1,123 research outputs found
Test Report: Cyclic Performance of Steel Sheet Connections for CFS Steel Sheet Shear Walls
Technical ReportThe objective of this report is to provide fastener-level force-deformation response appropriate for cold-formed steel (CFS) framed steel sheet sheathed shear walls under cyclic loads. A key feature of the fastened connection is the impact of the steel sheet shear buckling on the local fastener-level response. Recent CFS shear wall tests employing thin steel sheets screw fastened to cold-formed steel framing have examined the impact of thicker and stiffer boundary framing, double steel sheet sheathing, and sandwiching the steel sheet between boundary members - all demonstrating the potential for higher capacity and ductility for steel sheet sheathed CFS-framed shear walls. For the seismic performance of screw fastened, steel sheet sheathed shear walls, the cyclic nonlinear response of the fastener connection is particularly important and should incorporate the impact of the steel sheet local buckling on the strength and ductility of the connection. Minimal cyclic fastener-level shear test data exists, especially for combinations of screw fastened thin steel sheet and thick framing steel. A lap shear testing configuration, featuring either one thin steel sheet ply and one thick framing ply or one thin steel sheet ply and two thick framing plies connected by a single fastener with appropriate sensors is designed. The lap shear tests follow the AISI S905 test standard and are augmented for this particular configuration including adding asymmetric loading cycles following a modified FEMA 461 loading protocol. The asymmetric cyclic loading protocol is selected with a small displacement applied in the direction which buckles the thin steel sheet followed by progressively larger displacements in the opposite direction. A total of 156 tests, covering a wide range of framing thickness, sheet thickness, fastener type and size, and loading types are conducted. Key statistics from each test, including characterization with a multilinear backbone curve are provided. The testing is intended to provide critical missing information for the design and simulation of CFS-framed steel sheet sheathed shear walls.National Science Foundation, see report for complete acknowledgment and disclaimer
Application of ASCE 41 to a two-story CFS building
The objective of this paper is to summarize the evaluation results from applying the updated performance-based seismic design provisions: ASCE 41-17, on a cold-formed steel framed building sited in a location with high seismic demands. The assessment included examination of the existing design and consideration of retrofits required to bring the design into compliance with ASCE 41-17. The assessment of the building relies on the linear procedures and m-factors in ASCE 41-17 and follows the same basic process as the original design. Despite the fact that the studied building is compliant with ASCE 7 and AISI S400, and successfully withstood shake table testing in excess of maximum considered earthquake levels with no permanent damage and no residual drift, ASCE 41-17 finds the building to be deficient. The work highlights that, for cold formed steel framing, even though ASCE 41 is based on the same tested shear walls that ASCE 7/AISI S400 rely upon, the
component-based procedures of ASCE 41 do not easily account for the larger system overstrength and ductility that are included and validated for actual systems. Further work is needed to improve ASCE 41 to account for full system performance, this is particularly important given ASCE 41’s growing role as the benchmark performance-based standard for seismic assessment and design.The contributions of Ivana Olivares are gratefully acknowledged
Thermal compression of atomic hydrogen on helium surface
We describe experiments with spin-polarized atomic hydrogen gas adsorbed on
liquid He surface. The surface gas density is increased locally by
thermal compression up to cm at 110 mK. This
corresponds to the onset of quantum degeneracy with the thermal de-Broglie
wavelength being 1.5 times larger than the mean interatomic spacing. The atoms
were detected directly with a 129 GHz electron-spin resonance spectrometer
probing both the surface and the bulk gas. This, and the simultaneous
measurement of the recombination power, allowed us to make accurate studies of
the adsorption isotherm and the heat removal from the adsorbed hydrogen gas.
From the data, we estimate the thermal contact between 2D hydrogen gas and
phonons of the helium film. We analyze the limitations of the thermal
compression method and the possibility to reach the superfluid transition in 2D
hydrogen gas.Comment: 20 pages, 11 figure
Habitable Zones and UV Habitable Zones around Host Stars
Ultraviolet radiation is a double-edged sword to life. If it is too strong,
the terrestrial biological systems will be damaged. And if it is too weak, the
synthesis of many biochemical compounds can not go along. We try to obtain the
continuous ultraviolet habitable zones, and compare the ultraviolet habitable
zones with the habitable zones of host stars. Using the boundary ultraviolet
radiation of ultraviolet habitable zone, we calculate the ultraviolet habitable
zones of host stars with masses from 0.08 to 4.00 \mo. For the host stars with
effective temperatures lower than 4,600 K, the ultraviolet habitable zones are
closer than the habitable zones. For the host stars with effective temperatures
higher than 7,137 K, the ultraviolet habitable zones are farther than the
habitable zones. For hot subdwarf as a host star, the distance of the
ultraviolet habitable zone is about ten times more than that of the habitable
zone, which is not suitable for life existence.Comment: 5 pages, 3 figure
Cold Nuclear Matter Effects on Dijet Productions in Relativistic Heavy-ion Reactions at LHC
We investigate the cold nuclear matter(CNM) effects on dijet productions in
high-energy nuclear collisions at LHC with the next-to-leading order
perturbative QCD. The nuclear modifications for dijet angular distributions,
dijet invariant mass spectra, dijet transverse momentum spectra and dijet
momentum imbalance due to CNM effects are calculated by incorporating EPS, EKS,
HKN and DS param-etrization sets of parton distributions in nucleus . It is
