# principal axis

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Related to principal axis: centre of curvature

## principal axis

[′prin·sə·pəl ′ak·səs]
(crystallography)
The longest axis in a crystal.
(engineering acoustics)
A reference direction for angular coordinates used in describing the directional characteristics of a transducer; it is usually an axis of structural symmetry or the direction of maximum response.
(mathematics)
One of a set of perpendicular axes such that a quadratic function can be written as a sum of squares of coordinates referred to these axes.
For a conic, a straight line that passes through the midpoints of all the chords perpendicular to it.
For a quadric surface, the intersection of two principal planes.
(mechanics)
One of three perpendicular axes in a rigid body such that the products of inertia about any two of them vanish.
(optics)

## principal axis

Primary axes
In the illustration on the left, line A is the principal axis while in the illustration on the right, line B is the principal axis. The moment of inertia is maximum around these axes in these two cases.
i. The lateral, vertical, and longitudinal axes.
ii. The axis of relative wind.
iii. The principal inertial axis: that line passing through the center of gravity in a plane of symmetry about which a long, slender body tends to rotate when rolling.
iv. A rectilinear axis in the plane of a cross section of a structural member about which the moment of inertia is the maximum.
References in periodicals archive ?
insignis by moving the principal axis relative to the center of a geological stereonet accounting for the deviations from the sagittal and frontal planes.
Likewise, the iterated principal axis solution for four dimensions resulted in item-factor membership identical to that portrayed in Table 2, whether orthogonally or obliquely rotated.
The principal Axis I diagnoses for this group included Conduct Disorder (5), Oppositional Defiant Disorder (3), Post Traumatic Stress Disorder (7), and Major Depressive Disorder, primary or secondary (2).
The principal Axis I diagnoses for this group included Conduct Disorder (1),Oppositional Defiant Disorder (3), Post Traumatic Stress Disorder (4), and Major Depressive Disorder, primary or secondary (5).
This thoroughfare has remained a principal axis of the city since the early development plan was implemented in the nineteenth century.
p] = 0 [degrees] and principal axis 1 while the vertical axis corresponds to [[Theta].
p] = 90 [degrees] or principal axis 3, in relation with a velocity that increases with higher modulus.
The swooping, tensile mesh structure, designed by RFR, provides a new focus on the principal axis of the park.
The principal Axis I diagnoses for this group included Conduct Disorder (14), Oppositional Defiant Disorder (4), and Post Traumatic Stress Disorder (7).
The competition-winning scheme consists of several distinct elements, the largest of which is a temporary exhibition gallery, orientated parallel to the old building's principal axis, but separated from the nineteenth-century structure by a small garden.
Siemens has localized the procurement of wind turbine hulls, principal axis and gearboxes in China since 2008.
The main pavilion on two levels steps down the site along the principal axis to a paved courtyard and green lawn bounded by trees.

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