Fatigue Behavior of a Zirconium-Based Bulk Metallic Glass

Although the mechanical behavior of Zr-based bulk metallic glasses (BMGs) has been studied, fatigue studies in controlled environments and testing conditions have not been adequately performed or understood. Early fatigue examinations of rectangular bar specimens tested in bending had resulted in fatigue strengths substantially lower than anticipated [1,2,3,4,5]. Preliminary work performed by Peter et al. and Wang et al. on uniaxial button-head specimens have yielded in very different fatigue behavior with fatigue-endurance limits comparable to conventional high-strength, crystalline alloys [6,7,8,9,10]. Between all S-N results studied, the fatigue-endurance limits for Zr-based BMGs have been observed to range from 150 MPa to 1 GPa [1,2,3,4,5,6,7,8,9,10]. Testing conditions, sample preparation, and the quality of the amorphous alloy may provide the understanding for this variability in fatigue behavior. In the following thesis, several investigations were engaged to better understand changeability in the fatigue behavior of a Zr-based BMG, Zr52.5Al10Ti5Cu17.9Ni14.6 (at. %). The studies were primarily conducted to explain how the loading conditions, the sample preparation, the quality of the glass materials, the test environment, or the chemical composition affect the degradation behavior of BMGs. Fabrication, corrosion, metallography, and cyclic loading were types of investigations performed. Fatigue testing was conducted in air and vacuum environments. By comparing the results, the environmental effects due to water vapor (in air) on the fatigue lifetime of BMG-11 were evaluated. It was concluded that water vapor does not have a detrimental effect on the fatigue lifetime of BMG-11. Indeed, the observed lifetimes in vacuum were shorter than those in air. Early fatigue tests in vacuum with and without the use of an ionization gauge seemed to indicate that the dissociation of the residual water vapor to atomic hydrogen in vacuum via a hot tungsten-filament ionization gauge could be a factor in the shorter fatigue lifetimes in vacuum than in air. Further testing has disproved this hypothesis. Closer examinations of the surface of multiple samples has led to the discovery of mechanical wear and fused copper (from copper grips) near the crack initiation site. Because of the possible impact the ionization gauge may have had on the fatigue behavior of BMG-11, hydrogen-charged samples were tested in air and compared to uncharged samples in order to understand any detrimental effects hydrogen may have on the fatigue lifetime around the fatigue-endurance limit. Though the ionization gauge did not seem to play a detrimental role in the fatigue lifetime of amorphous samples tested in vacuum, charged hydrogen embrittles the material with increases in hardness values and lower fatigue lifetimes for cathodically-charged samples. These results could impact Zr-based BMGs’ usefulness in hydrogen-rich environments. Fatigue studies were performed on button head, uniaxial specimens with different surface finishes in order to better understand the influence the average surface roughness and/or critical surface defects may have on the fatigue behavior. It was hypothesized that geometric, surface flaws could lower the observed life of a BMG sample by shortening the crack initiation phase and providing local stress concentrators. Careful studies of surface conditions indicate that fatigue-endurance limits are greatly impacted by the average surface roughness with possible reductions over fifty percent. Lastly, a rectangular bend-bar sample was finished with a coarse grit paper on the tension side of the sample, and observed for the location of crack initiation. Four-point and three-point bending fatigue studies were conducted to observe the effect of variability in loading conditions versus uniaxial tension studies, and to observe any impact from testing volume on the fatigue life of BMG-11. Both, three point and four point bend results seemed to exhibit slightly better fatigue behavior compared to the uniaxial tests. However, little difference was observed between three-and four-point bending. These results are similar to those found with a preliminary study of uniaxial specimens with varying testing gauge lengths. Lastly, a study was performed to better understand the effect crystallinity has on the fatigue behavior of Zr-based bulk metallic glasses. The crystalline phases of BMG-11 have an extremely low ultimate bending strength, around 100 MPa, and are very brittle. Any interfaces between crystalline impurities and the glassy matrix are prime locations for crack-initiation sites. A large volume fraction of crystallinity has been shown to dramatically lower the fatigue lifetime of a Zr-based BMG. This careful study of fatigue behavior leads to the conclusion that the detrimental effect crystallinity and geometrical surface defects have on the fatigue-endurance limit and the fatigue lifetime explain the variability in previously reported results

