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排序方式: 共有98条查询结果,搜索用时 187 毫秒
51.
Haycock RA Yartsev A Michelsen U Sundström V Hunter CA 《Angewandte Chemie (International ed. in English)》2000,39(20):3616-3619
52.
53.
Milton SV Gluskin E Biedron SG Dejus RJ Den Hartog PK Galayda JN Kim K Lewellen JW Moog ER Sajaev V Sereno NS Travish G Vinokurov NA Arnold ND Benson C Berg W Biggs JA Borland M Carwardine JA Chae Y Decker G Deriy BN Erdmann MJ Friedsam H Gold C Grelick AE 《Physical review letters》2000,85(5):988-991
Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator. 相似文献
54.
Efficient integration of stiff kinetics with phase change detection for reactive reservoir processes
Morten R. Kristensen Margot G. Gerritsen Per G. Thomsen Michael L. Michelsen Erling H. Stenby 《Transport in Porous Media》2007,69(3):383-409
We propose the use of implicit one-step Explicit Singly Diagonal Implicit Runge–Kutta (ESDIRK) methods for integration of
the stiff kinetics in reactive, compositional and thermal processes that are solved using operator-splitting type approaches.
To facilitate the algorithmic development we construct a virtual kinetic cell model. The model serves both as a tool for the
development and testing of tailored solvers as well as a testbed for studying the interactions between chemical kinetics and
phase behavior. As case study, two chemical kinetics models with 6 and 14 components, respectively, are implemented for in
situ combustion, a thermal oil recovery process. Through benchmark studies using the 14 component reaction model the new ESDIRK
solvers are shown to improve computational speed when compared to the widely used multi-step BDF methods DASSL and LSODE.
Phase changes are known to cause convergence problems for the integration method. We propose an algorithm for detection and
location of phase changes based on discrete event system theory. Experiments show that the algorithm improves the robustness
of the integration process near phase boundaries by lowering the number convergence and error test failures by more than 50%
compared to direct integration without the new algorithm. 相似文献
55.
Infrared-to-visible wave-length conversion in the Yb3+−Er3+ doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the
range of 900–1000 nm of an IR-photon is first absorbed by Yb3+ ion as a sensitizer attributed to the resonant energy transition in Er3+ ion from 4
I
3/2 → 4
S
15/2 and 1
F
9/2 → 4
I
15/2, respectively for green and red emission. The essential energy transfer processes in this system i.e. upconversion from 4
I
11/2 and 1
I
13/2, cross-relaxation from 4
S
3/2 and 1
F
9/2 are taken into account. The limitations of the rate-equation approach are examined with a focus on the underlying dynamics
of this rare-earth system. 相似文献
56.
Derivation of a temperature-dependent accommodation coefficient for use in modeling laser-induced incandescence of soot 总被引:1,自引:0,他引:1
H. A. Michelsen 《Applied physics. B, Lasers and optics》2009,94(1):103-117
This paper presents a derivation of an expression to estimate the accommodation coefficient for gas collisions with a graphite
surface, which is meant for use in models of laser-induced incandescence (LII) of soot. Energy transfer between gas molecules
and solid surfaces has been studied extensively, and a considerable amount is known about the physical mechanisms important
in thermal accommodation. Values of accommodation coefficients currently used in LII models are temperature independent and
are based on a small subset of information available in the literature. The expression derived in this study is based on published
data from state-to-state gas-surface scattering experiments. The present study compiles data on the temperature dependence
of translational, rotational, and vibrational energy transfer for diatomic molecules (predominantly NO) colliding with graphite
surfaces. The data were used to infer partial accommodation coefficients for translational, rotational, and vibrational degrees
of freedom, which were consolidated to derive an overall accommodation coefficient that accounts for accommodation of all
degrees of freedom of the scattered gas distributions. This accommodation coefficient can be used to calculate conductive
cooling rates following laser heating of soot particles. 相似文献
57.
G. Kramer D. Michelsen H. Spiesberger 《The European Physical Journal C - Particles and Fields》1998,5(2):293-301
We calculate the corrections to the production of a hard and isolated photon accompanied by one or two jets in deep inelastic lepton nucleon
scattering at HERA. Numerical results are presented and the potential of this process for studies of parton distribution functions
is discussed.
