I	phonon radiation intensity, W/(m2 sr)
v	velocity of sound, m/s
Λ	phonon MFP, nm
TH, TL	boundary temperature, K
q	heat flux density, W/m2
λp , λs	thermal conductivity of primary and secondary particles, W/(m K)
Kn	Knudson number
dρ	diameter of nanometer-sized spheres, m
D	mean diameter of pores in aerogels, m
λc	effective thermal conductivity for nanometer-sized coupled conduction, W/(m K)
λg	thermal conductivity of gas in pores, W/(m K)
Π	porosity
S	specific area, m2/kg
B1, B2	parameters defined in Equations (7) and (8)
ρ	density of nano-insulation material, kg/m3
ka,R	spectrum averaged absorption coefficient, 1/m
kaλ	spectral absorption of nano-insulation material, 1/m
Ebλ	spectral emission power of black body, W/(m2 μm)
Eb	emission power of black body, W/m2
λ	Wavelength, μm
λr	radiative equivalent conductivity, W/(m K)
T	absolute temperature, K
λeq	equivalent thermal conductivity of nano-insulation material, W/(m K)
m	number of particles in swarm
Xi	position vector of a particle labeled i in a swarm
Vi	velocity vector of a particle labeled i particle in a swarm
Pbest	individual optimal adaptability
Gbest	global optimum position among all particles
Vij	jth component of velocity vector of a particle labeled i in a swarm, (i = 1,…,m)
Xij	jth component of position vector of a particle labeled i in a swarm, (i = 1,…,m)
C1 , C2	learning factors
w	inertial weight
t	number of iteration