Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Improvement of Joule Balance NIM-1 and the Design of New Joule
  Balance NIM-2   The development of the joule balance method to measure the Planck constant,
in support of the redefinition of the kilogram, has been going on at the
National Institute of Metrology of China (NIM) since 2007. The first prototype
has been built to check the feasibility of the principle. In 2011, the relative
uncertainty of the Planck constant measurement at NIM is $7.7\times10^{-5}$.
Self-heating of the coils, swing of the coil, are the main uncertainty
contributions. Since 2012, some improvements have been made to reduce these
uncertainties. The relative uncertainty of the joule balance is reduced to
$7.2\times10^{-6}$ at present. The Planck constant measured with the joule
balance is $h=6.6261041(470)\times10^{-34}$Js. The relative difference between
the determined h and the CODATA2010 recommendation value is $5\times10^{-6}$.
Further improvements are still being carried out on the NIM-1 apparatus. At the
same time, the design and construction of a brand new and compact joule balance
NIM-2 are also in progress and presented here.

28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio