18525 research outputs found
Sort by
Modelling and Simulation in Simulink of a Water-Based Automatic Cooling System to Reduce Efficiency Loss due to Heat in Photovoltaic Panels in Ecuador
No full textThe present project introduces a low energy consumption, low maintenance required, affordable and simple to install water based automatic cooling system modelling and simulation to reduce efficiency loss in photovoltaic panels due to heat. It is focused for residential applications in Ecuador due to the energetic crisis that happened last year and its geographical location that makes it ideal to implement this renewable solution improved by the proposed system. Photovoltaic panels efficiency is low, near 20%, which makes it extremely important to avoid losses. High irradiance in Ecuador causes panels to have maximum efficiency, but at the same time causes them to heat and have thermal loss at a rate of 0.5% per °C above room temperature. The substrate of the panels causes them to reach temperatures around 70°C at maximum irradiance peak values, even having a maximum temperature of 30°C approximately in this country. Low efficiency of the panels requires a low energy consumption solution resulting in avoiding using actuators like pumps, which also increases the system’s maintenance frequency. The system is designed using valves with a time-based algorithm to fill a water tank from regular faucets, cool the panels using gravitational fall while they are cleaned at the same time and the resultant hot water can be reused. Real elements are proposed with an economic analysis to observe the financial viability of the system. Water volume is limited to 4m3 daily, even being low the price of it in this location, to not misuse another resource. However, an analysis is presented too to compute the water volume needed to have no efficiency loss due to heat. In a worst-case scenario of irradiance peak of 1000W/m2, the system provides 6% efficiency improvement, being very significative compared to the efficiency that panels can reach. Finally, a rain detector is included in the system to avoid misuse of water in both filling and cooling processes when it is raining during the irradiance period
Effects of Remote Microphone System Use in Home Environments of Young Children with Autism Spectrum Disorder
No full textPurpose: Children with autism spectrum disorder (ASD) exhibit deficits in performance on auditory-based tasks, especially in the presence of background noise, as compared to neurotypical peers. Speech perception-in-noise difficulties could detrimentally impact speech and language development, communication within family units, social relationships, academic achievements, and eventual vocational success. This study explored the effects of short-term remote microphone (RM) system use in home environments on auditory and communicative behaviors in a cohort of children diagnosed with ASD (aged 3 to 6 years) and their caregivers.
Methods: Language Environmental Analysis (LENA™) recorders were used with 18 families during two consecutive weekends – one weekend while the child-caregiver used an RM system and one weekend without this device. To examine the impact of RM system use on auditory and communicative behaviors, the following measurements were collected using data from the LENA recorders: (1) child vocalization rate; (2) primary caregiver vocalization rate; (3) quantity of dyadic conversational turns between the child and caregiver; and (4) number of caregiver-produced repetitions and alerting phrases directed toward the child during verbal interactions. In addition, caregivers’ qualitative perceptions of RM system use were gathered via a self-report questionnaire. Of note, 13 other enrolled children could not tolerate RM system use and were eliminated from the study.
Results: Findings revealed that when using an RM system, caregivers produced fewer verbal repetitions and alerting phrases than when not using RM system technology, on average. Second, RM system use yielded, on average, no significant differences in caregivers’ number of vocalizations or frequency of child vocalizations between conditions. Third, on average, the quantity of conversational turn counts per minute per caregiver-child dyad differed both by condition (more conversational turns with RM use versus no RM use) and by distance (more turns from a close versus far range). Lastly, caregivers reported various listening improvements for their children with ASD, including enhanced responsiveness and greater ease of family communication, when using an RM system.
