Dissertations / Theses on the topic '120499 Engineering Design not elsewhere classified'

Teacher talk is a major way in which instructors support and provide scaffolding for their students, frame their pedagogies, model ways of thinking, and convey ideas. Effective teacher talk about engineering design at all levels of students’ educational experiences has the potential to better prepare students for success in engineering and increase the diversity of engineering fields. However, the most effective ways for teachers to talk to their students during engineering design are not well understood. This three-study dissertation examines the ways in which instructors use talk to interact with their students through a variety of different engineering design settings and contexts, with potential implications to improve and educate how teachers present engineering to their students. Overall, this thesis addresses the research question: How do instructors (teachers and professors) use talk interactions to scaffold students in engineering design? The first study is a case study that focuses on the whole class verbal interactions of an experienced and successful teacher throughout the entirety of a month-long life science-based STEM integration unit in a 6th grade classroom. Results show that this teacher’s talk helped to integrate engineering with the science and mathematics content of the unit and modeled the practices of informed designers to help students learn engineering in the context of their science classroom. He framed lessons around problem scoping, incorporated engineering ideas into scientific verbal interactions and aligned individual lessons and the overall unit with the engineering design process. The second study uses naturalistic inquiry to examine how six different teachers of 6^th, 7^th, and 8^th grades talked to their students while the students were actively working in small teams on engineering design projects. Results indicate that the teachers had conversations with the students about many areas of engineering, demonstrating that middle school teachers can have high-level conversations with their students about their design ideas. However, when students struggle to communicate their ideas, the different levels of support outlined in the coding framework and examples provide a structure of support for teachers to give their students. Additionally, there were many areas of engineering that were underemphasized in the teachers’ talk and each teacher had different emphasis. The third study examines how professors in mechanical and biomedical engineering talk to their students during introductory engineering design projects. Results show that the three professors used their talk to support their role as a guide and mentor to students during their projects, although they had different goals with their mentoring. They used their talk to push students’ ideas to consider their problems more broadly, encouraged students to brainstorm diverse out-of-the-box ideas, supported teaming, and modeled engineering language. They maintained a focus on non-technical content, including the iterative nature of design, teaming, and communication, but made references to how students would apply this knowledge in future, more technical projects. The professors supported many challenges for novice designers, including supporting prototype development to represent ideas and iterating to improve their ideas, but were not comprehensive in their support of other challenges, especially problem scoping, testing and troubleshooting, and reflecting on the process. The final chapter of this dissertation presents a synthesis across the three studies and a summary of the implications for teaching. These implications include many examples of high-quality engineering conversations with students at different levels of their education, identification of aspects of engineering education that are underemphasized in teachers’ talk to their students, and connections to needed areas of support and professional development for teachers.

Modern computing platforms, from servers to mobile devices, demand ever-increasing amounts of memory to keep up with the growing amounts of data they process, and to bridge the widening processor-memory gap. A large and growing fraction of chip area and energy is expended in memories, which face challenges with technology scaling due to increased leakage, process variations, and unreliability. On the other hand, data intensive workloads such as machine learning and data analytics pose increasing demands on memory systems. Consequently, improving the energy-efficiency and performance of memory systems is an important challenge for computing system designers.

Spintronic memories, which offer several desirable characteristics - near-zero leakage, high density, non-volatility and high endurance - are of great interest for designing future memory systems. However, these memories are not drop-in replacements for current memory technologies, viz. Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM). They pose unique challenges such as variable access times, and require higher write latency and write energy. This dissertation explores new approaches to improving the energy efficiency of spintronic memory systems.

The dissertation first explores the design of approximate memories, in which the need to store and access data precisely is foregone in return for improvements in energy efficiency. This is of particular interest, since many emerging workloads exhibit an inherent ability to tolerate approximations to their underlying computations and data while still producing outputs of acceptable quality. The dissertation proposes that approximate spintronic memories can be realized either by reducing the amount of data that is written to/read from them, or by reducing the energy consumed per access. To reduce memory traffic, the dissertation proposes approximate memory compression, wherein a quality-aware memory controller transparently compresses/decompresses data written to or read from memory. For broader applicability, the quality-aware memory controller can be programmed to specify memory regions that can tolerate approximations, and conforms to a specified error constraint for each such region. To reduce the per-access energy, various mechanisms are identified at the circuit and architecture levels that yield substantial energy benefits at the cost of small probabilities of read, write or retention failures. Based on these mechanisms, a quality-configurable Spin Transfer Torque Magnetic RAM (STT-MRAM) array is designed in which read/write operations can be performed at varying levels of accuracy and energy at runtime, depending on the needs of applications. To illustrate the utility of the proposed quality-configurable memory array, it is evaluated as an L2 cache in the context of a general-purpose processor, and as a scratchpad memory for a domain-specific vector processor.

