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Description
The flow of liquid PDMS (10:1 v/v base to cross-linker ratio) in open, rectangular silicon micro channels, with and without a hexa-methyl-di-silazane (HMDS) or poly-tetra-fluoro-ethylene (PTFE) (120 nm) coat, was studied. Photolithographic patterning and etching of silicon wafers was used to create micro channels with a range of widths (5-50 μm) and depths (5-20 μm). The experimental PDMS flow rates were compared to an analytical model based on the work of Lucas and Washburn. The experimental flow rates closely matched the predicted flow rates for channels with an aspect ratio (width to depth), p, between one and two. Flow rates in channels with p less than one were higher than predicted whereas the opposite was true for channels with p greater than two. The divergence between the experimental and predicted flow rates steadily increased with increasing p. These findings are rationalized in terms of the effect of channel dimensions on the front and top meniscus morphology and the possible deviation from the no-slip condition at the channel walls at high shear rates.
In addition, a preliminary experimental setup for calibration tests on ultrasensitive PDMS cantilever beams is reported. One loading and unloading cycle is completed on a microcantilever PDMS beam (theoretical stiffness 0.5 pN/ µm). Beam deflections are actuated by adjusting the buoyancy force on the beam, which is submerged in water, by the addition of heat. The expected loading and unloading curve is produced, albeit with significant noise. The experimental results indicate that the beam stiffness is a factor of six larger than predicted theoretically. One probable explanation is that the beam geometry may change when it is removed from the channel after curing, making assumptions about the beam geometry used in the theoretical analysis inaccurate. This theory is bolstered by experimental data discussed in the report. Other sources of error which could partially contribute to the divergent results are discussed. Improvements to the experimental setup for future work are suggested.
In addition, a preliminary experimental setup for calibration tests on ultrasensitive PDMS cantilever beams is reported. One loading and unloading cycle is completed on a microcantilever PDMS beam (theoretical stiffness 0.5 pN/ µm). Beam deflections are actuated by adjusting the buoyancy force on the beam, which is submerged in water, by the addition of heat. The expected loading and unloading curve is produced, albeit with significant noise. The experimental results indicate that the beam stiffness is a factor of six larger than predicted theoretically. One probable explanation is that the beam geometry may change when it is removed from the channel after curing, making assumptions about the beam geometry used in the theoretical analysis inaccurate. This theory is bolstered by experimental data discussed in the report. Other sources of error which could partially contribute to the divergent results are discussed. Improvements to the experimental setup for future work are suggested.
ContributorsSowers, Timothy Wayne (Author) / Rajagopalan, Jagannathan (Thesis advisor) / Herrmann, Marcus (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2014
Description
Due to decrease in fossil fuel levels, the world is shifting focus towards renewable sources of energy. With an annual average growth rate of 25%, wind is one of the foremost source of harnessing cleaner energy for production of electricity. Wind turbines have been developed to tap power from wind. As a single wind turbine is insufficient, multiple turbines are installed forming a wind farm. Generally, wind farms can have hundreds to thousands of turbines concentrated in a small region. There have been multiple studies centering the influence of weather on such wind farms, but no substantial research focused on how wind farms effect local climate. Technological advances have allowed development of commercial wind turbines with a power output greater than 7.58 MW. This has led to a reduction in required number of turbines and has optimized land usage. Hence, current research considers higher power density compared to previous works that relied on wind farm density of 2 to 4 W/m 2 . Simulations were performed using Weather Research and Forecasting software provided by NCAR. The region of simulation is Southern Oregon, with domains including both onshore and offshore wind farms. Unlike most previous works, where wind farms were considered to be on a flat ground, effects of topography have also been considered here. Study of seasonal effects over wind farms has provided better insight into changes in local wind direction. Analysis of mean velocity difference across wind farms at a height of 10m and 150m gives an understanding of wind velocity profiles. Results presented in this research tends to contradict earlier belief that velocity reduces throughout the farm. Large scale simulations have shown that sometimes, more than 50% of the farm can have an increased wind velocity of up to 1m/s
at an altitude of 10m.
at an altitude of 10m.
