Well-balanced finite difference WENO schemes for the blood flow model

The blood flow model maintains the steady state solutions, in which the flux gradients are non-zero but exactly balanced by the source term. In this paper, we design high order finite difference weighted non-oscillatory (WENO) schemes to this model with such well-balanced property and at the same time keeping genuine high order accuracy. Rigorous theoretical analysis as well as extensive numerical results all indicate that the resulting schemes verify high order accuracy, maintain the well-balanced property, and keep good resolution for smooth and discontinuous solutions

Preparation, properties and application of ionic liquid-derived carbon-based catalysts for the oxygen reduction reaction

Clean energy storage and conversion technologies are in high demand as the energy crisis and environmental concerns impose tremendous pressure on the sustainability of modern human society. However, the noble-metal catalysts required in oxygen reduction reaction (ORR) remain an obstacle impeding the broad application of clean technologies such as fuel cells and metal-air batteries. So far, many advancements have been achieved with non-noble metal alternative catalysts, especially carbon-based ones. Ionic liquids possess low volatility, high solubility, and tunable composition, making them ideal candidates as carbonaceous precursors. This thesis adopted ethyl-methyl-imidazolium dicyanamide, [emim] [DCA], as an example to prepare nitrogen-doped carbon nanotubes (N-CNTs) composites and porous nitrogen-doped carbons with core-shell structured FeCo alloy nanoparticles for ORR. The correlation between the obtained catalysts and ORR catalytic activity was investigated and their potentials in the rechargeable Zn-air battery were also presented.Saubere Energiespeicher- und -umwandlungstechnologien sind sehr gefragt, da die Energiekrise und Umweltbelange einen enormen Druck auf die Nachhaltigkeit der modernen menschlichen Gesellschaft ausüben. Die für die Sauerstoffreduktionsreaktion (ORR) erforderlichen Edelmetallkatalysatoren bleiben jedoch ein Hindernis, das die breite Anwendung sauberer Technologien wie Brennstoffzellen und Metall-Luft-Batterien behindert. Bisher wurden viele Fortschritte mit alternativen Nichtedelmetallkatalysatoren erzielt, insbesondere mit solchen auf Kohlenstoffbasis. Ionische Flüssigkeiten besitzen eine geringe Flüchtigkeit, eine hohe Löslichkeit und eine einstellbare Zusammensetzung, was sie zu idealen Kandidaten als kohlenstoffhaltige Vorstufen macht. Diese Dissertation nahm Ethyl-Methyl-Imidazolium-Dicyanamid, [emim] [DCA], als Beispiel zur Herstellung von Stickstoff-dotierten Kohlenstoff-Nanoröhren (N-CNTs)-Kompositen und porösen Stickstoff-dotierten Kohlenstoffen mit Kern-Schale-strukturierten FeCo-Legierungs-Nanopartikeln für die ORR. Die Korrelation zwischen den erhaltenen Katalysatoren und der katalytischen ORR-Aktivität wurde untersucht und ihr Potenzial in der wiederaufladbaren Zn-Luft-Batterie wurde ebenfalls vorgestellt

Chandra Observation of a Weak Shock in the Galaxy Cluster A2556

Based on a 21.5 ks \chandra\ observation of A2556, we identify an edge on the surface brightness profile (SBP) at about 160$h_{71}^{-1}$ kpc northeast of the cluster center, and it corresponds to a shock front whose Mach number $\mathcal{M}$ is calculated to be $1.25_{-0.03}^{+0.02}$. No prominent substructure, such as sub-cluster, is found in either optical or X-ray band that can be associated with the edge, suggesting that the conventional super-sonic motion mechanism may not work in this case. As an alternative solution, we propose that the nonlinear steepening of acoustic wave, which is induced by the turbulence of the ICM at the core of the cluster, can be used to explain the origin of the shock front. Although nonlinear steepening weak shock is expected to occur frequently in clusters, why it is rarely observed still remains a question that requires further investigation, including both deeper X-ray observation and extensive theoretical studies.Comment: 15 pages, 4 figures, accepted by Ap

Industrial Applications of Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is an analytical detection technique based on atomic emission spectroscopy to measure elemental composition. With the development of lasers and detection systems, applications of LIBS encompass a broad range, including physics, engineering, space missions, environment, etc. due to the unique features of little or no sample preparation, noncontact, fast response, and multielemental analysis. The fundamental and application have been extensively studied to improve LIBS technique. This chapter largely targets the engineering fields, especially practical applications. Laser-induced breakdown spectroscopy will be discussed in this chapter including its fundamentals, industrial applications, and challenges

Strong Optical and UV Intermediate-Width Emission Lines in the Quasar SDSS J232444.80-094600.3: Dust-Free and Intermediate-Density Gas at the Skin of Dusty Torus ?

Emission lines from the broad emission line region (BELR) and the narrow emission line region (NELR) of active galactic nuclei (AGNs) are extensively studied. However, between these two regions emission lines are rarely detected. We present a detailed analysis of a quasar SDSS J232444.80-094600.3 (SDSS J2324$-$0946), which is remarkable for its strong intermediate-width emission lines (IELs) with FWHM $\approx$ 1800 \kmps. The IEL component is presented in different emission lines, including the permitted lines \lya\ $\lambda$1216, \civ\ $\lambda$1549, semiforbidden line \ciii\ $\lambda$1909, and forbidden lines \oiii\ $\lambda\lambda$4959, 5007. With the aid of photo-ionization models, we found that the IELs are produced by gas with a hydrogen density of $n_{\rm H} \sim 10^{6.2}-10^{6.3}~\rm cm^{-3}$, a distance to the central ionizing source of $R \sim 35-50$ pc, a covering factor of CF $\sim$ 6\%, and a dust-to-gas ratio of $\leq 4\%$ times of SMC. We suggest that the strong IELs of this quasar are produced by nearly dust-free and intermediate-density gas located at the skin of the dusty torus. Such strong IELs, served as a useful diagnose, can provide an avenue to study the properties of gas between the BELR and the NELR

Industrial Applications of Tunable Diode Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) utilizes the absorption phenomena to measure the temperature and species concentration. The main features of the TDLAS technique are its fast response and high sensitivity. Extensive research has been performed on the utilization of diode laser absorption spectroscopy for the system monitoring and its control. The TDLAS technique gives self-calibrations to reduce the noise such as particles and dusts because the laser wavelength is rapidly modulated at kHz rates. In addition, two dimensional (2D) temperature and concentration distributions can be obtained by combining computed tomography (CT) with TDLAS. The TDLAS applications have been extensively studied with great progress. This chapter largely focuses on the engineering fields, especially the practical industrial applications