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Simulation and experimental work that compare the performance of straight and tapered monocapillaries when used with laboratory x-ray sources are reported. Detailed simulations for various taper profiles give several important conclusions for optimizing the design of a tapered monocapillary. Several tapered monocapillaries were prepared. With a 16W x-ray source, beam intensities of 4×105 photon/sec/μm2 and 3×105photon/sec/μm2 of Cu Kα x rays were obtained from the tapered monocapillaries for output diameters of 8μm and 3.5μm, respectively. These intensities are 1.4 and 1.5 times that obtained from straight capillaries with the same output beam sizes at the experimental set-up optimized for a straight capillary. In addition to the gain in x-ray flux, the tapered monocapillaries produce output beams with significantly reduced high energy bremsstrahlung radiation and increased flux stability with respect to shifts of the x-ray source spot.
We present results of a supernova lightcurve population synthesis, predicting the range of possible supernova lightcurves arising from a population of progenitor stars that include interacting binary systems. We show that the known diversity of supernova lightcurves can be interpreted as arising from binary interactions. Given detailed models of the progenitor stars, we are able to the determine what parameters within these stars determine the shape of their supernova lightcurve. The primary factors are the mass of supernova ejecta and the mass of hydrogen in the final progenitor. We find that there is a continuum of lightcurve behaviour from type IIP, IIL, to IIb supernovae related to the range of hydrogen and ejecta masses. Most type IIb supernovae arise from a relatively narrow range of initial masses from 10 to 15 M⊙. We also find a few distinct lightcurves that are the result of stellar mergers.
The present paper presents a novel method to cope with the difficulty that an N-order filter can introduce a maximum number of transmission zeros (TZs) – no more than N. The method is described by a coupling topology and realized by a regular fully canonical filter structure to increase one more TZ for an N-order filter without any filter size increase. Besides, the TZ shift property, as another advantage of the proposed topology, is investigated. The coupling topology consists of a group of fully canonical coupling nodes with the harmonic node (non-resonating node (NRN)) excited by a λ/4 resonator. Owing to the unique coupling topology and coupling node distribution as well as the inclusion of an NRN, N + 1 TZs are generated by an N-order bandpass filter, while all the TZs are close to the passband and far away from the harmonic passband resulting the highly selective passbands. For demonstration, two-, three-, and four-order filters are designed and measured with the experimental results that confirm the proposed technique.
The study of the mechanical properties of polycrystalline alloy materials under dynamic impact, namely, the prediction of mechanical behavior after yield stress and the establishment of a constitutive model, has attracted much attention in the field of engineering. The stress-strain curves of 5083 aluminum alloy were obtained under strain rates varying from 0.0002 s-1 to 7130 s-1 through uniaxial compression experiments. The equipment used included a CRIMS RPL100 tester, Instron tester, and split Hopkinson test system. In addition, based on dislocation dynamics and the strengthening mechanism of metals, the plastic flow of the 5083 aluminum alloy was systematically analyzed under a wide range of strain rates. It was found that the abnormal yield behavior of the 5083 aluminum alloy under a wide range of strain rates increased, and the experimental phenomenon of hardening rate decreased with an increase in strain rate. This study also revealed that the abnormal yield behavior is caused by the different dislocation mechanisms of two-phase alloy elements under different strain rates. Based on the thermal activation theory and the experimental data, a constitutive model was developed. A comparison showed good agreement between the experimental and model curves. This indicates that this model has good plastic flow stress prediction ability for such types of materials.
An updated compilation of published and new data of major-ion (Ca, Cl, K, Mg, Na, NO3, SO4) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, the United Kingdom, the United States and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of Antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http://www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized.
In this paper, a compact dual-band bandpass filter (DB-BPF) using new dual-mode resonator-loaded resonators (DM-RLRs) is presented and investigated to simultaneously achieve controllable return loss (RL), bandwidth (BW) and transmission zeros (TZs), and the simple strategy for this type of filter design is proposed. The DB-BPF consists of two high-flexibility DM-RLRs with separated electric and magnetic coupling (SEMC). Specifically, the proposed DM-RLR provides the DB-BPF with center frequency control as well as RL control, and SEMC is utilized for the BW and TZ control. To facilitate the design, a simple optimization-based design strategy is proposed and employed, resulting in an example layout. Finally, the example filter, with center frequencies of 1.57 GHz (channel 1 for GPS) and 3.5 GHz (channel 2 for WiMAX), is fabricated and measured. The measurement insertion loss and RL are 0.9/0.9 and 17/20 dB. The fabricated DB-BPF also exhibits a compact size of 0.12λg × 0.08λg at 1.57 GHz.
