highlights•We present algorithms to determine the most reliable strategy and path on stochastic and time-dependent networks.•The measure of reliability chosen is the on-time arrival probability at ...the destination.•We present a decreasing order-of-time algorithm for optimal time-adaptive strategy and a pruning algorithm for optimal path.•We derive the correctness of the proposed procedures and show their efficacy on large-scale transportation networks.
This study presents algorithms to determine the most reliable routes on stochastic and time-dependent networks. The measure of reliability adopted is the probability of on-time arrival at the destination, given a threshold arrival-time. We propose two distinct algorithms to determine optimal time-adaptive strategy and optimal apriori path on stochastic and time-dependent networks. First, a decreasing order-of-time algorithm is proposed to determine the optimal strategy to the sink from all node and departure-time combinations. Second, a label-correcting, network pruning algorithm is proposed to determine the optimal path between the source and the sink for a given departure-time. The correctness of both the proposed algorithms is proved and their computational complexity expressions are derived. The efficacy of the proposed procedures is demonstrated on large-scale transportation networks. This work has the potential to facilitate wider application of stochastic and time-dependent networks in reliability-based modeling and analysis.
Although Li-rich layered oxides (Li1+xNiyCozMn1-x-y-zO2 > 250 mAh g(-1)) are attractive electrode materials providing energy densities more than 15% higher than today's commercial Li-ion cells, they ...suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1-yTiyO3 phases with capacities of ~240 mAh g(-1) exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge-discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1-ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay.
Functionalized multiwalled carbon nanotubes (CNTs) are coated with a 4–5 nm thin layer of V2O5 by controlled hydrolysis of vanadium alkoxide. The resulting V2O5/CNT composite has been investigated ...for electrochemical activity with lithium ion, and the capacity value shows both faradaic and capacitive (nonfaradaic) contributions. At high rate (1 C), the capacitive behavior dominates the intercalation as 2/3 of the overall capacity value out of 2700 C/g is capacitive, while the remaining is due to Li-ion intercalation. These numbers are in agreement with the Trasatti plots and are corroborated by X-ray photoelectron spectroscopy (XPS) studies on the V2O5/CNTs electrode, which show 85% of vanadium in the +4 oxidation state after the discharge at 1 C rate. The cumulative high-capacity value is attributed to the unique property of the nano V2O5/CNTs composite, which provides a short diffusion path for Li+-ions and an easy access to vanadium redox centers besides the high conductivity of CNTs. The composite architecture exhibits both high power density and high energy density, stressing the benefits of using carbon substrates to design high performance supercapacitor electrodes.
•We present a label-correcting pruning-based algorithm to determine the least expected travel time path on stochastic time-dependent networks.•We construct a novel bi-level, bounds-based pruning ...criterion that efficiently determines whether a subpath can belong to the optimal path.•The empirical computational complexity is shown to be polynomial through extensive experiments on real-world networks.•The proposed algorithm outperforms the existing non-dominance based procedure and the performance gap increases exponentially with network- size.
This study addresses the problem of determining the path with the least expected travel time on stochastic and time-dependent networks. The Bellman’s optimality principle is not applicable to this problem —because of its non-linear objective function— making it difficult to solve. In this light, we propose a pruning-based algorithm that progressively determines subpaths from the source and eliminates those that are non-optimal. The algorithm uses a novel bi-level, bounds-based pruning criterion to determine whether subpath can belong to the optimal path. We show that the pruning criterion is valid and that the algorithm terminates with an exact solution. Computational experiments demonstrate that the algorithm can successfully solve the problem even on large real-world networks and that its practical computational complexity is polynomial. Finally, we show that the pruning algorithm outperforms the existing non-dominance based procedure by a factor proportional to the network size on medium-sized networks and more so on large-sized networks. This work has the potential to aid in a wider application of stochastic time-dependent networks for modeling and analysis.
In recent years, conversion-based mixed transition-metal oxides have emerged as a potential anode for the next generation lithium-ion batteries because of their high theoretical capacity and high ...rate performance. Herein, an interconnected cobalt molybdenum oxide (CoMoO4) nanoarchitecture derived from molybdenum sulfide (MoS2) nanoflowers is investigated as an anode for lithium-ion batteries. The interconnected CoMoO4 displayed an excellent discharge capacity of 1100 mA h g–1 over 100 cycles at a current rate of C/5. Moreover, the material exhibited an enhanced electrochemical stability, high rate performance, and delivered high discharge capacities of 600 and 220 mA h g–1, respectively, at 5 C and 10 C after 500 cycles. The excellent cycling stability and high rate performance of interconnected CoMoO4 are credited to its unique architecture and porous morphology. The above characteristics and the synergetic effect between the constituting metal ions not only provided a shorter diffusion path for the lithium-ion conduction but also improved the electronic conductivity and mechanical strength of the anode. The field-emission scanning electron microscopy analysis of the electrochemically cycled electrode revealed good structural integrity of the electrode. Further, the practical feasibility of interconnected CoMoO4 in the full cell was analyzed by integrating it with the LiNi0.8Mn0.1Co0.1O2 cathode, which demonstrated excellent cycling stability and high rate performance.
