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!$Author$
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c     file name: asd.for

      subroutine asd ( ak, bsagm0, gmdd, gmddmn )

c     + + + PURPOSE + + +
c calculate agg size distribution eq. S(67), and S(62) (deaggregation process)

c     + + + AUTHOR + + +
c     Imam Elminyawi

c     + + + KEY WORDS + + +
c     wind erosion, soil processes, aggregate size distribution

c     + + + ARGUMENT DECLARATIONS + + +
      real ak, bsagm0, gmdd, gmddmn

c     + + + LOCAL VARIABLES + + +
      real anc

c     + + + LOCAL DEFINITIONS + + +
c     anc

c     + + + END SPECIFICATIONS + + +

      anc=0.0
      if ( (gmdd .le. gmddmn) .or. (gmdd .ge. bsagm0) ) go to 100
         anc = -ak * alog(( gmdd - gmddmn) / ( bsagm0 - gmddmn )) +1.0
         gmdd = ( bsagm0 - gmddmn ) * exp(-anc/ak) + gmddmn
 100  continue

      return
      end