On the r

By presenting Riordan matrix as a triangle, the central coefficients are entries in the central column. Starting at the central column, the r-shifted central coefficients are entries in column r of the right part of the triangle. This paper aims to characterize the r-shifted central coefficients of Riordan matrices. Here we will concentrate on four elements of the subgroups of the Riordan group, that is, the Bell subgroup, the associated subgroup, the derivative subgroup, and the hitting time subgroup. Some examples are presented to show how we deduce the generating functions for interesting sequences by using different means of calculating these r-shifted central coefficients. Besides, we make some extensions in the Bell subgroup

Large Photonic Band Gaps in Certain Periodic and Quasi-Periodic Networks in two and three dimensions

The photonic band structures in certain two- and three-dimensional periodic networks made of one-dimensional waveguides are studied by using the Floquet-Bloch theorem. We find that photonic band gaps exist only in those structures where the fundamental loop exhibits anti-resonant transmission. This is also true for quasi-periodic networks in two and three dimensions, where the photonic band structures are calculated from the spectra of total transmission arising from a source inside the samples. In all the cases we have studied, it is also found that the gap positions in a network are dictated by the frequencies at which the anti-resonance occurs.Comment: 7 pages, 10 figures and 1 table. Published in Phys. Rev. B, 70, 125104 (2004

Atmospheric mercury footprints of nations.

The Minamata Convention was established to protect humans and the natural environment from the adverse effects of mercury emissions. A cogent assessment of mercury emissions is required to help implement the Minamata Convention. Here, we use an environmentally extended multi-regional input-output model to calculate atmospheric mercury footprints of nations based on upstream production (meaning direct emissions from the production activities of a nation), downstream production (meaning both direct and indirect emissions caused by the production activities of a nation), and consumption (meaning both direct and indirect emissions caused by final consumption of goods and services in a nation). Results show that nations function differently within global supply chains. Developed nations usually have larger consumption-based emissions than up- and downstream production-based emissions. India, South Korea, and Taiwan have larger downstream production-based emissions than their upstream production- and consumption-based emissions. Developed nations (e.g., United States, Japan, and Germany) are in part responsible for mercury emissions of developing nations (e.g., China, India, and Indonesia). Our findings indicate that global mercury abatement should focus on multiple stages of global supply chains. We propose three initiatives for global mercury abatement, comprising the establishment of mercury control technologies of upstream producers, productivity improvement of downstream producers, and behavior optimization of final consumers

Enhanced Cycle Life and Capacity Retention of Iron Oxide Ultrathin Film Coated SnO₂ Nanoparticles at High Current Densities

Tin oxide (SnO2) has a high theoretical capacity (∼782 mA h g-1), but it experiences large volume changes during charge and discharge cycles that cause rapid capacity fade, which limits its practical use as an anode material. In an attempt to solve this, we coated these particles with ultrathin electrochemically active iron oxide (FeOx) films that act as an artificial solid electrolyte interphase layer, thus stabilizing the SnO2 particles for better longevity of significantly improved performance at high current densities in a practical voltage window. Since there exists a tradeoff between species transport and protection of particles (expecting long life), a film with an optimum thickness was achieved by atomic layer deposition (ALD) of FeOx on SnO2 particles. With an optimum thickness of about 0.24 nm after 20 cycles of iron oxide ALD (20Fe), an initial capacity of ∼658 mA h g-1 was achieved at a high current density of 1250 mA g-1. After 1000 cycles of charge/discharge at 1250 mA g-1, the 20Fe sample showed a capacity retention of 94% as compared to 52% of the uncoated sample when cycled at room temperature; at 55°C, the capacity retention of the 20Fe sample was 93% compared to 33% of the uncoated sample

Ultrathin Conductive CeO₂ Coating for Significant Improvement in Electrochemical Performance of LiMn₁.₅Ni₀.₅O₄ Cathode Materials

LiMn1.5Ni0.5O4 (LMNO) has a huge potential for use as a cathode material in electric vehicular applications. However, it could face discharge capacity degradation with cycling at elevated temperatures due to attacks by hydrofluoric acid (HF) from the electrolyte, which could cause cationic dissolution. To overcome this barrier, we coated 3-5 micron sized LMNO particles with a ∼3 nm optimally thick and conductive CeO2 film prepared by atomic layer deposition (ALD). This provided optimal thickness for mass transfer resistance, species protection, and mitigation of cationic dissolution at elevated temperatures. After 1,000 cycles of chargedischarge between 3.5 V-5 V (vs. Li+/Li) at 55°C, the optimally coated sample, 50Ce (50 cycles of CeO2 ALD coated) had a capacity retention of ∼97.4%, when tested at a 1C rate, and a capacity retention of ∼83% at a 2C rate. This was compared to uncoated LMNO particles that had a capacity retention of only ∼82.7% at a 1C rate, and a capacity retention of ∼40.8% at a 2C rate

Experimental Study on the Bearing Capacity of Glass Deck under the Condition of Vehicle Traffic

In order to study the mechanical properties of the glass plate structure applied to the automobile bridge deck, the bearing capacity test of the glass bridge deck under the wheel load is carried out, and the failure mode, load displacement curve and safety function of the glass plate under the boundary, position and number of layers of the wheel load are analyzed. The results show that the ultimate bearing capacity of laminated glass under the condition of simply supported boundary on both sides is about four sides supported 71.8%. The ultimate bearing capacity of single-layer glass under the boundary condition of simple support on both sides is about four sides 51.4% from the point of view of meeting the structural strength requirements. The loading test is carried out by applying different multiple wheel loads at the plate angle and the center of the plate. The test results can provide reference for the application of the glass bridge deck in engineering

A variable corona during the transition from type-C to type-B quasi-periodic oscillations in the black hole X-ray binary MAXI J1820+070

We analyze a Neutron Star Interior Composition Explorer (NICER) observation of the black hole X-ray binary MAXI J1820+070 during a transition from type-C to type-B quasi-periodic oscillations (QPOs). We find that below ~2 keV, for the type-B QPOs the rms amplitude is lower and the magnitude of the phase lags is larger than for the type-C QPOs. Above that energy, the rms and phase-lag spectra of the type-B and type-C QPOs are consistent with being the same. We perform a joint fit of the time-averaged spectra of the source, and the rms and phase-lag spectra of the QPOs with the time-dependent Comptonization model vkompth to study the geometry of the corona during the transition. We find that the data can be well-fitted with a model consisting of a small and a large corona that are physically connected. The sizes of the small and large coronae increase gradually during the type-C QPO phase whereas they decrease abruptly at the transition to type-B QPO. At the same time, the inner radius of the disc moves inward at the QPO transition. Combined with simultaneous radio observations showing that discrete jet ejections happen around the time of the QPO transition, we propose that a corona that expands horizontally during the type-C QPO phase, from ~10^{4} km (~800 Rg) to ~10^{5} km (~8000 Rg) overlying the accretion disc, transforms into a vertical jet-like corona extending over ~10^{4} km (~800 Rg) during the type-B QPO phase.Comment: 22 pages, 16 figures, 2 tables, accepted for publication in MNRA