IOE 333: Homework #1 100 points Due: Friday, January 29, 2010, 11:30 am on CTools After the due time, CTools will not accept any homework. Please type your answers in this file below each question. Save your file name using your unique name in the following format: uniquename_IOE333HW1 And upload your file to CTools -> Assignment This homework covers 6 lectures from 1/6 to 1/27. Problem 1 (20 points; 4 pts each) Briefly describe the following in your own words: When and where are Professor Liu?s and the GSI?s office hours? Professor Liu Office: G622 IOE Office Hours: Wed. 2-3pm Shi Cao (GSI) Office hours/location: Tu/Thur 1-2:30 pm, 1824 IOE Flex lab What are the four principles on which the College of Engineering?s Honor Code is based? Engineers must have personal integrity. Students in the College of Engineering are expected to be trustworthy and honest. The students, faculty members, and administrators of the College of Engineering trust one other to uphold the principles of the Honor Code. Students should not claim work that is not their own. Regarding homework, what is considered a violation of the Honor Code? A violation of the Honor Code would be copying homework from someone else and claiming it as their own. How should homework be submitted for this class? What should the file format and file name be? Homework should be submitted on Ctools under Assignments. The file should be a .doc file not a .docx file. The file should also be named uniquename_filename. What is the time limit to submit re-grading requests for this class? What should be included in a re-grading request? The re-grading material should be turned in within one week from the date that the corrected exam or homework assignment was handed back. With the re-grading request the student must include a written explanation with name, email address, date of request submission, the question, and their answer. Also the original exam or homework should be attached. Problem 2 (50 points; 5 pts each) List FIVE design features that already exist or you propose in the design of mobile phones and briefly explain how each feature improves or could improve user interactions with the system by addressing one of the five goals of ergonomics discussed in class (i.e., list and discuss one feature for each goal. It is fine if one feature can simultaneously address more than one goal, but you must discuss why you say so). Reduce error When a person accidently presses the ?Delete Inbox? button, most phones will ask if the person is sure they want to delete. This reduces the error of deleting something the person does not want to be deleted Increase productivity Speed dial makes it easier to call people really quickly. Enhance safety Mobile phones have a feature where people can have conversations over the speaker. This allows people to talk on the phone while driving without worry holding the phone and steering. Enhance comfort The small size of cell phones makes it more comfortable to hold when talking to people. It also makes it more comfortable to carry around. Improve aesthetics Cell phones have many designs that are aesthetically pleasing. For example, the different cell phones covers make the phone look more appealing and personal. List FIVE design features that already exist or you propose in the design of any one product (other than mobile phones or hand-held devices), and briefly explain how each feature improves or could improve user interactions with the system by addressing one of the five goals of ergonomics discussed in class (i.e., list and discuss one feature for each goal. It is fine if one feature can simultaneously address more than one goal, but you must discuss why you say so). Product: Laptop Reduce error When a user wants to make a change to their laptop options, the laptop will ask if the user really wants to make this change Increase productivity Laptops allow the user to multiple tasks at once. For example, a person could check their mail, finish an assignment, and change their schedule all within minutes of each other. Enhance safety There are laptop screen protectors that reduce the glare reflected off of the screen, which is better for the user?s eyes. Enhance comfort Laptops are being made lighter which makes it more comfortable for people to carry them around. Improve aesthetics Some laptops allow the buyer to pick the color of their laptop which in turn makes it more aesthetically pleasing to the buyer. Go to HFES website: HYPERLINK "http://www.hfes.org/" www.hfes.org/ . Find out: What does HFES stands for? Human factors and Ergonomics Society What is their definition of ergonomics? Ergonomics is the scientific concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data, and other methods to design in order to optimize human well-being and overall system performance. Find the link to HFES student chapter at University of Michigan. What is the 1st place winner of 2009 Bad Designs on Campus Contest, U of M HFES? 1st Place: G.G. Brown Defibrillator Disaster An office worker complains of lower back pain. In response to her complaint, her supervisor purchases an adjustable chair for the worker to improve her posture. Is this an example of a proactive or reactive ergonomic solution? Why? Reactive ergonomics because the problem was not fixed until the problem arose. Proactive ergonomics, on the other hand, fixes the issue before it becomes a large problem List one reason why this ?solution? might not reduce her lower back pain. The worker might have bad posture even when she is not sitting in a chair so getting a new chair won?t change much. Ted works in a shop repairing watches. He works eight hours per day at what is considered extra fine bench work. From your