Conference Session

NSF Grantees Poster Session

Collection

2018 ASEE Annual Conference & Exposition

Authors

Amelito G. Enriquez, Canada College; Nicholas Langhoff, Skyline College; Erik N. Dunmire, College of Marin; Thomas Rebold, Monterey Peninsula College

Tagged Topics

Diversity, NSF Grantees Poster Session

, theCALSTEP team will have as one of its priorities connecting with organizations (e.g., theCalifornia Online Education Initiative, or OEI) to find resources to support the effort todisseminate the CALSTEP resources and prepare additional faculty to use the resources in theirclassrooms.AcknowledgementsThis project is supported by the National Science Foundation through the ImprovingUndergraduate STEM Education (IUSE) program, Award No. DUE 1430789. Any opinions,findings, and recommendations expressed in this paper are those of the authors and do notnecessarily reflect the views of the National Science Foundation.References[1] President’s Council of Advisors on Science and Technology (PCAST) (2012). Engage to excel: Producing one million additional

Conference Session

Best of DEED

Collection

2015 ASEE Annual Conference & Exposition

Authors

Ibrahim Mohedas, University of Michigan; Grace Louise Cravens, Sienko Research Group; Shanna R. Daly, University of Michigan; Kathleen H. Sienko, University of Michigan

Tagged Topics

Diversity

Tagged Divisions

Design in Engineering Education

capability.”During the final interview with Team 1, another student stated: “I mean, there was some stuff that [the lab] kind of thought of late, [features] that they sort of thought about and they wanted added in… they didn't really tell us about [the features] until way into the designing process.”These thoughts were reflected in the students’ post-course surveys. For example, one Team 1student added a caveat to their pre-course response about how stakeholders should have aprominent role during design: “Stakeholders should have a large role but they also need to understand the entire design process and know what kind of limitations there are.”The same Team 1 student also changed their pre-course response to Question 4

Conference Session

Women in Engineering Division Poster Session

Collection

2015 ASEE Annual Conference & Exposition

Authors

Tanya Stanko P.E., Innopolis University

Tagged Topics

Diversity

Tagged Divisions

Women in Engineering

have not chosen a career in IT were invited to participate ina focus group for one-to-one interviews, where young women reflected on the reasonsbehind their decision not to continue in IT. Here we present qualitative results of thesurvey.MethodologyFor the follow up survey we utilized the database of clients who enrolled inextracurricular courses in IT from Unium. We have been provided with data going backto 2007. From the broad range of educational courses offered by Unium we have focusedonly on those that are IT-related, namely: Web-design, computer flash graphics, andprogramming in C/C++. We limited the selection pool to over 900 pupils satisfying thosecriteria, including 142 girls.We aimed to form a group of 8-10 young women for a focus

Conference Session

Computers in Education Engineering Division Poster Session

Collection

2015 ASEE Annual Conference & Exposition

Authors

Debarati Basu, Virginia Tech; John Stanton Goldstein Purviance, Virginia Tech ; Darren K Maczka, Virginia Tech; Daniel S Brogan, VIrginia Tech; Vinod K. Lohani, Virginia Tech

Tagged Divisions

Computers in Education

based on the particular device, regardless of the order in which theywere detected. The instruments’ data collected by the python programs were stored in a local MySQLdatabase on the Raspberry Pi. This local database on the Raspberry Pi had seven data tables; twofor the acoustic Doppler current profiler, four for the weather transmitter and one for the waterquality Sonde. Some instruments used multiple tables to store data in a way that reflected howdata was retrieved from them. All of the tables in the local database had an index column thatserved as the primary key, a column with time stamps from the system time and columns of datavalues. The data values were stored as floating point numbers to preserve precision.6.0 System

Collection

2018 ASEE Annual Conference & Exposition

Authors

Waddah Akili, Iowa State University

Tagged Divisions

College Industry Partnerships

, Writing and Learning Disabilities Vol. 6, pp. 223-247.9. Johnson, D.W., Johnson, R.T. & Smith, K.A. (1991), “Active Learning Cooperation in the College Classroom,”Edina, MN: Interaction Book Company.10. Fairhurst, A.M., & Fairhurst, L.L. (1995), “Effective Teaching, Effective Learning,” Palo Alto, CA: Davies-black Publishing11. Dale, E. (1969), “Audiovisual Methods in Teaching,” (3rd ed.), New York: Dryden Press.12. Wankat, P.H. (1999), “Reflective Analysis of Student Learning in a Sophomore Engineering Course,” Journal ofEngineering Education, Vol.88, (no.2), 195 -203.13. Finelli, C., Klinger, A., & Budny, D.D. (2001), “Strategies for Improving the Classroom Environment,” Journalof Engineering Education, Vol 90, (no.4), pp. 491

