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991.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
992.
E. Mathieu Y. Foucher P. Dellamonica J. P. Daures 《Methodology and Computing in Applied Probability》2007,9(3):389-397
In AIDS control, physicians have a growing need to use pragmatically useful and interpretable tools in their daily medical
taking care of patients. Semi-Markov process seems to be well adapted to model the evolution of HIV-1 infected patients. In
this study, we introduce and define a non homogeneous semi-Markov (NHSM) model in continuous time. Then the problem of finding
the equations that describe the biological evolution of patient is studied and the interval transition probabilities are computed.
A parametric approach is used and the maximum likelihood estimators of the process are given. A Monte Carlo algorithm is presented
for realizing non homogeneous semi-Markov trajectories. As results, interval transition probabilities are computed for distinct
times and follow-up has an impact on the evolution of patients.
相似文献
993.
994.
Joseph Shipman 《Mathematical Intelligencer》2007,29(4):9-14
Theorems 2 and 3 establish the minimum algebraic conditions necessary for a field to be algebraically closed, and they can
therefore be said to “optimize” the Fundamental Theorem of Algebra. But each specific“degree implication” is a first-order
consequence of the axioms for fields, and could have been discovered two centuries ago; the existence of these finitary relationships
appears to have been unsuspected by practically everyone, with one important exception. 相似文献
995.
T. Hansel J. Müller C. Falldorf C. von Kopylow W. Jüptner R. Grunwald G. Steinmeyer U. Griebner 《Applied physics. B, Lasers and optics》2007,89(4):513-516
Digital holographic shape measurements using femtosecond laser pulses are reported. For contouring of very fast moving objects,
the simultaneous generation of at least two spectrally separated ultrashort pulses is required. To deliver this particular
spectral signature at high pulse energies, a chirped-pulse Ti:sapphire laser amplifier was modified to emit two spectrally
separated pulses with energies above 1 μJ each. The wavelength separation of these pulses was adjustable within the 50 nm
gain bandwidth, cutting out two distinct wavelength peaks by a variable double-slit assembly in a prism sequence. A Michelson-type
interferometer was employed to perform the two-wavelength contouring. The phases of the holograms and the phase differences
are calculated numerically, which allow us to deduce the contour lines of the topology of the object. The suitability of the
light source for digital holography is demonstrated with contouring of stationary objects and the potential for high-speed
applications is indicated.
PACS 42.40.-i; 42.60.By 相似文献
996.
L. Kováč 《Applied magnetic resonance》2007,31(1-2):11-28
The life course of the physicist and biologist George Feher may be seen as an epitome of science of the second half of the 20th century and the beginning of the 21st century. Feher, a native of Slovakia, barely escaped Nazism and communism and became a scientist in the USA. The Nazi concentration camps and the communist gulags have become a symbol of the 20th century. This symbol stands here to pose a question: How the two totalitarian systems, fraught with irrationality, may have arisen and thrived in parallel with an unprecedented expansion of science, the paragon of rationalism? The question has become even more urgent in the 21st century. The Ground Zero, an empty spot left after the collapse of the twin towers of the World Trade Center on 11 September 2001, has become the symbol of the entrance of humankind into the new millennium. We can do much, but we understand too little about who we are and what we are doing — this is a message that the two symbols convey about the precarious stage of our evolution. The second message concerns the role of artifacts, specifically scientific instruments, in the advancement of science. Human cultural evolution has been steadily progressing, in a form of a ratchet, only because artifacts have been continually evolving. Contrary to the common Popperian wisdom, the demarcation in science may not consist in the amenability to theoretical falsification, but rather in the amenability to instrumental grasping. Scientific instruments have empowered humans for impressive feats of manipulation with Nature and themselves. Knowledge arising in the course of autonomous evolution of artifacts may surpass the horizon of human understanding and grasping. New knowledge may still be power, but no longer the power of humans. We may need a revision of some fundamental ideas of European thought. Our understanding of the human mind may entirely reshape our comprehension of the nature of physical knowledge, and vice versa. 相似文献
997.
Ling-yan Tang Song-he Song 《应用数学学报(英文版)》2007,23(2):303-310
In this paper,we use Daubechies scaling functions as test functions for the Galerkin method,and discuss Wavelet-Galerkin solutions for the Hamilton-Jacobi equations.It can be proved that the schemesare TVD schemes.Numerical tests indicate that the schemes are suitable for the Hamilton-Jacobi equations.Furthermore,they have high-order accuracy in smooth regions and good resolution of singularities. 相似文献
998.
A. M. Kharitonov 《Thermophysics and Aeromechanics》2007,14(1):3-11
Sergey Alekseevich Khristianovich is one of the famous Russian mechanical engineers of the 20th century together with N.E.
Zhukovsky, S.A. Chaplygin, N.E. Kochin, and others. He made an immense contribution to some aspects of mechanics, such as
aerogasdynamics, rock mechanics, theory of plasticity, filtration theory, and environmental power engineering. All this was
preceded by a long, hard, and fruitful life full of outstanding events. 相似文献
999.
C. Guillermier 《Applied Surface Science》2006,252(19):6644-6647
The yield of CN from glycine rises from one CN per projectile impact to two when the sample is covered with a nominally 1 nm thick layer of silver. These yields were obtained for bombardment with Au4004+ projectile with 136 keV impact energy. A multitude of CN-based clusters, e.g. AgxOy(CN)z are produced concurrently. As a result, a total of three CN-based secondary ions are generated per projectile impact. The exceptionally high yield for CN is of interest for biological SIMS. 相似文献
1000.
There are many advantages in being able to perform positron annihilation lifetime spectroscopy (PALS) using a variable energy positron beam, the most obvious being the easy identification of different defect types at different depths. The difficulty in conducting variable energy (VE) PALS studies lies in the fact that a “start” signal is required to signal the entry of the positron into the target. Two methods have been used to overcome this problem, namely the bunching technique, which employs radio frequency (RF) cavities and choppers, and secondly the use of secondary electrons emitted from the target. The latter technique is in terms of experimental complexity much simpler, but has in the past suffered from poor time resolution (typically ∼500 ps). In this work, we present a series of computer simulations of a design based on the secondary electron emission from thin C-foils in transmission mode which shows that significant improvements in time resolution can be made with resolutions ∼200 ps being in principle possible. 相似文献