916 research outputs found
Black Hawk Countyâs Approach to Lead Poisoning
Scott County, IA is facing a community lead poisoning problem, much like other counties in the state. One of these are Black Hawk County, northwest of Scott. Black Hawk County approached the lead poisoning problem by partnering with organizations including the University of Northern Iowa, the Iowa Poison Control Center, and a multitude of medical groups. Funding, procedures for action, and education were also factors in assessing the lead problem. Black Hawk Countyâs number of lead poisonings decreased after approaching the problem, while Scott Countyâs problem worsened. By using similar methods, we hope that Scott County\u27s lead problem will also decrease
Crack-Net: Prediction of Crack Propagation in Composites
Computational solid mechanics has become an indispensable approach in
engineering, and numerical investigation of fracture in composites is essential
as composites are widely used in structural applications. Crack evolution in
composites is the bridge to elucidate the relationship between the
microstructure and fracture performance, but crack-based finite element methods
are computationally expensive and time-consuming, limiting their application in
computation-intensive scenarios. Here we propose a deep learning framework
called Crack-Net, which incorporates the relationship between crack evolution
and stress response to predict the fracture process in composites. Trained on a
high-precision fracture development dataset generated using the phase field
method, Crack-Net demonstrates a remarkable capability to accurately forecast
the long-term evolution of crack growth patterns and the stress-strain curve
for a given composite design. The Crack-Net captures the essential principle of
crack growth, which enables it to handle more complex microstructures such as
binary co-continuous structures. Moreover, transfer learning is adopted to
further improve the generalization ability of Crack-Net for composite materials
with reinforcements of different strengths. The proposed Crack-Net holds great
promise for practical applications in engineering and materials science, in
which accurate and efficient fracture prediction is crucial for optimizing
material performance and microstructural design
Preparation and structural properties of thin films and multilayers of the Heusler compounds Cu2MnAl, Co2MnSn, Co2MnSi and Co2MnGe
We report on the preparation of thin films and multilayers of the
intermetallic Heusler compound CuMnAl, Co2MnSn, Co2MnSi and Co2MnGe by
rf-sputtering on MgO and Al2O3 substrates. Cu2MnAl can be grown epitaxially
with (100)-orientation on MgO (100) and in (110)-orientation on Al2O3 a-plane.
The Co based Heusler alloys need metallic seedlayers to induce high quality
textured growth. We also have prepared multilayers with smooth interfaces by
combining the Heusler compounds with Au and V. An analysis of the ferromagnetic
saturation magnetization of the films indicates that the Cu2MnAl-compound tends
to grow in the disordered B2-type structure whereas the Co-based Heusler alloy
thin films grow in the ordered L21 structure. All multilayers with thin layers
of the Heusler compounds exhibit a definitely reduced ferromagnetic
magnetization indicating substantial disorder and intermixing at the
interfaces.Comment: 21 pages, 8 figure
Endoscopic Endonasal Transclival Approaches: Case Series & Outcomes for Different Clival Regions
Objective Transclival endoscopic endonasal approaches to the skull base are novel with few published cases.We report our institutionâs experience with this technique and discuss outcomes according to the clival region involved. Design Retrospective case series. Setting Tertiary care academic medical center Participants All patients who underwent endoscopic endonasal transclival approaches for skull base lesions from 2008 to 2012. Main Outcome Measures Pathologies encountered, mean intraoperative time, intraoperative complications, gross total resection, intraoperative cerebrospinal fluid (CSF) leak, postoperative CSF leak, postoperative complications, and postoperative clinical course. Results A total of 49 patients underwent 55 endoscopic endonasal transclival approaches. Pathology included 43 benign and 12 malignant lesions. Mean follow-up was 15.4 months. Mean operative time was 167.9 minutes, with one patient experiencing an intraoperative internal carotid artery injury. Of the 15 cases with intraoperative cerebrospinal fluid (CSF) leaks, 1 developed postoperative CSF leak (6.7%). There were six other postoperative complications: four systemic complications, one case of meningitis, and one retropharyngeal abscess. Gross total resection was achieved for all malignancies approached with curative intent. Conclusions This study provides evidence that endoscopic endonasal transclival approaches are a safe and effective strategy for the surgical management of a variety of benign and malignant lesions
Complications of Open Approaches to the Skull Base in the Endoscopic Era
Objective It is important to characterize the developing complication profile of the open approach as it becomes reserved for more complex disease during the endoscopic era. Our objective was to characterize complication rates of current open skull base surgery
A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide
A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was
initially prepared in water. This was concentrated by centrifugation and was
mixed with a liquid epoxy resin. The remaining water was removed by evaporation,
leaving a GO dispersion in epoxy resin. A stoichiometric amount of an
anhydride curing agent was added to this epoxy-resin mixture containing the
GO nanosheets, which was then cured at 90 C for 1 h followed by 160 C for
2 h. A second thermal treatment step of 200 C for 30 min was then undertaken
to reduce further the GO in situ in the epoxy nanocomposite. An examination of
the morphology of such nanocomposites containing reduced graphene oxide
(rGO) revealed that a very good dispersion of rGO was achieved throughout the
epoxy polymer. Various thermal and mechanical properties of the epoxy
nanocomposites were measured, and the most noteworthy finding was a
remarkable increase in the thermal conductivity when relatively very low contents
of rGO were present. For example, a value of 0.25 W/mK was measured at
30 C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO
present, which represents an increase of *40% compared with that of the
unmodified epoxy polymer. This value represents one of the largest increases in
the thermal conductivity per wt% of added rGO yet reported. These observations
have been attributed to the excellent dispersion of rGO achieved in these
nanocomposites made via this facile production method. The present results
show that it is now possible to tune the properties of an epoxy polymer with a
simple and viable method of GO addition.
A
Numerical modelling of the rise of Taylor bubbles through a change in pipe diameter
The rise of Taylor bubbles through expansions in vertical pipes is modelled using Computational Fluid Dynamics. The predictions from the models are compared against existing experimental work and show good agreement, both quantitatively and qualitatively. Many workers, including the present work, find that, as the bubble passes through the expansion, it will either remain intact or split into one or more daughter bubbles. We find that the critical length of bubble, defined as the maximum length that will pass through intact, is proportional to the cosecant of the angle of the expansion. Further, we show that for an abrupt expansion, the critical bubble length became unaffected by the walls of the upper pipe as the diameter was increased
Global well-posedness of the 3-D full water wave problem
We consider the problem of global in time existence and uniqueness of
solutions of the 3-D infinite depth full water wave problem. We show that the
nature of the nonlinearity of the water wave equation is essentially of cubic
and higher orders. For any initial interface that is sufficiently small in its
steepness and velocity, we show that there exists a unique smooth solution of
the full water wave problem for all time, and the solution decays at the rate
.Comment: 60 page
On the finite-time splash and splat singularities for the 3-D free-surface Euler equations
We prove that the 3-D free-surface incompressible Euler equations with
regular initial geometries and velocity fields have solutions which can form a
finite-time "splash" (or "splat") singularity first introduced in [9], wherein
the evolving 2-D hypersurface, the moving boundary of the fluid domain,
self-intersects at a point (or on surface). Such singularities can occur when
the crest of a breaking wave falls unto its trough, or in the study of drop
impact upon liquid surfaces. Our approach is founded upon the Lagrangian
description of the free-boundary problem, combined with a novel approximation
scheme of a finite collection of local coordinate charts; as such we are able
to analyze a rather general set of geometries for the evolving 2-D free-surface
of the fluid. We do not assume the fluid is irrotational, and as such, our
method can be used for a number of other fluid interface problems, including
compressible flows, plasmas, as well as the inclusion of surface tension
effects.Comment: 40 pages, 5 figures, to appear in Comm. Math. Phys, abstract added
for UK RE
Lightning strike damage resistance of carbonâfiber composites with nanocarbonâmodified epoxy matrices
Carbonâfiber reinforced polymer (CFRP) composites are replacing metal alloys in aerospace structures, but they can be vulnerable to lightning strike damage if not adequately protected due to the poor electrical conductivity of the polymeric matrix. In the present work, to improve the conductivity of the CFRP, two electrically conductive epoxy formulations were developed via the addition of 0.5 wt% of graphene nanoplatelets (GNPs) and a hybrid of 0.5 wt% of GNPs/carbon nanotubes (CNTs) at an 8:2 mass ratio. Unidirectional CFRP laminates were manufactured using resinâinfusion under flexible tooling (RIFT) and wet layâup (WL) processes, and subjected to simulated lightning strike tests. The electrical performance of the RIFT plates was far superior to that of the WL plates, independent of matrix modification, due to their greater carbonâfiber volume fraction. The GNPâmodified panel made using RIFT demonstrated an electrical conductivity value of 8 S/cm. After the lightning strike test, the CFRP panel remains largely unaffected as no perforation occurs. Damage is limited to matrix degradation within the top ply at the point of impact and localized charring of the surface. The GNPâmodified panel showed a comparable level of resistance against lightning damage with the existing copper mesh technology, offering at the same time a 20% reduction in the structural weight. This indicates a feasible route to improve the lightning strike damage resistance of carbonâfiber composites without the addition of extra weight, hence reducing fuel consumption but not safety
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