Collection

2018 ASEE Annual Conference & Exposition

Authors

Waddah Akili, Iowa State University

Tagged Divisions

Design in Engineering Education

Sciences, Vol.9, No.3, pp.313-314.26. Oakes, W. C., Jamieson, L. H., and Coyle, E. j.,(2001), “EPICS: Meeting EC 2000 Through Service Learning,” Proc., ASEE Conference and Exhibition, Session 3461.27. Bright, A., and Dym, C. L., (2004), “General Engineering at Harvey Mudd: 1957-2003,” Proc., ASEE Conf. and Exhibition, Session 1471.28. Adams, R. S., Turns, J., and Atman, C. J., (2003), “Educating Effective Engineering Designers: The Role of Reflective Practice,” Design Studies, Vol. 24, No. 3, pp.275—294.29. Mills, J. E., and Treagust, D. F., (2004), “Engineering Education- Is Problem – Based or Project - Based Learning the Answer?” Australasian Journal of Engineering Education, www.aaee.com. Au/journal/mills_treagust03.pdf.30

Collection

2019 CIEC

Authors

Andrew Grossfield

mappings are actuallyassigning points in the 2-dimensional w-plane to points in the 2-dimensional z-plane.w = az + b w = ln(z) az+b w = sin(z) , w= arcsin(z)w= cz+d w = cos(z) , w= arccos(z)w = z2 , w = √z w = tan(z) , w = arctan(z) 𝑛w=z n . w = √𝑧w = e z = e (x + iy) = e x e iyThe reflection in the horizontal axis x – iy of a complex number z = x + iy is called the conjugateof z and is represented by the symbol z*. The conjugate of z can be used to

Conference Session

Factors Affecting Minority Engineering Students

Collection

2007 Annual Conference & Exposition

Authors

Leo McAfee, University of Michigan

Tagged Divisions

Minorities in Engineering

percentages reflect that engineering majors often take more than four years toearn the bachelor degree. Table 4 shows these comparisons in table form, with counts andpercentages. Table 3 --- Demographics of LSAMP REU Participants for Summer 2005 and Summer 2006, Plus WIMS REU Summary for Summers 2002 to 2004 --- Gender, Race/Ethnicity, Academic Level, and Academic MajorCategory Summer Summer Summers 2005 2006 2002 to 2004 REU Programs (LSAMP REU) (LSAMP REU)Totals 7 6

Conference Session

Leadership Perspectives in Engineering Technology

Collection

2007 Annual Conference & Exposition

Authors

Hamad Albadr, Riyadh College of Technology

Tagged Divisions

Engineering Technology

simply expressed – the provision of free health servicesfor the benefit of all the citizens of Saudi Arabia – and King Fahd has shown, throughout hisreign, a very real understanding of the importance of adequate health provision for those whoneed it, both within and outside the Kingdom.The Ministry of Health policy reflects the Government’s national development strategy,which is committed to improving the quality of life of the Saudi people, and to helping themto participate fully in the development plan and to benefit from it.To carry out this policy, the Ministry of Health provides a whole range of health services(preventive, corrective, educational and rehabilitative) to the entire population. This isachieved through a network of hospitals

Conference Session

An International Perspective

Collection

2007 Annual Conference & Exposition

Authors

Mary Anderson-Rowland, Arizona State University; Bianca Bernstein, Arizona State University; Nancy Felipe Russo, Arizona State University

Tagged Divisions

Women in Engineering

. Actually this argument is also astrong reason why engineering needs more women trained in engineering to increasediversity in the values and perspectives of engineering personnel and to change methodsand processes of delivering material to future generations of engineers.In 2001, Lazarus, Ritter, and Ambrose underscored the seriousness of the lack of womenin engineering and science doctoral programs in “The Woman’s Guide to Navigating thePh.D. in Engineering & Science.”2 They reported that of the 5,919 engineeringdoctorates awarded in 1998, only 769 (13%) were earned by women. These figures donot reflect the continued under representation of domestic women in engineeringprograms. Table 1 presents the national summary of PhD degrees in

