462 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
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
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
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