Matching Items (298)
Description
With the increasing focus on developing environmentally benign electronic packages, lead-free solder alloys have received a great deal of attention. Mishandling of packages, during manufacture, assembly, or by the user may cause failure of solder joint. A fundamental understanding of the behavior of lead-free solders under mechanical shock conditions is lacking. Reliable experimental and numerical analysis of lead-free solder joints in the intermediate strain rate regime need to be investigated. This dissertation mainly focuses on exploring the mechanical shock behavior of lead-free tin-rich solder alloys via multiscale modeling and numerical simulations. First, the macroscopic stress/strain behaviors of three bulk lead-free tin-rich solders were tested over a range of strain rates from 0.001/s to 30/s. Finite element analysis was conducted to determine appropriate specimen geometry that could reach a homogeneous stress/strain field and a relatively high strain rate. A novel self-consistent true stress correction method is developed to compensate the inaccuracy caused by the triaxial stress state at the post-necking stage. Then the material property of micron-scale intermetallic was examined by micro-compression test. The accuracy of this measure is systematically validated by finite element analysis, and empirical adjustments are provided. Moreover, the interfacial property of the solder/intermetallic interface is investigated, and a continuum traction-separation law of this interface is developed from an atomistic-based cohesive element method. The macroscopic stress/strain relation and microstructural properties are combined together to form a multiscale material behavior via a stochastic approach for both solder and intermetallic. As a result, solder is modeled by porous plasticity with random voids, and intermetallic is characterized as brittle material with random vulnerable region. Thereafter, the porous plasticity fracture of the solders and the brittle fracture of the intermetallics are coupled together in one finite element model. Finally, this study yields a multiscale model to understand and predict the mechanical shock behavior of lead-free tin-rich solder joints. Different fracture patterns are observed for various strain rates and/or intermetallic thicknesses. The predictions have a good agreement with the theory and experiments.
ContributorsFei, Huiyang (Author) / Jiang, Hanqing (Thesis advisor) / Chawla, Nikhilesh (Thesis advisor) / Tasooji, Amaneh (Committee member) / Mobasher, Barzin (Committee member) / Rajan, Subramaniam D. (Committee member) / Arizona State University (Publisher)
Created2011
Description
A dual-channel directional digital hearing aid (DHA) front-end using a fully differential difference amplifier (FDDA) based Microphone interface circuit (MIC) for a capacitive Micro Electro Mechanical Systems (MEMS) microphones and an adaptive-power analog font end (AFE) is presented. The Microphone interface circuit based on FDDA converts the capacitance variations into voltage signal, achieves a noise of 32 dB SPL (sound pressure level) and an SNR of 72 dB, additionally it also performs single to differential conversion allowing for fully differential analog signal chain. The analog front-end consists of 40dB VGA and a power scalable continuous time sigma delta ADC, with 68dB SNR dissipating 67u¬W from a 1.2V supply. The ADC implements a self calibrating feedback DAC, for calibrating the 2nd order non-linearity. The VGA and power scalable ADC is fabricated on 0.25 um CMOS TSMC process. The dual channels of the DHA are precisely matched and achieve about 0.5dB gain mismatch, resulting in greater than 5dB directivity index. This will enable a highly integrated and low power DHA
ContributorsNaqvi, Syed Roomi (Author) / Kiaei, Sayfe (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Chae, Junseok (Committee member) / Barnby, Hugh (Committee member) / Aberle, James T., 1961- (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis explores concept of "global bioethics" in both its development as well as its current state in an effort to understand exactly where it fits into the larger field of bioethics. Further, the analysis poses specific questions regarding what it may contribute to this field and related fields, and the possibility and scope associated with the continued development of global bioethics as its own discipline. To achieve this, the piece addresses questions regarding current opinions on the subject, the authorities and their associated publications related to global bioethics, and what the aims of the subject should be given its current state. "Global Bioethics" is a term that, while seen frequently in bioethics literature, is difficult to define succinctly. While many opinions are provided on the concept, little consensus exists regarding its application and possible contributions and, in some cases, even its very possibility. Applying ethical principles of health and medicine globally is undoubtedly complicated by the cultural, social, and geographical considerations associated with understanding health and medicine in different populations, leading to a dichotomy between two schools of thought in relation to global bioethics. These two sides consist of those who think that universality of bioethics is possible whereas the opposing viewpoint holds that relativism is the key to applying ethics on a global scale. Despite the aforementioned dichotomy in addressing applications of global bioethics, this analysis shows that the goals of the subject should be more focused on contributing to ethical frameworks and valuable types of thinking related to the ethics health and medicine on a global scale. This is achieved through an exploration of bioethics in general, health as a function of society and culture, the history and development of global bioethics itself, and an exploration of pertinent global health topics. While primarily descriptive in nature, this analysis critiques some of the current discussions and purported goals surrounding global bioethics, recommending that the field focus on fostering valuable discussion and framing of issues rather than the pursuit of concrete judgments on moral issues in global health and medicine.