The dissertation also explores the design of caches with Domain Wall Memory (DWM), a more advanced spintronic memory technology that offers unparalleled density arising from a unique tape-like structure. However, this structure also leads to serialized access to the bits in each bit-cell, resulting in increased access latency, thereby degrading overall performance. To mitigate the performance overheads, the dissertation proposes a reconfigurable DWM-based cache architecture that modulates the active bits per tape with minimal overheads depending on the application's memory access characteristics. The proposed cache is evaluated in a general purpose processor and improvements in performance are demonstrated over both CMOS and previously proposed spintronic caches.

In summary, the dissertation suggests directions to improve the energy efficiency of spintronic memories and re-affirms their potential for the design of future memory systems.

With a stable center of mass, pneumatic-aided movement, and the ability to scale multiple terrain types, the uniquely efficient and lightweight form of spiders has changed the way we think about robotic design. While the number of papers on arachnid biomechanics and spider-based biomimetic robots has been increasing in recent years, the style of analysis and the motion-types analyzed have barely changed since the 1980s. Current analyses are based on a force plate and treadmill design, in which the spider is induced into an escape run. This environmental change can affect the movements of the spider. Here I propose a novel method of testing the biomechanical and kinematic properties of spiders using a tank with a built-in sensor matrix which allows for a more natural environment for the specimens and provides force data from individual legs. The system detects a minimum force of .0196 N and has a sampling rate of 1,000 samples /second, which allows for the analysis of forces during the step. Aphonopelma seemanni, a tarantula commonly used in such research, but whose forces during movement have to date not been analyzed, was recorded walking across the matrix, and the forces, step patterns, joint angles, and center of mass deviations were recorded. Walking indicated significantly different step pattern traits than current literature, and forces per leg (.07281 N±.0235) recorded were much smaller than expected in comparison to other spiders. Statistical analysis also indicated no changes in walking movement over a range of temperatures, which also varies from literature. These findings indicate that further research on spiders should be done with respect to walking gaits in order to improve upon current biomimetic models.

Research in pre-college engineering education has been on a sharp rise in the last two decades. However, less research has been conducted to explore and characterize the engineering thinking and engagement of young children, with limited attention to children with special needs. Conversations on broadening participation and diversity in engineering usually center around gender, socio-economic status, race and ethnicity, and to a lesser extent on neurodiversity. Autism is the fastest growing neurodiverse population who have the potential to succeed in engineering. In order to promote the inclusion of children with autism in engineering education, we need to gain a deep understanding of their engineering experiences.

The overarching research question that I intend to answer is how do children with mild autism engage in engineering design tasks? Grounding this study in theories of Constructivism and Defectology, I focused on children’s engagement in engineering design practices and the ways their parents supported their engagements. To engage children with mild autism in engineering, I have developed an engineering design activity by considering suggestions from these theories and previous literature on elementary-aged children’s engagement in engineering design, and by focusing on individuals with mild autism strengths in STEM. This activity provides opportunities for children to interact with their parents while solving engineering design problems. The families are asked to use a construction kit and design their solutions to the problem introduced in the engineering design activity. The engineering design activity consists of a series of five challenges, ranging from well- to ill-structed.

This is an exploratory qualitative case study, using a multiple case approach. These cases include 9-year-old children with autism and their families. Video recordings of the families are the main source of data for this study. Triangulation of data happens through interviewing parents and children, pictures of children’s artifacts (i.e. their prototypes), and use of the Empathizing-Systemizing survey to capture background information and autism characteristics. Depending on the data source, I utilized different methods including video analysis, thematic analysis and artifact analysis.

This study expands our understanding of what engineering design can look like when enacted by children with mild autism, particularly as engineering design is considered to be a very iterative process with multiple phases and actions associated with it. The findings of this study show that these children can engage in all engineering design phases in a very iterative process. Similarities and differences between these children’s design behaviors and the existing literature were discussed. Additionally, some of the behaviors these children engaged in resemble the practices of experienced designers and engineers. The findings of this study suggest that while children were not socially interacting with their family members when addressing the challenges, their parents played an important role in their design engagement. Parents used different strategies during the activity that supported and facilitated children’s engineering design problem-solving. These strategies include soliciting information, providing guidance, assisting both verbally and hands-on, disengagement and being a student of the child.

