Software Simulation Enhances Science Experiments
The physical testing at the heart of science experiments conducted by students is not a terribly efficient use of time, or a school districtís money. Students with varying degrees of mechanical aptitude must contend with a variety of instruments, negotiate the sharing of units with classmates, and block off time to run their tests. The time and cost required for students to examine more than just a few factors are often prohibitive. It is difficult to justify the expense of exploring new ideas and "hunches," even though that is where real breakthroughs in learning take place. For that matter, teachers must also spend a significant amount of time coordinating the use of instruments among students and managing a sizable inventory of devices.
Although there is no replacement for studentsí hands-on experience with instrumentation and the physical processes, we can lend much greater efficiency to experimentation by letting students use software simulation models in the place of much of physical testing. A simulation runs in minutes, instead of the several days or weeks required by physical methods. Along with giving students greater efficiency, it enables them to investigate many more variables.
Simulation not only provides a timesaving but also an important opportunity to make learning experiences come alive for students. It lets them interact with the system under study and receive immediate responses. Simulation lets them explore, come up with hunches and test them, then make some well-considered conclusions. This dynamic approach enables students to understand the workings of a system much better.
Another advantage of exposing students to software simulation is that they will get a taste of the same approach used by many engineers and research scientists in the world of product design and development. These professionals have replaced a significant amount of their physical testing with software simulation.
Better, Graphical Software Brings It to High School
Extensive experience with simulation concepts is not required for a student to benefit from the software models, as most of todayís simulation packages are visual and menu-driven. Typical programs graphically depict the flow of components visually on the screen as students develop the diagram. During simulation, onscreen graphs immediately show the response of the components.
In the past few years, simulation software has joined the widespread evolution led by Microsoft and Apple toward a graphic-oriented interface. I was introduced to one simulation packages in the summer of 1995, while working at the University of Mississippi Medical Center in Jackson under a grant from the American Physiology Societyís "Frontiers in Science" program for high school teachers. Finding the software easy to use, I thought of my students and the opportunity they could have to embark on explorations through simulation. (The software was certainly more visual than the simulation program I used years ago during my Ph.D. dissertation research. The extent of that programís graphic interface was a dark screen and a stack of pin-feed paper.)
Students in all scientific disciplines can apply simulation to their experiments. Practically anything that can be measured -- pressure, flow rates, electrical fields, diameters -- can be simulated. Physics students can simulate electronic or mechanical systems. Geology students can simulate the effect of rainfall on water tables and erosion. Chemistry students can simulate the effect of temperature on pH levels or chemical reaction rates. Biology students can simulate the response of living organisms to outside stimuli. While most students will manually enter data, advanced students can obtain more accurate "real-time" input during an experiment by linking an instrument, such as a voltmeter, to the computer through a data acquisition card (DAQ, in the vernacular).
Some of my biology students have set up and run models of human body systems. These simulations explored the effect of various gas pressures on the respiration rate, the effect of exercise on bone mass, and other topics.
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| Amanda Raley (left) and J.T. Newman (right) Work on Thier Simulations |
Model Building & Testing by Steps
After I taught the students the basics of block diagrams and flowcharting, they began creating models on their own. They built the graphical diagrams by first representing each component as an icon (or block). They selected these from a library of several dozen pre-defined blocks, including time constants, summing junctions, gains and slide blocks. To set the operating parameters of the blocks, students clicked on them and a dialog box prompted them for the information. To "wire" the blocks together, students pointed the cursor between two blocks and clicked.
The modelís main diagram contained boxes indicating sub-blocks for the components, along with graphs that depict the systemís response. Students were able to move to a sub-block simply by double-clicking. Later, by double-clicking in any white space in the sub-block, they were able to return to the main block. They were free to move about the models extensively. A main block diagram, for example, could contain boxes for the components, along with graphs for respiration rate and blood pressure. A sub-block could also contain graphs.
As a student conducts a simulation, he or she enters a round of data, runs a simulation, then waits to see what happens. Simulations can be continuous or in steps; the student can stop and resume at any time. The student takes "snapshots" of the system, makes adjustments to the simulated model and immediately sees the effect.
One important visual aid in simulation software packages is a "real-time" graphing feature. These graphs can be attached to any block to visually show its response over the course of the simulation. They let students actually see system behavior and the effect of any changes. It is particularly important to let students actually see the effect of their changes. Typical graphs include respiration rates, pH levels or water flow rates. More sophisticated graphs plot two feeds together, such as commanded and actual position, commanded and actual velocity, or commanded and actual current.
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| Jamar Kincaid (left) and Adam Klye (right) also Work on Thier Simulations |
Examples of Students' UseA junior at Weir High School in Choctaw County, Amanda Raley wanted to find out how partial pressures of oxygen, hydrogen and carbon dioxide in the blood affected the bodyís respiration rate. She set up blocks for each pressure and a block for the respiration rate. Then she constructed a complete loop between the respiratory block and pressure blocks. As she changed any of the partial pressures, that changed the respiration rate. Amanda added graphs showing the relationships between partial pressure and respiration. The output was the respiratory rate. See her diagram in Figure 1.
Jamar Kincaid, a junior at Weir, wanted to know how bio-receptors affected the bodyís blood pressure. He set up several blocks in his model of bio-receptors. As these receptors inform the brain of changes in blood pressure, the brain adjusts the pressure by increasing or decreasing heart rate and constricting or relaxing the blood vessels. Jamarís blocks included the receptors, brain, blood pressure, heart, and a block representing blood vessel diameter.
J.T. Newman, a sophomore at Ackerman High School, wanted to know the effect that exercise would have on calcification of the bones, especially regarding osteoporosis. In his model, J.T. had nearly 20 blocks, which included exercise, calcitonin (a parathyroid hormone), vitamin D and calcium. At the end of the loop was a block for the rate of bone calcification. J.T. did a lot of research on how exercise and other factors affected bone mass. With the simulation model, he concluded that exercise should indeed be used to prevent or treat osteoporosis. See J.T.'s diagram in Figure 2.
EJ- FIGURE 2 -- -- near here
Adam Kyle, a junior a few miles north at Ackerman High School, wanted to know where a personís wound would bleed more, on earth or in an airplane. Adam set up a block for atmospheric pressure (to simulate conditions in an airplane, on the earth, under water), a block for blood pressure, and a block showing the bleeding rate from a wound. It was hard to find research on bleeding in these three environments, so Adamís data was limited.
To an extent, these students could not acquire data from personal research. But use of existing data did not keep their simulations from being genuinely exploratory in nature. Students often combined sets of data as well as sets of conditions, which frequently led to original -- and unexpected -- results.
Rewarding for Us
Our approach and the students' achievement have been rewarded. The students received recognition for their work, placing high at the annual science fair. To our delight, we were one of the few candidates in the nation to win a TAPESTRY Grant, funded by Toyota Motor Sales, USA. The automaker annually awards 25 grants in environmental science and 25 in physical science.
Educators no longer have to limit studentsí participation in dynamic learning experiences to physical experiments. The use of visual simulation software is one of the best opportunities for students to actively participate in learning about system behavior and responses.
Frances Coleman is a Science Teacher and also serves as Technology Coordinator for Choctaw County School District, in Ackerman, Mississippi. E-mail: [email protected]