Conference Session

Instrumentation and Laboratory Systems

Collection

2007 Annual Conference & Exposition

Authors

Hassan Rajaei, Bowling Green State University; Mohammad Dadfar, Bowling Green State University

Tagged Divisions

Computers in Education

t T 3000 i m e 2000 1000 0 4 1 2 3 Basic Aggressive Lookahead Nodes Requested Multiple Queue Figure 7: Nodes Requested versus Waiting Time6.2 Gang Scheduling and BackfillingA policy is evaluated by scheduling criteria which reflect user’s parameters of interest. A fairand quick response time is

Conference Session

Teaching Ethics

Collection

2007 Annual Conference & Exposition

Authors

Cynthia Finelli, University of Michigan; Trevor Harding, California Polytechnic State University; Donald Carpenter, Lawrence Technological University; Matthew Mayhew, New York University

Tagged Divisions

Engineering Ethics

from 11% to 49%, and the percentage who admitsto copying on examinations has increased from 26% to 52%.It has been well documented that the rate of undergraduate cheating differs by college major4, 8, 9,31, 33, 40, 44, 49, 52, 53 , and for the E3 Team, the pattern of cheating among engineering students is ofparticular interest. The findings in this regard are consistent, and they reflect those reported byMcCabe40–the percentage of undergraduates who report engaging in any type of cheating ishighest for those students enrolled in “vocationally-oriented majors such as business andengineering”: business (91%), engineering (82%), social sciences (73%), and natural sciences(71%).Over the past seven years, the E3 Team has designed

Conference Session

Special programs and activities for minorities in engineering

Collection

2007 Annual Conference & Exposition

Authors

Peter Stroot, University of South Florida; Bernard Batson, University of South Florida; BK Robertson, Alabama State University

Tagged Divisions

Minorities in Engineering

biomolecular tools for engineering applications.The initial cohort will consist of 10 students divided into groups of two students each. With theassistance of the instructor, each student group will select and present one article to the class.Presentation of the article will be followed by group discussion. Also students will be requiredto keep a journal of their thoughts and reflections on the reading and lecture material. Supportmaterial from initial teaching of this course is posted on the course homepage:www.engr.colstate.edu/ce/homepages/pruden/classes/ce58/ce581/index.shtml. This course wasoriginal developed at the University of Cincinnati and has been taught in schools withengineering programs 1. The model for ASU is new since this is the first

Conference Session

Emerging Trends in Engineering Education Poster Session

Collection

2007 Annual Conference & Exposition

Authors

Cher Cornett, East Tennessee State University

her hand guides the eye down through the image.1 I think the reflection should be farther to the right. It's too centered right now. Draws too much attention to an unimportant part.1 Lights around the mirror give good motion. The angle looks good.1 The lights on each side of the picture really keep your eye onto the center of the page on her, which is good since she's the main focal point.1 You’re right about not using a straight on shot. The angle is more dynamic.10. How well did the color fit the mood or theme of the piece. Does the image havean attractive and/or appropriate color scheme?1="Just didn't do it for me", 10="fabulous!!" Average rank 1 2 3 4 5 6 7 8

Conference Session

Engineering Professional Development for K-12 Teachers – II

Collection

2007 Annual Conference & Exposition

Authors

Daphne Duncan, Purdue University; Euridice Oware, Purdue University; Monica Cox, Purdue University; Heidi Diefes-Dux, Purdue University

Tagged Divisions

K-12 & Pre-College Engineering

indicate that these adaptations were successful.The Reading Certificate MEA was unexpectedly very difficult to implement. The local teacherswere perhaps too familiar with the context of the problem. Issues arose with the data set thatprevented the teachers from engaging in the mathematics of the problem. The teachers maderecommendation to improve the book list for each child and the level of difficulty associatedwith each book on the list. They also recommended the addition of a reading level for eachchild. Certainly, the assessment results reflect teachers dislike of this problem. This MEA wasnot carried over into INSPIRE Academy II.The NASA MEA was originally targeted for first-year engineering students. Attempts to adjustthe MEA to a 5th-6th

