552 research outputs found
Numerical and experimental development of cupronickel filler brazed joints for divertor and first wall components in DEMO fusion reactor
The brazeability of a cupronickel commercial alloy (Cu10Ni) was evaluated for its use as a filler alloy for high-
temperature joining of tungsten to the reduced activation ferritic/martensitic steel EUROFER 97 (W-E) and
between tungsten base materials (W-W) for its application at the first wall and divertor of future fusion reactors.
In addition, given the importance of the residual stresses in these heterogenous joints, a study of the brazing
conditions and the impact of the selected filler has been conducted using numerical software to understand its
impact on the quality of the joint.
Two thermal cycles were evaluated (1165 C and 1190C) and selected based on the thermal characterization
of the filler alloy. The microstructural examination revealed that, in W-E joints, nickel acts as an activator
element, reacting and forming interfacial layers at the EUROFER 97 - Cu10Ni interface. In the case of the W-W
joints, a lower level of diffusion phenomenon and metallurgical interaction between Cu10Ni and base materials
were observed. The hardness profile indicated that the hardening process of EUROFER 97 was associated with
the formation of untempered martensite. On the other hand, tungsten kept the received hardness. The me-
chanical characterization by shear test reported similar values between both types of joints carried out at 1190C
but different when the temperature was increased (1165 C), associated with the brittle character of tungsten and
its lower metallurgical interaction.
The numerical analysis of the brazing process carried out with ANSYS software shows that residual stresses are
accumulated mainly at the interfaces. The information provided by the simulation shows, for a 50 μm filler
thickness, the importance of mitigating the residual stress by selecting a filler with an intermediate Coefficient of
Thermal Expansion (CTE) that alleviates mechanical stresses relative to the base materials
Identification of animal species housed and herding practices in ancient sediments from the Vallone Inferno rock-shelter (Scillato, Sicily, Italy) using faecal biomarkers, hormones, and their metabolites
The interest in the identification of animal species housed in caves or rock-shelters used as livestock pen and herding management along prehistoric and historic ages, is increasing to understand better the development of pastoral activities. In this manuscript, a method for the quantification of β-sterol/phytosterols, bile acids, hormones and hormones metabolites has been developed to determine the main pastoral activities carried out in Vallone Inferno rock-shelter (Scillato, Sicily, Italy) from Middle Neolithic to Early Middle Age. According to the result obtained, the main animals housed in the rock-shelter went gradually changing from ovicaprids in Middle Neolithic to pigs in Early Middle Age. Additionally, new proxies (progesterone/Ʃbile acids and metabolites of progesterone/Ʃbile acids) were used to detect a high hormonal activity at Early Middle Age samples related with female pig management
In Vitro
Purpose. To evaluate the dose effect of vitamin K3 on wound healing mechanisms. Methods. Conjunctival fibroblasts were incubated for 24 hours. An artificial wound was made and the cells were incubated with fresh medium plus doses of vitamin K3 to be tested. Wound repair was monitored at 0, 18, 24, and 48 hours. Proliferation was measured in actively dividing cells by [3H]thymidine uptake. Six different groups were tested: group 1/no drugs added, group 2/ethanol 0.1%, group 3/vitamin K3 1 mg/L, group 4/vitamin K3 2 mg/L, group 5/vitamin K3 4 mg/L, and group 6/vitamin K3 6 mg/L. Each experiment was carried out in triplicate and 4 times. Results. There were no differences among groups at the initial time. In vitro wound repair was slower in groups 4, 5, and 6. There were no differences between control and ethanol groups and between control and vitamin K3 1 mg/L groups. Fibroblast mitogenic activity was statistically decreased in all vitamin K groups; statistical differences were found among vitamin K3 1 mg/mL and higher doses too. In groups 5 and 6, cellular toxicity was presented. Conclusions. Vitamin K3 is able to inhibit fibroblast proliferation. Vitamin K3 2 mg/L or higher doses inhibit wound healing repair, exhibiting cellular toxicity at 4 and 6 mg/L
Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab
MeV-GeV dark matter (DM) is theoretically well motivated but remarkably
unexplored. This Letter of Intent presents the MeV-GeV DM discovery potential
for a 1 m segmented plastic scintillator detector placed downstream of the
beam-dump at one of the high intensity JLab experimental Halls, receiving up to
10 electrons-on-target (EOT) in a one-year period. This experiment
(Beam-Dump eXperiment or BDX) is sensitive to DM-nucleon elastic scattering at
the level of a thousand counts per year, with very low threshold recoil
energies (1 MeV), and limited only by reducible cosmogenic backgrounds.
