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Quasi-biennial oscillations and Rieger-type periodicities in a Babcock–Leighton solar dynamo
No full textContext. The Sun’s magnetic field exhibits the 11 year solar cycle as well as shorter periodicities, popularly known as the quasi-biennial oscillations (QBOs) and Rieger-type periods. Although several theories have been proposed to explain the origin of QBOs and Rieger-type periods, no single theory has had widespread acceptance.
Aims. We explore whether the Babcock–Leighton dynamo can produce Rieger-type periodicity and QBOs and investigate their underlying physical mechanisms.
Methods. We used the observationally guided 3D kinematic Babcock–Leighton dynamo model, which has emerged as a successful model for reproducing many characteristic features of the solar cycle. We used Morlet wavelet and global wavelet power spectrum techniques to analyze the data obtained from the model.
Results. In our model, we report QBOs and Rieger-type periods for the first time. Further, we investigated the individual Babcock–Leighton parameters (fluctuations in flux, latitude, time delay, and tilt scatter) role in the occurrence of QBOs and Rieger-type periods. We find that while fluctuations in the individual parameters of the Babcock–Leighton process can produce QBOs and Rieger-type periodicity, their occurrence probability is enhanced when considering combined fluctuations of all parameters in the Babcock–Leighton process. Finally, we find that with the increase in dynamo supercriticality, the model tends to suppress the generation of Rieger-type periodicity. Thus, this result supports earlier studies that suggest the solar dynamo is not highly supercritical.
Conclusions. The Babcock–Leighton dynamo model successfully reproduces QBOs and Rieger-type periodicities that are observed in various solar activity data
A novel distributed decision-making method for project portfolio risk response considering differences in decision-maker perspectives
No full textRisk response is an important measure for ensuring success of a project portfolio (PP). To address the limitations of the existing centralized decision-making for PP risk response, a new distributed decision-making method for PP risk response is proposed. Initially, a comprehensive risk interaction evaluation method is proposed integrating Interval Neutrosophic Sets (INSs) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) along with Decision-making Trial and Evaluation Laboratory (DEMATEL). Subsequently, project risk interaction evaluation in different scenarios of project decision-maker (PDM) is defined. The methods for the comprehensive evaluation of risks from the perspectives of PDM and of PP decision-maker (PPDM) are also given. Following this, a bi-level programming model is constructed in which the decision-maker of the upper layer is PPDM and that of the lower layer is PDM. A case study is conducted on a display research and development (R&D) PP to validate the feasibility of the method. The results of the case study show that PP risk response decision (PPRRD) can be affected by different scenarios of PDM and the hierarchical model can effectively resolve conflicts caused by differences in decision-making perspectives between PPDM and PDM
The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)
No full textContext. CO gas has been detected in ~20 debris discs, typically classified as CO-poor or CO-rich. We present observations of the CO-rich HD 121617 debris disc as part of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS).
Aims. We model local CO line profiles in the HD 121617 debris disc to investigate optical depth, CO mass, and temperature. HD 121617 is a well-suited ARKS target due to its previously detected CO emission and moderate inclination, reducing the effect of Keplerian shear.
Methods. Using high-resolution ALMA Band 7 observations of 12CO J=3–2 (26 m s−1, 0⋅′′ 1), we create local line profiles by aligning and stacking spectra in concentric annuli of 0⋅′′ 02 width. These profiles are modelled with both a toy model and a RADMC-3
J-PAS: A neural network approach to single stellar population characterisation
No full textJ-PAS (Javalambre Physics of the Accelerating Universe Astrophysical Survey) will present a groundbreaking photometric survey covering 8500 deg2 of the visible sky from Javalambre, capturing data in 56 narrow-band filters. This survey promises to revolutionise galaxy evolution studies by observing ∼108 galaxies with low spectral resolution. A crucial aspect of this analysis involves predicting stellar population parameters from the observed galaxy photometry. In this study, we combined the exquisite J-PAS photometry with state-of-the-art single stellar population (SSP) libraries to accurately predict stellar age, metallicity, and dust attenuation with a neural network (NN) model. The NN was trained on synthetic J-PAS photometry from different SSP libraries (E-MILES, Charlot & Bruzual, and XSL) to enhance the robustness of our predictions against individual SSP model variations and limitations. To create mock samples with varying observed magnitudes, we added artificial noise in the form of random Gaussian variations within typical observational uncertainties in each band. Our results indicate that the NN was able to accurately estimate stellar parameters for SSP models without any evident degeneracies, surpassing a Bayesian SED-fitting method on the same test set. We obtained the median bias, scatter, and the percentage of outliers: μ= (0.01 dex, 0.00 dex, 0.00 mag), σNMAD= (0.23 dex, 0.29 dex, 0.04 mag), fo= (17%, 24%, 1%) at i ∼ 17 mag for the age, metallicity and dust attenuation, respectively. The accuracy of the predictions is highly dependent on the signal-to-noise ratio (S/N) of the photometry, achieving robust predictions up to i ∼ 20 mag
Evidence for an isomeric
No full textWe report on the identification of a new isomeric state in Ta populated via the ground-state -decay of Hf. The experiment was performed at the KISS setup at RIKEN, where neutron-rich hafnium isotopes were produced via multi-nucleon transfer (MNT) reactions, followed by laser ionization of hafnium atoms, mass separation, and detection using an electron-gamma coincidence system. Isomeric spectroscopy was carried out by gating on different electron-gamma time correlations. A 459.1 keV -ray transition was identified in delayed spectra, and a half-life of 41^{+6}_{-4}~\upmu s was extracted through time-distribution fitting. The 459.1 keV state in Ta is known from previous work and has been assigned a Nilsson orbital configuration of , while a proposed new isomeric state above it is interpreted as a configuration that decays to via a low-energy, unobserved E2 transition. This is consistent with the systematic trends in neighbouring odd-A nuclei and transition rate calculations
