3D-Printed Quasi-Absolute Electromagnetic Encoders for Chipless-RFID and Motion Control Applications

This paper presents electromagnetic encoders useful for chipless-RFID and motion control applications. The encoders consist in a pair of linear chains of rectangular apertures implemented by means of 3D printing. One of these chains is periodic and acts as a clock, whereas the other chain contains an identification (ID) code. With these two aperture chains, the ID code can be synchronously read, so that the relative velocity between the tag and the reader is irrelevant. Additionally, it is shown in the paper that by properly designing the reader, it is possible to determine the motion direction. The sensitive part of the reader is a microstrip line loaded with three complementary split ring resonators (CSRRs) etched in the ground plane and fed by three harmonic signals. By encoder motion, the characteristics of the local medium surrounding the CSRRs are modified, and the harmonic signals are amplitude modulated (AM) at the output port of the line, thereby providing the clock signal (which gives the encoder velocity), the ID code (providing also the quasi-absolute position) and the direction of motion. A fabricated prototype encoder is characterized by reading it with a dedicated reader.

Interstellar anatomy of the TeV gamma-ray peak in the IC443 supernova remnant

Context. Supernova remnants (SNRs) represent a major feedback source from stars in the interstellar medium of galaxies. During the latest stage of supernova explosions, shock waves produced by the initial blast modify the chemistry of gas and dust, inject kinetic energy into the surroundings, and may alter star formation characteristics. Simultaneously, γ-ray emission is generated by the interaction between the ambient medium and cosmic rays (CRs), including those accelerated in the early stages of the explosion. Aims. We study the stellar and interstellar contents of IC443, an evolved shell-type SNR at a distance of 1.9 kpc with an estimated age of 30 kyr. We aim to measure the mass of the gas and characterize the nature of infrared point sources within the extended G region, which corresponds to the peak of γ-ray emission detected by VERITAS and Fermi. Methods. We performed 10′ × 10′ mapped observations of 12CO, 13CO J = 1–0, J = 2–1, and J = 3–2 pure rotational lines, as well as C18O J = 1–0 and J = 2–1 obtained with the IRAM 30 m and APEX telescopes over the extent of the γ-ray peak to reveal the molecular structure of the region. We first compared our data with local thermodynamic equilibrium models. We estimated the optical depth of each line from the emission of the isotopologs 13CO and C18O. We used the population diagram and large velocity gradient assumption to measure the column density, mass, and kinetic temperature of the gas using 12CO and 13CO lines. We used complementary data (stars, gas, and dust at multiple wavelengths) and infrared point source catalogs to search for protostar candidates. Results. Our observations reveal four molecular structures: a shocked molecular clump associated with emission lines extending between −31 and 16 km s−1, a quiescent, dark cloudlet associated with a line width of ~2 km s−1, a narrow ring-like structure associated with a line width of ~1.5 km s−1, and a shocked knot. We measured a total mass of ~230, ~90, ~210, and ~4 M⊙, respectively, for the cloudlet, ring-like structure, shocked clump, and shocked knot. We measured a mass of ~1100 M⊙ throughout the rest of the field of observations where an ambient cloud is detected. We found 144 protostar candidates in the region. Conclusions. Our results emphasize how the mass associated with the ring-like structure and the cloudlet cannot be overlooked when quantifying the interaction of CRs with the dense local medium. Additionally, the presence of numerous possible protostars in the region might represent a fresh source of CRs, which must also be taken into account in the interpretation of γ-ray observationsin this region.

Treatment of Wastewater from Pulp and Paper Mill using Coagulation and Flocculation

In this work, an effluent sample from a local medium-scale paper mill has been treated using alum as a coagulant and chitosan (natural polymer) as a flocculant. Initially, the dose of alum has been optimized by adjusting the zeta potential to near zero for best coagulation results. The dose of 0.04 g/L was able to merely coagulate and unable to cause sweep flocculation of impurities. Then, at the optimised dose of 0.04 g/L various concentrations of chitosan in the range of 0.1-0.5 g/L were investigated for obtaining maximum flocculation of the suspended impurities. The physico-chemical parameters like pH, total suspended solids (TSS), chemical oxygen demand (COD), absorbance, and zeta potential were studied for comprehending the flocculation behavior. The observed results exhibited that the maximum flocculation was achieved at the chitosan concentration of 0.3 g/L. At the flocculant concentration of 0.3 g/L, 81% TSS removal and maximum 78% COD were reduced. Moreover, zeta potential value of the collected supernatant was close to zero (–1.49 mV) which showed larger floc formation and easy settleability of the impurities. In all, it can be said that the utilization of chitosan along with alum may be a better option for the treatment of pulp and paper wastewater as well as other similar types of wastewater.

