16484 research outputs found
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Optimization of Additively Manufactured Sandwich Panels with Composite Face Sheets
No full textSandwich structures are of great interest to researchers all around the world for their flexural stiffness, strength-to-weight ratio, and high energy absorption. These structures are extensively used in the aerospace, naval, and automotive industries. In this work, we describe a novel method to make monolithic sandwich panels with fiber-reinforced face sheets using a DLP 3D printer. The method was tuned to achieve high fidelity parts with accurate dimensions. For example, the amount of photo absorber was adjusted and found to be essential in achieving high print resolution. Samples with and without fiber-reinforced face sheets were printed using two different core geometries, honeycomb and rectangular, and printed in two different orientations, in-plane and out-of-plane. The specific stiffness of each of these four sample categories was then analyzed via 3-Point-Bending tests. In both reinforced and non-reinforced sandwich panels, the honeycomb structure showed the highest stiffness-to-weight ratio for out-of-plane orientation, while the rectangular structure showed the highest stiffness-to-weight ratio for in-plane orientation. Reinforced samples had a specific stiffness that was 130% and 240% more than that of non-reinforced samples in out-of-plane and in-plane samples, respectively.M.S., Chemical Engineering -- Drexel University, 202
Executive Function Professional Development: A Curriculum Review
No full textThis study explored to what extent teacher professional development on executive functions, a student's cognitive ability to regulate academic behavior (Dawson & Guare, 2010), is meeting the needs of teachers as adult learners. Primary and elementary school teachers are continually engaged in professional development to refine and advance their craft. The purpose of this instrumental case study was to explore the extent to which a school district's professional development on executive functions is providing teachers with the knowledge they need to support students' growth of execution functions and meeting the teachers' needs as an adult learner. The researcher investigated the design of an existing executive function professional development curriculum and reviewed teacher perception of the impact of the training on their understanding and practice. The study was guided by the following research questions: 1. How do teachers in a rural K-12 school district located in the northeastern United States perceive the impact of the existing curriculum on their understanding of executive functions and their classroom practices? 2. To what extent does the existing curriculum reflect current research in executive functions and brain development? 3. To what extent does the existing curriculum utilize elements of effective teacher professional development and adult learning? Conceptually the researcher framed the literature review around three topics: research on executive functions, adult learning theory, and teacher professional development. The researcher obtained the existing executive function curriculum used by the school district and conducted a review. Primary and elementary school teachers from the selected district were asked to participate in a Qualtrics survey to collect qualitative data about the perceived impact of the curriculum on their understanding of executive functions and their classroom practices. Based upon the data collected, analyzed, and interpreted, recommendations were made regarding the use of the existing executive function professional development curriculum to enhance skill development in students.Ed.D., Educational Leadership and Management -- Drexel University, 202
Nondestructive Approach for Defect Detection in Hard Armor Protective Inserts
No full textDelamination detection in hard body armor is uniquely challenging and has affected the defense acquisition plan while generating uncertainty with respect to ballistic performance. The ability to confidently detect armor delamination is necessary to protect the warfighter and manage risk. The tap test has long been a benchmark in nondestructive inspection (NDI), including the investigation of composite structure delamination. The application of impact-based NDI to composite parts, although widely reported, is still hampered by a number of challenges. In a simple summary, NDI can be characterized as an inverse problem with the goal of inferring the presence of a defect by interpreting and extrapolating the system's "reaction" under controlled conditions. The fundamental challenge is that realistic armor delaminations (e.g. from manufacturing) may be too deep or too slight to be confidently deconvolved from the noise generated by armor system complications using an impact-based NDI approach. The subject research postulates that existing impact-based methods are not sensitive enough to detect small defects in thick-sectioned, finite-geometry, laminar composites such as hard body armor; however, modifications to the impact-based approach may provide greater sensitivity in discerning the presence of small delaminations. The research approach has three objectives: (1) define the target defect in hard armor protective inserts (2) evaluate the capabilities and limitations of impact-based NDI (3) propose methodology improvements that may achieve the desired sensitivity for hard armor inserts. Defect characterization, method sensitivity, potential confounds, and the extension to small defects are discussed. Impact-based NDI is a rudimentary tool that is deceivingly simple, yet versatile and widely applied. Under the right conditions, it can illuminate delamination in complex material systems.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 202
A Phenomenology Study into How Parents Understand and Perceive the Effect of Reading Aloud on Children's Emergent Literacy Skill Development and Reading Readiness
