F ¯ v ⁢ ( i ) = ∑ i ≠ j | ∑ k = 1 N C c N U ⁢ ( i ) , N C ⁢ ( k ) , N U ⁢ ( j ) ⁢ ϕ ^ ¨ N C ⁢ ( k ) | ¯ 𝐹 𝑣 𝑖 𝑖 𝑗 𝑘 1 Nc 𝑐 𝑁 𝑈 𝑖 𝑁 𝐶 𝑘 𝑁 𝑈 𝑗 2 ^ italic-ϕ 𝑁 𝐶 𝑘 \displaystyle\overline{F}_{v}(i)=\sum_{i\neq j}|\sum_{k=1}^{N_{C}}c_{N_{U}(i),N_{C}(k),N_{U}(j)}\hat{\ddot{\phi}}_{N_{C}(k)}|