a

real part of a complex number, length, acceleration

b

imaginary part of a complex number, shaft bow, length

c

viscous damping coefficient, clearance

d

static offset

f(t)

generalized forces vector

modal force vector

g

gravitational acceleration

h

thickness

i

imaginary unit (i = ), current

i ₀

bias current

k

stiffness

l

length

m

mass

q _i

ith Lagrangian coordinate

q(z)

principal function

complex conjugate of q

q(t)

Vector of the generalized coordinates (real or complex)

r

complex coordinate (r = x + iy), radius

complex conjugate of r

s

Laplace variable, complex frequency (as in x = x ₀e ^st)

s ?

complex frequency in the rotor fixed frame

s

state vector (transfer matrices methods)

t

time, air gap

u _X, u _y, u _z,

displacements in xyz frame

uvw,

components of the displacement

xyz

reference frame

z

state vector

A

area of the cross section

A

dynamic matrix

B

magnetic field

B

input gain matrix, matrix for discretization of stresses

C

damping matrix, output gain matrix

modal damping matrix

E

Young's modulus

E

stiffness matrix of the material

force

Rayleigh dissipation function

G

Shear modulus

G

gyroscopic matrix

modal gyroscopic matrix

H

circulatory matrix, angular momentum

I

area moment of inertia

I

identity matrix

Im

imaginary part

J

inertia tensor

J

moment of inertia

J _p

polar moment of inertia

J _t

transversal moment of inertia

K

stiffness, gain, constant

K

stiffness matrix

modal stiffness matrix