ContributorsRuffenach, Stephen Charles (Author) / Robert, Jason S (Thesis advisor) / Maienschein, Jane (Committee member) / Hruschka, Daniel J (Committee member) / Arizona State University (Publisher)
Created2011
Description
The COVID-19 pandemic places significant strain on the U.S. healthcare system due to the high number of coronavirus cases. During the pandemic, there was much unknown about the virus, its course of the disease, COVID-19 diagnosis, treatments, or other imperative information needed to contain the virus. Resources within the healthcare system, such as PPE and healthcare workers, were in short supply and exacerbated the difficulty of managing the viral outbreak. Peer-reviewed articles suggest that telehealth, the application of electronic information and telecommunication technologies in healthcare, proved useful in public health and clinical care during the 2020 public health emergency due to a novel virus. The scoping review broadly assessed themes of telehealth’s strengths and weaknesses during the COVID-19 pandemic. These findings could suggest how virtual medicine may be a helpful tool to improve access in addition to the quality of care in the future of medicine. Assessments of case studies suggest that telehealth helped provide care to large patient volumes by aiding with communication, data collection, triage, remote patient monitoring, and critical care. Limitations of expanding telehealth subsequent to the pandemic include, but not limited to, a lack of national standards for practice and restrictions of utility for certain populations. Populations may include those with low socioeconomic status, specific cultural practices, and beliefs, or physical and cognitive ability barriers. Outlining the benefits and limitations of telehealth may suggest how virtual medicine can provide valuable in day-to-day medical practices and other pathogenic outbreaks.
ContributorsBlock, Andrea (Author) / Tanner, Rene (Thesis director) / Maienschein, Jane (Committee member) / Marvasti, Farshad (Committee member) / School of Life Sciences (Contributor, Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Increasing demand for high strength powder metallurgy (PM) steels has resulted in the development of dual phase PM steels. In this work, the effects of thermal aging on the microstructure and mechanical behavior of dual phase precipitation hardened powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 538oC in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite hardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties. Due to the complex non-uniform stresses and strains associated with conventional nanoindentation, micropillar compression has become an attractive method to probe local mechanical behavior while limiting strain gradients and contributions from surrounding features. In this study, micropillars of ferrite and martensite were fabricated by focused ion beam (FIB) milling of dual phase precipitation hardened powder metallurgy (PM) stainless steels. Compression testing was conducted using a nanoindenter equipped with a flat punch indenter. The stress-strain curves of the individual microconstituents were calculated from the load-displacement curves less the extraneous displacements of the system. Using a rule of mixtures approach in conjunction with porosity corrections, the mechanical properties of ferrite and martensite were combined for comparison to tensile tests of the bulk material, and reasonable agreement was found for the ultimate tensile strength. Micropillar compression experiments of both as sintered and thermally aged material allowed for investigation of the effect of thermal aging.
