3,651 research outputs found
Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell
A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via
Low cycle fatigue behaviour of wire arc additively manufactured ER70S-6 steel
Wire arc additive manufacturing (WAAM) is a method of 3D printing that is well suited to the cost-sensitive construction industry. Fundamental test data on the mechanical properties of WAAM materials, especially under cyclic loading, are however lacking. To bridge this gap, an experimental study into the low cycle fatigue (LCF) behaviour of WAAM ER70S-6 steel has been conducted and is presented herein. Following quasi-static mechanical and geometric characterisation, a series of as-built and machined coupons was tested in different directions relative to the print layer orientation (θ = 0°, 45° and 90°) under constant amplitude LCF loading, covering a range of strain amplitudes from ±0.2% to ±2.0%. Fractographic analysis of the tested coupons was also performed to assess their failure mechanisms. On the basis of the experimental results, strain-life relationships and cyclic stress-strain curves were derived. The geometric undulations of the as-built coupons resulted in a weakening in the LCF properties, and the weakening effect increased with the loading angle θ and strain amplitude. The cyclic hardening/softening response of the WAAM material varied with the imposed strain amplitudes, while significant non-Masing behaviour was observed
Calculation of the Chiral Lagrangian Coefficients
We present a systematic way to combine the global color model and the
instanton liquid model to calculate the chiral
Lagrangian coefficients. Our numerical results are in agreement well with the
experimental values.Comment: 7 pages, To appear in Chin.Phys.Lett, Year 200
The Calculation of Vacuum Properties from the Global Color Symmetry Model
A modified method for calculating the non-perturbative quark vacuum
condensates from the global color symmetry model is derived. Within this
approach it is shown that the vacuum condensates are free of ultraviolet
divergence which is different from previous studies. As a special, the
two-quark condensate and the mixed quark-gluon condensate are calculated. A
comparision with the results of the other nonperturbative QCD approaches is
given.Comment: 17 page
Neutrinos and Nucleosynthesis in Supernova
The type II supernova is considered as a candidate site for the production of
heavy elements. The nucleosynthesis occurs in an intense neutrino flux, we
calculate the electron fraction in this environment.Comment: RevTex4 style, 3 pages including 1 figure. Presented at Mexican
School of Astrophysics 2002, Guanajuato, Mexico, 31 Jul - 7 Aug 2002. Final
version to appear in the Proceedings of IX Mexican Workshop on Particles and
Fields Physics Beyond the Standard Model, Colima Col. Mexico, November 17-22,
200
Experimental study of breathers and rogue waves generated by random waves over non-uniform bathymetry
Experimental results describing random, uni-directional, long crested, water
waves over non-uniform bathymetry confirm the formation of stable coherent wave
packages traveling with almost uniform group velocity. The waves are generated
with JONSWAP spectrum for various steepness, height and constant period. A set
of statistical procedures were applied to the experimental data, including the
space and time variation of kurtosis, skewness, BFI, Fourier and moving Fourier
spectra, and probability distribution of wave heights. Stable wave packages
formed out of the random field and traveling over shoals, valleys and slopes
were compared with exact solutions of the NLS equation resulting in good
matches and demonstrating that these packages are very similar to deep water
breathers solutions, surviving over the non-uniform bathymetry. We also present
events of formation of rogue waves over those regions where the BFI, kurtosis
and skewness coefficients have maximal values.Comment: 41 pages, 21 figure
Habitat effects on hoarding plasticity in the Eurasian red squirrel (Sciurus vulgaris).
Hoarding patterns can be classified into two general types: scatter-hoarding and larder-hoarding, but there are intermediate types. Various factors affect hoarding patterns. Animals hoarding identical seeds in different habitats may use different hoarding patterns to adapt to habitat variation.