ContributorsKadiyala, Yogesh Rao (Author) / Huang, Huei-Ping (Thesis advisor) / Rajagopalan, Jagannathan (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2015
Description
A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in rotation rate and the tilting of isotherms gives rise to baroclinic source of vorticity. Research by (Smirnov et al. [2010a]) showed the differences in evolution of instabilities when Dirichlet and Neumann thermal boundary conditions were applied at top and bottom walls. Study of parametric variations carried out in this dissertation confirmed the instability patterns observed by them for given aspect ratio and Rossby number values greater than 0.5. Also results reveal that flow maintained axisymmetry and stability for short aspect ratio containers independent of amount of rotational increment imparted. Investigation on vorticity components provides framework for baroclinic vorticity feedback mechanism which plays important role in delayed rise of instabilities when Dirichlet thermal Boundary Conditions are applied.
ContributorsKher, Aditya Deepak (Author) / Chen, Kangping (Thesis advisor) / Huang, Huei-Ping (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
Description
From the instructional perspective, the scope of "active learning" in the literature is very broad and includes all sorts of classroom activities that engage students with the learning experience. However, classifying all classroom activities as a mode of "active learning" simply ignores the unique cognitive processes associated with the type of activity. The lack of an extensive framework and taxonomy regarding the relative effectiveness of these "active" activities makes it difficult to compare and contrast the value of conditions in different studies in terms of student learning. Recently, Chi (2009) proposed a framework of differentiated overt learning activities (DOLA) as active, constructive, and interactive based on their underlying cognitive principles and their effectiveness on students' learning outcomes. The motivating question behind this framework is whether some types of engagement affect learning outcomes more than the others. This work evaluated the effectiveness and applicability of the DOLA framework to learning activities for STEM classes. After classification of overt learning activities as being active, constructive or interactive, I then tested the ICAP hypothesis, which states that student learning is more effective in interactive activities than constructive activities, which are more effective than active activities, which are more effective than passive activities. I conducted two studies (Study 1 and Study 2) to determine how and to what degree differentiated activities affected students' learning outcomes. For both studies, I measured students' knowledge of materials science and engineering concepts. Results for Study 1 showed that students scored higher on all post-class quiz questions after participating in interactive and constructive activities than after the active activities. However, student scores on more difficult, inference questions suggested that interactive activities provided significantly deeper learning than either constructive or active activities. Results for Study 2 showed that students' learning, in terms of gain scores, increased systematically from passive to active to constructive to interactive, as predicted by ICAP. All the increases, from condition to condition, were significant. Verbal analysis of the students' dialogue in interactive condition indicated a strong correlation between the co-construction of knowledge and learning gains. When the statements and responses of each student build upon those of the other, both students benefit from the collaboration. Also, the linear combination of discourse moves was significantly related to the adjusted gain scores with a very high correlation coefficient. Specifically, the elaborate type discourse moves were positively correlated with learning outcomes; whereas the accept type moves were negatively correlated with learning outcomes. Analyses of authentic activities in a STEM classroom showed that they fit within the taxonomy of the DOLA framework. The results of the two studies provided evidence to support the predictions of the ICAP hypothesis.
ContributorsMenekşe, Muhsin (Author) / Chi, Michelene T.H. (Thesis advisor) / Baker, Dale (Committee member) / Middleton, James (Committee member) / Arizona State University (Publisher)
Created2012
Description
Energy production is driven by economic needs, which sometimes results in the environment and wildlife being an afterthought. Unfortunately, many animals are killed as a result of flying too close to wind turbines, and the addition of animal deterrent devices are a promising alternative. This thesis seeks to provide a solution as a part of post- construction considerations regarding wildlife and wind turbine interactions through the introduction of a blade mounted ecological device. After testing the hypothesis, the data revealed the device is effective for increasing power output when placed at the root, middle, and tip of the blade. The middle position yielded the lowest increase at all speeds tested. The device was designed and attached to blades along the estimated line of separation. The blades were then mounted on a tower and tested with wind speed as an input and power as an output. The data was analyzed by fixing speed as a parameter and then looking at the distribution of the power output data. A comparison of blades with and without the device demonstrates a potential for increasing power output by 144% when the device is attached at the blade’s root, 7.5% in the middle, and 21% near the tip. The analysis for this study was descoped due to the constraints of the system to be scaled up. As such, this analysis will hold for turbines with a blade length of no more than approximately eight feet. Blades of this type would be used in single building energy grid supplement turbines or turbines in areas with power requirements of equal or less than 1kW per turbine installed. Single building energy grid supplement turbines are most often mounted to the tops of buildings and take advantage of higher speeds of wind at those heights. As the ecological devices are designed to be similar to vortex generators, which have been tested on large blades, their addition to large blades could prove to have a similar effect.