Molecular separations are essential in the production of many chemicals and purified products. Of all the available separation technologies, distillation, which is a thermally driven process, has been and continues to be one of the most utilized separation methods in chemical and petrochemical plants. Although distillation and other commercial technologies fulfilled most of the current separation needs, the energy-intensive nature of many molecular separations and the growing concern of reducing CO₂ emissions has led to intense research to seek for more energy-efficient separation processes.

Among the emerging separation technologies alternative to distillation, there is special attention on non-thermally driven methods, such as membranes. The growing interest in non-thermal methods, and particularly in the use of membranes, has been influenced significantly from the widespread perception that they have a potential to be markedly less energy-intensive than thermal methods such as distillation. Even though many publications claim that membranes are more energy-efficient than distillation, except for water desalination, the relative energy intensity between these processes in the separation of chemical mixtures has not been deeply studied in the literature. One of the objectives of this work focuses on introducing a framework for comparative analysis of the energy intensity of membranes and distillation.

A complication generally encountered when comparing the energy consumption of membranes against an alternative process is that often the purity and recovery that can be achieved through a single membrane stage is limited. While using a multi-stage membrane process is a plausible solution to achieve both high purity and recovery, even for a simple binary separation, finding the most suitable multistage membrane process is a difficult task. This is because, for a given separation, there exists multiple cascades that fulfill the separation requirements but consume different amounts of energy. Moreover, the energy requirement of each cascade depends on the operating conditions. The first part of this work is dedicated to the development of a Mixed Integer Non-linear Program (MINLP) which allows for a given gaseous or liquid binary separation, finding the most energy-efficient membrane cascade. The permeator model, which is derived from a combination of the cross-flow model and the solution diffusion theory, and is originally expressed as a differential-algebraic equation (DAE) system, was integrated analytically before being incorporated in the optimization framework. This is in contrast to the common practice in the literature, where the DAE system is solved using various discretization techniques. Since many of the constraints have a non-convex nature, local solvers could get trapped in higher energy suboptimal solutions. While an option to overcome this limitation is to use a global solver such as BARON, it fails to solve the MINLP to the desired optimality in a reasonable amount of time for most of the cases. For this reason, we derive additional cuts to the problem by exploiting the mathematical properties of the governing equations and from physical insights. Through numerical examples, we demonstrate that the additional cuts aid BARON in expediting the convergence of branch-and-bound and solve the MINLP within 5%-optimality in all the cases tested in this work.

The proposed optimization model allows identifying membrane cascades with enhanced energy efficiency that could be potentially used for existing or new separations. In addition, it allows to compare the optimum energy consumption of a multistage membrane process against alternative separations methods and aid in the decision of whether or not to use a membrane system. Nevertheless, it should be noted that when a membrane process or any other non-thermal separation process is compared with a thermal process such as distillation, an additional complication often arises because these processes usually use different types of energies. Non-thermal processes, such as membranes, consume electrical energy as work, whereas thermal processes, such as distillations, usually consume heat, which is available in a wide range of temperatures. Furthermore, the amount of fuel consumed by a separation process strongly depends on how its supplied energy is produced, and how it is energy integrated with the rest of the plant. Unfortunately, common approaches employed to compare the energy required by thermal and non-thermal methods often lead to incorrect conclusions and have driven to the flawed perception that thermal methods are inherently more energy-intensive than non-thermal counterparts. In the second part of this work, we develop a consistent framework that enables a proper comparison of the energy consumption between processes that are driven by thermal and non-thermal energy (electrical energy). Using this framework, we refute the general perception that thermal separation processes are necessarily the most energy-intensive and conclusively show that in several industrially important separations, distillation processes consume remarkably lower fuel than non-thermal membrane alternatives, which have often been touted as more energy efficient.

