Damage detection in direct metal laser sintered parts using vibration mode shapes

Direct metal laser sintering (DMLS) is an additive manufacturing process that can be used to manufacture complex parts that are difficult or impractical to produce using traditional methods. However, this relatively new technology does not have the same base of knowledge as other processes. This makes it challenging to design parts that need to be manufactured using DMLS since many aspects related to this method are not fully comprehended.This study investigates the use of vibrational mode shapes as a possible means of detecting damage in parts that are manufactured from DMLS. Using vibration-based damage detection is a common testing technique due to the non-destructive nature of the test. The damage detection method chosen for this study involves the use of vibrational mode shape curvatures since the change in mode shape curvature has a unique pattern at the damage location. The parts that have been used for this study were printed from the EOS M 290 machine using 316L Stainless Steel. A notch is introduced into the geometry of several parts and damage is further propagated by sawing a slot at the end of the notch. A Polytec PSV-400 Laser Doppler Vibrometer has been used to identify the vibration mode shapes, these mode shapes are then compared to the mode shapes attributed to undamaged parts. Mode shapes have been analyzed using the wavelet transform as well as a curvature damage index.This study also investigates the possible effect of varying part densities on damage propagation. The properties of DMLS parts that increase cost efficiency and productivity, such as layer thickness and hatch distance, inversely affect the density of parts. Damaged parts are printed with varying process parameters and the mode shapes of damaged parts are compared to one another as well as the undamaged parts. The questions that this study seeks to answer are: Can damage of DMLS parts be detected from the mode shapes measured with a laser vibrometer? Can these mode shapes be used to predict or locate damage in parts? Do mode shapes of damaged parts differ with process parameters associated with the selective laser sintering process?Results indicate that damage can be successfully detected in the parts analyzed in this study. Additionally, it is observed that other unknown anomalies that are similar to damage can also be successfully detected. However, varying process parameters do not seem to exhibit any influence on damage detection

“A Wound So Deep and Ragged:” The Vulnerable Body of Appalachia in Ron Rash’s Short Stories

To read the work of Ron Rash is to run one’s hands across the scars, wounds, and callouses of the Appalachian region, and to become immersed in a collection of authentic, traumatic, and complex narratives that settle themselves along the ridges and foothills of the Appalachian mountains. This paper places Rash’s short stories within the context of this vulnerable, yet resilient Appalachian landscape and culture he is writing within: one traumatized by extractive industry, cultural exploitation, economic disadvantage, and widespread public misperception. Focusing specifically on Rash’s use of traumatized characters, this thesis analyzes the ways in which Rash humanizes the plight of Appalachia and its people by embodying its trauma within the vulnerable bodies, minds, and lives of such characters. By establishing the lens of Rash’s Appalachia as another kind of traumatized body, this project examines the social impact of Rash’s stories, interrogating how and why readers come to feel empathy for his vulnerable bodies, and whether this empathy provides a pathway towards healing for the Appalachian region. This paper contends that, through shifting perceptions surrounding Appalachia and providing an authentically human Appalachian narrative, Rash promotes a more intimate understanding of the Appalachian experience, combating the sentimentalization and oversimplification of the region’s trauma and history

Components of the health belief model and HIV testing decisions

An individual infected with HIV may have no visible symptoms of the illness. Therefore, it is important for individuals who are sexually active to practice selfprotective behaviors (e.g. discussing HIV testing with potential sex partners). The current descriptive study assessed the self-protective behavior of obtaining an HIV-antibody test within the framework of The Health Belief Model (HBM). Perceptions regarding susceptibility to HIV infection, severity of the disease, benefits or barriers to HIVantibody testing, and personal self-efficacy for engaging in protective behaviors were assessed in “Testers” (those who have been tested for HIV infection) and “Non-testers” (those who have not been tested). Phase 1 of the current study validated the HIV Testing Attitude Scale (HTAS) using introductory psychology students and clients from the county health department (n=203). Six items not included on the original HTAS reached significance with correlations ranging from 0.39 to 0.52 and were added to the scale. In Phase 2, participants (n=362) recruited from three health facilities and introductory psychology students were assessed using the HTAS, Self Efficacy Scale, Health Locus of Control, AIDS Health Belief Scale, Social Desirability, and specific items measuring attitudes and perceptions towards self-protective behaviors. Significant differences between Testers and Non-testers were found in HTAS, SES, HLOC, AHBS, SD, age, education level, drug or alcohol use associated with sexual activity, age of first coitus, knowledge of self-protective behaviors, and perception of personal susceptibility. Limitations of the HBM to differentiate between those who have and those who have not been tested for HIV infection were discussed along with limitations of the current study and suggestions for future research

