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  • 11
    Electronic Resource
    Electronic Resource
    Iterative exponential filtering for large discrete ill-posed problems (1999)
    Springer
    Numerische Mathematik 83 (1999), S. 535-556 
    Details
    ISSN: 0945-3245
    Keywords: Mathematics Subject Classification (1991):G65F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary. We describe a new iterative method for the solution of large, very ill-conditioned linear systems of equations that arise when discretizing linear ill-posed problems. The right-hand side vector represents the given data and is assumed to be contaminated by measurement errors. Our method applies a filter function of the form $\varphi_\beta(t):=1-\exp(-\beta t^2)$ with the purpose of reducing the influence of the errors in the right-hand side vector on the computed approximate solution of the linear system. Here $\beta$ is a regularization parameter. The iterative method is derived by expanding $\varphi_\beta(t)$ in terms of Chebyshev polynomials. The method requires only little computer memory and is well suited for the solution of large-scale problems. We also show how a value of $\beta$ and an associated approximate solution that satisfies the Morozov discrepancy principle can be computed efficiently. An application to image restoration illustrates the performance of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002119900077
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  • 12
    Electronic Resource
    Electronic Resource
    Whole-Wafer Mapping of Dislocations in 4H-SiC Epitaxy (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 556-557 (Sept. 2007), p. 295-298 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A non-destructive technique to image the dislocations and other extended defects in SiCepitaxial layers has been developed. Basal plane dislocations (BPDs) and threading dislocations(TDs) are imaged. Photoluminescence from the dislocations is excited with the 364 and/or 351 nmlines of an argon ion laser and near-infrared light is collected. A computer controlled probe stationtakes multiple images and the mm-sized images are stitched together to form whole-wafer maps.The technique is applied to a set of four n+ wafers from the same boule with 50 um n- epitaxiallayers. The epitaxy was grown with Cree’s low-BPD process. BPDs form as either single, isolateddislocations or as clusters encircling micropipes. The concentration of TDs is on the order 104/cm2and the local concentration varies more than an order of magnitude. The advantages of mappingdislocations by UV-PL imaging compared to other techniques are discussed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/17/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.556-557.295.pdf
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  • 13
    Electronic Resource
    Electronic Resource
    Identification Method of Structure Transfer Function for Machine Tools Based on Pseudo-Random Process (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 315-316 (July 2006), p. 366-369 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The contact rigidity and damping between joints of machine tools could vary greatlybecause of the difference of static and dynamic loading conditions. The pseudo-random gashingcutting is adopted in this paper, which makes the identification of structure transfer function ofmachine tools close to actual machining condition and improve the identification accuracy. Themain idea of this method is to decouple the transfer function in two directions based on left edgeand right edge cutting. Therefore, the structure transfer function identification of machine tools inactual cutting excitation is implemented. Finally, this method is compared with the traditionaltransfer function identification based on electromagnetism excitation and the qualified error isgiven
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/51/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.315-316.366.pdf
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  • 14
    Electronic Resource
    Electronic Resource
    Occupation Measures of Singularly Perturbed Markov Chains with Absorbing States (2000)
    Springer
    Acta mathematica sinica 16 (2000), S. 161-180 
    Details
    ISSN: 1000-9574
    Keywords: Key words Singularly perturbed Markov chain, Occupation measure, Aggregation, Absorbing state, Weak convergence, Switching diffusion ; 1991MR Subject Classification 60J27, 60B10, 34E05, 60F17
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper develops asymptotic properties of singularly perturbed Markov chains with inclusion of absorbing states. It focuses on both unscaled and scaled occupation measures. Under mild conditions, a mean-square estimate is obtained. By averaging the fast components, we obtain an aggregated process. Although the aggregated process itself may be non-Markovian, its weak limit is a Markov chain with much smaller state space. Moreover, a suitably scaled sequence consisting of a component of scaled occupation measures and a component of the aggregated process is shown to converge to a pair of processes with a switching diffusion component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101140050013
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  • 15
    Electronic Resource
    Electronic Resource
    Condensation and structure of amorphous ices: A computational study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1512-1513 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458113
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  • 16
    Electronic Resource
    Electronic Resource
    Polar molecules in planar interfaces. Role of the triplet direct correlation function in the asymptotic behavior of the profile (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4609-4619 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the density-orientation profile of a polar liquid in planar interfaces. This liquid, which represents one side of the interface, is coupled with a second medium which can be an ideal solid characterized only by its dielectric constant or another polar liquid. We derive an expression for the asymptotic behavior of the profile which is exact provided the molecules interact by an additive pairwise potential. As a consequence of the renormalization of bonds, we show that the result does not depend explicitly on the particular form of the short range part of the pair potential. Moreover, the asymptotic behavior of the profile does not depend on the physical origin of the second medium provided it behaves as a dielectric. In addition, we show that the result remains exact in presence of a soft wall and can be extended to the liquid–vapor interface. As established in a previous paper, we show that the isotropic part of the profile is intimately connected with the electrostriction phenomena observed in bulk phase when a strong electrical field is applied. In order to clarify this point, we derive the expression of the electrostriction constant from the relation density-one body direct correlation function which has been used for studying the profile. We point out that the electrostriction and the long tail of the profile represent two ways for investigating some orientational components of the triplet direct correlation function in bulk phase. More generally, we show that the triplet direct correlation function largely determines the orientational structure of the profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457722