Keywords: Wind turbine ecosystem, post-construction turbine considerations, wildlife deterrents
Keywords: Wind turbine ecosystem, post-construction turbine considerations, wildlife deterrents
ContributorsBooth, Stephanie (Author) / Trimble, Steve (Thesis advisor) / Middleton, James (Thesis advisor) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2018
Description
Laser radars or lidar’s have been used extensively to remotely study winds within the atmospheric boundary layer and atmospheric transport. Lidar sensors have become an important tool within the meteorology and the wind energy community. For example, Doppler lidars are used frequently in wind resource assessment, wind turbine control as well as in atmospheric science research. A Time of Flight based (ToF) direct detection lidar sensor is used in vehicles to navigate through complex and dynamic environments autonomously. These optical sensors are used to map the environment around the car accurately for perception and localization tasks that help achieve complete autonomy.
This thesis begins with a detailed discussion on the fundamentals of a Doppler lidar system. The laser signal flow path to and from the target, the optics of the system and the core signal processing algorithms used to extract velocity information, were studied to get closer to the hardware of a Doppler lidar sensor. A Doppler lidar simulator was built to study the existing signal processing algorithms to detect and estimate doppler frequency, and radial velocity information. Understanding the sensor and its processing at the hardware level is necessary to develop new algorithms to detect and track specific flow structures in the atmosphere. For example, the aircraft vortices have been a topic of extensive research and doppler lidars have proved to be a valuable sensor to detect and track these coherent flow structures. Using the lidar simulator a physics based doppler lidar vortex algorithm is tested on simulated data to track a pair of counter rotating aircraft vortices.
At a system level the major components of a time of flight lidar is very similar to a Doppler lidar. The fundamental physics of operation is however different. While doppler lidars are used for radial velocity measurement, ToF sensors as the name suggests provides precise depth measurements by measuring time of flight between the transmitted and the received pulses. The second part of this dissertation begins to explore the details of ToF lidar system. A system level design, to build a ToF direct detection lidar system is presented. Different lidar sensor modalities that are currently used with sensors in the market today for automotive applications were evaluated and a 2D MEMS based scanning lidar system was designed using off-the shelf components.
Finally, a range of experiments and tests were completed to evaluate the performance of each sub-component of the lidar sensor prototype. A major portion of the testing was done to align the optics of the system and to ensure maximum field of view overlap for the bi-static laser sensor. As a laser range finder, the system demonstrated capabilities to detect hard targets as far as 32 meters. Time to digital converter (TDC) and an analog to digital converter (ADC) was used for providing accurate timing solutions for the lidar prototype. A Matlab lidar model was built and used to perform trade-off studies that helped choosing components to suit the sensor design specifications.
The size, weight and cost of these lidar sensors are still very high and thus making it harder for automotive manufacturers to integrate these sensors into their vehicles. Ongoing research in this field is determined to find a solution that guarantees very high performance in real time and lower its cost over the next decade as components get cheaper and can be seamlessly integrated with cars to improve on-road safety.
This thesis begins with a detailed discussion on the fundamentals of a Doppler lidar system. The laser signal flow path to and from the target, the optics of the system and the core signal processing algorithms used to extract velocity information, were studied to get closer to the hardware of a Doppler lidar sensor. A Doppler lidar simulator was built to study the existing signal processing algorithms to detect and estimate doppler frequency, and radial velocity information. Understanding the sensor and its processing at the hardware level is necessary to develop new algorithms to detect and track specific flow structures in the atmosphere. For example, the aircraft vortices have been a topic of extensive research and doppler lidars have proved to be a valuable sensor to detect and track these coherent flow structures. Using the lidar simulator a physics based doppler lidar vortex algorithm is tested on simulated data to track a pair of counter rotating aircraft vortices.