ContributorsStewart, Jennifer (Author) / Chawla, Nikhilesh (Thesis advisor) / Jiang, Hanqing (Committee member) / Krause, Stephen (Committee member) / Arizona State University (Publisher)
Created2011
Description
Programmable Metallization Cell (PMC) is a technology platform which utilizes mass transport in solid or liquid electrolyte coupled with electrochemical (redox) reactions to form or remove nanoscale metallic electrodeposits on or in the electrolyte. The ability to redistribute metal mass and form metallic nanostructure in or on a structure in situ, via the application of a bias on laterally placed electrodes, creates a large number of promising applications. A novel PMC-based lateral microwave switch was fabricated and characterized for use in microwave systems. It has demonstrated low insertion loss, high isolation, low voltage operation, low power and low energy consumption, and excellent linearity. Due to its non-volatile nature the switch operates with fewer biases and its simple planar geometry makes possible innovative device structures which can be potentially integrated into microwave power distribution circuits. PMC technology is also used to develop lateral dendritic metal electrodes. A lateral metallic dendritic network can be grown in a solid electrolyte (GeSe) or electrodeposited on SiO2 or Si using a water-mediated method. These dendritic electrodes grown in a solid electrolyte (GeSe) can be used to lower resistances for applications like self-healing interconnects despite its relatively low light transparency; while the dendritic electrodes grown using water-mediated method can be potentially integrated into solar cell applications, like replacing conventional Ag screen-printed top electrodes as they not only reduce resistances but also are highly transparent. This research effort also laid a solid foundation for developing dendritic plasmonic structures. A PMC-based lateral dendritic plasmonic structure is a device that has metallic dendritic networks grown electrochemically on SiO2 with a thin layer of surface metal nanoparticles in liquid electrolyte. These structures increase the distribution of particle sizes by connecting pre-deposited Ag nanoparticles into fractal structures and result in three significant effects, resonance red-shift, resonance broadening and resonance enhancement, on surface plasmon resonance for light trapping simultaneously, which can potentially enhance thin film solar cells' performance at longer wavelengths.
ContributorsRen, Minghan (Author) / Kozicki, Michael (Thesis advisor) / Schroder, Dieter (Committee member) / Roedel, Ronald (Committee member) / Barnaby, Hugh (Committee member) / Arizona State University (Publisher)
Created2011
Description
The goal of science education in the United States is promoting scientific literacy for all students. The goal necessitates understanding the nature of science-what science is as a body of knowledge, explanatory tool, and human enterprise. The history of science is one of the most long-standing pedagogical methods of getting at the nature of science. But scientific literacy also encompasses education in scientific inquiry, and in the relationships among science, technology, and society (STS), as well as fact and theory-based subject-matter content. Since the beginning of the standards-based reform movement (circa 1983) many attempts have been made to codify the components of scientific literacy. National level voluntary standards have lead to state standards. Under No Child Left Behind, those state standards have become integral parts of the educational system. Standards are political in nature, yet play the role of intended curriculum. I examine one thread of scientific literacy, the history and nature of science, from its beginnings in science education through the political perturbations of the last thirty years. This examination of "the history and nature of science" through the history of standards-based reform sheds light on our changing conception of scientific literacy.
ContributorsLawrence, Cera Ruth (Author) / Maienschein, Jane (Thesis advisor) / Luft, Julie (Committee member) / LePore, Paul (Committee member) / Arizona State University (Publisher)
Created2011
Description
Optical receivers have many different uses covering simple infrared receivers, high speed fiber optic communication and light based instrumentation. All of them have an optical receiver that converts photons to current followed by a transimpedance amplifier to convert the current to a useful voltage. Different systems create different requirements for each receiver. High speed digital communication require high throughput with enough sensitivity to keep the bit error rate low. Instrumentation receivers have a lower bandwidth, but higher gain and sensitivity requirements. In this thesis an optical receiver for use in instrumentation in presented. It is an entirely monolithic design with the photodiodes on the same substrate as the CMOS circuitry. This allows for it to be built into a focal-plane array, but it places some restriction on the area. It is also designed for in-situ testing and must be able to cancel any low frequency noise caused by ambient light. The area restrictions prohibit the use of a DC blocking capacitor to reject the low frequency noise. In place a servo loop was wrapped around the system to reject any DC offset. A modified Cherry-Hooper architecture was used for the transimpedance amplifier. This provides the flexibility to create an amplifier with high gain and wide bandwidth that is independent of the input capacitance. The downside is the increased complexity of the design makes stability paramount to the design. Another drawback is the high noise associated with low input impedance that decouples the input capacitance from the bandwidth. This problem is compounded by the servo loop feed which leaves the output noise of some amplifiers directly referred to the input. An in depth analysis of each circuit block's noise contribution is presented.