coursepack, what is the minimum illuminance level you would recommend for him to have while he works? What modifications to your recommendation would you make if you know Ted is 22 years old? For Ted I would recommend a minimum illuminance level of 5000 Lux (464 Footcandles). If Ted was 22 years old I What is the major physiological difference between the fovea and the periphery of the eye in terms of photoreceptor cells? Comparing the two kinds of cells, which has better sensitivity to light? Which has lower acuity? Which enables people to distinguish between different colors? The fovea is inhabited by cones, while the periphery is inhabited by rods as well as cones, but the concentration of cones decreases moving farther away from the fovea. Rods have a higher sensitivity to light and lower acuity. Cones enable people to distinguish between different colors. Very briefly define the three methods of visual search. Briefly describe two factors that can affect visual search. Serial search: systematic movement of the eye Random search: is the scanning of a field of view of a particular object Parallel Search: looking for more than one object List 9 object-centered cues and 3 observer-centered cues for the visual perception of depth. Describe the process of accommodation. Object-center cues Linear perspective Interposition Height in the plane Light and shadow Relative size Textural gradients Proximity-luminance covariance Aerial perspective Relative motion gradient or parallax Observer-Centered Cues Binocular disparity Convergence Accommodation A cue provided to the brain by the eye muscles. Images are brought to focus by the result of muscles adjusting to the shape of the lens. i. Calculate the sound pressure level of a source generating a sound pressure equal to 15 Pascal. 10*log10(P12 / Po2) 10*log10(152/ (2*10-5)2) = 117.5 dB ii. Briefly explain what an equal loudness contour is. What does it mean if two points lay on the same contour? Equal loudness contour is a measure of sound pressure over the frequency spectrum, for which a listener perceives loudness. If two points lay on the same contour then those two noises sound the same to that person. Briefly explain how to perform octave band analysis. What device do you use? Octave band analysis is performed using a Sound Level Meter fitted with a set of Octave Band Filters. To perform the analysis, each center frequency is doubled and a measurement is made at each center point to find the corresponding sound pressure. ALWAYS SHOW ALL COMPUTATIONS. Final answers alone are not accepted when computation is required. Problem 3 (15 pts) (Show your work, including computation, units, and data found on the Cobb-Moss curve CP page 83) Officers Mike and Angelo are on the lookout for the getaway car used in a devious art theft, but know only the license plate number. As Mike cruises slowly past a number of driveways and alleys, Angelo shines the squad car?s spotlight on the license plate of any parked car he sees. The thief (Scarlet Scammer, who has stolen ?The Hearts of a Thousand Men? from the Sistine Art Museum) has parked the car in an alley, but before she can hide the license plate from view, the squad car passes by. Given information 1) Angelo is 50 feet from the getaway car?s license plate. 2) The text is 2 inches high with a stroke width/height ratio of 1/8. 3) The license plate background has a reflectance of 25%. 4) The text has a reflectance of 70% and a luminance of 1.4 Ft-L. 5) Angelo wears glasses, which corrects his vision to 20/20. (12 pts) Using the Cobb-Moss curves, can Angelo identify the getaway car with 95% or better accuracy? VAletters = 57.3*60*(2*(1/8)*(1/12))/50 =1.4mins L = R*E Text 1.4=.7E E=2 Background L = .25*2 L =.5 C(%) = (L-D)/(L+D)*100 C(%) = (1.4-.5)/(1.4+.5)*100 = 47.37% Using Cobb-Moss Curves graph the corresponding visual angle is about 3.6 min with a 95% accuracy. Since this visual angle is larger than the calculated visual angle of 1.4mins, Angelo should be able to identify the getaway car. (3 pts) Suppose Mike has very good visual acuity. Scarlet, realizing she might be caught, decides to use her knowledge about the detrimental effects of glare to hinder Mike?s ability to see her car. After quickly removing the car?s rear-view mirror, she uses this to reflect some of the spotlight back into Mike?s eyes. What type of glare is this? Could her strategy work? Why or why not? This is indirect glare because it is a reflecting glare. Her strategy could work because reflected glares can reduce task visibility, like looking at a license plate. Problem 4 (15 pts) During a regular workday, a worker is exposed to the following noise levels: 85 dB for 1 hour, 105 dB for 0.5 hours, 75 dB for 1 hour, and 90 dB for 5.5 hours. Calculate the noise dose. Is this exposure within the permissible exposure level set by OSHA? (5 pts) QUOTE This exposure exceeds the permissible exposure level set by OSHA. During a regular workday a worker is exposed to the following noise levels: 60 dB for 4 hours , 80 dB for 3.95 hours, and 120 dB for .05 hours. Calculate the noise dose. Is this exposure permissible according to OSHA? (5 pts) This exposure is permissible according to OSHA but the company should consider taking action to lower the noise dose, especially since a level of 120 dB is being reached on a regular workday. A new machine is added to the workplace described in question A. If the new machine alone generates a noise level of 95 dB for the entire 8-hour shift, what would be the new noise dose after adding the machine? (5 pts) QUOTE L1=91.6 dB L2 = 95 dB L2 ? L1 = 3.4 dB Correction (from chart) = 1.4 Total Noise = 95 + 1.4 = 96.4 PAGE PAGE 6
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