The effect of response format and presentation conditions on comprehension assessments for students with and without a reading disability

Previous studies (Collins, 2015; Kennan & Meenan, 2014) have shown how variations in text and task factors and individual reader skills affect performance on reading comprehension assessments. The present study examined whether different presentation conditions (silent reading, watching a video) and response formats (open-ended vs. multiple-choice questions) influenced comprehension performance for students with and without reading disabilities. In addition, measures of word-level reading, vocabulary, working memory, listening comprehension, and prior knowledge were also assessed to determine the best predictors of performance on comprehension assessments. Participants were 32 fifth grade students, 17 with reading disabilities (RD) and 15 typically developing (TD) students. All students were initially administered measures of word-level reading, vocabulary, listening comprehension, working memory, and decoding. Students were then administered four passages. Two of the passages were read silently and two were presented with videos. For each condition (text and video), comprehension was assessed with open-ended and multiple-choice questions. All assessments were administered individually to each student across two 60-minute testing sessions. All students were found to perform significantly better on the multiple-choice questions than the open-ended questions. As expected, the TD group had significantly higher comprehension scores on all measures. Presentation condition did not significantly affect performance for either group. Listening comprehension, working memory, and prior knowledge contributed unique variance to performance on the different response formats. For the open-ended questions, 67% of the variance was explained by the measures of listening comprehension and prior knowledge. In contrast, only 38% of the variance was explained by working memory for the multiple-choice questions. Even though students performed better on the multiple-choice questions, the regression analyses indicated that the open-ended questions were better reflections of basic language abilities and prior knowledge. Open-ended questions appear to provide a better measure of reader and text factors than multiple-choice questions which are more influenced by task factors. Future studies should continue to examine how reader, text and task factors influence comprehension performance

A language of signs : obtaining power in Elizabeth Inchbald's A simple story

Elizabeth Inchbald’s A Simple Story (1791) is a groundbreaking novel that makes a complicated argument concerning feminine power and the possibility of undermining masculine authority. Inchbald, a trained dramatist and actress, uses her knowledge of theatrical gesture to demonstrate how eighteenth-century women could obtain a significant level of power by using their bodies as communicative instruments. The female characters in the novel forge an authentic feminine language for themselves through the performance of emotion and force their male counterparts to communicate with them in a discourse the women control. By impelling the male characters to use their system of language, the female characters forward their own desires and obtain a significant level of power and autonomy, thus, usurping the patriarchal system to a notable extent

A case study of the supports that foster teachers’ awareness of students with disabilities experiencing homelessness

Students with disabilities experiencing homelessness are a growing and vulnerable population in the United States (Bassuk et al., 2014). They have a myriad of unique and complex needs, many of which teachers are ill prepared to meet. In this study, the researcher conducted a case study (Yin, 2014), set within the context of Ecological Systems Theory (EST; Bronfenbrenner, 1979), to investigate existing school and district level supports for teachers of students with disabilities experiencing homelessness, and teachers’ and other school personnel’s perceptions of those supports. The researcher interviewed six school and district level personnel, and analyzed several school and district level documents and web resources regarding homeless education to triangulate the data. Data were coded at three levels, the first two employing deductive logic and a priori codes based on the EST theoretical framework (Level I) and extant literature (Level II; Fereday & Muir-Cochrane, 2006). The third level of analysis was conducted using an inductive process, during which codes emerged from the data (Leech & Onwuegbuzie, 2007). Results from Level I coding indicated microsystem supports (to students and families) were provided most frequently, followed by exosystem supports (to teachers and other school professionals). Level II coding revealed teachers and other school professionals have drastically different perceptions of the absence or presence of teacher supports. Furthermore, the roles of teachers and other school professionals are concentrated on providing supports to students and families far more frequently than providing them to teachers. Level III analysis resulted in four overarching themes: homeless education norms, perceptions of the experience of homelessness, assumptions about teacher awareness and supports, and culture of support. While other school professionals often worked together formally and informally, they rarely involved teachers in their teams, but reported they provide adequate teacher support. The special educator’s perceptions indicated a lack of knowledge and support as well as a desire to improve both. Although the majority of participants held a deficit perspective of students with and without disabilities experiencing homelessness, overall they conveyed the importance of establishing a culture of support for those students and their families. Implications for future research include an investigation of the descriptive (the way things are done) and injunctive (the way things ought to be done) norms (Cialdini et al., 1990) within schools and districts. Specifically, the siloed nature of homeless education appears to be an emerging descriptive norm, when existing research supports homeless education ought to be carried out in a coordinated, team-based manner (i.e., injunctive). Professionals from other systems must be included in future research, as the norms from various systems can result in further contradictions. Similarly, additional investigations of rural homeless education are warranted to further unveil norms that impact the education of rural students with disabilities experiencing homelessness. Finally, considerations for practice include overhauling professional development to include teacher leadership and coaching as valid and sustainable options for improving the supports for teachers of students with and without disabilities experiencing homelessness