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  • 17
    Electronic Resource
    Electronic Resource
    Computational study of formation dynamics and structure of amorphous ice condensates (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5004-5016 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Condensation dynamics and structure of low temperature ≤100 K amorphous ices is studied using the classical trajectory simulation technique. Specifically, classical equations of motion are solved for a sequence of H2O molecules impinging at random on an initial nucleus of ten water molecules. The sticking probability to the cluster is found to be unity. Using this technique we accumulated three amorphous clusters of 100–300 water molecules. The analysis of the results included collision dynamics and molecular structure. Upon collision with the cluster, the impinging H2O molecule forms typically two hydrogen bonds. The two new bonds are almost always asymmetric, i.e., one bond is via an O atom of the new molecule, and the other via one of its H atoms. We identified two distinct types of collision trajectories—"simple'' trajectories and "complex'' ones. In a simple trajectory, a new molecule is attached to the surface, without disrupting the preexisting hydrogen bond network in the cluster. In a complex trajectory, the preexisting bond network is modified significantly during the collision. Up to ∼15 hydrogen bonds can be changed (formed or destroyed) during such a trajectory; and the spatial extent of the changes can be as large as ∼20 A(ring).The complex trajectories comprise 60%∼70% of all the collision trajectories. Thus, the hydrogen bond network evolves continuously during the growth of the ice sample; the net trend being towards the four coordinated molecular configuration around each molecule. The average coordination number of a molecule in the final clusters is 3.5∼3.7, despite the fact that most of the water molecules are on the exposed surface of the cluster. The main features of the local molecular structure in the clusters are (a) ordering of OO and OH distances within hydrogen bonds (b) very significant disorder in O–O–O angles between adjacent hydrogen bonds; the width of the O–O–O angle distribution is ∼40°. The molecular structure seems to be closely related to that of liquid water. The experimental electron diffraction patterns of amorphous clusters are reproduced very well by our models. Comparison was also made with the radial distribution functions derived for bulk amorphous ice from x-ray and neutron diffraction experiments. Reasonable agreement was obtained within the range (approximately-less-than)4 A(ring), while at larger distances finite size effects become important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458536
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  • 18
    Electronic Resource
    Electronic Resource
    Symmetry breaking in a simple electron–phonon model with electron correlation (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4899-4906 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider a simple model which contains both electron phonon coupling, electron transfer, and electron correlation, which can be a prototype of a mixed valence system with three nearby electronic states. We treat the adiabatic solution, simple corrections to that, and the effect of symmetry breaking terms on the solutions. We find that the adiabatic solutions in the symmetric case can show a (false) symmetry breaking which is removed in the nonadiabatic calculation. These solutions are extremely unstable with respect to the addition of a non-symmetric term in the Hamiltonian.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457707
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  • 19
    Electronic Resource
    Electronic Resource
    Photodissociation of semiconductor positive cluster ions (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1670-1677 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser photofragmentation of Si, Ge, and GaAs positive cluster ions prepared by laser vaporization and supersonic beam expansion has been investigated using tandem time-of-flight mass spectrometry. Si clusters up to size 80, Ge clusters to size 40, and GaAs clusters up to a total of 31 atoms were studied. Si+n and Ge+n for n=12–26 give daughter ions of about half their original size. For both Si and Ge, this apparent positive ion fissioning appears to go over with increasing n to neutral loss of seven and ten, but for Si+n the range of n values where this is observed is rather small. At low fluences, the larger Ge+n clusters up to the maximum size observed (50) sequentially lose Ge10 (and in some cases with lower intensity Ge7). Larger Si+n clusters (n〉30) always fragment primarily to produce positive ion clusters in the 6–11 size range with a subsidiary channel of loss of a single Si atom. At high laser fluences, Ge+n also fragments to produce primarily positive ion clusters in the 6–11 size range with an intensity pattern essentially identical to Si+n at similar fluences. GaxAs+y clusters lose one or more atoms in what is probably a sequential process with positive ion clusters in which the total number of atoms, x+y, is odd being more prominent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454145
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  • 20
    Electronic Resource
    Electronic Resource
    SHELF-LIFE EVALUATIONS OF LIQUID FOODS TREATED BY PILOT PLANT PULSED ELECTRIC FIELD SYSTEM (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food processing and preservation 25 (2001), S. 0 
    Details
    ISSN: 1745-4549
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: There is a pressing need to validate the shelf-life extension of Pulsed Electric Field (PEF) treated foods. This study was designed to evaluate the shelf-lives of cranberry juice and chocolate milk as a function of PEF and the interaction of PEF+heat treatments. Cranberry juice was exposed to PEF and PEF+heat (60C), and chocolate milk to PEF+heat (105 and 112C). Microbial analysis and color measurement were performed on untreated and treated cranberry juice and chocolate milk aseptically packaged and stored at 4, 22, and 37 C for 197 and 119 days, respectively. Microbial analysis of cranberry juices demonstrated that the shelf-life of PEF and PEF+heat treated juices stored at 22 and 37 C increased significantly during 197 days (p〈0.05). The shelf-life of chocolate milk treated by PEF+105C and PEF+112C increased significantly at all storage temperatures (p〈0.05). The PEF nor PEF+heat treatments did not result in any significant differences in color retention of either cranberry juice or chocolate milk (p〉0.05). This study presented that PEF and PEF+heat treatments were very effective to increase shelf-lives of cranberry juice and chocolate milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4549.2001.tb00461.x
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