Status Offenders Should Be Removed From the Juvenile Court

Inadequate financial resources and overcrowded juvenile placement facilities have frequently been cited as grounds for the abrogation of the juvenile court\u27s practice of retaining jurisdiction over status offenders. In this article, Judge Quinn suggests the existence of even more compelling reasons which support diversion of status offenders to programs better suited to their particular needs. The author contends that the juvenile court\u27s jurisdiction should be confined to matters of fact-finding and adjudication, rather than intruding into areas within the domain of the parents, and into areas in which the court lacks the necessary expertise. It is argued that diversion of status offenders would also eliminate the traumatic experience of courtroom appearances and the frequently unnecessary period of incarceration. Abrogation of jurisdiction would enable the court to devote its energies and resources to its primary concerns of abuse and juvenile crime

Metal-catalyst-free growth of silica nanowires and carbon nanotubes using Ge nanostructures

The use of Ge nanostructures is investigated for the metal-catalyst-free growth of silica nanowires and carbon nanotubes (CNTs). Silica nanowires with diameters of 10-50 nm and lengths of ? 1 ?m were grown from SiGe islands, Ge dots, and Ge nanoparticles. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) reveal that the nanowires grow from oxide nanoparticles on the sample surface. We propose that the growth mechanism is thermal diffusion of oxide through the GeO2 nanostructures. CNTs with diameters 0.6-2.5 nm and lengths of less than a few ?m were similarly grown by chemical vapor deposition from different types of Ge nanostructures. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. HRTEM images reveal that the CNTs also grow from oxide nanoparticles, comprising a mixture of GeO2 and SiO2

Growth of Carbon Nanotubes on HfO2 towards Highly Sensitive Nano-Sensors

Carbon nanotube (CNT) growth on HfO2 is reported for the first time. The process uses a combination of Ge and Fe nanoparticles and achieves an increase in CNT density from 0.15 to 6.2 mm length/mm2 compared with Fe nanoparticles alone. The synthesized CNTs are assessed by the fabrication of back-gate CNT field-effect transistors with Al source/drain contacts for nano-sensor applications. The devices exhibit excellent p-type behavior with an Ion=Ioff ratio of 105 and a steep sub-threshold slope of 130 mV/dec

Managing the opportunities and risks associated with disruptive technologies: space law in New Zealand

A key challenge for regulators is how to enable entrepreneurship and innovation while managing the risks associated with rapidly evolving technologies and associated market change. A number of technologies could be used to illustrate this problem, such as the internet, gene editing and driverless vehicles. However, the Ministry of Business, Innovation and Employment (MBIE) recently had to face  this specific issue in relation to space activities

Bayesian naturalness of the CMSSM and CNMSSM

The recent discovery of the 125.5 GeV Higgs boson at the LHC has fueled interest in the next-to-minimal supersymmetric standard model (NMSSM) as it may require less fine-tuning than the minimal model to accommodate such a heavy Higgs. To this end we present Bayesian naturalness priors to quantify fine-tuning in the (N)MSSM. These priors arise automatically as Occam razors in Bayesian model comparison and generalize the conventional Barbieri-Giudice measure. In this paper we show that the naturalness priors capture features of both the Barbieri-Giudice fine-tuning measure and a simple ratio measure that has been used in the literature. We also show that according to the naturalness prior the constrained version of the NMSSM is less tuned than the CMSSM.Comment: 8 pages and 5 figure