Conference Session

Technology Literacy for Non-Engineers

Collection

2007 Annual Conference & Exposition

Authors

David Ollis, North Carolina State University

Tagged Divisions

Technological Literacy Constituent Committee

variousengineering labs across the campus.Science, technology, society projectsAll students completed two science, technology, and society projects. Working in teamsof three and imitating the work in the “take-apart” lab, they studied an artifact of theHispanic world. Their task was to research and describe the historical significance andengineering importance of the artifact and then to explain how the artifact reflects theculture which produced it. The fruits of these activities were two group presentations inthe course of the semester –practicing the final methodology of the end project—and agroup paper in English to summarize their project in Sevilla, Spain, and inMilwaukee,Wisconsin, two cities seemingly disparate in culture.Evaluation and assessment

Conference Session

Development of Undergraduate Distance Education Programs

Collection

2007 Annual Conference & Exposition

Authors

Frank Fisher, Stevens Institute of Technology; Hamid Hadim, Stevens Institute of Technology; Sven Esche, Stevens Institute of Technology; Robert Ubell, Stevens Institute of Technology; Constantin Chassapis, Stevens Institute of Technology

Tagged Divisions

Continuing Professional Development

low very high LowIt is anticipated that a major obstacle to realizing a truly successful online undergraduateengineering curriculum is the development of an appropriate combination of virtual experiments(simulations), laboratory exposure through on-site visits, simple experiments conducted at home,and remotely accessible laboratory experiments, which is necessary to contribute towardsenhanced learning in accordance with the respective ABET criteria. The vital importance of acomprehensive laboratory experience in the engineering curricula is widely acknowledged by allconstituents and reflected prominently in the ABET Engineering Criteria 2000.42 ABET hasalready begun the process to establish criteria for assessing the

Conference Session

Multidisciplinary Engineering Poster Session

Collection

2007 Annual Conference & Exposition

Authors

Howard Evans, National University; Shekar Viswanathan, National University

Tagged Divisions

Multidisciplinary Engineering

Safety and Security Engineering11. X X X Capstone Course Safety and Security Engineering12. X X X Capstone CourseOutcomes for the overall program will be measured by: 1) trends in the numbers of studentsenrolling; 2) student, alumni and employer surveys; and, 3) assessment of final student thesis andproject reports and presentations by internal (faculty) and external expert review boards. Long-term success of this program will be reflected by increased numbers of individuals whosuccessfully graduate and enter security and safety careers as a result of this unique

Conference Session

Multidisciplinary and Liberal Education

Collection

2007 Annual Conference & Exposition

Authors

David Ollis, North Carolina State University

Tagged Divisions

Multidisciplinary Engineering

importance of the artifact and then to explain how the artifact reflects theculture which produced it. The fruits of these activities were two group presentationsduring the course of the semester –practicing the final methodology of the end project—and a group paper in English to summarize their project in Sevilla, Spain, and inMilwaukee, Wisconsin, two cities seemingly disparate in culture.Evaluation and assessment of collaborative effortThe end-of-semester student questionnaire results appear in Table 1. Page 12.53.5 Proceedings of the 2007 American Society of Engineering Education Conference and Exposition Copyright @ 2007

Conference Session

Electromechanical Capstone and Design Projects in ET

Collection

2007 Annual Conference & Exposition

Authors

James Everly, University of Cincinnati; Laura Wilson, University Cincinnati

Tagged Divisions

Engineering Technology

all started with this assignment. Studentswere asked to compile a list of course texts; these texts were a large part of forming the threads Page 12.1597.14for the capstone tapestry. Each text listed on the annotated bibliography had to be relevant to theknowledge the students used while completing the assigned project. If the course fulfilled theauthors’ expectations, these annotated bibliographies would reflect the incorporation ofknowledge from all previous technical and humanities-related courses. Organizing material andcreating a model to understand the students’ level of comprehension were two main goals of thisassignment. Larry

Conference Session

Environmental Engineering Curricula II

Collection

2007 Annual Conference & Exposition

Authors

Elizabeth Eschenbach, Humboldt State University; Jami Montgomery, WATERS Network - CLEANER Project Office; James Johnson, Howard University; Chris Brus, University of Iowa; Dan Giammar, Washington University; Patricia Carlson, Rose-Hulman Institute of Technology; Bette Grauer, McPherson High School; Liesl Hotaling, Stevens Institute of Technology; Gbekeloluwa Oguntimein, Morgan State University; Steven Safferman; Tim Wentling, National Center for Supercomputing Applications