Received: 18 December 1997 / Published online: 10 March 1998 相似文献
58.
Lan Liu Alyson Baergen Klaus Michelsen Elena N. Kitova Paul D. Schnier John S. Klassen 《Journal of the American Society for Mass Spectrometry》2014,25(5):742-750
This work explores the energetics of intermolecular H-bonds inside a hydrophobic protein cavity. Kinetic measurements were performed on the gaseous deprotonated ions (at the ?7 charge state) of complexes of bovine β-lactoglobulin (Lg) and three monohydroxylated analogs of palmitic acid (PA): 3-hydroxypalmitic acid (3-OHPA), 7-hydroxypalmitic acid (7-OHPA), and 16-hydroxypalmitic acid (16-OHPA). From the increase in the activation energy for the dissociation of the (Lg + X-OHPA)7– ions, compared with that of the (Lg + PA)7– ion, it is concluded that the –OH groups of the X-OHPA ligands participate in strong (5 – 11 kcal mol–1) intermolecular H-bonds in the hydrophobic cavity of Lg. The results of molecular dynamics (MD) simulations suggest that the –OH groups of 3-OHPA and 16-OHPA act as H-bond donors and interact with backbone carbonyl oxygens, whereas the –OH group of 7-OHPA acts as both H-bond donor and acceptor with nearby side chains. The capacity for intermolecular H-bonds within the Lg cavity, as suggested by the gas-phase measurements, does not necessarily lead to enhanced binding in aqueous solution. The association constant (Ka) measured for 7-OHPA [(2.3 ± 0.2) × 105 M–1] is similar to the value for the PA [(3.8 ± 0.1) × 105 M–1]; Ka for 3-OHPA [(1.1 ± 0.3) × 106 M–1] is approximately three-times larger, whereas Ka for 16-OHPA [(2.3 ± 0.2) × 104 M–1] is an order of magnitude smaller. Taken together, the results of this study suggest that the energetic penalty to desolvating the ligand –OH groups, which is necessary for complex formation, is similar in magnitude to the energetic contribution of the intermolecular H-bonds. Fig. a
? 相似文献
59.
A potential drug candidate containing a multiplicity of sulphur atoms, and one unknown in vivo main metabolite, were analysed with an high performance liquid chromatograph time-of-flight mass spectrometer (LC/TOF-MS). Sensitivity and resolution were compared with those obtained with a quadrupole instrument. The LC/TOF-MS provided a more than 200-fold advantage in sensitivity, higher resolving power for the isotopic envelopes of the molecular ions produced by electrospray, and simple procedures for the determination of elemental composition. The exact masses of the candidate and its main metabolite were determined to within 1.5 to 3 ppm, using a single lock mass correction. 相似文献
60.
J. M. Headrick F. Goulay P. E. Schrader H. A. Michelsen 《Applied physics. B, Lasers and optics》2011,104(2):439-450
We have measured time-resolved laser-induced incandescence of flame-generated soot under high-vacuum conditions (4.1×10−6 mbar) at an excitation wavelength of 532 nm with laser fluences spanning 0.06–0.5 J/cm2. We generated soot in an ethylene/air diffusion flame, introduced it into the vacuum system with an aerodynamic lens, heated
it using a pulsed laser with a spatially homogeneous and temporally smooth laser profile, and recorded LII temporal profiles
at 685 nm. At low laser fluences LII signal decay rates are slow, and LII signals persist beyond the residence time of the
soot particles in the detection region. At these fluences, the temporal maximum of the LII signal increases nearly linearly
with increasing laser fluence until reaching a plateau at ∼0.18 J/cm2. At higher fluences, the LII signal maximum is independent of laser fluence within experimental uncertainty. At these fluences,
the LII signal decays rapidly during the laser pulse. The fluence dependence of the vacuum LII signal is qualitatively similar
to that observed under similar laser conditions in an atmospheric flame but requires higher fluences (by ∼0.03 J/cm2) for initiation. These data demonstrate the feasibility of recording vacuum LII temporal profiles of flame-generated soot
under well-characterized conditions for model validation. 相似文献