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Lecture 6An Exercise on Writing
MathLuis San Andres
Mast-Childs Tribology ProfessorTexas A&M University
http://rotorlab.tamu.edu/me489
February 8, 2011
ME 489 Practices of Modern Engineering
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Lecture 6Date: February 8, 2011
Today: Writing MathSolve a technical problem and write it
Classic Style
presents:Assignments & reading: A2 due today
Other: complete ONE MINUTE PAPER
? A surprise ?
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Schedule group presentations
• Select ONE EW, listen and discuss as a group• Group prepares presentation (15 slides max) for (max 15 min) +discussion in class• Play EW and lead discussion in class
Note: MUST reference all material copied from URLs, journals,
textbooks, etc
Group Name
The Wrecking Crew
A&M Team
Classic Style
The Better Team
Team Alpha
Last Pick
Gilligan's Blade
LeftOvers
Feb 15 TuesdayUnder the Alps
Feb 10 Thursday The Reactor Down The Street
PLEASE E-mail me a pdf file of presentation for
posting on class URL site
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Comments on last lecture and group presentation
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China New Year
In China they no longer light fireworks to celebrate due to environmental issues & safety. In America, we obviously don’t follow this.
Practices of Modern Engineering – Spring 2011
Every city in the US has the strictest rules on fireworks handling and lighting. One can only do it outside the city limits or under strict safety guidelines.
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About Virtual Rehabilitation
How are other countries using technology to help their veterans?
I’d like to know more about the technical design of the CAREN system
Practices of Modern Engineering – Spring 2011
How much research is being done linking neurology to prosthetics?
I also thought of innocent victims of war (land mines) in poor countries. To manufacture inexpensive prosthesis is a worthy pursuit
PLEASE SEND PDF for posting
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Questions on communication
The article sent(*) listed oral communication as more important than written communication. How can we be better oral communicators?
Practices of Modern Engineering – Spring 2011
Oral communication is paramount in the workplace (daily activities). To become a better oral communicator, begin to ask questions
(*) Nixing Engineerese
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Questions on communication
Need good resources/examples of how to write technical memos/reports and/or lab reports
Practices of Modern Engineering – Spring 2011
Please visit TAMU Writing Center: Business & Professional Writing
http://writingcenter.tamu.edu/c/how-to/business/
Includes CVs, Memos, Executive Summaries, Lab reports, etc
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Questions on writing
When writing a tech report for an experiment you performed, how can you avoid both 1st person and passive voices? Examples:
Practices of Modern Engineering – Spring 2011
“We measured…” Active but 1st person
“…. was measured” Third person but passive
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Avoiding passive voice
Practices of Modern Engineering – Spring 2011
AWFUL
We measured the temperatures at the inlet and exhaust of the engine ..
Inlet and exhaust engine temperatures were measured….
BETTER
During the experiments, thermocouples recorded temperatures at the inlet and exhaust of the engine….
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From technical memo examples
Practices of Modern Engineering – Spring 2011
AWFUL
Seal loads were reported by Authors () …….
The loads were shown to decrease with increasing rotor speeds…..
The results are shown in Figure X
To improve the accuracy, Authors () introduced a 3 control volume method to calculate seal forces
BETTER
Authors () report(ed) loads for seals
The experimental results show the load to decrease as the rotor speed increases
Figure X depicts the results
Authors ( ) introduced a three control volume method to predict more accurately seal forces
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Questions on oil prices
Practices of Modern Engineering – Spring 2011
Why do oil prices have such an effect on jobs lost? Does the $ rise in cost means an increase in # jobs for engineers?
Gas prices influence directly the cost of transportation (goods and people). Companies struggle to keep costs down (ask an airline company). The $ increase reflects the uncertainty in the supply market. It will not create new jobs.
A $10 increase in a barrel of oil (causes in the US) 25 cent increase in gallon of gasoline drop of ¼% in economic growth a reduction of 200,000 jobs!
NPR 02/03/117:30 am
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More about the world
I’d like to learn more about other economies. I feel like some of the comments brought up about GDP and other countries’ economies are valid points that should be explored further
Practices of Modern Engineering – Spring 2011
Soon, I hope. Topic is too broad. Give me a few pointers, pleeeeaaasssssssssse!
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Exercise Writing mathematics
Zero gravity(?) flight
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A weightless flight (zero-g) ??
http://gozerog.com (weightless flight experience)
The experience starts at 7,700 m while the AIRBUS A300 cruises at 500 miles/hour. Engines are shut off! An instant later, the world inside the plane becomes chaos: people screaming as they are lifted, as if they are weightless. 20 seconds later, the engines roar back to life. The people inside, some pinned to the cabin roof, slam back against the floor.
