These are projects posted by the students of Dr. Gove Allen at Brigham Young University. These students have taken one semester-long course on VBA and generally have had no prior programming experience

Tuesday, April 13, 2010

Cowtail Biomechanics Analysis

Biomechanics is a field of science exploring the mechanical properties and functions of the body. In the BYU Applied Biomechanical Engineering Laboratory (BABEL), properties of spinal intervertebral discs are studied. Research includes studying the degeneration of discs as induced by chemical and mechanical initiation. For the research associated with this project, bovine tail segments were dissected and put into a machine that cycles the specimen through three different modes of loading: compression/tension, flexion/extension, and axial rotation. Throughout the test, data points consisting of angular position and force/torque data were collected at 1000 Hz and smooted to 100 Hz. Raw data for a single test consists, on average of approximatedly 6000 data points representing deadtime on either side of fifteen 100-data-point cycles. Then there were 50 samples with two runs of 3 tests each, or approximately 300 datasets.

For each data set, only the last of the fifteen cycles is needed. It needs to have a few characteristic pieces pulled from the data including maximum, minimum, and an exponential, least-squares regression model. There is also a neutral zone which is a quasi-linear portion of the curve in the center allowing for more displacement with less force resistance. The length of that neutral zone is a key differentiator in intervertebral disc degeneration levels. For this research, the neutral zone is determined as being between the two points that first break from the linear pattern. Then, statistical analyses can be performed after the characteristic components are pulled from each data set.

The VBA routines assembled to analyze the data go through the following steps:
  • Finds and copies the 15th cycle of data to a new worksheet named after the data set
  • Calls a userform with a Microsoft Chart Object to allow a user to indicate the inflection points, which define the boundaries of the neutral zone
  • Centers the neutral zone on the origin of the graph and offsets all of the data to match
  • Calls the Solver add-in routines to provide three constants for four exponential best-fit models
  • Calculates the total range, neutral zone range and the hysteresis in each sample
  • Summarizes the data on a separate worksheet for ease in statistical analysis

Excel File: Cowtail Analysis

Write-up: Written Report

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