On the scaling of fragmentation and energy dissipation in collisions of dust aggregates

Fragmentation of granular clusters may be studied by experiments and by granular mechanics simulation. When comparing results, it is often assumed that results can be compared when scaled to the same value of $$E/E_{\mathrm{sep}}$$ E / E sep , where E denotes the collision energy and $$E_{\mathrm{sep}}$$ E sep is the energy needed to break every contact in the granular clusters. The ratio $$E/E_{\mathrm{sep}}\propto v^2$$ E / E sep ∝ v 2 depends on the collision velocity v but not on the number of grains per cluster, N. We test this hypothesis using granular-mechanics simulations on silica clusters containing a few thousand grains in the velocity range where fragmentation starts. We find that a good parameter to compare different systems is given by $$E/(N^{\alpha }E_{\mathrm{sep}})$$ E / ( N α E sep ) , where $$\alpha \sim 2/3$$ α ∼ 2 / 3 . The occurrence of the extra factor $$N^{\alpha }$$ N α is caused by energy dissipation during the collision such that large clusters request a higher impact energy for reaching the same level of fragmentation than small clusters. Energy is dissipated during the collision mainly by normal and tangential (sliding) forces between grains. For large values of the viscoelastic friction parameter, we find smaller cluster fragmentation, since fragment velocities are smaller and allow for fragment recombination. Graphic abstract

Explanation of the cluster structures melting mechanism and their influence on the molten state’s physical and chemical nature

There are results of the melts of semimetals and semiconductors of various structural groups research in the article. On the example of simplified regular Bethe lattice one can model destruction and aggregation of structures in clusters and on it’s basis to substantiate the metal melts properties in the form of nanolayers. The variety of compressibility polytherms forms in electronic melts requires typing, since their analysis makes it possible to explain the mechanism of the aggregation and dissolution processes of extended objects in melts. The article contains formulas that allow explaining the mechanism of the dissolution of cluster structures and their influence on the physicochemical nature of the molten state. There is considered the process of cluster fragmentation. Larger fragments of clusters are formed in the process of crushing, and this fact leads to the compressibility that decreases more rapidly, only after passing through the extremum it begins to increase due to the thermal loosening. The study of the function's compressibility for an extremum in the compressibility's temperature dependence also indicates the changing process of the clusters decomposition mechanisms in melts with an increase in temperature and vice versa to aggregation with a decrease in the melt temperature to the melting temperature.

Methods For Generation Of Cluster Particles Of Different Stochiometry

The main purpose from this paper, in semiconductor technology silicon oxide is to study notable of the surface and catalysis process. As a result, cluster fragmentation processes, we obtained information about the emission of the clusters and the chemical and physical properties of the clusters. We found during the study that oxide clusters are heterogeneous clusters. In heterogeneous clusters, the bonds in the main chain are different from the bonds in the side chain, as in organic polymers. We tried to prove on the basis of the analysis of experimental data that the formation, excitation and molecular decomposition of SinO2n + 1Hk- (k = 1-3) cluster ions are based on the model of the combinatorial synthesis mechanism.

How well can we predict cluster fragmentation inside a mass spectrometer?

We measured the fragmentation of clusters inside an MS and we developed a model to describe and predict their fragmentation.

Hadronization properties in   e e annihilation at S  60GeV centre of mass energy

The hadronic events from the experimental data , as well as the PYTHIA Monte-carlo data at the 60 GeV centreof mass energies are studied.We present the general properties of multihadron final states produced by e e   .Globalshape, inclusive charged-particle, and particle-flow distributions are presented. Our measurements are comparedwith QCD + fragmentation models that use either leading-logarithmic parton-shower evolution or QCD matrixelements at the parton level, and either string or cluster fragmentation for hadronization. Possible explanations forourcompariaon are presented in this paper.