At a system level the major components of a time of flight lidar is very similar to a Doppler lidar. The fundamental physics of operation is however different. While doppler lidars are used for radial velocity measurement, ToF sensors as the name suggests provides precise depth measurements by measuring time of flight between the transmitted and the received pulses. The second part of this dissertation begins to explore the details of ToF lidar system. A system level design, to build a ToF direct detection lidar system is presented. Different lidar sensor modalities that are currently used with sensors in the market today for automotive applications were evaluated and a 2D MEMS based scanning lidar system was designed using off-the shelf components.
Finally, a range of experiments and tests were completed to evaluate the performance of each sub-component of the lidar sensor prototype. A major portion of the testing was done to align the optics of the system and to ensure maximum field of view overlap for the bi-static laser sensor. As a laser range finder, the system demonstrated capabilities to detect hard targets as far as 32 meters. Time to digital converter (TDC) and an analog to digital converter (ADC) was used for providing accurate timing solutions for the lidar prototype. A Matlab lidar model was built and used to perform trade-off studies that helped choosing components to suit the sensor design specifications.
The size, weight and cost of these lidar sensors are still very high and thus making it harder for automotive manufacturers to integrate these sensors into their vehicles. Ongoing research in this field is determined to find a solution that guarantees very high performance in real time and lower its cost over the next decade as components get cheaper and can be seamlessly integrated with cars to improve on-road safety.
ContributorsBhaskaran, Sreevatsan (Author) / Calhoun, Ronald J (Thesis advisor) / Dahm, Werner (Committee member) / Huang, Huei-Ping (Committee member) / Chen, Kang Pin (Committee member) / Choukulkar, Aditya (Committee member) / Arizona State University (Publisher)
Created2018
Description
The flipped classroom is a teaching method that flips the activities done in and out of class, i.e., concepts are learned out of class and problems are worked in class under the supervision of the instructor. Studies have indicated several benefits of the FC, including improved performance and engagement. In the past years, further studies have investigated the benefits of FC in statics, dynamics, and mechanics of materials courses and indicate similar performance benefits. However, these studies address a need for additional studies to validate their results due to the short length of their research or small classroom size. In addition, many of these studies do not measure student attitudes, such as self-efficacy, or the difference in time spent out of class on coursework. The objective of this research is to determine the effectiveness of the flipped classroom system (FC) in comparison to the traditional classroom system (TC) in a large mechanics of materials course. Specifically, it aims to measure student performance, student self-efficacy, student attitudes on lecture quality, motivation, attendance, hours spent out of class, practice, and support, and difference in impact between high, middle, and low achieving students. In order to accomplish this, three undergraduate mechanics of materials courses were analyzed during the spring 2015 semester. One FC section served as the experimental group (92 students), while the two TC sections served as the control group (125 students). To analyze student self-efficacy and attitudes, a survey instrument was designed to measure 18 variables and was administered at the end of the semester. Standardized core outcomes were compared between groups to analyze performance. This paper presents the specific course framework used in this FC, detailed results of the quantitative and qualitative analysis, and discussion of strengths and weaknesses. Overall, an overwhelming majority of students were satisfied with FC and would like more of their classes taught using FC. Strengths of this teaching method include greater confidence, better focus, higher satisfaction with practice in class and assistance received from instructors and peers, more freedom to express ideas and questions in class, and less time required outside of class for coursework. Results also suggest that this method has a greater positive impact on high and low achieving students and leads to higher performance. The criticisms made by students focused on lecture videos to have more worked examples. Overall, results suggest that FC is more effective than TC in a large mechanics of materials course.
ContributorsLee, Andrew Ryan (Author) / Zhu, Haolin (Thesis director) / Middleton, James (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The exhaust system is an integral part of any internal combustion engine. A well- designed exhaust system efficiently removes exhaust gasses expelled from the cylinders. If tuned for performance purposes, the exhaust system can also exhibit scavenging and supercharging characteristics. This project reviews the major components of an exhaust system and discusses the proper design techniques necessary to utilize the performance boosting potential of a tuned exhaust system for a four-stroke engine. These design considerations are then applied to Arizona State University's Formula SAE vehicle by comparing the existing system to a properly tuned system. An inexpensive testing method, developed specifically for this project, is used to test the effectiveness of the current design. The results of the test determined that the current design is ineffective at scavenging neighboring pipes of exhaust gasses and should be redesigned for better performance.