No full textTo address the void in scholarly literature, this study explored how parents approach and understand the read aloud experience and its effect on young children's emergent literacy development, reading readiness, and future reading success. Many children start school every year without the necessary skills to learn how to read, and it is virtually impossible to close the gap in this deficit. Choosing the most effective way of teaching emergent literacy skills to young children presents the current challenge for many early childhood educators and administrators. Much work has been done in the area of emergent literacy skills and their link to reading success. At a young age, children develop a desire to learn how to read as well as the self-confidence in their abilities to become readers. The problem addressed in this phenomenological study was a need to explore parental perceptions about emergent literacy and reading aloud to kindergarteners to understand the influence on children's literacy development, reading readiness, and future success. The purpose of this qualitative study was to explore parents read aloud experiences with their children to understand how parents perceive children's emergent literacy skill development and the effects of their reading aloud approach on reading readiness. Research in the areas of emergent literacy skills and their links to reading success, best practices for delivering early literacy instruction, and the home literacy environment with the role parents play in developing emergent literacy skills, were examined to provide background germane to addressing the reading readiness issue. The study sought to answer the following research questions. 1. How do parents describe their perceptions about the effects of the read aloud experience on emergent literacy development for kindergarten learners in a south central Pennsylvania school? 2. How do parents of kindergartners experience and understand the read aloud approach to developing emergent literacy skills in a south central Pennsylvania school? 3. How does the prosody of parents reading aloud to their children affect kindergarteners' interest in reading in a south central Pennsylvania school? 4. How do parental reading aloud techniques inform or shape the reading experience of kindergarten learners in a south central Pennsylvania school? Parents of kindergarten students were surveyed with a demographic questionnaire and interviewed to gather qualitative data. Parents were also observed reading aloud with their children using observational notes and a reading observation checklist. Descriptive, structural, and in vivo coding were used to analyze the data. Keywords: Emergent Literacy, Fluency, Print Referencing, Prosody, Read Aloud, Reading Readiness, Text CodeEd.D., Educational Leadership and Management -- Drexel University, 202
A Differential Capacitive Sensing System for Knitted Textiles
No full textTextiles, in combination with advances in materials, intelligent sensing and signal processing, offer exciting new possibilities for fabric-based human interfaces and flexible, touch-sensitive devices. This thesis introduces a novel touch detection method and applies signal processing techniques towards measuring distributed capacitive touch across knitted fabric circuits. This work introduces differential capacitive sensing--a technique to measure capacitive touch along a continuous linear conductor using paired input and output voltage waveforms. A framework for constructing compatible knitted circuits from conductive yarns is introduced that enables the creation of extensible fabric touch interfaces using digital weft knitting. Touch localization, through differential capacitive sensing, is improved by applying Bode analysis to measure frequency-specific signal attenuation invariant to distortion from electromagnetic interference. A real-time sensing controller is constructed to generate, acquire and process voltage waveforms measured from the fabric circuit. The processed data are recorded as a time series of paired gain measurements with respect to input frequency. The contributions of this work make possible the development of Mixed-Source Description, a method to extract scale-space features from time-frequency measurements. A scale-space representation of temporal gestures, such as press-and-release, is constructed and compared using a novel distance metric, the Euclidean Levenshtein Distance, developed to quantify the similarity between temporal touch data. This work provides the foundation for quantifying high-level user input using textile-based sensors and a robust capacitive touch sensing system.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 202
A Six-Degrees of Freedom Dynamic Ankle Simulator
No full textA clear understanding of foot locomotion and the function of each of its bones, muscles and ligaments, would allow for a fast identification of pathologies as well as the improvement of surgical procedures. So far, many different methods have been used in the hopes that they will provide thorough information on the mechanics and physiology of the foot, while also stay non-invasive and ethical for the living subjects. However, these approaches come with limitations, such as the impossibility to determine individual bone kinematics. It is due to this that researchers depend on in vitro experiments of the foot. These highly invasive studies on cadavers provide information on the kinetic interaction between bones, including particularly shielded ones like the talus. Their application in reproducible and repetitive testing is also welcome for implant evaluation or any other surgical procedure. Different ankle simulators have been used for in vitro investigations in the past aiming to replicate foot dynamic functional activities. However, an accurate reproduction of gait would require a complicated