Sensitivity to DM-electron elastic scattering and/or inelastic DM would be
below 10 counts per year after requiring all electromagnetic showers in the
detector to exceed a few-hundred MeV, which dramatically reduces or altogether
eliminates all backgrounds. Detailed Monte Carlo simulations are in progress to
finalize the detector design and experimental set up. An existing 0.036 m
prototype based on the same technology will be used to validate simulations
with background rate estimates, driving the necessary RD towards an
optimized detector. The final detector design and experimental set up will be
presented in a full proposal to be submitted to the next JLab PAC. A fully
realized experiment would be sensitive to large regions of DM parameter space,
exceeding the discovery potential of existing and planned experiments by two
orders of magnitude in the MeV-GeV DM mass range.Comment: 28 pages, 17 figures, submitted to JLab PAC 4
Flow climatology for physicochemical properties of dichotomous aerosol over the western North Atlantic Ocean at Bermuda
Dichotomous aerosols (nominal super- and sub-μm-diameter size
fractions) in sectored on-shore flow were sampled daily from July 2006
through June 2009, at the Tudor Hill Atmospheric Observatory (THAO) on the
western coast of Bermuda (32.27° N, 64.87° W) and
analyzed for major chemical and physical properties. FLEXPART retroplumes
were calculated for each sampling period and aerosol properties were
stratified accordingly based on transport from different regions. Transport
from the northeastern United States (NEUS) was associated with significantly
higher (factors of 2 to 3 based on median values) concentrations of bulk
particulate non-sea-salt (nss) SO42-,
NO3-, and NH4+
and associated scattering and absorption at 530 nm, relative to transport
from Africa (AFR) and the oceanic background. These differences were driven
primarily by higher values associated with the sub-μm size fraction
under NEUS flow. We estimate that 75(±3)% of the NEUS nss
SO42- was anthropogenic in origin, while only 25(±9)% of the
AFR nss SO42- was anthropogenic. Integrating over all transport
patterns, the contribution of anthropogenic sulfate has dropped 14.6% from
the early 1990s. Bulk scattering was highly correlated with bulk nss
SO42- in all flow regimes but the corresponding regression slopes
varied significantly reflecting differential contributions to total
scattering by associated aerosol components. Absorption by super-μm
aerosol in transport from the NEUS versus AFR was similar although the
super-μm aerosol size fraction accounted for a relatively greater
contribution to total absorption in AFR flow. Significantly greater
absorption Ångström exponents (AAEs) for AFR flow reflects the
wavelength dependence of absorption by mineral aerosols; lower AAEs for NEUS
flow is consistent with the dominance of absorption by combustion-derived
aerosols. Higher AOD associated with transport from both the NEUS and AFR
relative to oceanic background flow results in a top of atmosphere direct
radiative forcing on the order of −1.6 to −2.5 W m−2,
respectively, showing these aerosols drive cooling. The dominance of
transport from the NEUS on an annual basis coupled with the corresponding
decreases in anthropogenic nss SO42- aerosols since the early 1990s
implies that emission reductions in the US account for a decline in
atmospheric cooling over the western North Atlantic Ocean during this period
Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks
In this report we review recent theoretical progress and the latest
experimental results in jet substructure from the Tevatron and the LHC. We
review the status of and outlook for calculation and simulation tools for
studying jet substructure. Following up on the report of the Boost 2010
workshop, we present a new set of benchmark comparisons of substructure
techniques, focusing on the set of variables and grooming methods that are
collectively known as "top taggers". To facilitate further exploration, we have
attempted to collect, harmonise, and publish software implementations of these
techniques.Comment: 53 pages, 17 figures. L. Asquith, S. Rappoccio, C. K. Vermilion,
editors; v2: minor edits from journal revision
Where the Sidewalk Ends: Jets and Missing Energy Search Strategies for the 7 TeV LHC