Tagged Divisions

Environmental Engineering

shared research and education tools.With proper training and financial support, it is anticipated that the WATERS Network will leadto: • modernization of curricula content and pedagogical approaches to reflect critical competencies for the 21st century including trans-disciplinary instructional units and project learning that integrate advanced information and instructional technologies into teaching, learning, and advocacy of water resources issues Page 12.1595.8 • reciprocal relationships between research and education and increased vertical collaboration among all levels within the education community

Conference Session

Mentoring Graduate Students

Collection

2007 Annual Conference & Exposition

Authors

Lisa Frehill; Amanda Lain, New Mexico State University; Ricardo Jacquez, New Mexico State University; Lauren Ketcham, New Mexico State University; Karen Luces, New Mexico State University

Tagged Divisions

Graduate Studies

Page 12.402.7more information when we reframed the query to focus on their graduate advisor in particular.Many men recalled that they felt like a member of their faculty advisor’s family: they were ofteninvited to dinner, were included in holiday festivities, and indicated that their faculty advisorprovided career supports. The provision of career and psychosocial supports reflected in theseinterviews is a hallmark of “mentoring,” as opposed to advisement.Many (but not all) women faculty4, on the other hand, reported that they earned their doctoraldegrees in spite of their advisors. Unlike the “family” relationship that their male colleaguesreported, female faculty indicated that their faculty advisors often failed to provide guidance ontheir

Conference Session

Engineering Professional Development for K-12 Teachers – I

Collection

2007 Annual Conference & Exposition

Authors

Shanna Daly, Purdue University; Lynn Bryan, Purdue University

Tagged Divisions

K-12 & Pre-College Engineering

concept, none of the teachers suggested the criteria were any different for models ofnanoscale phenomena compared to science models in general. As put by one teacher, there were“no differences, since a model is used to represent difficult concepts regardless of scale.” Intheir selection of a model, teachers selected one to represent a nanoscale concept. The nature ofthe directions of the assignment may have affected their choice of one model versus multiplemodels to represent a nanoscale phenomena concept. Upon reflecting on this issue, we do notwant the selection of one model to be a limiting factor for teachers. Research has indicated thatmultiple models prove to be more effective with the presentation of abstract or non-observableconcepts. The

Conference Session

Assessment and Evaluation in Engineering Education I

Collection

2007 Annual Conference & Exposition

Authors

rebecca devasher, Rose-Hulman Institute of Technology; Patrick Ferro, Rose-Hulman Institute of Technology; Sudipa Mitra-Kirtley; David Mutchler, Rose-Hulman Institute of Technology; shannon sexton, Rose-Hulman Institute of Technology; Anneliese Watt, Rose-Hulman Institute of Technology; Julia Williams, Rose-Hulman Institute of Technology

Tagged Divisions

Educational Research and Methods

differently from students in RH 330and PH 113. Therefore, post-course comparisons were run after computing difference scores foreach course. This was done by subtracting students’ post-course ratings from their pre-courseratings. An ANOVA to compare courses was then run on the difference scores. This is done sothat any differences found better reflect actual differences between courses rather than inflateddifferences due to the unequal starting point. Page 12.514.6When comparing student survey responses across courses, 1 statistically significant differenceappeared. Students in CSSE 371 reported a significantly lower increase in tablet PC usage frompre

Conference Session

Design Projects

Collection

2007 Annual Conference & Exposition

Authors

Frederick Berry, Rose-Hulman Institute of Technology; Patricia Carlson, Rose-Hulman Institute of Technology; William Eccles, Rose-Hulman Institute of Technology; Bruce Ferguson, Rose-Hulman Institute of Technology; Daniel Moore, Rose-Hulman Institute of Technology; Mihaela Radu, Rose-Hulman Institute of Technology; Terry Schumacher, Rose-Hulman Institute of Technology; David Voltmer, Rose-Hulman Institute of Technology; Mark Yoder, Rose-Hulman Institute of Technology; Edward Wheeler, Rose-Hulman Institute of Technology

