The geometric definition suggests a simple method for drawing an ellipse. Place a
sheet of paper on a drawing board, and insert thumbtacks at the two points that are to
be the foci of the ellipse. Attach the ends of a string to the tacks, as shown in Figure
2(a). With the point of a pencil, hold the string taut. Then carefully move the pencil

حيث ان فراغ العينةوعدد الحالات التي تحقق حدثا معينا يستخدم في حساب الاحتمالات بهذا الحدث ,وفي بعض الأحيان يكون عدد عناصر فراغ العينة عددا كبيرا لذلك يمكن تحديد عناصره

Asphalt mix design is a complex issue with a lot of variables involved. It is a mixture of course aggregate, fine aggregate, mineral filler and bitumen. Well graded aggregates, mineral filler and optimum quantity of bitumen results a mix with maximum density and very high stability. Marshall Mix design is the most popular method that widely been used in road industry.

Function of Base (or Subbase):

 1) Drainage purpose

 2) Reduce the effect of subgrade volume change on concrete layer 

3) Prevent pumping of fines through joints & edges 

4) Increase "K" modulus of subgrade reaction Rigid Pavement Characteristics: - Can resist unlimited loading - Minor defects are not reflected. - More skid resistance, safe. - More economical for same projects at certain location. - Concrete layer is less thickness than other layers.