To correct for this bias, Terzaghi [8] 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.