Fourier-based image sharpness sensor for adaptive optics correction

Adaptive optics reduces undesirable turbulence effects present during propagation and imaging through the atmosphere or another random medium. Within an adaptive optics system, wavefront sensing determines the incoming wavefront errors. Image sharpening is one method of wavefront sensing where the sharpness value is measured from the image intensity based on a given sharpness metric. The wavefront correction device is then perturbed until the sharpness value is maximized. The key to image sharpening is defining sharpness with a sharpness metric that reaches a maximum when wavefront error is zero. Present image sharpness metrics often use the image intensity. In contrast, this dissertation introduces four novel sharpness metrics based on the Fourier transform of the image. Since high spatial frequencies carry information about the image’s edges and fine details, taking the Fourier transform and maximizing the high spatial frequencies sharpens the image. Coherence of the illumination source and the sharpness metric choice determine which of the presented optical system configurations to use. Performances of the Fourier-based sharpness metrics are observed and compared by measuring the sharpness value while adding defocus to the system. If the sharpness value reaches a maximum with zero wavefront error then the sharpness metric is successful. This investigation continues by adding astigmatism, coma, and spherical aberration and measuring the sharpness value to see the affect of these higher order aberrations. The sharpness metrics are then implemented into a simple manual closed-loop correction system. This dissertation presents successful performance results of these novel Fourier-based sharpness metrics showing great promise for use in adaptive optics correction

Predictors of high risk teenage pregnancies

To identify variables that predict birthweight among teenagers participating in a prenatal program? data were analyzed from 25,945 women, including 5,270 teenagers. Of black teenagers in the program* 8 to 17%. had low birthweight births, compared to 8 to 10'/. of the white teenagers. The percentages were significantly different only at age 15. Whereas black teenage mothers more often were unmarried, had previous abortions, and used public prenatal care providers, white teenage mothers more often smoked and were employed. Birthweight was regressed on a number of variables selected from the medical histories of the pregnant women. To obtain a risk score, the standardized regression coefficients were used to calculate weights that could be summed for each woman. Women who scored 10 or more were considered at risk. Risk weights for teenagers and for young adult women (ages 20 and 21) were calculated and compared with the risk weights for women of all ages who were in the prenatal program

Design of Fault Tolerant Control systems

This research designs a Fault Tolerant Control (FTC) approach that compensates for both actuator and sensor faults by using multiple observers. This method is shown to work for both linear time-variant and linear time-invariant systems. This work takes advantage of sensor redundancy to compensate for sensor faults. A method to calculate the rank of available sensor redundancy is developed to determine how many independent sensors can fail without losing observability. This rank is the upper bound on the number of simultaneous sensor failures that the system can tolerate. Based on this rank, a series of reduced order Kalman observers are created to remove sensors presumed faulty from the internal feedback of the estimators. Actuator redundancy is examined as a potential way to compensate for actuator faults. A method to calculate the available actuator redundancy is designed. This redundancy would allow for the correction of partial and full actuator failures, but few systems exhibit sufficient actuator redundancy. Actuator faults are instead tolerated by replacing the Kalman estimators with Augmented State Observers (ASO). The ASO adds estimates of the actuator faults as additional states of the system in order to isolate and estimate the actuator faults. Then a supervisor is designed to select the observer that correctly identifies the sensor fault set. From that observer, the supervisor collects state estimates and calculates estimates of the sensors and faults. These estimates are then used in feedback with a controller that performs pole placement on the original system

The status of elementary school general music programs in selected elementary schools in the Charlotte-Mecklenburg County school system in North Carolina

The purpose of this research study was to describe the status of public elementary school general music programs of Charlotte and Mecklenburg County, North Carolina. Specifically, the goals of the investigation were: (1) to describe the current status of elementary general music programs in selected public schools of the Charlotte- Mecklenburg School System; (2) to compare music goals, objectives, and criteria for each elementary grade as documented by the Charlotte-Mecklenburg School System with those of the North Carolina Department of Public Instruction; and (3) to determine the extent to which music goals, objectives, and criteria of the Char1otte-Meck1enburg School System have been implemented in the selected schools. Data collection instruments for the study included the "Elementary Music Teachers' Questionnaire" and the Silver Burdett Music Competency Tests (1979). A comparison was also made between the state (North Carolina) and local (Charlotte-Mecklenburg)elementary music curriculum guides