CHAPTERS 3

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CHAPTERS 3 4

• Freshman Clinic 1
• 27 NOVEMBER 2006 Lecture Week 11
• ROWAN UNIVERSITY
• College of Engineering
• Dr Peter Mark Jansson, PP PE
• Associate Professor
• DEPARTMENT OF ELECTRICAL COMPUTER ENGINEERING
• Autumn Semester 2006

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Admin

• Will Grade Mid-Term as a Class
• HW 7 due next week at 9.50 AM

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Freshman Clinic I

• Todays Learning Objectives
• Engineering Problem analysis
• Engineering Method
• Problem Presentation
• Documentation
• Representing Technical Information

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Chapter 3 Engineering Solutions

• The Art Science of Engineering Solutions
• Engineering Science
• Mathematics, chemistry, physics, mechanics, other
  technical subjects
• Engineering Art
• Judgment, experience, common sense, know-how in
  real life, knowing when science can and may not
  be applicable

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What is the Engineering Method?

• 1. Recognizing and defining the right problem
• 2. Accumulate data and verify accuracy
• 3. Select appropriate theory or principle
• 4. Make necessary assumptions
• 5. Solve the problem
• 6. Verify and check your results

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What are the key steps in problem presentation?

• 1. Problem statement
• 2. Diagram or sketch of problem
• 3. Theory or principle that is applicable
• 4. List necessary assumptions
• 5. Solution steps
• 6. Identify results Verify/Check them

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Learning to Present Effectively

• Nine helpful guidelines
• Using ruled (engineering) paper
• Complete headings (name, course, p , problem
  set)
• Work in pencil (HB, F or H)
• Good, legible lettering style
• Correct spelling
• Set up work as easy to follow
• Separate problems clearly
• Clear and understandable sketches/diagrams
• Properly use symbols and notation

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Chapter 4 - Graphical Representation of Technical
Data
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Graphing Data

• A graph of data usually gives more information
  than tables of numbers
• Graphs for oral presentation will usually look
  different that those for written reports
• There are several methods for generating graphs
  from data.
• Spreadsheet (e.g., Excel)
• Computational software (e.g., Matlab,
  Mathematica, MathCAD)
• By hand (not suitable for presentation!)

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Graphing Data

• Types of graphs.
• Professional looking graphs.
• Axes
• Smooth curves.

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Types of Graphs
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Types of Graphs

• XY (scatter) is widely used in Engineering.
• Bar, Column, Pie are more often used in Business,
  but some Engineering data is best presented using
  these types, e.g., Gantt chart.
• Presenting complex data is challenging and may
  require you to be creative in graphing it.

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Professional Looking GraphsWhats wrong with
this graph?
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Professional Looking Graphs

• Lettering sizes are inconsistent.
• Ordinate label is better written as
• electron temperature (keV)
• Abscissa should be fully indentified.
• 10-2 cm or 16 x 10-2.
• Data symbols are too small and there is a
  duplication. Should be as large as superscripts.
• Ordinate axis is too long.
• Graph should be fully enclosed with tick marks.

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Professional Looking Graphs
When the previous graph is reduced in size to fit
into a paper, it is difficult to read.
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Professional Looking Graphs
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Professional Looking Graphs
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Axes

• The choice of axes can affect how the data is
  perceived.
• Proper selection of axes can assist in
  determining an appropriate analytical solution
  for the data.
• Proper selection of axes can also assist in
  creating smooth curves.
• Log axes allow large ranges to be covered.

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Axeslinear-linear
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Axeslinear-linear
For the graph on the previous slide, we have
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Axessemilog log y, linear x
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Where does the log axis come from?
102 100 101.9 79.4 101.8 63.1 101.7
50.1 101.6 39.8 101.5 31.6 101.4 25.1 101.3
20.0 101.2 15.8 101.1 12.6 101 10
2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0
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Why use a log axis?
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Axessemilog
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Axessemilog
4 3 2 1 0
log (sample Y data)
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Axessemilog
Find a and c for the semilog graph shown.
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Axessemilog
The semilog plot works with any base logarithm,
not only base 10. In particular, it works with
the natural logarithm. This is because of the
following property of logarithms
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Axeslog-log log x, log y
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Axeslog-log
A straight line on a log-log plot can be
represented as follows
A straight line on a log-log plot is represented
by a power equation. Note, this also applies to a
ln-ln plot.
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Axeslog-log
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Axeslog-log
Find the equation of the line for the log-log
plot shown below.
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Smooth Curves

• Experimental data rarely follows theory exactly
  because of a variety of measurement errors.
• It is often desirable to fit the experimental
  data to a smooth curve.
• Several methods of curve fitting
• method of selected points
• method of averages
• method of least squares.
• Method of Least Squares is the most accurate and
  was covered when we did statistics.

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Smooth Curves

• Method of Selected Points Assuming the data set
  is linear, a straight line is drawn that appears
  to fit the data the best, going through as many
  observed data points as possible and
  approximately the same number of data points on
  each side of the line. Two points exactly on the
  line are used to determine the equation of the
  line.
• Method of Averages A line is drawn to make the
  algebraic sum of the difference between observed
  data points and calculated points on the ordinate
  equal zero.

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HW Assignment 7

• Due Monday, 4 December, 9.25 AM at Lecture
•  Intro. To Engineering Design and Problem
  Solving, pp. 139-141
• 3.9, 3.12, 3.19
•  Intro. To Engineering Design and Problem
  Solving, pp. 175-122
• 4.4, 4.11 (in Excel or on graph paper)