Kinematic scaling relations of disc galaxies from ionised gas at
No full textWe derive the Tully-Fisher (TFR; M* − Vcirc, f) and Fall (FR; j* − M*) relations at redshift z = 0.9 using a sample of 43 main-sequence disc galaxies with Hα IFU data and JWST/HST imaging. The strength of our analysis lies in the use of state-of-the-art 3D kinematic models to infer galaxy rotation curves, the inclusion of near-IR bands and their morphological modelling, and the application of homogeneous spectral energy distribution modelling to our photometry measurements to estimate stellar masses. After correcting the inferred Hα velocities for asymmetric drift, we find a TFR of the form log(M*/M⊙) = a log(Vcirc,f/ 150 km s−1 + b, with and , as well as a FR of the form log(j*/kpc km s−1) = alog(M*/1010.5 M⊙)+b, with and . Compared with their z = 0 counterparts, we found moderate evolution in the TFR and strong evolution in the FR over the past 8 Gyr. We interpreted our findings in the context of the galaxy-to-halo scaling parameters fM = M*/Mvir and fj = j*/jvir. We inferred that fj shows little redshift evolution and depends very weakly on M*, with typical values around fj ∼ 0.8. As for fM, we find it to be higher and less dependent on M* at z = 0.9 than at z = 0. We discuss how interpreting our observed fM − M* relations within the cold dark matter framework implies necessarily that the galaxy populations at z = 0.9 and z = 0 are not the progenitor nor descendant of one another. The alternative scenario is that the z = 0.9 scaling relations are incorrect due to strong selection effects, unidentified systematics, or the possibility that Hα kinematics may not be a reliable dynamical tracer. Such problems would affect not only our work but also previous studies on the same subject
Chiral particles in Taylor–Couette turbulence
No full textThis work investigates chiral particles, which break mirror symmetry, in turbulent Taylor–Couette flow. These particles generally display a translation-rotation coupling moving through a quiescent fluid. Here, we performed experiments using large chiral particles (typical size 5mm) in turbulent Taylor–Couette flow, for Reynolds numbers . The density-matched chiral particles are studied in a dilute regime , where their location and orientation are tracked over time to investigate the particle-fluid coupling. We investigate whether the translation-rotation coupling observed at low Reynolds numbers is still observable over the measured high Reynolds numbers, using the tracked location and orientation. Similarly, we verify whether the chiral particles display a preferred location or orientation, and whether the left-handed and right-handed particles show different rotation statistics. The location data show that the chiral particles closely follow the structure of Taylor vortices. Hence, the orientation data and rotation data of the chiral particles are split between the Taylor vortices and particle chiralities. The results show no difference in rotation and orientation dynamics between chiralities. Rather, the particle dynamics are flow-dominated, where the flow vorticity determines the specific particle dynamics
Anisotropic soft X-ray emission spectroscopy study of the valence electron state of Lu(Al,
No full textLu(Al,T)B4 (T= Cr, Mn, Fe, Mo) have the alternate stacking structure of B-layer and Lu(Al,T)-layer along the c-axis. B-K emission spectra of these materials are measured at two take-off angles of 20° and 70° from the c-plane. The energy region corresponding to the top of valence band (VB) shows a larger spectrum intensity at the smaller take-off angle, responsible for pz character. The bottom region shows the opposite angle dependence, responsible for px and py character. The middle of the VB of a large peak intensity shows almost no angle dependence, suggesting an isotropic distribution of bonding charge. As a whole, the angle-dependence of the B-K emission intensity is smaller than that of graphite. This rather isotropic bonding-charge distribution of the boron-layer can make the inter-layer bonding between B-layer and adjacent Lu(Al,T) layer and is presumably related to the hardness of those bulk materials
Sensitive boron detection with a table-top wavelength dispersive spectrometer
No full textBoron has many applications in science and industry yet there don't exist any easy-to-use X-ray fluorescence analysis techniques to detect low concentrations of boron in a sample. Wavelength dispersive X-ray spectrometry (WDX) after excitation by scanning electron microscope (SEM-WDX) combines high spatial resolution obtained with an electron microprobe and a spectrometer with sub-eV energy resolution, and high sensitivity in the soft X-ray range. The sensitivity necessary for low concentration boron detection is achieved by a wide sagittal acceptance, high diffraction efficiency and the focussing effect of the used reflection zone plate (RZP). The RZP and a CCD camera form a compact WDX spectrometer (309 × 156 × 165 mm3), suitable for tabletop laboratory setups and as an add-on to beamlines at large-scale facilities. In order to test the detection limit for boron, three samples were measured: Duran glass with ~ 9 at% boron, Si (55 %) / Ge (45 %) with 1 at% boron implantation and Si (55 %) / Ge (45 %) with 0.1 at% boron implantation. After optimising the setup, a signal to noise (S/N) ratio of 7.2 was achieved at 0.1 at% boron, indicating a detection limit of 500 ppm for the current setup. Effects of radiation damage and energy shifts depending on the boron binding state were observed as well
SAFER – A way to achieve affordable large-scale radiological survey network
No full textSafer is a low cost, low power connected radiological beacon, deployed as a network of sensors around cities and industrial sites, it creates an early warning system and enhance situational awareness, post-action assessment, and decision-making. Working continuously, it collects data in real time in order to protect workers, first responders and population