ContributorsLaFevre, Kyle (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Vermeire, Bert (Committee member) / Arizona State University (Publisher)
Created2011
Description
More than 90 million Americans suffer from low health literacy levels that can lead to detrimental health practices. One of the greatest issues stemming from low health literacy is the misuse of medication, which results in 125,000 deaths per year and close to $200 billion dollars in health care funds (Ngoh 2009). With their implementation into neighborhood settings and consequently the everyday lives of individuals, pharmacies show potential in being great assets towards increasing health literacy on an individual and societal level. However, pharmacists must first be made aware of the opportunities and challenges that exist concerning this effort. Through a three step literature review and corresponding comparative analysis, the results of this study show that pharmacists should focus on four main areas: overall assessment of health literacy in a pharmacy setting, individualization and tailoring of health/ medication plans, development of verbal and written communication tools, and the pharmacist-patient relationship. Each area presents a set of opportunities and challenges that must be accounted for in order to design more effective initiatives and tools in the pharmacists' aim to increase health literacy.
ContributorsMergens, Rianna Lynn (Author) / Robert, Jason Scott (Thesis director) / Maienschein, Jane (Committee member) / Kinzig, Ann (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
ABSTRACT Whole genome sequencing (WGS) and whole exome sequencing (WES) are two comprehensive genomic tests which use next-generation sequencing technology to sequence most of the 3.2 billion base pairs in a human genome (WGS) or many of the estimated 22,000 protein-coding genes in the genome (WES). The promises offered from WGS/WES are: to identify suspected yet unidentified genetic diseases, to characterize the genomic mutations in a tumor to identify targeted therapeutic agents and, to predict future diseases with the hope of promoting disease prevention strategies and/or offering early treatment. Promises notwithstanding, sequencing a human genome presents several interrelated challenges: how to adequately analyze, interpret, store, reanalyze and apply an unprecedented amount of genomic data (with uncertain clinical utility) to patient care? In addition, genomic data has the potential to become integral for improving the medical care of an individual and their family, years after a genome is sequenced. Current informed consent protocols do not adequately address the unique challenges and complexities inherent to the process of WGS/WES. This dissertation constructs a novel informed consent process for individuals considering WGS/WES, capable of fulfilling both legal and ethical requirements of medical consent while addressing the intricacies of WGS/WES, ultimately resulting in a more effective consenting experience. To better understand components of an effective consenting experience, the first part of this dissertation traces the historical origin of the informed consent process to identify the motivations, rationales and institutional commitments that sustain our current consenting protocols for genetic testing. After understanding the underlying commitments that shape our current informed consent protocols, I discuss the effectiveness of the informed consent process from an ethical and legal standpoint. I illustrate how WGS/WES introduces new complexities to the informed consent process and assess whether informed consent protocols proposed for WGS/WES address these complexities. The last section of this dissertation describes a novel informed consent process for WGS/WES, constructed from the original ethical intent of informed consent, analysis of existing informed consent protocols, and my own observations as a genetic counselor for what constitutes an effective consenting experience.
ContributorsHunt, Katherine (Author) / Hurlbut, J. Benjamin (Thesis advisor) / Robert, Jason S. (Thesis advisor) / Maienschein, Jane (Committee member) / Northfelt, Donald W. (Committee member) / Marchant, Gary (Committee member) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2013