combination of applied high-speed motions and large loadings. Due to this, some simplifications and assumptions are often needed during the design of the simulator. Current simulators do provide six-degree-of-freedom controlled movement. However, these are highly coupled, which leads to control difficulties and accumulative inaccuracies. In addition, the existing systems are slow and expensive. For this study, it was then considered that a new more accurate device was required to address these deficiencies. This led to the development of an innovative structure of the linkage with decoupled degrees of freedom, which provides a significant advantage over other simulators. Therefore, its control is much simpler and quick, it requires minimum online computation and its accuracy increases since error is not propagated. This is also a much cheaper solution, capable of delivering high forces. The design process of the linkage included dynamic simulations that were performed iteratively to ensure smooth performance free of collisions. These analyses showed the components are able to rotate perfectly, having enough available space to meet the ranges of motion required. Additionally, extremely high loads are applied by the linear actuators connected to the simulator, which may lead to unwelcome deformations. Therefore, the design process also included iterative FEM analysis to evaluate stresses and deformations, as well as to modify the design in order to produce proper mechanical loading on the elements of the structure. While some parts of the device proved to have minimal stresses, other parts showed a dangerous amount of deformation. This led to a change in their design which greatly improved their ability to withstand the required loads.M.S., Mechanical Engineering and Mechanics -- Drexel University, 202
An Exploration of Preschool Teachers' Training for English Language Learners: An Instrumental Case Study
No full textEarly childhood classroom diversity has increased significantly in the United States in recent years (Genishi & Dyson, 2015); however, this diversity has not been echoed by a similar diversification of teaching practices (Genishi & Dyson, 2015). The purpose of this qualitative case study was to explore the current level of ELL training possessed by nine female preschool teachers teaching in a Head Start program located in north central California; and to explore these preschool teachers' perceptions of how effective their training had been. The following research questions guided this study: (a) How do preschool teachers describe their level of training and preparedness to teach ELL children? (b) How is a preschool teacher's level of preparedness and training for teaching ELL children reflected in his or her instruction? (c) How do preschool teachers perceive ELL children as responding to their instructions? Analysis of the study results identified five themes a) level of teacher training and preparedness, b) classroom instruction techniques, c) challenges and opportunities of working with ELL preschoolers d) working with ELL parents, and e) Needs and Recommendations from Teachers. Consistent with previous findings in the literature, the findings of the research suggested, a lack of education and training for the teachers working with ELL students, teachers relying on their experiences and teachers' creativity to adapt tools at their disposal to animate and engage ELL students. Since there are gaps in the existing formal training and skills provided to teachers for ELLs, a recommendation is for administrators and educators to be mindful of creating a culturally responsive classroom and to address cultural competency in curriculum and teacher development.Ed.D., Education -- Drexel University, 202
Play By K – Building A Successful Model for Scholastic Athletics in Urban Schools: A Collective Case Study
No full textThe intersection of athletics and academics have been a focal point of numerous research studies since schools began sponsoring sports teams and competing against local rival districts. Many recent high-profile scandals that have exposed the National Collegiate Athletic Association (NCAA) and other national governing bodies brought to light an unfortunate by-product of education-based athletics: winning at all costs. This "need to win" mentality is negatively impacting our scholastic athletic programs, which are beginning to lose their focus. The purpose of this qualitative, collective case study is to examine perceptions of district-level athletic administrators on successful models of scholastic athletics in urban schools. Urban school districts, which are chronically under-resourced when it comes to scholastic athletic opportunities for students, are disorganized across the K-12 grade span. In schools that lack programming, students are often shuffled to their local playground or community center - facilities that typically do not have the capacity to operate quality programming. This study aims to address the central research questions on developmentally appropriate programming, leadership development in scholastic athletics, and the impact of scholastic athletics on student outcomes. The research analyzed common themes among the urban school districts and the scholastic athletic programming they offer at different levels of a student's educational experience. "Play By K" is used as a benchmark initiative to ensure all students have the opportunity to engage in open play by the time they start kindergarten - and to be able to continue with their love of sport through their high school years and beyond. The researcher explores models of successful scholastic athletic programs in urban schools by conducting individual interviews with district-level athletic administrators in order to better support opportunities for all students-athletes through construction of an inclusive and comprehensive K-12 model
Chondroitin Sulfate Conjugated Nanofiber Shish Kebabs as Biomimetic Bone Templates