This work explores the potential reach of the 7 TeV LHC to new colored states
in the context of simplified models and addresses the issue of which search
regions are necessary to cover an extensive set of event topologies and
kinematic regimes. This article demonstrates that if searches are designed to
focus on specific regions of phase space, then new physics may be missed if it
lies in unexpected corners. Simple multiregion search strategies can be
designed to cover all of kinematic possibilities. A set of benchmark models are
created that cover the qualitatively different signatures and a benchmark
multiregion search strategy is presented that covers these models.Comment: 30 pages, 8 Figures, 3 Tables. Version accepted at JHEP. Minor
changes. Added figur
Mechanical properties of pristine and nanoporous graphene
We present molecular dynamics simulations of monolayer graphene under uniaxial tensile loading. The Morse, bending angle, torsion and Lennard-Jones potential functions are adopted within the mdFOAM library in the OpenFOAM software, to describe the molecular interactions in graphene. A well-validated graphene model using these set of potentials is not yet available. In this work, we investigate the accuracy of the mechanical properties of graphene when derived using these simpler potentials, compared to the more commonly used complex potentials such as the Tersoff-Brenner and AIREBO potentials. The computational speed-up of our approach, which scales O(1.5N), where N is the number of carbon atoms, enabled us to vary a larger number of system parameters, including graphene sheet orientation, size, temperature and concentration of nanopores. The resultant effect on the elastic modulus, fracture stress and fracture strain is investigated. Our simulations show that graphene is anisotropic, and its mechanical properties are dependant on the sheet size. An increase in system temperature results in a significant reduction in the fracture stress and strain. Simulations of nanoporous graphene were created by distributing vacancy defects, both randomly and uniformly, across the lattice. We find that the frac- ture stress decreases substantially with increasing defect density. The elastic modulus was found to be constant up to around 5% vacancy defects, and decreases for higher defect densities
The fine-scale structure of the trade wind cumuli over Barbados – An introduction to the CARRIBA project
The CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) project, focused on high resolution and collocated measurements of thermodynamic, turbulent, microphysical, and radiative properties of trade wind cumuli over Barbados, is introduced. The project is based on two one-month field campaigns in November 2010 (climatic wet season) and April 2011 (climatic dry season). Observations are based on helicopter-borne and ground-based measurements in an area of 100 km2 off the coast of Barbados. CARRIBA is accompanied by long-term observations at the Barbados Cloud Observatory located at the East coast of Barbados since early in 2010 and which provides a longer-term context for the CARRIBA measurements. The deployed instrumentation and sampling strategy are presented together with a classification of the meteorological conditions. The two campaigns were influenced by different air masses advected from the Caribbean area, the Atlantic Ocean, and the African continent which led to distinct aerosol conditions. Pristine conditions with low aerosol particle number concentrations of ∼100 cm3 were alternating with periods influenced by Saharan dust or aerosol from biomass burning resulting in comparably high number concentrations of ∼ 500 cm3. The biomass burning aerosol was originating from both the Caribbean area and Africa. The shallow cumulus clouds responded to the different aerosol conditions with a wide range of mean droplet sizes and number concentrations. Two days with different aerosol and cloud microphysical properties but almost identical meteorological conditions have been analyzed in detail. The differences in the droplet number concentration and droplet sizes appear not to show any significant change for turbulent cloud mixing, but the relative roles of droplet inertia and sedimentation in initiating coalescence, as well as the cloud reflectivity, do change substantially
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