STK_TESTFUN_BOREHOLE computes the "borehole model" response function

 CALL: Y = stk_testfun_borehole (X)

    computes the responses Y(i, :) of the "borehole model" [1-3] for the
    input vectors X(i, :).

    The output Y is the water flow rate through the borehole (m3/yr).

    The input variables (columns of X) are:

       X(:, 1) = rw   radius of borehole (m),
       X(:, 2) = r    radius of influence (m),
       X(:, 3) = Tu   transmissivity of upper aquifer (m2/yr),
       X(:, 4) = Hu   potentiometric head of upper aquifer (m),
       X(:, 5) = Tl   transmissivity of lower aquifer (m2/yr),
       X(:, 6) = Hl   potentiometric head of lower aquifer (m),
       X(:, 7) = L    length of borehole (m),
       X(:, 8) = Kw   hydraulic conductivity of borehole (m/yr),

    and their usual domain of variation is:

       input_domain = stk_hrect ([                                  ...
           0.05    100   63070    990   63.1    700  1120   9855;   ...
           0.15  50000  115600   1110  116.0    820  1680  12045],  ...
          {'rw',  'r',    'Tu',  'Hu',  'Tl',  'Hl',  'L',  'Kw'})

 REFERENCES

  [1] Harper, W. V. & Gupta, S. K. (1983).  Sensitivity/uncertainty analysis
      of a borehole scenario comparing Latin Hypercube Sampling and determinis-
      tic sensitivity approaches.  Technical report BMI/ONWI-516,  Battelle
      Memorial Inst., Office of Nuclear Waste Isolation, Columbus, OH (USA).

  [2] Morris, M. D., Mitchell, T. J. & Ylvisaker, D. (1993).  Bayesian design
      and analysis of computer experiments: use of derivatives in surface
      prediction.  Technometrics, 35(3):243-255.

  [3] Surjanovic, S. & Bingham, D.  Virtual Library of Simulation Experiments:
      Test Functions and Datasets.  Retrieved February 1, 2016, from
      http://www.sfu.ca/~ssurjano/borehole.html.