Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center, we present an update of the main results from this unique data set: a measurement of mass and distance ...to Sgr A*. Our progress is not only due to the eight-year increase in time base, but also to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to Sgr A*; the statistical errors of 0.13 × 10 6 M and 0.12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, the star S1 also yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass and distance: M = 4.28 0.10 stat . 0.21 sys × 10 6 M and R 0 = 8.32 0.07 stat . 0.14 sys kpc . These numbers are in agreement with the recent determination of R0 from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from Sgr A*, and of the radio source Sgr A* agree to within 1 mas. In total, we have determined orbits for 40 stars so far, a sample which consists of 32 stars with randomly oriented orbits and a thermal eccentricity distribution, plus eight stars that we can explicitly show are members of the clockwise disk of young stars, and which have lower-eccentricity orbits.
•The authors employ the non-toxic and safe adsorbent for MG removal.•The effect of some parameters on adsorption interpreted by this model.•Applicability and surface adsorption capacity of this novel ...adsorbent is high.•Using small amount of adsorbent in short time is necessary for complete dye removal.
In this research, a novel adsorbent, zinc oxide nanoparticle loaded on activated carbon (ZnO-NP-AC) was synthesized by a simple, low cost and efficient procedure. Subsequently, this novel material was characterizated and identified by different techniques such as Brunauer, Emmett and Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis. Unique properties such as high surface area (>603m2/g) and low pore size (<61Å) and average particle size lower than 100Å in addition to high reactive atom and presence of various functional groups make it possible for efficient removal of malachite green (MG). In batch experimental set-up, optimum conditions for quantitative removal of MG by ZnO-NP-AC was attained following searching effect of variables such as adsorbent dosage, initial dye concentration and pH. Optimum values were set as pH of 7.0, 0.015g of ZnO-NP-AC at removal time of 15min. Kinetic studies at various adsorbent dosage and initial MG concentration show that maximum MG removal was achieved within 15min of the start of every experiment at most conditions. The adsorption of MG follows the pseudo-second-order rate equation in addition to interparticle diffusion model (with removal more than 95%) at all conditions. Equilibrium data fitted well with the Langmuir model at all amount of adsorbent, while maximum adsorption capacity was 322.58mgg−1 for 0.005g of ZnO-NP-AC.
The reverse supply chain and disassembly processes are getting more and more important for tackling the burden of waste electrical and electronic equipment. The disassembly's complexity and frequent ...manual operation makes this process relatively expensive compared to its potential profit. The collection of end-of-life product is also a big issue dealing with vehicle routing. Thus, the decisions taken for collection and disassembly of end-of-life products need to be optimised. In this work, an optimisation model is developed for incorporating these problems. Our experimental study shows joint optimisation of collection and disassembly with coordination between them improves the global performance of the reverse supply chain including lower total cost corresponding to the component demand satisfaction.
•A reverse supply chain with disassembly operations is studied.•Integrated collection and disassembly problem is considered.•A model for joint optimisation of collection and disassembly is developed.•The impact of problem parameters is evaluated via an experimental study.•The simultaneous optimisation of collection and disassembly increases performances.
Pharmaceutically active compounds (PhACs), including prescription drugs, over-the-counter medications, drugs used in hospitals and veterinary drugs, have been found throughout the water cycle. A desk ...study was initiated by the Global Water Research Coalition to consolidate a uniform selection of such compounds in order to judge risks of PhACs for the water cycle. By identifying major existing prioritization efforts and evaluating the criteria they use, this study yields a representative and qualitative profile ('umbrella view') of priority pharmaceuticals based on an extensive set of criteria. This can then be used for further studies on analytical methods, occurrence, treatability and potential risks associated with exposure to PhACs in water supply, identifying compounds most likely to be encountered and that may have significant impact on human health. For practical reasons, the present study excludes veterinary drugs. The pragmatic approach adopted provides an efficient tool to manage risks related to pharmaceuticals and provides assistance for selecting compounds for future studies.