Eta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.
We present a pilot study of using the Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum observations to constrain the density structure in the intermediate wind zone of massive stars, in which the wind is extremely sensitive to clumping.
The role of massive stars in the Galactic evolution is crucial. During their lifetime these stars change the kinematics around them through stellar winds, affect the formation of new stars, ionise and chemically enrich the media with the final supernova explosion. But the census of both massive stars and their host clusters is still poor. We expect that still ~100 of galactic massive stellar clusters remains unknown (Hanson & Popescu, 2008).
Because polarization encodes geometrical information about unresolved scattering regions, it provides a unique tool for analyzing the 3-D structures of supernovae (SNe) and their surroundings. SNe of all types exhibit time-dependent spectropolarimetric signatures produced primarily by electron scattering. These signatures reveal physical phenomena such as complex velocity structures, changing illumination patterns, and asymmetric morphologies within the ejecta and surrounding material. Interpreting changes in polarization over time yields unprecedentedly detailed information about supernovae, their progenitors, and their evolution.
Begun in 2012, the SNSPOL Project continues to amass the largest database of time-dependent spectropolarimetric data on SNe. I present an overview of the project and its recent results. In the future, combining such data with interpretive radiative transfer models will further constrain explosion mechanisms and processes that shape SN ejecta, uncover new relationships among SN types, and probe the properties of progenitor winds and circumstellar material.
Large magnetometric surveys have contributed to the detection of an increasing number of magnetic massive stars, and to the recognition of a population of magnetic massive stellar objects with distinct properties. Among these, NGC 1624-2 possesses the largest magnetic field of any O-type star; such a field confines the stellar wind into a circumstellar magnetosphere, which can be probed using observations at different wavelength regimes. Recent optical and X-ray observations suggest that NGC 1624-2’s magnetosphere is much larger than that of any other magnetic O star. By modeling the variations of UV resonance lines, we can constrain its velocity structure. Furthermore, recent spectropolarimetric observations raise the possibility of a more complex field topology than previously expected. Putting all of these multi-wavelength constraints together will allow us to paint a consistent picture of NGC 1624-2 and its surprising behavior, giving us valuable insight into the very nature of massive star magnetospheres.
The Of?p category was introduced more than 40 years ago to gather several Galactic stars with some odd properties. Since 2000, spectropolarimetry, high-resolution spectroscopy, long-term photometry, and X-ray observations have revealed their nature: magnetic oblique rotators - they all have magnetic fields that confine their winds. Several Of?p stars have now been detected in the Magellanic Clouds, likely the prototypes of magnetic massive stars at low metallicity. This contribution will present the most recent photometric, spectroscopic, and spectropolarimetric data, along with the first modeling of these objects.
We gathered a multiwavelength dataset of two well-known LBVs. We found a complex mass-loss, with evidence of variability, such as has been seen previously. In addition, our data reveal signatures of collimated stellar winds. We propose a new scenario for these two stars where the nebula shaping is influenced by the presence of a companion star and/or fast rotation.
We have made 12CO(J=1-0) observations in the LMC with NANTEN, and compared the detected giant molecular clouds (GMCs) with HII regions and stellar clusters. It is found that ~ 80% of the GMCs are associated with HII regions. The results of comparisons of the GMCs with the HII regions and the stellar clusters are presented.
We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.
We have made 12CO(J=1−0) observations of the LMC with NANTEN. We report the results of a comparison between CO clouds and SNRs in the LMC. Among the 35 known SNRs, only 10 are possibly associated with CO clouds. These 10 CO clouds and SNRs deserve follow-up studies for possible interactions. We present overlays of CO clouds on the optical images of some of these SNRs.
Fully sampled 12CO(J=1−0) observations of the whole extent of the LMC have been made with a linear resolution of ~ 30 pc at a detection limit of N(H2) = 2 × 1021 cm−2. In addition, several selected regions have been mapped with higher sensitivity corresponding to a detection limit of 1 × 1021 cm−2. Based on these results, a new estimate of the molecular mass in the LMC is presented.
We have made 12CO(J=1−0) observations of the LMC with the NANTEN millimeter-wave telescope and identified about 100 distinct giant molecular clouds (GMCs). A detailed comparison of the GMCs with stellar clusters and a UV image is discussed.