In order to gain more understanding of the conditions where membranes or distillation are more energy-efficient, we carried out a comprehensive analysis of the energy consumed by these two processes under different operating conditions. The introduced energy comparison analysis was applied to two important separation examples; the separation of p-xylene/o-xylene, and propylene/propane. Our results showed that distillation is more energy favored than membranes when the target purity and recovery of the most volatile (resp. most permeable) component in the distillate (resp. permeate) are high, and particularly when the feed is not too concentrated in the most volatile (resp. most permeable) component. On the other hand, when both the recovery and purity of the most volatile (resp. most permeable) component are required at moderate levels, and particularly when the feed is highly enriched in the most volatile (resp. most permeable) component, membranes show potential to save energy as compared to distillation.

In this study, a novel and systematic methodology for the design and optimization of conductor-backed coplanar waveguide (CB-CPW) based low pass filter (LPF) is proposed. The width of the signal trace is continuously varied using a truncated Fourier series, and the adjacent gaps are designed in several types established on a specific optimization setup to obtain predefined electrical characteristics with maximum compactness taking into account physical constraints. Trust-region-reflective algorithm (TRRA), genetic algorithm (GA), and particle swarm optimization algorithm (PSO) are taken into account to minimize the developed bound-constrained non-linear objective function respectively.

All types are programmed and analytically verified in MATLAB. Solutions include design parameters such as the physical length and width of the structure, which will be drawn in AutoCAD later on. Also, the optimized layouts are exported to Ansys High Frequency Structure Simulation (HFSS) software for simulation and validation. Non-uniform CB-CPW LPFs are optimized and simulated over a frequency range of 0-6 GHz with a cutoff frequency of 2 GHz. Simulation results show a good agreement with the analytical ones.

In recent years lithium-ion battery electric vehicles and stored hydrogen electric vehicles have been developed to address the ever-present threat of climate change and global warming. These technologies have failed to achieve profitability at costs consumers are willing to bear when purchasing a vehicle. IFBattery, Inc. has developed a unique primary battery chemistry which simultaneously produces both electricity and hydrogen-on-demand while being both low cost and without carbon emissions. In order to determine the feasibility of the IFBattery chemistry for mobile applications, a prototype golf cart was constructed as the first public application of IFBattery technology. The legacy lead acid batteries of the prototype golf cart were replaced with an IFBattery chemistry tuned to primarily produce hydrogen-on-demand with supplemental electricity. Hydrogen produced by the IFBattery was purified and then fed into a hydrogen fuel cell where electricity was produced to power the vehicle. Electricity from the IFBattery was converted to the common voltage of the golf cart and also used to power the vehicle. Validation testing of the IFBattery powered golf cart demonstrated favorable results as an alternative to both lithium-ion battery and stored hydrogen technologies, and displayed potential for future applications.

Socially engaged design programs, community development coalitions, and intentional and unintentional design spaces are rich with expertise and thinkers who are developing solutions to very pressing, yet complicated problems. Little research has been conducted on the expertise and sense-making of the community partners who participate in these situations. The goal of this research endeavor is to unpack the ways various community partners make meaning of their design experiences by answering the question: What evidence of system’s thinking can be seen in the way community partners describe their work or context? A qualitative research study was conducted in which three community partners were interviewed at various points during their engagement with socially engaged design programs. They demonstrated their systems thinking ability most strongly across the following domains: differentiate and qualify elements, explore multiple perspectives, consider issues appropriately, recognize systems, identify and characterize relationships. These findings imply that the community partners are not only capable of systems thinking but have the potential to be more deeply involved in developing solutions within these settings. Future studies should investigate systems thinking beyond socially engaged design in formal settings and should consider investigation protocols that more directly surface systems thinking domains. Overall, this study contributes to existing work in systems thinking by calling for a more expansive and inclusive engagement of community partners in socially engaged work.

Space and water heating contribute over 50% of all the residential building energy consumption and are especially major energy consumers in the cold climates. Meanwhile, conventional furnaces and boilers with energy efficiency limited to below 100% dominate the residential heating in the cold climate, and the electric vapor-compression heat pump capacity and efficiency decline drastically at low ambient temperatures. Thermally driven ammonia-based chemical adsorption (chemisorption) heat pump (CSHP) systems utilize the reversible chemical reaction between the ammonia vapor and solid sorbent to generate heat pumping effect, which can provide heating with much higher energy efficiency than existing cold-climate heating technologies. Despite the significant potential of energy efficiency improvement from existing technologies, most studies in the literature on chemisorption heat pump systems focus on adopting the technology for refrigeration and energy storage applications, with very limited investigations available for using the technology for producing heating in cold climates.