We describe new implementations of leptonic and hadronic models for the broadband emission from relativistic jets in active galactic nuclei in a temporary steady state. For the leptonic model, a ...temporary equilibrium between particle injection/acceleration, radiative cooling, and escape from a spherical emission region is evaluated, and the self-consistent radiative output is calculated. For the hadronic model, a temporary equilibrium between particle injection/acceleration, radiative and adiabatic cooling, and escape is evaluated for both primary electrons and protons. A new, semianalytical method to evaluate the radiative output from cascades initiated by internal gamma gamma pair production is presented. We use our codes to fit snapshot spectral energy distributions (SEDs) of a representative set of Fermi-LAT-detected blazars. We find that the leptonic model provides acceptable fits to the SEDs of almost all blazars with parameters close to equipartition between the magnetic field and the relativistic electron population. However, the hard gamma -ray spectrum of AO 0235+164, in contrast to the very steep IR-optical-UV continuum, poses a severe problem for the leptonic model. If charge neutrality in leptonic models is provided by cold protons, the kinetic energy carried by the jet should be dominated by protons. We find satisfactory representations of the snapshot SEDs of most blazars in our sample with the hadronic model presented here. However, in the case of two quasars the characteristic break at a few GeV energies cannot be well modeled. All of our hadronic model fits require powers in relativistic protons in the range Lp ~ 10 super(47)-10 super(49) erg s super(-1).
Salt exclusion at the roots and salt secretion in the leaves were examined in a mangrove, Avicennia officinalis. The non‐secretor mangrove Bruguiera cylindrica was used for comparative study of ...hydrophobic barrier formation in the roots. Bypass flow was reduced when seedlings were previously treated with high salt concentration. A biseriate exodermis was detected in the salt‐treated roots, along with an enhanced deposition of hydrophobic barriers in the endodermis. These barriers reduced Na⁺ loading into the xylem, accounting for a 90–95% salt exclusion in A. officinalis. Prominent barriers were found in the roots of B. cylindrica even in the absence of salt treatment. A cytochrome P450 gene that may regulate suberin biosynthesis was up‐regulated within hours of salt treatment in A. officinalis roots and leaves, corresponding with increased suberin deposition. X‐ray microanalysis showed preferential deposition of Na⁺ and Cl⁻ in the root cortex compared with the stele, suggesting that the endodermis is the primary site of salt exclusion. Enhanced salt secretion and increased suberin deposition surrounding the salt glands were seen in the leaves with salt treatment. Overall, these data show that the deposition of apoplastic barriers increases resistance to bypass flow leading to efficient salt exclusion at the roots in mangroves.
This work aims to prepare potential solar thermal energy storage coating using melamine-formaldehyde (MF) microcapsules with an n-Tetracosane (n-Tetra) core as phase change material (PCM). The shell ...material was prepared by reacting melamine with formaldehyde using a two-step process. After centrifuging and drying, these microcapsules were incorporated (0–25 wt%) into an epoxy primer-polyurethane (EP-PU) topcoat system for thermal energy storage applications. The microcapsules were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM) & Scanning Electron Microscopy (SEM), respectively. n-Tetra, incorporated in the microcapsule (MF-n-Tetra), has been found to melt at 53.07 °C with the latent heat of melting 134.74 J/g and crystallizes at 48.81 with latent heat crystallization 133.32 J/g. The phase change properties of the coated material were found to increase with the increase in the microcapsule loading. The thermal energy transfer rate was quantified in terms of the time taken by the coated panels to reach an equilibrium temperature of 60 °C. The microcapsule incorporated coatings were also subjected to salt spray analysis to understand any potential effects of phase change material (PCM) loading on the corrosion resistance aspect of the primer-topcoat system. The corrosion resistance was found to increase with microcapsule addition. Thermogravimetric Analysis (TGA) indicated enhanced thermal stability of Tetra in the microcapsule.
•MF-n-Tetracosane microcapsules of size between 2 μm and 20 μm were synthesized.•Increased PCM loading results in higher solar thermal energy storage capacity in coating applications.•Larger solar thermal storage capacity results in a long time for the coating to reach an equilibrium temperature.•Increasing the PCM loading also increased the corrosion resistance due to reduced substrate temperature.
Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new ...materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li(1+x)Ni(y)Co(z)Mn(1-x-y-z)O₂) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li₂Ru(1-y)Sn(y)O₃ materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g(-1). Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (M(n+)→M((n+1)+)) and anionic (O(2-)→O₂(2-)) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li₂MO₃ is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.
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