Microsecond polarimetry of the repeating FRB 20180916B

Fast radio bursts (FRBs) exhibit a wide variety of spectral, temporal and polarimetric properties, which can unveil clues into their emission physics and propagation effects in the local medium. FRBs are challenging to study at very high time resolution due to the precision needed to constrain the dispersion measure, signal-to-noise limitations, and also scattering from the intervening medium. Here we present the high-time-resolution (down to 1 μs) polarimetric properties of four 1.7-GHz bursts from the repeating FRB 20180916B, which were detected in voltage data during observations with the European VLBI Network. In these bursts we observe a range of emission timescales spanning three orders of magnitude, the shortest component width reaching 3-4 μs (below which we are limited by scattering). We demonstrate that all four bursts are highly linearly polarised (≥ 80%), show no evidence for significant circular polarisation (≤ 15%), and exhibit a constant polarisation position angle during and between bursts. On short timescales (≤ 100 μs), however, there appear to be subtle (few degree) polarisation position angle variations across the burst profiles. These observational results are most naturally explained in an FRB model where the emission is magnetospheric in origin, as opposed to models where the emission originates at larger distances in a relativistic shock.

Temporal evolution of oscillating coronal loops

Context. Transverse oscillations of coronal structures are currently intensively studied to explore the associated magnetohydrodynamic wave physics and perform seismology of the local medium. Aims. We make a first attempt to measure the thermodynamic evolution of a sample of coronal loops that undergo decaying kink oscillations in response to an eruption in the corresponding active region. Methods. Using data from the six coronal wavelengths of SDO/AIA, we performed a differential emission measure (DEM) analysis of 15 coronal loops before, during, and after the eruption and oscillation. Results. We find that the emission measure, temperature, and width of the DEM distribution undergo significant variations on timescales relevant for the study of transverse oscillations. There are no clear collective trends of increases or decreases for the parameters we analysed. The strongest variations of the parameters occur during the initial perturbation of the loops, and the influence of background structures may also account for much of this variation. Conclusions. The DEM analysis of oscillating coronal loops in erupting active regions shows evidence of evolution on timescales important for the study of oscillations. Further work is needed to separate the various observational and physical mechanisms that may be responsible for the variations in temperature, DEM distribution width, and total emission measure.

Evolution of rectangular and triangular initial beam profiles in positive Kerr local medium

The hyperbolic secant (Sech) shape, as the initial beam profile, is the well-know profile that compensates the diffraction and self-focusing effect during propagation in Kerr medium, and evolves as the bright spatial soliton. The Sech beam can be confined in the Kerr medium andinduces its own waveguide. In this work, two initial beam profiles, rectangular and triangular functions, that are different than Sech profile, are considered, and the propagation of these beam profiles in third-order nonlinear (Kerr) medium is investigated. As a result, the initialbeam-width played an important role in confining the beam profiles in direction of propagation. In addition, the intensity profiles change to the Sech profile after some initial step of propagation. All the calculations and simulations have been done by the Split-Step numericalmethod with MATLAB program.

On the use of the coda of seismic noise autocorrelations to compute H/V spectral ratios

SUMMARY The horizontal to vertical spectral ratio (HVSR) of seismic ambient noise has been proven to be a fast and efficient method for characterizing the 1-D resonance frequency of the local subsurface in a practical framework. Over the last decades, theories have been developed in order to extend the exploitation of HVSR beside the frequency of its first peak, notably the diffuse field assumption (DFA) which links the HVSR to the Green’s function of the local medium assuming the diffuseness of the seismic ambient noise wavefield. However, the underlying assumption of the seismic ambient noise being a diffuse, equipartitioned field may not be satisfied under certain circumstances. In order to exploit the contribution of scattering in forging diffuse wave fields, we leverage the advantages of coda waves and present a novel procedure for computing the HVSR, using the coda part of ambient noise correlations. We applied this technique to data gathered at the plio-quaternary sedimentary basin of Argostoli, Greece. Results on this data set show the potential of the method to improve the temporal stability of the HVSR measurements compared to the classical computation, and the fit with the theoretical HVSR curve derived from the DFA theory. These results suggest that this procedure could help in extracting physical information from the HVSR and thus could lead to an extended use of these measurements to characterize the mechanical properties of the medium.