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排序方式: 共有158条查询结果,搜索用时 31 毫秒
91.
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93.
RE Tribble A Azhari HL Clark CA Gagliardi Y-W Lui AM Mukhamedzhanov A Sattaroy X Tang L Trache V Burjan J Cejpek V Kroha S Piskor J Vincour F Carstoiu 《Pramana》1999,53(3):585-594
S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which
provide the normalization of the tail of the overlap function. For example the overlap for 8B → 7Be+p defines the S-factor for 7Be (p, γ)8B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of
the technique, the 16O(3He, d)17F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited
states of 17F. The S-factors for 16O(p, γ)17F calculated from these 17F → 16O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same
technique, the 10B(7Be, 8B)9Be and 14N(7Be, 8B)13C reactions have been used to measure the asymptotic normalization coefficient for 7Be(p, γ)8B. This result provides an indirect determination of S
17(0). 相似文献
94.
AM Cardoso SM Alexandre CM Barros AJ Correia NM Nibbering 《Rapid communications in mass spectrometry : RCM》1999,13(19):1885-1888
The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
95.
AM Johnston CM Scrimgeour MO Henry LL Handley 《Rapid communications in mass spectrometry : RCM》1999,13(14):1531-1534
The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
96.
O. Adriani G. A. Bazilevskaya G. C. Barbarino T. R. Bellotti M. A. Bzheumikhova E. A. Bogomolov V. M. Boezio V. Bonvicini M. Bongi L. Bonechi S. Bottai A. Bruno A. Vacchi E. Vannuccini G. V. Vasiliev S. A. Voronov A. M. Galper L. A. Grishantseva G. Zampa N. Zampa V. G. Zverev M. Casolino T. D. Campana P. Carlson G. Castellini F. Cafagna A. N. Kvashnin S. V. Koldashov S. Yu. Krutkov A. A. Leonov V. V. Malakhov V. Malvezzi L. Marcelli W. Menn V. V. Mikhailov E. Mocchiutti S. Orsi G. Osteria P. Papini M. P. De Pascale T. P. Picozza M. Pearce G. De Rosa M. Ricci S. B. Ricciarini M. Simon N. De Simone R. Sparvoli P. Spillantini Yu. I. Stozhkov E. Taddei V. Di Felice D. Fedele P. Hofverberg Yu. T. Yurkin 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(3):364-366
Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350–600 km. It is shown that positrons dominate over electrons by a factor of up to 4–5 in the geomagnetic equator region (L < 1.2 and B > 0.25). 相似文献
97.
O. Adriani G. A. Bazilevskaya G. C. Barbarino R. Bellotti M. Boezio E. A. Bogomolov L. Bonechi M. Bongi V. Bonvicini S. V. Borisov S. Bottai A. Bruno F. Cafagna D. Campana P. Carlson M. Casolino G. Castellini M. P. De Pascale G. De Rosa D. Fedele V. Di Felice A. M. Galper L. A. Grishantseva P. Hofverberg A. A. Leonov S. V. Koldashov S. Yu. Krutkov A. N. Kvashnin V. Malvezzi L. Marcelli W. Menn V. V. Mikhailov M. Minori E. Mocchiutti S. Orsi G. Osteria P. Papini M. Pearce P. Picozza M. Ricci S. B. Ricciarini M. Simon N. De Simone R. Sparvoli P. Spillantini Yu. I. Stozhkov E. Taddei A. Vacchi E. Vannuccini G. V. Vasil’ev S. A. Voronov Yu. T. Yurkin G. Zampa N. Zampa V. G. Zverev 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(5):568-570
The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ~100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≈ 10 GeV from the 2006–2007 measurements are reported in this work. 相似文献
98.
The paper deals with the existence of positive periodic solutions to a system of degenerate parabolic equations with delayed nonlocal terms and Dirichlet boundary conditions. Taking in each equation a meaningful function as a control parameter, we show that for a suitable choice of a class of such controls we have, for each of them, a time-periodic response of the system under different assumptions on the kernels of the nonlocal terms. Finally, we consider the problem of the minimization of a cost functional on the set of pairs: control-periodic response. The considered system may be regarded as a possible model for the coexistence problem of two biological populations, which dislike crowding and live in a common territory, under different kind of intra- and inter-specific interferences. 相似文献
99.
Control of an oscillating water column wave energy converter based on dielectric elastomer generator
Gastone Pietro Rosati Papini Giacomo Moretti Rocco Vertechy Marco Fontana 《Nonlinear dynamics》2018,92(2):181-202
This paper introduces a model-based control strategy for a wave energy converter (WEC) based on dielectric elastomer generators (DEGs), i.e. a device that can convert the energy of ocean waves into electricity by employing deformable elastomeric transducers with variable capacitance. The analysed system combines the concept of oscillating water column WEC with an inflated circular diaphragm DEG (ICD-DEG). The device features strongly nonlinear dynamics due to the ICD-DEG electro-hyperelastic response and the compressibility of the air volume comprised between the water column and the ICD-DEG, while the hydrodynamic loads can be approximated as linear. The optimal control solution that maximises the power extraction of the device is numerically investigated in the case of monochromatic waves over the typical frequency and amplitude ranges of sea waves. The more realistic case of panchromatic waves is also analysed through the implementation, in simulation environment, of a real-time controller. This regulator is based on a simple sub-optimal control logic that is deduced from the monochromatic case. The performance of the proposed control strategy is illustrated in comparison with unoptimised algorithms. 相似文献
100.
Consider a finite subset F of a real normed space. In this paper we try to evaluate the largest possible distance between pairs of points which are, for F, the centroid, a center, or a median. The results seem to show that only when X is a two-dimensional, strictly convex space, or when X is a Hilbert space, what the geometrical intuition indicates is more or less true. We give some examples showing some of the 'pathological' situations which can arise. Also, we indicate some open problems. 相似文献