Abstract
We present the first fully simultaneous fits to the near-infrared (NIR) and X-ray spectral slope (and its evolution) during a very bright flare from Sgr A*, the supermassive black hole at ...the Milky Way's centre. Our study arises from ambitious multiwavelength monitoring campaigns with XMM–Newton, NuSTAR and SINFONI. The average multiwavelength spectrum is well reproduced by a broken power law with ΓNIR = 1.7 ± 0.1 and ΓX = 2.27 ± 0.12. The difference in spectral slopes (ΔΓ = 0.57 ± 0.09) strongly supports synchrotron emission with a cooling break. The flare starts first in the NIR with a flat and bright NIR spectrum, while X-ray radiation is detected only after about 103 s, when a very steep X-ray spectrum (ΔΓ = 1.8 ± 0.4) is observed. These measurements are consistent with synchrotron emission with a cooling break and they suggest that the high-energy cut-off in the electron distribution (γmax) induces an initial cut-off in the optical–UV band that evolves slowly into the X-ray band. The temporal and spectral evolution observed in all bright X-ray flares are also in line with a slow evolution of γmax. We also observe hints for a variation of the cooling break that might be induced by an evolution of the magnetic field (from B ∼ 30 ± 8 G to B ∼ 4.8 ± 1.7 G at the X-ray peak). Such drop of the magnetic field at the flare peak would be expected if the acceleration mechanism is tapping energy from the magnetic field, such as in magnetic reconnection. We conclude that synchrotron emission with a cooling break is a viable process for Sgr A*'s flaring emission.
In this study, the mechanical properties, formability and forming limit diagrams (FLDs) of the tailor-welded blanks (TWBs) produced by friction stir welding (FSW) were analyzed experimentally. At ...first, the suitable FSW parameters were achieved. The formability and FLDs of TWBs were evaluated for sheets with the same or different thicknesses and compared to the base metal sheet. This study was performed on low carbon steel (St14) sheets with a lot of applications in automobile industries. The welded zone properties were evaluated by some experiments. The tensile test, micro hardness testing, and metallographic studies were done. The effect of welding seam directions on formability and FLD were investigated concerning two aspects. The welding process was carried out in rolling and transverse directions with no effect on formability, and then the welding process was performed in the principal stress direction and perpendicular to it; these directions had a significant effect on formability. Also, it was revealed that welding caused formability decrease, and in TWBs with different thicknesses, this negative effect was higher. In addition, the initial orientation of sheets had none effect on FSW process.
This article compares the effectiveness of pure and modified TiO2 for photocatalytic degradation of different organic matters and clarifies the advantages of the modified TiO2 with photoactivity ...under visible light. Photocatalytic degradation technique with titanium dioxide is generally applied for treating wastewater containing refractory organic contaminants with the purpose of reuse due to its ability to achieve complete mineralization of the compounds under mild conditions such as ambient temperature and pressure. Performance of different types of photocatalytic reactors, effects of important parameters on the reactors performance, effect of various methods used to enhance the photocatalytic activity of TiO2 including doping, sensitization of TiO2 and surface modification are discussed in details. So far, a few review papers have been published and extensive information have been reported on the structure and electronic properties of TiO2, difference between TiO2 with other common semiconductors used for photocatalytic applications, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling, the effects of various operating parameters on the photocatalytic degradation of phenols and dyes and types of reactors, comparison between effective modes of TiO2 application as immobilized on surface or as suspension, and photocatalytic hybrid membrane system are presented. However, in the published review papers, performance of the different modified photocatalysts is rarely compared quantitatively. Therefore, in order to provide an inclusive and effective comparison among the studies, specific removal rate (SRR) (mgcompoundremoved/gcat.h) was calculated as a response.
•A collaborative hub location problem with uncertainty is studied.•The uncertainty is related to supplementary costs of collaborative hub setup costs.•Forming a collaboration depends on the ...uncertainty and the cost sharing strategy.•Parameters increasing the CPU time are identified by a sensitivity analysis.•The solutions of the regret-based MILP model are robust notably in the worst case.
Collaboration in supply chains by sharing resources has an important role in Physical Internet. It allows the participating supply chains reducing their own and common objective costs. Due to a lack of literature, we focus on hub location problem in collaborative context of two distribution networks belong to different supply chains. The uncertainty corresponding to the supplementary cost included in the setup cost of establishing a shared hub facility is taken into account. Three cases of collaboration and four cost sharing strategies are investigated. Our work allows to verify whether a collaboration proposes better decision and how the total cost is shared among each network to obtain profitable solutions.
The Galactic Center black hole Sgr A* is the archetypical example of an underfed massive black hole. The extremely low accretion rate can be understood in radiatively inefficient accretion flow ...models. Testing those models has proven to be difficult due to the lack of suitable probes. Radio and submillimeter polarization measurements constrain the flow very close to the event horizon. X-ray observations resolving the Bondi radius yield an estimate roughly four orders of magnitude further out. Here, we present a new, indirect measurement of the accretion flow density at intermediate radii. We use the dynamics of the gas cloud G2 to probe the ambient density. We detect the presence of a drag force slowing down G2 with a statistical significance of 9 . This probes the accretion flow density at around 1000 Schwarzschild radii and yields a number density of 4 × 103 cm−3. Self-similar accretion models where the density follows a power-law radial profile between the inner zone and the Bondi radius have predicted similar values.
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