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排序方式: 共有359条查询结果,搜索用时 31 毫秒
61.
It is shown that the recent CERN beam dump experiment implying direct neutrino production provides a straightforward way to detect W-bosons via ultrahigh energy cosmic rays hitting the atmosphere. This occurs because (1) at high energies, direct neutrinos will dominate over the standard π, K produced flux due to time dilation effects and (2) direct π-production produces a large fraction of . 相似文献
62.
Á. Nemcsics L. Tóth L. Dobos Ch. Heyn A. Stemmann A. Schramm H. Welsch W. Hansen 《Superlattices and Microstructures》2010
Self-assembled strain-free quantum dot (QD) structures were grown on AlGaAs surface by the droplet epitaxal method. The QDs were developed from pure Ga droplets under As pressure. The QDs were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Both techniques show that the QDs are very uniform in size and their distribution on the surface is also homogeneous. The high resolution cross-sectional TEM investigation shows perfect lattice matching between the QD and the substrate, and also the faceting of the side walls of QD can be identified exactly by lattice planes. Analytical TEM (elemental mapping by EELS) unambiguously identifies the presence of Al in the QD. 相似文献
63.
A. D. Debus M. Bussmann M. Siebold A. Jochmann U. Schramm T. E. Cowan R. Sauerbrey 《Applied physics. B, Lasers and optics》2010,100(1):61-76
We present a novel high-yield Thomson scattering geometry that takes advantage of compact electron bunches, as available in
advanced, low-emittance linear accelerators or laser wakefield accelerators. In order to avoid the restrictions on the X-ray
photon yield imposed by the Rayleigh limit, we use ultrashort, pulse-front tilted laser pulses in a side-scattering geometry.
Such a traveling-wave setup allows an overlap of electron and laser beams, even after propagating over distances much longer
than the Rayleigh length. Experimental designs are discussed and optimized for different scattering angles. Specifically,
to minimize group delay dispersion at large scattering angles >10°, we propose the use of varied-line spacing (VLS) gratings
for spatio-temporal laser pulse shaping. Compared to head-on (180°) Thomson scattering, interaction lengths are in the centimeter
to meter range and photon numbers for ultrashort X-ray pulses can increase by several orders of magnitudes. 相似文献
64.
65.
Osterhoff J Popp A Major Z Marx B Rowlands-Rees TP Fuchs M Geissler M Hörlein R Hidding B Becker S Peralta EA Schramm U Grüner F Habs D Krausz F Hooker SM Karsch S 《Physical review letters》2008,101(8):085002
Laser-driven, quasimonoenergetic electron beams of up to approximately 200 MeV in energy have been observed from steady-state-flow gas cells. These beams emitted within a low-divergence cone of 2.1+/-0.5 mrad FWHM display unprecedented shot-to-shot stability in energy (2.5% rms), pointing (1.4 mrad rms), and charge (16% rms) owing to a highly reproducible gas-density profile within the interaction volume. Laser-wakefield acceleration in gas cells of this type provides a simple and reliable source of relativistic electrons suitable for applications such as the production of extreme-ultraviolet undulator radiation. 相似文献
66.
Schollmeier M Becker S Geissel M Flippo KA Blazević A Gaillard SA Gautier DC Grüner F Harres K Kimmel M Nürnberg F Rambo P Schramm U Schreiber J Schütrumpf J Schwarz J Tahir NA Atherton B Habs D Hegelich BM Roth M 《Physical review letters》2008,101(5):055004
This Letter demonstrates the transporting and focusing of laser-accelerated 14 MeV protons by permanent magnet miniature quadrupole lenses providing field gradients of up to 500 T/m. The approach is highly reproducible and predictable, leading to a focal spot of (286 x 173) microm full width at half maximum 50 cm behind the source. It decouples the relativistic laser-proton acceleration from the beam transport, paving the way to optimize both separately. The collimation and the subsequent energy selection obtained are perfectly applicable for upcoming high-energy, high-repetition rate laser systems. 相似文献
67.
By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date. 相似文献
68.
Christian Schramm Beate Rinderer Wolfgang H. Binder Richard Tessadri Heinz Duelli 《Journal of Sol-Gel Science and Technology》2008,45(1):83-88
(3-Triethoxysilylpropyl)succinic anhydride (TESP-SA) is an organo-functional silicon compound that can be converted into a
polysilsesquioxane when it is hydrolyzed and subsequently subjected to a condensation reaction at elevated temperatures (>160 °C).
If this process is performed without sodium hypophosphite (SHP), a hard solid material is obtained. In contrast, the condensation
reaction of TESP-SA in conjunction with SHP results in the formation of a foamed, brittle material with closed macro cells.
The foam was characterized by means of various analytical methods (FT-IR, 29Si MAS NMR, XRD, TG-MS, SEM).
相似文献
Christian SchrammEmail: |
69.
Cotton fabric is modified by means of polycarboxylic acids in combination with an inorganic or an organic catalyst in order
to impart durable press properties. After the curing process the cellulosic specimen is washed off to remove both the portion
of the polycarboxylic acid that has not reacted and the catalyst applied. The treated cellulosic fabric is saponified with
a sodium hydroxide solution to extract the PCA that has reacted with the cellulosic material. Both the wash liquor and the
saponification liquor are investigated by means of isocratic HPLC using Aminex HPX-87-H as stationary phase. Excellent separation
of the various polycarboxylic acids that are applied as crosslinking agents or as organic catalysts is achieved. The HPLC
method presented enables the identification and quantification of the polycarboxylic acids.
Received: 19 January 1999 / Revised: 24 March 1999 / Accepted: 28 March 1999 相似文献
70.