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Weightless (?) flight experience
jotting formulas w/o explanatory sentences counts very little
Tasks At the end of the weightless experience, at t=20 sec, (a) What is the aircraft speed (km/hour) and its acceleration (g‘s)?
How many meter does the aircraft fall? How many km does the aircraft travel along the horizontal direction?
(b) Demonstrate that the relationship between Y and X is indeed a parabola, i.e. Y~ X2
(c) At a price tag of $ 4,950 USD, would you pay for the weightless experience?
(d) Tell about other examples where you already feel the weightless experience?
Objective: Develop mathematical analysis, based on physical principles and assumptions, towards prediction of the plane motion
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The fundaments in words
Airplanes fly by forcing air over their wings so there is an
excess of the upwards force, lift. While in the air, the plane stays up thanks to lift and the engines thrust that makes the plane move forward. The aircraft works against two forces trying to slow it down and pull it out of the sky; air drag and gravity. On a normal flight, the amount of thrust is equal or greater than air drag and the lift equals the weight so that the plane stays up.
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The fundaments in physics
ThrustDrag
Weight
Lift
speed
M
Abstraction: the concept of forces
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The fundaments in mathematics (I)
Free body diagram
T: Thrust
D=Drag
W=Weight
L= Lift
VX: velocityM
D T
L
W
g
g=gravity
M: mass
a =dV/dt: accel.
V: velocity
Define Symbols:
Forces
Constant
Parameter
Variables
VY: velocity
Tell the tale: count assumptions
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The fundaments in mathematics (II)
Newton’s Law of motion
VX: speedM
D T
L
W g M aX = T - D
M aY = L - W
X
Y
Define INERTIAL coordinate system
(1)
(2)
Note beauty and simplicity
(in description of natural phenomena
& economy of words)
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The fundaments in mathematics (II)
Newton’s Law of motion (equilibrium)
VX: speedM
D T
L
W g
T = D
L = WX
Y(1’)
(2’)
For flight at constant speed and height:
aX = dVX/dt=0
aY = dVY/dt=0
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Parabolic flight
During a parabolic flight, thrust is set to equal drag while lift is removed (L=0)Hence, weight is the only force
acting on the plane and, like any unpowered object fired into the air, the plane will move along a parabolic path as it free falls.
0 = T - D
M aY = - WEOMS simplify to
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Weightless flight experience
jotting formulas w/o explanatory sentences counts very little
Tasks At the end of the weightless experience, at t=20 sec, (a) What is the aircraft speed (km/hour) and its acceleration (g‘s)?
How many meter does the aircraft fall? How many km does the aircraft travel along the horizontal direction?
(b) Demonstrate that the relationship between Y and X is indeed a parabola, i.e. Y~ X2
(c) At a price tag of $ 4,950 USD, would you pay for the weightless experience?
(d) Tell about other examples where you already feel the weightless experience?
Objective: Develop mathematical analysis, based on physical principles and assumptions, towards prediction of the plane motion
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Weightless flight experience
Objective: To develop mathematical analysis to predict the plane motion
In short:(a) Where is airplane after 20 s?(b) Demonstrate flight path is
parabolic(c) Is the zero-g claim true? (d) Would you pay for it?
Known: At t=0 s, when plane is at 7,700 m and flying with speed of 500 miles/hour; engines are shut off (?). Time elapsed for zero-g experience is 20 s
0 5000 1 104
1.5 104
1 104
1.5 104
2 104
2.5 104
3 104
parabolic gravity fall
X [ft]
Y [
ft]
*
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Weightless flight experience
Work problem individually & as a group – tell me how you solve it (during class)
Ask questions – I am a part of your group (team)
No need to turn in anything but work problem (writing math and words)
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Summary
(a) Engineers work with different physical units. Conversion of units is a must knowledge.
(b) Formulation of problem statement (need) is crucial. It must convey all information (knowledge and assumptions). WORDING is IMPORTANT.
(c) Combining mathematical statements (equations) with prose sentences must be learned and practiced.
(d) Do not leave out anything. Do not assume the reader knows as much as you do or is familiar with your way of doing things.
Knowledge acquired today
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See “solution” posted on classURL site
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Questions?
Next lectureAbout plagiarism in academia and engineering practice
Ethics in the Workplace
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Practices of Modern
Engineering© Luis San AndresTexas A&M University2011
http://rotorlab.tamu.edu/me489