if !d.name eq 'PS' then begin
  device,xsize=18,ysize=14,yoffset=3
  !p.charthick=3 & !p.thick=3 & !x.thick=3 & !y.thick=3
end

!p.charsize=1.5
!x.margin=[7.5,2.]
!y.margin=[3.2,0.3]
;
!p.multi=0
!x.range=0
!y.range=0

restore,'./pvar_file/pvar2.sav'
;restore,'../'+'/var_file/var10.sav'
;uu2=uu

xp=xx[*,0]
yp=xx[*,1]
zp=xx[*,2]

;------------------Swarm f(x,a,t)-------------------
;run 'stokes_lag.pro'
;--find the size corresponding to St--
St=1.
fact=2.0/9.0*density_ratio/nu
ac=sqrt(St*tau/fact)
ac_delta=1.e-6
ac_p=ac+ac_delta
ac_m=ac-ac_delta
ac_index=where(a GT ac_m and a LT ac_p)
xpc=xp[ac_index]
ypc=yp[ac_index]
zpc=zp[ac_index]


;----determine the slice to be plotted----
xcener=0.
xthick=10*eta
xcenterp=xcener+xthick
xcenterm=xcener-xthick
xcener_index=where(xpc GT xcenterm and xpc LT xcenterp)
yy=ypc(xcener_index)
zz=zpc(xcener_index)

;plot,every(yy,1),every(zz,1),/nodata,xr=minmax(x),yr=minmax(z),xtit='!8x !6[m]',ytit='!8z !6[m]'
plot,every(yy,1),every(zz,1),/nodata,xtit='!8x !6[m]',ytit='!8z !6[m]'
circ_sym,0.4,1.
oplot,every(yy,10),every(zz,10),ps=8
STOP
circ_sym,0.4,1.
oplot,xpc,zpc,ps=8,color=122
s=size(x) & nx=s[1]
s=size(z) & nz=s[1]
xxx=spread(x,[1],[nz])
zzz=spread(z,[0],[nx])
vel_a,reform(uu2(*,*,0)),reform(uu2(*,*,2)),xxx,zzz,nvec=500,len=.01,/over,col=0

print,'mv idl.ps ~/tex/nils/particles_coag/fig/vf_St.ps'
END