Tagged Divisions

Design in Engineering Education

was due in part to the process ofproposing new, “workable” problems and in part due to the heavy load of grading the many documents required Page 12.235.5from the students. In addition to this pressure, several other factors were coming to bear upon the junior level courseas well. It became apparent that entrepreneurial and project management skills were becoming increasinglyimportant in engineering. Changing community needs resulted in an increasing number of requests from non-profitand charitable organizations for product development. With these factors in mind, the junior level course wasrevised to reflect a more service

Conference Session

Capstone Design II

Collection

2007 Annual Conference & Exposition

Authors

Mason Webster, Brigham Young University; Daniel Korth; Owen Carlson, Brigham Young University; C. Greg Jensen, Brigham Young University

Tagged Divisions

Design in Engineering Education

dragons, while others were motivated by aircraft design. One Koreanstudent used the current trend of “destroyed” blue jeans to create a design that exposed thechassis in a way similar to the way these popular jeans expose the wearer’s leg. These sketcheswere then posted on TcC for others to review. Critiques of these sketches including initial 2Dflow analysis using Fluent were sent back to the ID schools. The students then produced newsketches reflecting changes induced by their peers’ evaluations. After these later sketches weregenerally approved by the flow and substructure analysis teams, the industrial design studentsbegan to create 3D models of their designs using Alias. They again posted their models to TcCfor peer scrutiny. The frame team

Conference Session

NSF Grantees Poster Session

Collection

2007 Annual Conference & Exposition

Authors

Ning Fang, Utah State University; Randy Cook, Utah State University; Karina Hauser, Utah State University

framework of the course, its major contents, and thestep-by-step demonstration of how the Lean Lego Simulatiońa new instructional pedagogy wedesigned for and implemented in the coursécan be performed.We believe our experiences gained and lessons learned from the teaching of the lean course canserve as an important basis for future continuous improvement in the Lean curriculum; thus, theexperiences and lessons reported in this paper are valuable to our educational community.AcknowledgementsThis material is based upon work supported by the National Science Foundation under Grant No.0511421. Any opinions, findings, and conclusions or recommendations expressed in this materialare those of the authors and do not necessarily reflect the views of the

Conference Session

ECE Pedagogy and Assessment

Collection

2007 Annual Conference & Exposition

Authors

Tokunbo Ogunfunmi, Santa Clara University

Tagged Divisions

Electrical and Computer

SSCI Test had 34 students. The statistical distribution of theresults may be less than expected due to this small sample size but the trends are as expected. Weintend to keep up doing these pre- and post-assessment tests for future offerings of the class. Thiswill increase our sample sizes and we will then be able to accumulate the results over time sothat the statistical analysis of the results will become better reflective of the sample space, thestudent population at Santa Clara University.One of the major lessons learnt from this exercise is that the presentation of the material needs tobe done conceptually as well as mechanically. The regular exams take care of determining thestudents’ capability in the mechanistic methods of solving the

Conference Session

Design Experiences in Energy Systems

Collection

2007 Annual Conference & Exposition

Authors

Andrew Lau, Pennsylvania State University

Tagged Divisions

Energy Conversion and Conservation

. Gears Motor Spool with fishing line Weights Figure 6 Small motor dynamometer.Knowing the torque/speed output characteristic of the motor as a function of I/V input allows usto combine the motor and solar panel I/V output to get the torque/speed characteristic of thesystem. The process is as follows: 1. First the I/V motor characteristic curve for each of the tested loads (torque) is plotted along with the solar panel I/V curve, see Figure 7. Note that the motor data in Figure 7 reflects additional data taken to investigate the stalled motor and subsequent start

Conference Session

Best of the NEE

Collection

2007 Annual Conference & Exposition

Authors

James Squire, Virginia Military Institute; Charles Bott, Virginia Military Institute; Matthew Hyre, Virginia Military Institute

Tagged Divisions

New Engineering Educators

manner similar to a “real” engineering job 3. Students who enjoy the work, and who are paid for it, are often a project’s best advertisingNegatives 1. It can be very difficult to hold students accountable to project goals if their interest in the project wanes 2. Classroom work often takes priority over work for pay 3. Student motivation can cycle with external events that have nothing to do with the project (i.e., you will find a high degree of motivation on work for pay projects in the weeks leading up to spring break)Students Working for CreditPositives 1. Students understand that poor performance is reflected in a bad grade. There are both positive and negative reinforcement mechanisms