Conclusions: Findings from this study could serve to inform clinical management recommendations for children with ASD and to educate professionals about potential benefits and limitations of RM system use for families
Characterizing the Temporal-Dependent System Vulnerability in Deep Neural Network Applications on GPUs for Cost-Effective Fault Tolerant Design
No full textWith the escalating complexity of Deep Neural Network (DNN) tasks, heterogeneous computing systems are widely employed in real-time, safety-critical systems like autonomous vehicles. These systems, while highly versatile and proficient in parallel computing, face reliability challenges due to factors such as: (1) radiation effects, (2) process, voltage, and temperature (PVT) variations, and (3) potential malicious attacks. Most fault mitigation techniques introduce significant power, performance, or area (PPA) overheads. The cost-reliability tradeoff underscores the need to explore the temporal variation in system resiliency to optimize fault-tolerant design. This dissertation presents an in-depth evaluation of system resiliency across program lifetime using a customized hierarchical fault injection methodology. This approach dynamically segments CUDA applications to enable scalable, lifetime-aware analysis of program vulnerability. The time-dependent vulnerability of four variants of YOLO, a popular real-time object detection framework that uses the Convolutional Neural Network (CNN) as its backbone, is analyzed. Though the average Silent Data Corruption (SDC) rates for YOLO variants are around 5%, the SDC rate can spike as high as 65% at certain phases of execution. The SDC rates of repeated dynamic invocations of the same static kernel also fluctuate significantly; these SDC rates can range from 0% to 30%. We observed that data transformation kernels, which accelerate convolutions and matrix multiplications on GPUs, are likely to demonstrate high vulnerability fluctuations. A case study of temporal-dependent guided selective hardening demonstrated temporal variance of program vulnerability can further improve system resiliency and reduce overheads compared to uniform protection. Results show selective hardening can reduce 56% runtime overheads and keep 97% SDC coverage for implicit convolution kernels. This research also investigates the most prominent computing patterns to characterize the intra-kernel phase-based vulnerability behavior. Temporal variance patterns are observed at the instruction Basic Block level for kernels in implicit convolution routines
Semi-Fluorinated Polymer Membranes by Ring Opening Metathesis Polymerization During Spin Coating
No full textMembrane technologies can offer an order of magnitude greater energy efficiency than thermally driven separations such as distillation. The fabrication of robust, solvent-stable active layers on inexpensive supports is essential for the widespread utilization of this technology by industry. To generate robust films, we introduce a method named spin coating ring opening metathesis polymerization (scROMP) of 5-(perfluoro-n-alkyl)norbornenes (NBFn) with perfluoroalkyl side chain lengths (n) of 4, 6, 8, and 10 to generate semi-fluorinated films on polyacrylonitrile (PAN) supports. The scROMP method combines the polymerization and deposition of the membrane selective layer into a rapid and sustainable 2 min process with well under 1 mL of solvent. The polymer films grown by this innovative method were then characterized and their effectiveness as pervaporation membranes for the dehydration of a 90 wt% aqueous ethanol solution was analyzed. pNBFn membranes exhibited greater solvent stability than their nonfluorinated polynorbornene (pNB; n = 0) counterpart while retaining excellent thermal stability, evidenced by reduced swelling in polar and nonpolar solvents, inhibition of oxidation reactions at the polymer backbone, and 40 h of continuous operation for ethanol/water separations. This performance surpasses that of commercial amorphous perfluoropolymers (APFP) studied in literature while matching their favorable stability and reducing the risk of perfluoro alkyl substance (PFAS). This study successfully demonstrates the ability of the scROMP technique to efficiently fabricate and screen specialty polymers for membrane applications and sets the stage for additional research into the use of pNBFn in polymer blends, co-polymers, or as a homopolymer for ethanol dehydration and other chemical separations including organic solvent nanofiltration
Ultra-Low-Overhead Arbitrary-Waveform Generation as a Circuit Macro: Augmenting the Characterization of Radiation-Induced Transient Effects in Highly Scaled Integrated Circuits
No full textArbitrary waveform generators (AWGs) are not typically feasible as subsystems on integrated circuits due to their size and complexity, but they are versatile circuits that are broadly useful. The purpose of this work is to show that by prioritizing minimal overhead and designing for targeted performance, as necessary for the application, it is possible to create a reusable on-chip AWG circuit macro in a small form factor. To support this claim, details and results are provided for a proof-of-concept implementation in a 45nm partially depleted silicon-on-insulator process. The presented design is able to achieve a small size by eliminating the complicated calibration and filtering circuitry commonly used in contemporary designs, instead relying on intrinsic accuracy of the base circuits. The reliability and accuracy of the AWG are driven by careful design down to the layout level, including the development of a variant of the traditional common-centroid layout technique called distributed-centroid layouts (DCL), which addresses the importance of bias circuitry in mitigating process-induced mismatch. A custom simulation workflow was developed to investigate the effectiveness of this technique at the circuit level as compared to other designs from the literature. The proof-of-concept circuit was designed to improve the characterization of radiation-induced transient effects in highly scaled integrated circuits by providing built-in self-test and hardware-emulation capabilities to a custom photocurrent measurement circuit (PMC). Details of this specific application are explored in detail, along with experimental measurements made using flash x-ray and pulsed laser sources. Alternative AWG designs that might benefit a broader application space beyond radiation effects are also provided
