On input-to-state stability for stochastic multi-group models with multi-dispersal

This paper focuses on the input-to-state stability for a general class of stochastic multi-group models with multi-dispersal. By incorporating graph theory with Lyapunov method as well as stochastic analysis techniques, novel sufficient criteria are derived, which are in the form of Lyapunov-type theorem and coefficient-type criterion, respectively. Moreover, to show the applicability of our findings, we employ coefficient-type criterion to analyze the input-to-state stability for stochastic coupled oscillators. Finally, a numerical example and its simulations are offered to demonstrate the validity and feasibility of the theoretic results.     

Universal inequalities on complete noncompact smooth metric measure spaces

In this paper, we obtain universal inequalities for the eigenvalues of the Dirichlet problem and clamped plate problem of drifting Laplacian on (\(n+1\))-dimensional (\(n\ge 4\)) complete noncompact simply connected smooth metric measure spaces which meet some conditions of the sectional curvature and radial weighted Ricci curvature.     

Tin nanoparticles embedded in ordered mesoporous carbon as high-performance anode for sodium-ion batteries

Tin (Sn) has been considered as an attractive anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity (847 mAh g^?1). Nevertheless, its low conductivity and large volume change during cycling essentially prevent the possibility of high capacity and long-term cycle for SIBs. In this work, Sn nanoparticles are well embedded into the highly ordered mesoporous carbon (CMK-3) matrix (Sn@CMK-3) using a facile sonochemical method combined with heat treatment. The resultant Sn@CMK-3 nanohybrid electrode delivers an initial charge capacity of 412 mAh g^?1 at 100 mA g^?1. A reversible capacity of 337 mAh g^?1 is obtained after 200 cycles, indicating the good cycle stability of the nanohybrid structure. The electrode also shows a potential rate capability, which maintains a capacity of 228 mAh g^?1 at 1000 mA g^?1. When the current density returns to 50 mA g^?1, the capacity goes back to 381 mAh g^?1, with a capacity retention of 86.9%. The enhanced sodium storage performance of Sn@CMK-3 nanohybrid can be related to the synergistic effect between CMK-3 and Sn.

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Graphical abstract Sn@CMK-3 nanohybrid with Sn nanoparticles uniformly distributed into the highly ordered mesoporous carbon matrix exhibited good cycling performance and rate capability.

     

Effects of some nucleating agents on the supercooling of erythritol to be applied as phase change material

Nine nucleating agents, calcium pimelate (CaPi), bicyclic [1, 2, 2]heptane di-carboxylate (HPN-68), a commercially obtained aryl amide nucleating agent (TMB-5), calcium salt of hexahydrophthalic acid (HPN-20E), 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS) and sodium, potassium, magnesium and calcium salt of benzene-1, 3, 5-tricarboxylic acid (Na₃BTC, K₃BTC, Mg₃BTC₂ and Ca₃BTC₂, respectively), were applied to reduce the supercooling of erythritol, and their effects were investigated by cyclic differential scanning calorimetry (DSC). The results revealed that Na₃BTC and K₃BTC could not induce erythritol to crystallize under the experiment condition. MDBS could only make erythritol to crystallize at a temperature slightly higher than that of pure erythritol, and the effect was unstable. Mg₃BTC₂, Ca₃BTC₂ and HPN-68 could induce erythritol to crystallize at relatively high temperature, but the peak temperature of crystallizing (T _{p, cr}) and the phase change enthalpy of crystallizing (Δ_cr H) decreased greatly as the melting–crystallizing cycles increased. HPN-20E-doped erythritol crystallized at a high temperature with the T _{p, cr} of 69.3 °C at the first cycle, but the T _{p, cr} and Δ_cr H varied greatly during the melting–crystallizing cycles. CaPi and TMB-5 could induce erythritol to crystallize at a stable temperature with the T _{p, cr} of about 69 °C and 64 °C, respectively, and with a stable Δ_cr H of about 204 and 185 J g^?1, respectively, in all melting–crystallizing cycles. Hence, CaPi- and TMB-5-doped erythritol could be used as PCMs and applied in thermal energy storage in which the energy was absorbed at a high temperature and released at a lower but stable temperature.     

Improving effect of boron carbide on the combustion and thermal oxidation characteristics of amorphous boron

Boron carbide (B₄C) is one of the main products from the primary combustion of boron (B)-based propellants and has a significant influence on the secondary combustion of B. To systematically evaluate its effects on the secondary combustion of B, mixtures of B₄C and B in different mass ratios were prepared. To study the ignition temperatures and combustion flames of the samples, a xenon lamp ignition experimental system and a flame shape test system were designed, respectively. A thermogravimetry–differential scanning calorimetry–Fourier transform infrared spectroscopy combined thermal analysis system was used to study the thermal oxidation characteristics and analyze the gaseous products of the samples. The results indicate that B₄C reduces the heat absorption at the beginning of the ignition, but subsequently prevents the rapid rise of sample temperature. During the stable combustion stage, the maximum flame length under optical density 10⁻⁴ (OD4) filter was 20.4 mm, and the maximum flame length under 580 nm + OD4 filters (represents the combustion of B element) was 16.7 mm. The samples contained a small amount of HBO₂ and H₃BO₃, which led to slight mass loss during the low temperature section of the thermal oxidation process. During the high temperature section, the oxidation of B and B₄C caused considerable mass gain. The gaseous products of the thermal oxidation process include CO₂, CO, and H₂O. In general, the B content of 60% was the most beneficial to decrease the oxidation temperature, increase the combustion intensity, and improve the heat-releasing ability of the samples.

     

Synthesis,characterization of new bisphenol-based benzoxazines and the thermal properties of their polymers

Journal of Thermal Analysis and Calorimetry - New bisphenol-based benzoxazines (BBA-a and BBA-bra) were synthesized from bisphenol containing trityl group, paraformaldehyde, aniline and...     

Standard molar enthalpy of formation of [(C12H8N2)2Bi(O2NO)3] and its biological activity on Schizosaccharomyces pombe

The title complex [(C₁₂H₈N₂)₂Bi(O₂NO)₃] was synthesized by reaction of 1,10-phenanthroline (phen) and Bi(NO₃)₃·5H₂O. The structure of the complex was characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. An advanced solution-reaction isoperibol microcalorimeter was applied to determine the standard molar enthalpies of formation at 298.15 K of the complex and Bi(NO₃)₃·5H₂O, giving –(798.92 ± 5.99) and –(1986.87 ± 0.20) kJ mol⁻¹, respectively. The biological effect of the complex was evaluated by microcalorimetry on the growth of Schizosaccharomyces pombe (S. pombe). According to thermogenic curves, the corresponding thermokinetics and thermodynamic parameters were derived. The complex had good bioactivity on the growth metabolism of S. pombe, with the value of IC₅₀ being 2.8 × 10⁻⁵ mol L⁻¹.

     

The role of MgO in the thermal behavior of MgO–silica fume pastes

The compounds of MgO–silica fume (SF) pastes constitute magnesium silicate hydrate (M–S–H) in a new generation of basic castables. However, Mg(OH)₂ is a common reaction product with the formation of M–S–H. This study aims to reduce the formation of Mg(OH)₂ in MgO–SF pastes. In this study, MgO powders were prepared by calcining magnesite at different temperatures and then mixed with SF and water to prepare MgO–SF pastes. The properties of MgO powders were characterized, and the pH values in the pore solutions of MgO–SF pastes were measured. The MgO–SF pastes cured for 90 days were calcined at 500, 700, 900 and 1200 °C, and the microstructure was characterized afterward. The results showed that both the reactivity of MgO powders and the pH value of the pore solution of MgO–SF pastes were diverse, which essentially depended on the grain sizes and the crystalline degree of MgO. Increasing the calcination temperature of MgO was beneficial to reduce the formation of Mg(OH)₂ or even stop it when using MgO calcined at 1450 °C. Enstatite and forsterite formed for all MgO–SF pastes after calcination. However, the microstructure of MgO–SF paste with MgO calcined at 1450 °C was denser than others. MgO–SF pastes were suitable for the new-generation refractory castables. Notably, using MgO calcined at 1450 °C is more appropriate.     

Porous nitrogen-doped graphene for high energy density supercapacitors in an ionic liquid electrolyte

Porous nitrogen-doped graphene (PNG) has been prepared via simple thermal treatment of graphene oxide and urea, and the morphology and structure of the PNG have been characterized by using a range of electron microscopy, X-ray photoelectron spectroscopy, and other techniques. The electrochemical performances of the PNG have been investigated in an ionic liquid electrolyte by cyclic voltammetry and galvanostatic charge-discharge via both three-electrode and two-electrode configurations. The PNG electrode delivers a specific capacitance of 310 F g^?1 at 1 A g^?1 with good cycling stability over 4000 cycles. The high electrochemical performance is ascribed to the porous structure and nitrogen-doping in the PNG. The porous structure enables high specific surface area and rapid ion mobility, contributing to double layer capacitance, while the N-doping enhances electrochemical activity and electric conductivity, contributing to pseudocapacitance. Meanwhile, the ionic liquid electrolyte enables a very wide working voltage of 3 V, leading to a high energy density up to 163.8 W h kg^?1. The fabricated supercapacitor can light up a LED for a long while with low self-discharge, showing good potential for practical application.