ContributorsKnutsen, Jeffrey Scott (Author) / Huang, Huei-Ping (Thesis director) / Steele, Bruce (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
The focus of education in the classroom traditionally is one of fact memorization and recall. The teaching process of linear knowledge progression is not always in tune with the way that the human brain actually processes, conceptualizes, and comprehends concepts and information. In an introductory engineering class, focused on materials engineering and its related concepts, a system of lecture interventions has been put in place to increase concept comprehension by supplementing lecture units with various activities, from additional worksheets, explicit concept discussions, and most recently, YouTube videos showcasing specific concepts and situations. In an attempt to correct the lack of actual concept comprehension, these interventions seek to interact with the human mind in a way that capitalizes on its ability to process and interpret non-linear knowledge and information.
Using a concept test given prior to the lecture unit, and after, the difference in scores is used to recognize if the concepts presented have actually been comprehended. Used specifically in a lecture unit on solubility and solutions, the concept test tested student’s knowledge of supersaturated, saturated, and unsaturated solutions. With a visual identification and a written explanation, the student’s ability to identify and explain the three solutions was tested.
In order to determine the cause of the change in score from pre- to post-test, an analysis of the change in scores and the effects of question type and solution type was conducted. The significant results are as follows:
The change in score from pre- to post-test was found to be significant, with the only difference between the two tests being the lecture unit and intervention
From pre- to post-test, solution type had a significant effect on the score, with the unsaturated solution being the most easily recognized and explained solution type
Students that felt that the YouTube videos greatly increased their concept comprehension, on average, performed better than their counterparts and also saw a greater increase their score from pre- to post-test
Using a concept test given prior to the lecture unit, and after, the difference in scores is used to recognize if the concepts presented have actually been comprehended. Used specifically in a lecture unit on solubility and solutions, the concept test tested student’s knowledge of supersaturated, saturated, and unsaturated solutions. With a visual identification and a written explanation, the student’s ability to identify and explain the three solutions was tested.
In order to determine the cause of the change in score from pre- to post-test, an analysis of the change in scores and the effects of question type and solution type was conducted. The significant results are as follows:
The change in score from pre- to post-test was found to be significant, with the only difference between the two tests being the lecture unit and intervention
From pre- to post-test, solution type had a significant effect on the score, with the unsaturated solution being the most easily recognized and explained solution type
Students that felt that the YouTube videos greatly increased their concept comprehension, on average, performed better than their counterparts and also saw a greater increase their score from pre- to post-test
ContributorsLinich, Christopher Graham (Author) / Krause, Stephen (Thesis director) / Middleton, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
The purpose of this project is to determine the feasibility of a water tunnel designed to meet certain constraints. The project goals are to tailor a design for a given location, and to produce a repeatable design sizing and shape process for specified constraints. The primary design goals include a 1 m/s flow velocity in a 30cm x 30cm test section for 300 seconds. Secondary parameters, such as system height, tank height, area contraction ratio, and roof loading limits, may change depending on preference, location, or environment. The final chosen configuration is a gravity fed design with six major components: the reservoir tank, the initial duct, the contraction nozzle, the test section, the exit duct, and the variable control exit nozzle. Important sizing results include a minimum water weight of 60,000 pounds, a system height of 7.65 meters, a system length of 6 meters (not including the reservoir tank), a large shallow reservoir tank width of 12.2 meters, and height of 0.22 meters, and a control nozzle exit radius range of 5.25 cm to 5.3 cm. Computational fluid dynamic simulation further supports adherence to the design constraints but points out some potential areas for improvement in dealing with flow irregularities. These areas include the bends in the ducts, and the contraction nozzle. Despite those areas recommended for improvement, it is reasonable to conclude that the design and process fulfill the project goals.
ContributorsZykan, Brandt Davis Healy (Author) / Wells, Valana (Thesis director) / Middleton, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05