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991.
992.
Sandor Divenyi Marcelo A. Savi Hans I. Weber Luiz Fernando P. Franca 《Chaos, solitons, and fractals》2008,38(3):685-695
Non-smooth characteristics are, in general, the source of difficulties for the modeling and simulation of natural systems. These characteristics are usually related to either the friction phenomenon or the discontinuous behavior as intermittent contacts. This article develops an experimental investigation concerning non-smooth systems with discontinuous support. An experimental apparatus is developed in order to analyze the nonlinear dynamics of a single-degree of freedom system with discontinuous support. The apparatus is composed by an oscillator constructed by a car, free to move over a rail, connected to an excitation system. The discontinuous support is constructed considering mass–spring systems separated by a gap to the car position. This apparatus is instrumented to obtain all the system state variables. System dynamical behavior shows a rich response, presenting dynamical jumps, bifurcations and chaos. Different configurations of the experimental set up are treated in order to evaluate the influence of the internal impact within the car and also support characteristics in the system dynamics. 相似文献
993.
Andrew Taylor Robert L. Jones Alain Leblanc Olav Mazarrasa Mi-Young Lee Patrick J. Parsons Marina Patriarca Jean-Philippe Weber Cas Weykamp 《Accreditation and quality assurance》2009,14(8-9):461-466
An under-recovery of inorganic mercury added to urine and a wide range of results is observed in quality assessment schemes (EQAS) for trace elements. Furthermore, the under-recoveries are inconsistent suggesting features associated with the urine matrix may make the mercury unavailable for measurement. To investigate the instability of mercury in urine the following experiments were set up: (1) a sample of Hg2+ in water with various ‘stabilizers’ added was sent to UK external quality assessment scheme participants. (2) Urine was collected from volunteers who also completed a 3-day food diary. Hg, Ca, Mg, Se, uric acid, phosphate, creatinine, reducing substances and protein were measured. Inorganic mercury was spiked into the urine, stabilizers were added and the mercury determined following storage. The results confirmed under-recovery of mercury in association with the urine matrix. Further investigations of how urinary components affect the measurement of mercury are necessary. 相似文献
994.
Anja Baumgaertel Christine Weber Katrin Knop Anna Crecelius Ulrich S. Schubert 《Rapid communications in mass spectrometry : RCM》2009,23(6):756-762
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) coupled with CID (collision‐induced dissociation) has been used for the detailed characterization of two poly(2‐ethyl‐2‐oxazoline)s as part of a continuing study of synthetic polymers by MALDI‐TOF MS/MS. These experiments provided information about the variety of fragmentation pathways for poly(oxazoline)s. It was possible to show that, in addition to the eliminations of small molecules, like ethene and hydrogen, the McLafferty rearrangement is also a possible fragmentation route. A library of fragmentation pathways for synthetic polymers was also constructed and such a library should enable the fast and automated data analysis of polymers in the future. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
995.
M. Weber P. Birrer F. N. Gygax B. Hitti E. Lippelt H. Maletta A. Schenck 《Hyperfine Interactions》1991,63(1-4):93-101
The muon spin relaxation was measured in the high-T
c superconductors Bi2Sr1.3Ca0.7 CuO6.15, Bi2Sr2CaCu2O8 and Bi2Pb
x
Sr2Ca2Cu3O10. We present our method to determine the London penetration depth perpendicular toc-axis λ⊥ (0) taking also contributions from the anisotropic magnetization and nuclear dipoles to the muon frequency spectrum into
account. 相似文献
996.
Femtosecond ablation of ultrahard materials 总被引:4,自引:0,他引:4
G. Dumitru V. Romano H.P. Weber M. Sentis W. Marine 《Applied Physics A: Materials Science & Processing》2002,74(6):729-739
Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their
response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported
for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried
out in air, in a regime of 5–8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with
a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident
energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the
highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates
determined (under the above-mentioned experimental conditions) were in the range 0.1–0.2 μm per pulse for all the materials
investigated.