No full textBone defects affect over 2.2 million people worldwide through diseases, injuries, aging, or the combination of these. The gold standards for bone defects are autografts harvested generally from the iliac crest or the hip bone of the patient. The use of autografts is limited and require additional surgery, which increases the risk of infection and donor site morbidity. Although there is no immune or compatibility issue, some autografts still fail due to non-union of bone and related complications. There is a medical need to synthesize polymeric bone grafts that can perform similarly if not better than bone autografts. To this end, we have previously fabricated a polycaprolactone (PCL) nanofiber shish kebab (NFSK) template as synthetic bone scaffolds via polymer crystallization of a block copolymer of PCL-b-PAA. The novelty of this work is the ability to control the mineral crystal orientation and spatial location on the nanofiber, which mimics the molecular structure of bone or mineralized collagen fibrils. The objective of this thesis is two-fold: 1) to investigate the cell to biomaterial surface interaction provided by the unique NFSK surface features and 2) to use the NFSK platform to design biomimetic bone templates. The advantage of using NFSK templates is ease of modifying the template surface with different functional groups and biomimetic nature of NSFK-templated mineralization. As a result, the surface roughness and chemistry can be manipulated and designed towards an osteogenic microenvironment. For these reasons, it was hypothesized that the NFSK templates will promote cell differentiation and marker expression of mineralization of MC3T3 E1 pre-osteoblast cells. In the first part of the dissertation, NFSK templates were used to investigate the topological effect, e.g. fiber alignment and kebab size, on pre-osteoblast cell proliferation and ALP activity, which the latter is an important enzyme related to bone mineralization and osteogenesis. Aligned nanofiber with larger kebab size increased both ALP activity and cell proliferation because of the surface roughness of NFSK. NFSK templates were then mineralized in simulated body fluid to mimic mineralized collagen fibrils, which was showed to increase ALP and cell proliferation as well. Interestingly, the kebab period did not influence proliferation or ALP activity when mineralized indicating that surface chemistry played a more dominant role than surface roughness. The NFSK templates was further designed to also mimic the bone matrix by conjugating chondroitin sulfate (CS) onto the PAA region of the kebab. CS is an important glycosaminoglycan that is important in collagen fiber organization in the bony matrix. CS-NFSK templates were characterized using FTIR and mass balance, which showed formation of an amide bone between the CS amine group and the PAA carboxylic acid group and increases in the template mass after conjugation. Thermal analysis and contact angle also showed difference in thermal degradation, heat flow, and hydrophilicity. Lastly, CS-NFSK templates promoted ALP activity and cell proliferation compared to the control. Osteoblast gene expression including RUNX2, ALP, COL1, and BGLAP were also upregulated in the CS-NFSK templates indicating mineralization and formation of matrix. For the first time, CS-NFSK were molecularly engineered to mimic the bone structure and matrix, which showed promise as a biomimetic bone template.Ph.D., Biomedical Engineering -- Drexel University, 202
A Phenomenological Study: Exploring High School Students' Experiences Earning an Entrepreneurship Diploma in an Entrepreneurship Education Secondary School Program
No full textAs of 2015, 42 states reported some type of entrepreneurship education standards, guidelines, or proficiencies and 18 states required entrepreneurship education courses to be offered at the high school level. Yet, there is limited qualitative literature on students' experiences in degree-granting entrepreneurship education secondary school programs that promote an entrepreneurial mindset. This leads to a limited understanding for secondary school leaders and curricula developers designing and implementing these programs, which potentially results in the design and implementation of ineffective programs. The purpose of this qualitative, phenomenological study was to explore high school students' lived experiences earning a high school Entrepreneurship Diploma (ED) that was designed to promote an entrepreneurial mindset. This study collected and analyzed qualitative data from ED Cohort 1 members, their parents, and former program faculty, primarily through questionnaires, interviews, and reflection matrices. Four results emerged from the study's findings: (a) Uncertain and Non-Traditional Future Work Landscape Necessitates Diverse and Holistic Skillset, which the ED Promoted; (b) Participation in Numerous and Reoccurring Experiences that Enable High School Students to Apply Classroom Learning to Real World Problem-Solving and Presentation Empowers Students to Develop Confidence and Take Risks; (c) Sustained Collaborative and Teamwork-Based Learning Leverages Social Relationships and Helps Students Develop and Understand the Value of Support Networks; and (d) Self-Reflection and Feedback in the Context of Entrepreneurial Mindset Development Enable Powerful and Purposeful Self-Discovery of Authentic Identity. These results are valuable to secondary school leaders and curricula developers designing and implementing entrepreneurship education programs that promote an entrepreneurial mindset in students. Since these results also indicate the skills with which high school students might be entering college or the workforce, these results are indirectly valuable to college administrators and employers, who desire entrepreneurially minded individuals or employees.Ed.D., Educational Leadership and Management -- Drexel University, 202