Selecting, Implementing and Adapting Youth Empowerment Solutions

YES is an evidence-based program that empowers youth to make positive changes in their communities and to work with adults who support their efforts. The goals of the YES program are to: 1) provide youth with opportunities for meaningful involvement in preventing youth violence and creating community change; 2) enhance the ability of adults to support youth in an empowerment framework; and 3) change the social and physical environment to reduce and prevent violence (especially youth violence). The purpose of this guide is to assist organizations and communities in making decisions about selecting, implementing and adapting the Youth Empowerment Solutions (YES) program. It is designed for individuals who are responsible for choosing, supervising and carrying out youth programs. This guide is intended to be used in conjunction with the Youth Empowerment Solutions for Peaceful Communities curriculum, which is available for download through the YES website: http://yes.sph.umich.edu/curriculum/CDC Foundationhttp://deepblue.lib.umich.edu/bitstream/2027.42/110221/1/YES Adaptation Guide FINAL.pdfDescription of YES Adaptation Guide FINAL.pdf : YES Adaptation Guid

A modelling evaluation of electromagnetic fields emitted by buried subsea power cables and encountered by marine animals : considerations for marine renewable energy development

Part of this work was supported by the Bureau of Ocean Energy Management (contract number M14PC00009).The expanding marine renewable energy industry will increase the prevalence of electromagnetic fields (EMFs) from power cables in coastal waters. Assessments of environmental impacts are required within licensing/permitting processes and increased prevalence of cables will increase questions concerning EMF emissions and potential cumulative impacts. It is presumed that protecting a cable by burial, may also mitigate EMF emissions and potential impacts on species. Focussing on a bundled high voltage direct current (HVDC) transmission cable, we use computational and interpretive models to explore the influence of cable properties and burial depth on the DC magnetic field (DC-MF) potentially encountered by receptive species. Greater cable pair separation increased the deviations from the geomagnetic field and while deeper burial reduced the deviations, the DC-MF was present at intensities perceivable by receptive species. An animal moving along a cable route may be exposed to variable EMFs due to varied burial depth and that combined with an animal’s position in the water column determines the distance from source and EMF exposure. Modelling contextually realistic scenarios would improve assessments of potential effects. We suggest developers and cable industries make cable properties and energy transmission data available, enabling realistic modelling and environmental assessment supporting future developments.PostprintPeer reviewe

Jungle perch Kuhlia rupestris fingerling production manual

This manual consists of written descriptions of jungle perch Kuhlia rupestris production and video material to demonstrate each of the key production steps. Video links are at the end of each major written section in the document. To activate the link use ctrl click. The videos enhance the instructive ability of this manual. The keys to producing jungle perch are: - maintaining broodstock in freshwater or low salinity water less than 5 ppt - spawning fish in full seawater at 28C - incubating eggs in full seawater. Salinities must not be less than 32 ppt - ensuring that first feed jungle perch larvae have an adequate supply of copepod nauplii - rearing larvae in full seawater under bright light - use of gentle aeration in tanks - postponing spawns until adequate densities of copepod nauplii are present in ponds - sustaining copepod blooms in ponds for at least 20 days - avoiding use of paddlewheels in ponds - supplementary feeding with Artemia salina and weaning diets from 20 days after hatch - harvesting of fingerlings or fry after they are 25-30 mm in length (50 to 60 days post hatch) - covering tanks of fingerlings with 5 mm mesh and submerging freshwater inlets to prevent jumping

A security architecture for high performance computing facilities

High Performance Computing facilities that use cluster computing to provide computational services to scientists and engineers have become widespread, with such facilities available at most major research universities worldwide, as well as in government and industrial research settings. Until recently HPC facilities have largely neglected security, or at the very least treated security as an afterthought in a world where performance is the number one priority. In this paper we present a security architecture, and associated security best practices, for high performance computing facilities. Our architecture aims to address concerns about HPC security raised in the literature [1-4], and specifically to mitigate the risks identified in the leading threat model for cluster computing [5], developed at the National Center for Supercomputing Applications. Our architecture and best practices attempt to provide the best tradeoff between adequate security measures and high performance. We also consider privacy and intellectual property issues, and how shared HPC facilities may put measures in place to convince their users that their data is protected from both external threats and internal, authorized cluster users not affiliated with their projects