Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Physics of Protoplanetesimal Dust Agglomerates. X. Mechanical
  properties of dust aggregates probed by a solid-projectile impact   Dynamic characterization of mechanical properties of dust aggregates has been
one of the most important problems to quantitatively discuss the dust growth in
protoplanetary disks. We experimentally investigate the dynamic properties of
dust aggregates by low-speed ($\lesssim 3.2$ m s$^{-1}$) impacts of solid
projectiles. Spherical impactors made of glass, steel, or lead are dropped onto
a dust aggregate of packing fraction $\phi=0.35$ under vacuum conditions. The
impact results in cratering or fragmentation of the dust aggregate, depending
on the impact energy. The crater shape can be approximated by a spherical
segment and no ejecta are observed. To understand the underlying physics of
impacts into dust aggregates, the motion of the solid projectile is acquired by
a high-speed camera. Using the obtained position data of the impactor, we
analyze the drag-force law and dynamic pressure induced by the impact. We find
that there are two characteristic strengths. One is defined by the ratio
between impact energy and crater volume and is $\simeq 120$ kPa. The other
strength indicates the fragmentation threshold of dynamic pressure and is
$\simeq 10$ kPa. The former characterizes the apparent plastic deformation and
is consistent with the drag force responsible for impactor deceleration. The
latter corresponds to the dynamic tensile strength to create cracks. Using
these results, a simple model for the compaction and fragmentation threshold of
dust aggregates is proposed. In addition, the comparison of drag-force laws for
dust aggregates and loose granular matter reveals the similarities and
differences between the two materials.

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The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th