One can see that the normal density allocates little probability mass to the regions far from the mean ( " has thin tails " ), compared with the blue curve of the leptokurtic Pearson type VII density with excess kurtosis of 2.
32.
Neutron reflectors, compressing the fissile core via implosion, fusion boosting, and " tamping ", which slows the expansion of the fissioning core with inertia, allow nuclear weapon designs that use less than what would be one bare-sphere critical mass at normal density.
33.
The Epanechnikov kernel is optimal in a mean square error sense, though the loss of efficiency is small for the kernels listed previously, and due to its convenient mathematical properties, the normal kernel is often used, which means " ? " ( " x " ) } }, where " ? " is the standard normal density function.
34.
The resulting inward directed compression is expected to compress the fuel in the center of the target to a density of about 1, 000 g / cm 3 ( or 1, 000, 000 kg / m 3 ); for comparison, lead has a normal density of about 11 g / cm 3 ( 11, 340 kg / m 3 ).
