of multi-walled carbon nanotubes with organic aromatic compounds.
Lemek, Tadeusz,Mazurkiewicz, Jó,zef,Stobinski, Leszek,Lin, Hong Ming,Tomasik, Piotr American Scientific Publishers 2007 Journal of nanoscience and nanotechnology Vol.7 No.9
<P>Several aromatic compounds derived from benzene by its annelation (naphthalene, anthracene, phenanthrene, pyrene) and exocyclic substitution (e.g., nitrobenzene, dinitrobenzenes, trinitrobenzene, chlorobenzene, N,N-dimethylaniline, and others) and endocyclic substitution (pyridine, quinoline, isoquinoline) efficiently sorbed on multi-walled carbon nanotubes (MWCNTs). Equilibrium constants for the sorption process have been determined. Computations of the energy of formation were performed for surface complexes of those arenes on single-walled carbon nanotubes (SWCNTs). Formation energies of those complexes were correlated against the experimental equilibrium constants. The latter were also correlated against calculated LUMO energy of the arenes. Solely, limited tendencies to the linearity could be observed. The analysis of the results of the correlations indicated that the arenes acting as the charge acceptors formed stronger complexes than arenes with a high electron density in the molecular orbital, for instance, N, N-dimethylaniline. The area of the arene--SWCNT contact was very essential for the complexation. The proximity of the HOMO orbital of SWCNT and LUMO of the arene was another essential factor. Bulky substituents in the arene molecules obscured their efficient contact with SWCNT.</P>
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