To correct for this bias, Terzaghi  proposed a well-known method that weighs the observed frequencies by a bias-compensatory factor, which is the reciprocal of the sine of the intersection angle
between the scanline and discontinuity.
where [gamma] is the intersection angle
of the discrete ray and center ray S (Figure 3); [I.sub.1] is the radiation intensity of the center ray.
Thus, among the many parameters of joint geometry, the joint inclination angle, intersection angle
, and persistency are considered in this study.
The intersection angle
we measured between the tibia plafond and the articular facet of the medial
The intersection angle
[[theta].sub.i,j] of the line segments [l.sub.i] and [l.sub.j] is the angle between the two vectors that correspond to [l.sub.i] and [l.sub.j], and the starting points of the two vectors are the pair of end points that have the shortest distance, as shown in Figure 4(b).
Where, [[alpha].sub.x], [[beta].sub.x], [[gamma].sub.x] is the intersection angle
between X-axis and X', Y', Z' axis respectively, [[alpha].sub.y], [[beta].sub.y] [[gamma].sub.y] is intersection angle
between Y-axis and X', Y, Z' axis respectively, [[alpha].sub.z], [[beta].sub.z], [[gamma].sub.z] is intersection angle
between Z-axis and X', Y', Z' axis respectively.
N+2) of an interval D.' N+1 between a V" design unit N and a N+l th design unit N+1l adjacent thereto to an interval Dr4+1 DN+l.about.N+2 between the N+1 th design unit N+1 and a N+2 th design unit N+2 adjacent thereto falls within a range from 0.95 to 1.05, and the secpnd arrangement directions of the designunits change regularly such that an intersection angle
that is formed between an extended line of a straight line connecting the Nth design unit N and the N+1 th design unit N+1l adjacent thereto and a straight line connecting the N+1.sup.th design unit N+1l and the N+2 th design unit N+2 adjacent thereto falls within a range of 1 degree to +1 degree.
(2) Helix slope angle [beta], the intersection angle
between tangent line of helical slope surface and the entrance plane normal.
Notice that the intersection angle
between the tangent and g is the same as the angle between the respective normal directions of the fibre and of the line.