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921.
Roman Böttger Karl-Heinz Heinig Lothar Bischoff Bartosz Liedke Stefan Facsko 《Applied Physics A: Materials Science & Processing》2013,113(1):53-59
We show that hole patterns and sponge-like layers at irradiated Ge surfaces originate from the same driving force, namely the kinetics of ion beam induced defects in the amorphous Ge surface layer. Ge hole patterns reported earlier for irradiation with low energy (5 keV) Ga+ ions were reproduced for low energy Bi+ but also for Ge+ self-irradiation, which proves that the dominating driving force for morphology evolution cannot originate from the implanted impurities. At higher ion energies the well-known formation of sponge-like Ge surface layers after heavy ion irradiation was found for Bi+ irradiation and Ge+ self-irradiation, also. The transition from smooth surfaces via hole patterns to sponge-like morphologies with increasing ion energies was studied in detail. A model based on the kinetics of ion beam induced defects was developed and implemented in 3D kinetic Monte Carlo simulations, which reproduce the transition from hole patterns to sponge-like layers with increasing ion energy. 相似文献
922.
Sungwook Chung Donovan N. Leonard Virginia Altoe Shaul Aloni James J. De Yoreo Stefan Franzen 《Particle & Particle Systems Characterization》2013,30(3):280-286
As‐grown platelets formed from tris‐(dibenzylideneacetone) dipalladium(0) [Pd2(dba)3] precursor in the presence of Pd17 RNA are investigated before and after thermal annealing. Results show that as‐grown platelets are disordered crystals of Pd2(dba)3 containing 1?2 nm Pd clusters and platelets grown in the absence of RNA are morphologically and structurally similar to those formed with RNA. The initially formed crystals are so sensitive to environmental variables that the degree of crystallinity can not be determined accurately by electron diffraction. X‐ray crystallography on as‐grown platelets gives a crystal structure consistent with Pd2(dba)3, but reveals a composition of ≈Pd1.07(dba)3, indicating one Pd atom in Pd2(dba)3 is lost from the structure. Both electron beam and thermally induced decomposition of as‐grown Pd2(dba)3 platelets having a hexagonal habit on the micrometer scale produces elemental Pd platelets having a hexagonal habit on the nanometer scale. These hexagonal platelets are composed of a partially sparse form of Pd2(dba)3 that is initially crystalline but rapidly degrades due to the loss of Pd atoms from organic ligand cages. Once released, Pd atoms aggregate to form Pd clusters, which grow and transform into well‐formed Pd nanocrystals under electron‐beam irradiation or through thermal annealing. 相似文献
923.
Advanced Genetic Programming Based Machine Learning 总被引:1,自引:0,他引:1
Stephan Winkler Michael Affenzeller Stefan Wagner 《Journal of Mathematical Modelling and Algorithms》2007,6(3):455-480
A Genetic Programming based approach for solving classification problems is presented in this paper. Classification is understood
as the act of placing an object into a set of categories, based on the object’s properties; classification algorithms are
designed to learn a function which maps a vector of object features into one of several classes. This is done by analyzing
a set of input-output examples (“training samples”) of the function. Here we present a method based on the theory of Genetic
Algorithms and Genetic Programming that interprets classification problems as optimization problems: Each presented instance
of the classification problem is interpreted as an instance of an optimization problem, and a solution is found by a heuristic
optimization algorithm. The major new aspects presented in this paper are advanced algorithmic concepts as well as suitable
genetic operators for this problem class (mainly the creation of new hypotheses by merging already existing ones and their
detailed evaluation). The experimental part of the paper documents the results produced using new hybrid variants of Genetic
Algorithms as well as investigated parameter settings. Graphical analysis is done using a novel multiclass classifier analysis
concept based on the theory of Receiver Operating Characteristic curves.
The work described in this paper was done within the Translational Research Project L282 “GP-Based Techniques for the Design
of Virtual Sensors” sponsored by the Austrian Science Fund (FWF). 相似文献
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The Scanning Electron Microscope (SEM) is an excellent tool for the characterization of surfaces. In order to evaluate the
accuracy of the reconstruction of a 3D dataset, a known depth standard for tactile depth measurement devices with a step height
of 92 μm was investigated by SEM. The reconstruction of surfaces using two tilted images (StereoCreator) or three different
tilted images (TriCreator) is affected by the tilt angle itself, the image resolution and the working distance. We compare
the results of the obtained data from different combinations of tilt angles and working distances in relation with the type
of reconstruction…. To compare the accuracy and reliability of the 3D datasets from the new Infinite Focus Measurement Machine
(IFM) with the datasets reconstructed from the well known SEM technique, we utilized a groove standard with six trapezoidal
grooves with known width and depth certified by the PTB – Braunschweig – Germany (Physikalisch – Technische Bundesanstalt
Braunschweig – calibration mark 035PTB04 – measured with a traceable stylus instrument according to DIN EN ISO 3274). The
great advantage of the SEM/ESEM (Environmental Scanning Electron Microscope) and IFM technique compared to tactile-profile-measurement
instruments is that it is a non-tactile and a non-destructive method. The potential and accuracy of these methods in comparison
to tactile measurement systems is shown and discussed in this paper. 相似文献
930.