Received: 31 August 2001 / Accepted: 3 December 2001 / Published online: 20 March 2002 相似文献
997.
Andreas Knierzinger Willy Walther Beat Weber Robert Karl Müller Thomas Netscher 《Helvetica chimica acta》1990,73(4):1087-1107
A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl Compounds A new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)-L -diisopropyl-tartrate acetals derived from dihydrocitronellal ( 6 ), hexahydropseudoionone ( 3 ), hexahydrofarnesal ( 7 ), and hexahydro far nesy lace tone ( 4 ), the C10, C13, C15, and C18 intermediates in various syntheses of naturally occurring tocopherols and vitamin K1, can be achieved by capillary GC on a cyanopropylsilicon-coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present-day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C-atoms bearing two stereogenic centres is performed in a single operation for the first time. 相似文献
998.
M. Block D. Ackermann K. Blaum A. Chaudhuri Z. Di S. Eliseev R. Ferrer D. Habs F. Herfurth F. P. Heßberger S. Hofmann H.-J. Kluge G. Maero A. Martín G. Marx M. Mazzocco M. Mukherjee J. B. Neumayr W. R. Plaß W. Quint S. Rahaman C. Rauth D. Rodríguez C. Scheidenberger L. Schweikhard P. G. Thirolf G. Vorobjev C. Weber 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):39-45
The Penning-trap mass spectrometer SHIPTRAP allows precision mass
measurements of rare isotopes produced in fusion-evaporation reactions. In
the first period of operation the masses of more than 50 neutron-deficient
radionuclides have been measured.
In this paper the perspectives for direct mass measurements
of rare isotopes around nobelium are discussed and the achievable precision is addressed.
The temporal stability of the magnetic field, an important issue for the long
measurement times resulting from the low production rates, was investigated and the
time-dependent uncertainty due to magnetic field fluctuations was determined.
Based on the present performance direct mass measurements of nobelium isotopes are
already feasible. With several technical improvements heavier elements between Z=102–105 will be in reach. 相似文献
999.
J. Kurpeta V. -V. Elomaa T. Eronen J. Hakala A. Jokinen P. Karvonen I. Moore H. Penttilä A. Płochocki S. Rahaman S. Rinta-Antila J. Rissanen J. Ronkainen A. Saastamoinen T. Sonoda W. Urban Ch. Weber J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):263-266
Exotic, neutron-rich 111Mo and 115Ru nuclei, produced in proton-induced fission of 238U target, were separated with the IGISOL mass separator. The separator was coupled to the JYFLTRAP Penning trap to select
the ions of a single, desired element out of the isobaric IGISOL beam. Monoisotopic samples of 115Ru and 111Mo ions were observed with a microchannel plate detector after the trap or were implanted on a catcher foil for gamma- and
beta-ray coincidence spectroscopy. In spite of short data taking time new gamma transitions were identified in the beta decay
of very neutron-rich 115Ru. 相似文献
1000.
A. Martın D. Ackermann G. Audi K. Blaum M. Block A. Chaudhuri Z. Di S. Eliseev R. Ferrer D. Habs F. Herfurth F. P. Heßberger S. Hofmann H. -J. Kluge M. Mazzocco M. Mukherjee J. B. Neumayr Yu. Novikov W. Plaß S. Rahaman C. Rauth D. Rodrıguez C. Scheidenberger L. Schweikhard P. G. Thirolf G. Vorobjev C. Weber 《The European Physical Journal A - Hadrons and Nuclei》2007,34(4):341-348
Direct mass measurements of nuclides near to the supposed end-point region of the astrophysical rp-process were performed
at SHIPTRAP, the Penning trap mass spectrometer at GSI Darmstadt. The masses of 24 nuclides were measured with relative uncertainties
between 5 . 10-8 and 2 . 10-7 . Three of them, 107Sb , 111I and 112I , were determined experimentally for the first time. The data analysis and mass evaluation are presented in detail. 相似文献