Segmenting and Modeling the Human Airway with Voicing or Breathing Disorders
No full textUpper airway disorders encompass various conditions that hinder breathing and/or voicing. They may arise from factors such as past airway trauma, prolonged use of breathing tubes, tracheotomy history, vocal fold nerve damage, or specific autoimmune ailments. This work is focused on the segmentation and modeling of two prominent upper airway disorders: Obstructive Sleep Apnea (OSA) and Unilateral Vocal Fold Paralysis (UVFP). For UVFP, segmentation is carried out for three rabbit larynges in various vocal fold adduction conditions. For OSA, segmentation is carried out for a patient going through Ansa Cervicalis Stimulation (ACS), a novel surgical procedure to treat OSA. Our segmentation identifies the critical components that are needed to understand the upper airway disorders and their treatment. The
OSA study also seeks to establish the theoretical and biomechanical foundation of experimental results. The finite-element model shows promising results in capturing the effects of the ACS on the movements of the tongue, epiglottis, pharynx wall, soft palate, and their interactions. Future work would aim to expand this study to include patient-specific features and more subjects to improve the robustness of the computational model and offer more insights into the ACS treatment
Governance, Competition, & Extremism: How the Structure of Social Media Platforms Radicalizes Communities
No full textIn this project, I argue that social media platform governance drives variation in online political extremism at the community level. My argument makes two claims: first, social media platforms are a kind of private governance, a new iteration of non-Weberian political authority specializing in control over information and access to public goods like attention and engagement. Whereas much of the work on platform governance has focused on interaction with existing state (primarily Western) legal systems or new transformations of human-centered design and social organization, the political institutions and processes of digital platforms are best understood within the framework of competitive state-building. This approach re-frames platforms as the result of progressive consolidation around and monopolization of information and attention. This, I argue, is the source of authority, legitimacy, and sovereignty for social media platforms. Technically, platforms have absolute sovereignty over information: control over code means control over bits. However, their claims to authority and legitimacy vary widely based on the political institutions and practices through which they exercise sovereignty. It is this political environment--and the authority and legitimacy that it generates--that can determine the network structure and level of extremism in online political communities. Second, I argue that the mechanism that connects platform political regimes and extremism in online spaces is community competition for public goods. When platforms govern through the algorithmic imposition of small, angry micro-identities and pit them against each other in a contest for information, attention, and engagement, political communities tend towards extremist ideological commitments and behaviors
Tennessee Association of Independent Schools (TAIS) Mentorship Analysis
No full textLeadership Policy and Organizations Department capstone projectThe Tennessee Association of Independent Schools (TAIS) is a non-profit organization that advocates for and supports independent schools in Tennessee. TAIS sought to understand the current state of mentorship in their 61 member schools, intending to provide tailored resources to these schools. We conducted a mixed-methods explanatory sequential study to understand how mentorship is defined across TAIS schools, the extent to which TAIS schools utilize adult-student mentoring programs in grades 5-12, and the perceived outcomes of adult-student mentorship programs in TAIS schools. We surveyed 300 educators and interviewed educators at three case study schools. Key findings include the following:
1) School characteristics, such as boarding, non-sectarian affiliation, and regional location, influence mentorship participation and program type–group advisory, one-to-one mentorship, and opt-out.
2) Relationships are the definition and the outcome of these mentorship programs.
3) Multiple goals of mentorship influence implementation challenges such as training, time, and structure.
4) With supports lacking, opportunity costs are high, particularly in the area of teacher capacity and bandwidth.Peabody College of Education and Human DevelopmentDepartment of Leadership Policy and Organization
The Unkilled: White Supremacy’s Insidious Preservation of Black Lives
No full textAlongside white supremacy’s long history of death and erasure is an equally long shadow history of its preserving black lives for its own economic and ideological ends.
Drawing a line from nineteenth century artifacts like black automatons, artifacts of lynchings made from black flesh, and plantation practices that force survival, to contemporary art, poetry, and policy, my dissertation examines the preservative impulse of white supremacy and the black response to it, both in the literal and the literary world.
Far from a benevolent action of white supremacy, this impulse toward what I call “colonial preservation” is selfishly motivated. Whether it is done by a nineteenth century plantation owner preserving the lives of the enslaved by combatting suicides or the British Museum claiming to protect rare artifacts, this is a form of preservation that in fact ends the life of those it is visited upon in order to convert them for use in the ego formation of empire.
Using the nineteenth century as a starting point rather than a container, I am able to put texts from that period, ranging from the writings on automata of Mark Twain, Edgar Allan Poe, and Frederick Douglass to novels such as Ellis’ Steam Man of the Plains and Martin Delany’s Blake; or Huts of America in conversation with twenty-first century works including the poetry of Danez Smith, the graphic novel Black, and visual art by Steve McQueen and Hiro Murai
