Internal Variations in Empirical Oxygen Abundances for Giant HII Regions in the Galaxy NGC 2403

This paper presents a spectroscopic investigation of 11 HII regions in the nearby galaxy NGC 2403. The HII regions are observed with a long-slit spectrograph mounted on the 2.16 m telescope at XingLong station of National Astronomical Observatories of China. For each of the HII regions, spectra are extracted at different nebular radii along the slit-coverage. Oxygen abundances are empirically estimated from the strong-line indices R23, N2O2, O3N2, and N2 for each spectrophotometric unit, with both observation- and model-based calibrations adopted into the derivation. Radial profiles of these diversely estimated abundances are drawn for each nebula. In the results, the oxygen abundances separately estimated with the prescriptions on the basis of observations and models, albeit from the same spectral index, systematically deviate from each other; at the same time, the spectral indices R23 and N2O2 are distributed with flat profiles, whereas N2 and O3N2 exhibit apparent gradients with the nebular radius. Because our study naturally samples various ionization levels which inherently decline at larger radii within individual HII regions, the radial distributions indicate not only the robustness of R23 and N2O2 against ionization variations but also the sensitivity of N2 and O3N2 to the ionization parameter. The results in this paper provide observational corroboration of the theoretical prediction about the deviation in the empirical abundance diagnostics. Our future work is planned to investigate metal-poor HII regions with measurable T_e, in an attempt to recalibrate the strong-line indices and consequently disclose the cause of the discrepancies between the empirical oxygen abundances.Comment: 16 pages, 10 figures, 5 tables; accepted for publication in The Astrophysical Journal; with a minor correction in the tex

Characterizing Ultraviolet and Infrared Observational Properties for Galaxies. II. Features of Attenuation Law

Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-beta relation), offered a widely used recipe for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Angstrom bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Angstrom bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.Comment: 25 pages, 23 figures, 5 tables; accepted for publication in The Astrophysical Journa

Prompt heavy quarkonium production in association with a massive (anti)bottom quark at the LHC

In this work, we investigate the associated production of prompt heavy quarkonium with a massive (anti)bottom quark to leading order in the NRQCD factorization formalism at the LHC. We present numerical results for the processes involving $J/\psi,\chi_{cJ},\Upsilon$ and $\chi_{bJ}$. From our work, we find that the production rates of these processes are quite large, and these processes have the potential to be detected at the LHC. When $p_T$ is smaller than about 10 GeV, the $c\bar{c} [ ^1S_0^{(8)} ]$ state give the main contribution to the $p_T$ distribution of prompt $J/\psi$ with a (anti)bottom quark production. For the process of $pp \to \Upsilon+b(\bar{b})$, the contribution of the CSM is larger than that in the COM at low $p_T$ region. We also investigate the processes of $pp\to \chi_{cJ}+b(\bar{b})$ and $pp \to \chi_{bJ}+b(\bar{b})$, in these processes, the $p_T$ distribution are dominated by the CO Fock state contribution at the large $p_T$ region. These processes provide an interesting signature that could be studied at the LHC, and the measurement of these processes is useful to test the CSM and COM.Comment: 14 pages, 11 figures, accepted by Phys.Rev.

Counting Independent Sets and Colorings on Random Regular Bipartite Graphs

We give a fully polynomial-time approximation scheme (FPTAS) to count the number of independent sets on almost every Delta-regular bipartite graph if Delta >= 53. In the weighted case, for all sufficiently large integers Delta and weight parameters lambda = Omega~ (1/(Delta)), we also obtain an FPTAS on almost every Delta-regular bipartite graph. Our technique is based on the recent work of Jenssen, Keevash and Perkins (SODA, 2019) and we also apply it to confirm an open question raised there: For all q >= 3 and sufficiently large integers Delta=Delta(q), there is an FPTAS to count the number of q-colorings on almost every Delta-regular bipartite graph

Towards a Simple Relationship to Estimate the Capacity of Static and Mobile Wireless Networks

Extensive research has been done on studying the capacity of wireless multi-hop networks. These efforts have led to many sophisticated and customized analytical studies on the capacity of particular networks. While most of the analyses are intellectually challenging, they lack universal properties that can be extended to study the capacity of a different network. In this paper, we sift through various capacity-impacting parameters and present a simple relationship that can be used to estimate the capacity of both static and mobile networks. Specifically, we show that the network capacity is determined by the average number of simultaneous transmissions, the link capacity and the average number of transmissions required to deliver a packet to its destination. Our result is valid for both finite networks and asymptotically infinite networks. We then use this result to explain and better understand the insights of some existing results on the capacity of static networks, mobile networks and hybrid networks and the multicast capacity. The capacity analysis using the aforementioned relationship often becomes simpler. The relationship can be used as a powerful tool to estimate the capacity of different networks. Our work makes important contributions towards developing a generic methodology for network capacity analysis that is applicable to a variety of different scenarios.Comment: accepted to appear in IEEE Transactions on Wireless Communication

Urban Scaffold for Renewing Derelict Fabric

In a historic Italian town, opportune innovations in automated parking provide solutions to multifaceted challenges in urban renewal and economic revitalization. A single automated parking facility alleviates pressure in urban infrastructure, simultaneously stabilizing an endangered building shell, and becoming a catalyst for phased urban redevelopment. Strategic opportunities in geography and context are pursued to produce upfront and long-term project feasibility

The Appearance of College Students’ Labor View in New Era

The concept is the forerunner of action, and the view of labor is the reflection of labor. As a kind of ideological concept, the view of labor has its own independence at the same time. The new era has given birth to new ideas. As a result, a correct view of labor that meets the requirements of the development of the times and the laws of the physical and mental development of contemporary college students has emerged. As a new thing, the appearance of university students’ labor view in the new era has its profound theoretical origin, multiple logics and rich connotation