We used a sample-plot investigation method to study cache features and recovery rate of seeds of Arolla pine (Pinus cembra) by Eurasian red squirrels (Sciurus vulgaris) in 2009 and 2010 in two subalpine forests with different tree-species composition in the Italian Alps. Hoarding patterns
of red squirrels varied among habitats: the typical scatter-hoarding pattern with most caches including 2-6 seeds is found in spruce (Picea abies) dominated forest, while a combination of few large caches (10 seeds) and many small caches (less than 10 seeds) is found in Arolla pine dominated forest. Consequently, average number of seeds/cache was higher in the latter habitat. Among five microhabitats, shrubs, grass, moss, fallen leaves, and stone, Eurasian red squirrels preferred
fallen leaves and moss as hoarding substrate. Cache recovery investigation indicated that recovery rate was 62% in spruce forest and only 21% in Arolla pine forest. A lower availability of suitable
hoarding microhabitat resulted in changes in hoarding patterns of red squirrels in Pinus cembra dominated forest. We suggest that the main factor influencing differences in recovery rate was a higher cone production per tree in Pinus cembra forest
Establishing the entatic state in folding metallated Pseudomonas aeruginosa azurin
Understanding how the folding of proteins establishes their functional characteristics at the molecular level challenges both theorists and experimentalists. The simplest test beds for confronting this issue are provided by electron transfer proteins. The environment provided by the folded protein to the cofactor tunes the metal's electron transport capabilities as envisioned in the entatic hypothesis. To see how the entatic state is achieved one must study how the folding landscape affects and in turn is affected by the metal. Here, we develop a coarse-grained functional to explicitly model how the coordination of the metal (which results in a so-called entatic or rack-induced state) modifies the folding of the metallated Pseudomonas aeruginosa azurin. Our free-energy functional-based approach directly yields the proper nonlinear extra-thermodynamic free energy relationships for the kinetics of folding the wild type and several point-mutated variants of the metallated protein. The results agree quite well with corresponding laboratory experiments. Moreover, our modified free-energy functional provides a sufficient level of detail to explicitly model how the geometric entatic state of the metal modifies the dynamic folding nucleus of azurin
Constraints on ultracompact minihalos from extragalactic {\gamma}-ray background
It has been proposed that ultracompact minihalos (UCMHs) might be formed in
earlier epoch. If dark matter consists of Weakly Interacting Massive Particles
(WIMPs), UCMHs can be treated as the {\gamma}-ray sources due to dark matter
annihilation within them. In this paper, we investigate the contributions of
UCMHs formed during three phase transi- tions (i.e., electroweak symmetry
breaking, QCD confinement and e+ e- annihilation) to the extragalactic
{\gamma}-ray background. Moreover, we use the Fermi-LAT observation data of the
extragalactic {\gamma}-ray background to get the constraints on the current
abundance of UCMHs produced during these phase transitions. We also compare
these results with those obtained from Cosmic Microwave Background (CMB)
observations and find that the constraints from the Fermi-LAT are more
stringent than those from CMBComment: 13 pages, 4 figures, 1 tabl
Three-dimensional magnetic flux rope structure formed by multiple sequential X-line reconnection at the magnetopause
On 14 June 2007, four Time History of Events and Macroscale Interactions during Substorms spacecraft observed a flux transfer event (FTE) on the dayside magnetopause, which has been previously proved to be generated by multiple, sequential X-line reconnection (MSXR) in a 2-D context. This paper reports a further study of the MSXR event to show the 3-D viewpoint based on additional measurements. The 3-D structure of the FTE flux rope across the magnetospheric boundary is obtained on the basis of multipoint measurements taken on both sides of the magnetopause. The flux rope's azimuthally extended section is found to lie approximately on the magnetopause surface and parallel to the X-line direction; while the axis of the magnetospheric branch is essentially along the local unperturbed magnetospheric field lines. In the central region of the flux rope, as distinct from the traditional viewpoint, we find from the electron distributions that two types of magnetic field topology coexist: opened magnetic field lines connecting the magnetosphere and the magnetosheath and closed field lines connecting the Southern and Northern hemispheres. We confirm, therefore, for the first time, the characteristic feature of the 3-D reconnected magnetic flux rope, formed through MSXR, through a determination of the field topology and the plasma distributions within the flux rope. Knowledge of the complex geometry of FTE flux ropes will improve our understanding of solar wind-magnetosphere interaction.Astronomy & AstrophysicsSCI(E)5ARTICLE51904-191111
- …