found that dijet angular distributions and dijet momentum imbalance are
insensitive to the initial-state CNM effects and thus provide optimal tools to
study the final-state hot QGP effects such as jet quenching. On the other hand,
the invariant mass spectra and the transverse momentum spectra of dijet are
generally enhanced in a wide region of the invariant mass or transverse
momentum due to CNM effects with a feature opposite to the expected suppression
because of the final-state parton energy loss effect in the QGP. The difference
of EPS, EKS, HKN and DS parametrization sets of nuclear parton distribution
functions is appreciable for dijet invariant mass spectra and transverse
momentum spectra at p+Pb collisions, and becomes more pronounced for those at
Pb+Pb reactions.Comment: 10 pages, 11 figure
Habitable Zones of Host Stars During the Post-MS Phase
A star will become brighter and brighter with stellar evolution, and the
distance of its habitable zone will become farther and farther. Some planets
outside the habitable zone of a host star during the main sequence phase may
enter the habitable zone of the host star during other evolutionary phases. A
terrestrial planet within the habitable zone of its host star is generally
thought to be suited to life existence. Furthermore, a rocky moon around a
giant planet may be also suited to life survive, provided that the planet-moon
system is within the habitable zone of its host star. Using Eggleton's code and
the boundary flux of habitable zone, we calculate the habitable zone of our
Solar after the main sequence phase. It is found that Mars' orbit and Jupiter's
orbit will enter the habitable zone of Solar during the subgiant branch phase
and the red giant branch phase, respectively. And the orbit of Saturn will
enter the habitable zone of Solar during the He-burning phase for about 137
million years. Life is unlikely at any time on Saturn, as it is a giant gaseous
planet. However, Titan, the rocky moon of Saturn, may be suitable for
biological evolution and become another Earth during that time. For low-mass
stars, there are similar habitable zones during the He-burning phase as our
Solar, because there are similar core masses and luminosities for these stars
during that phase.Comment: 6 pages, 7 figures. Accepted by Ap & S
Modelling and Interpreting The Effects of Spatial Resolution on Solar Magnetic Field Maps
Different methods for simulating the effects of spatial resolution on
magnetic field maps are compared, including those commonly used for
inter-instrument comparisons. The investigation first uses synthetic data, and
the results are confirmed with {\it Hinode}/SpectroPolarimeter data. Four
methods are examined, one which manipulates the Stokes spectra to simulate
spatial-resolution degradation, and three "post-facto" methods where the
magnetic field maps are manipulated directly. Throughout, statistical
comparisons of the degraded maps with the originals serve to quantify the
outcomes. Overall, we find that areas with inferred magnetic fill fractions
close to unity may be insensitive to optical spatial resolution; areas of
sub-unity fill fractions are very sensitive. Trends with worsening spatial
resolution can include increased average field strength, lower total flux, and
a field vector oriented closer to the line of sight. Further-derived quantities
such as vertical current density show variations even in areas of high average
magnetic fill-fraction. In short, unresolved maps fail to represent the
distribution of the underlying unresolved fields, and the "post-facto" methods
generally do not reproduce the effects of a smaller telescope aperture. It is
argued that selecting a method in order to reconcile disparate spatial
resolution effects should depend on the goal, as one method may better preserve
the field distribution, while another can reproduce spatial resolution
degradation. The results presented should help direct future inter-instrument
comparisons.Comment: Accepted for publication in Solar Physics. The final publication
(including full-resolution figures) will be available at
http://www.springerlink.co
Higgs-Boson Production Associated with a Single Bottom Quark in Supersymmetric QCD
Due to the enhancement of the couplings between Higgs boson and bottom quarks
in the minimal sypersymmetric standard model (MSSM), the cross section of the
process pp(p\bar{p}) \to h^0b(h^0\bar{b})+X at hadron colliders can be
considerably enhanced. We investigated the production of Higgs boson associated
with a single high-p_T bottom quark via subprocess bg(\bar{b}g) \to
h^0b(h^0\bar{b}) at hadron colliders including the next-to-leading order (NLO)
QCD corrections in MSSM. We find that the NLO QCD correction in the MSSM
reaches 50%-70% at the LHC and 60%-85% at the Fermilab Tevatron in our chosen
parameter space.Comment: accepted by Phys. Rev.
Break-taking behaviour pattern of long-distance freight vehicles based on GPS trajectory data
This paper focuses on the break-taking behaviour pattern of long-distance freight vehicles, providing a new perspective on the study of behaviour patterns and simultaneously providing a reference for transport management departments and related enterprises. Based on Global Positioning System (GPS) trajectory data, we select stopping points as break-taking sites of long-distance freight vehicles and then classify the stopping points into three different classes based on the break-taking duration. We then explore the relationship of the distribution of the break-taking frequency between the three single classifications and their combinations, on the basis of the break-taking duration distribution. We find that the combination is a Gaussian distribution when each of the three individual classes is a Gaussian distribution, contrasting with the power-law distribution of the break-taking duration. Then we experimental analysis the distribution of the break-taking durations and frequencies, and find that, for the durations, the three single classifications can be fitted individually by an Exponential distribution and together by a Power-law distribution, for the frequencies, both the three single classifications and together can be fitted by a Gaussian distribution,so that can validate the above theoretical analysis.
Key words: break-taking behaviour, long-distance freight vehicle, statistical analysi
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