Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimization of Wireless Power Transfer Systems Enhanced by Passive
  Elements and Metasurfaces   This paper presents a rigorous optimization technique for wireless power
transfer (WPT) systems enhanced by passive elements, ranging from simple
reflectors and intermedi- ate relays all the way to general electromagnetic
guiding and focusing structures, such as metasurfaces and metamaterials. At its
core is a convex semidefinite relaxation formulation of the otherwise nonconvex
optimization problem, of which tightness and optimality can be confirmed by a
simple test of its solutions. The resulting method is rigorous, versatile, and
general -- it does not rely on any assumptions. As shown in various examples,
it is able to efficiently and reliably optimize such WPT systems in order to
find their physical limitations on performance, optimal operating parameters
and inspect their working principles, even for a large number of active
transmitters and passive elements.

21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg