The behavior of capillary suspensions at diverse length scales: From single capillary bridges to bulk

Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure.     

Enhanced Power Density of Alcohol Biofuel Cell by Polymer-assisted Crosslinks of 3D Graphene on Carbon Paper as the Bioanode

Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.     

INFLUENCE OF FRICTION ON THE MOTION OF BASE WITH AN ECCENTRIC ROTOR

偏心转子惯性力引起的底座运动受到地面摩擦的影响，与光滑情形的理论结果存在定性差异。转子逆时针匀速旋转的惯性力若小于构件总重，则底座随摩擦因子增加而出现连续、一次停顿和两次停顿的振动及完全静止的4种状态。因惯性力对正压力及摩擦力的影响，底座在连续及一次停顿的振动时右向位移较大；而底座跳起时如``蛤蟆夯'则整体向左移动。     

Inducement of ferromagnetic–metallic phase and magnetoresistance behavior in charged ordered monovalent-doped Pr0.75Na0.25MnO3 manganite by Ni substitution

In this communication, the study on the effect of Ni²⁺ substitution on structural, magnetic and electrical transport properties were performed in Pr_0.75Na_0.25Mn_1-xNi_xO₃ (x = 0–0.10) ceramics synthesized using conventional solid-state method. X-ray diffraction patterns showed that all samples were present in single phase and crystallized in orthorhombic structure with Pnma space group. Rietveld refinement analysis revealed unit cell volume slight increase with increase Ni concentration, thereby indicating partial substitution of Ni²⁺ at Mn³⁺. The presence majority of Ni²⁺ states in the compound were confirmed by X-ray photoelectron spectrum. Tolerance factor calculation suggested that Ni substitution exerted no strong effect on structural distortion. For un-doped sample (x = 0), AC susceptibility (χ′) against temperature (T) curve showed paramagnetic (PM)–antiferromagnetic(AFM) behavior at Neel temperature (T_N) of approximately 170 K. Furthermore, resistivity (ρ) against temperature (T) curve showed an insulating behavior for the whole measured temperature range. The χ′ against T curve of x = 0 sample showed broad peak at approximately 218 K which was attributed to the onset of charge ordered (CO) state. No such broad peak was observed in Ni-substituted samples which indicated the weakening of CO state. Moreover, χ′ measurements exhibited successful inducement of PM–FM transition with Curie temperature (T_C), decreasing from 132 K (x = 0.02) to 92 K (x = 0.08). Electrical resistivity measurement on samples (x = 0.02–0.08) displayed inducement of metal–insulator transition, where transition temperature (T_MI) decreased and resistivity increased, with x before re-entrant insulating behavior at x = 0.10. Notably, upturn resistivity was observed below 40 K for x = 0.06 and 0.08 samples. The suppression of CO state and inducement of ferromagnetic-metallic (FMM) state beginning from x = 0.02 sample was attributed to the reduced degree of Jahn–Teller distortion and Coulomb interaction among Mn ions, as well as the presence of ferromagnetic superexchange (FM SE) interaction among Ni²⁺–O–Mn⁴⁺ which improved the alignment charge carrier spins and induced the double-exchange (DE) interaction among Mn³⁺–O–Mn⁴⁺. The decrease in T_C and T_MI with increased x may be due to the enhanced AFM SE interactions of Mn³⁺–O–Mn³⁺, Mn⁴⁺–O–Mn⁴⁺ and Ni²⁺–O–Ni²⁺ which decreased the FM SE interaction of Ni²⁺–O–Mn⁴⁺. Consequently, the effective DE interaction was decreased. In addition, the decreased metallic behavior and re-entrant insulating behavior for x = 0.10 sample was due to the strong AFM interaction between Ni²⁺ ions which consequently contributed to the suppression of FM SE and DE interactions. The observed upturn resistivity below 40 K for x = 0.06 and 0.08 samples was attributed to the Kondo-like effect which resulted from the interaction between itinerant conduction electron spin and localized spin impurity.     

Effects of van der Waals force on nonlinear vibration of electromechanical integrated electrostatic harmonic actuator

An electromechanical integrated electrostatic harmonic actuator is promising for the miniaturization of electromechanical devices. As the dimensions of the actuator decrease, the effects of the van der Waals force become obvious. In this study, by considering the nonlinearity of electrostatic and van der Waals forces, nonlinear vibration equations of the flexible ring of an electrostatic harmonic actuator are deduced. Using these equations, the nonlinear free vibration and nonlinear forced response of the actuator are investigated. The effects of the van der Waals force on the nonlinear vibration of the flexible ring are analyzed. Results show that these effects of the van der Waals force are relatively obvious under some conditions and should be considered.     

Ab initio and Monte Carlo studies of phase transitions and magnetic properties of YCrO3: Heisenberg model

By using the density functional theory (DFT) and Monte Carlo simulations (MCS) with the Heisenberg model, we have studied magnetic properties of the bulk perovskite YCrO₃. The exchange couplings of the Heisenberg model and the magnetic anisotropy are investigated. The 110 direction in the crystalline structure of the compound has shown the minimum energy, it is the easy magnetic direction. Using Monte Carlo simulations, the magnetizations behavior, the effects of system parameters and the critical exponents of the compound YCrO₃ are implemented. It is shown that the bulk perovskite YCrO₃ belongs to the 3D Heisenberg universality class.     

Effect of rotation in magneto-thermoelastic transversely isotropic hollow cylinder with three-phase-lag model

This article deals with the various heat source responses in a transversely isotropic hollow cylinder under the purview of three-phase-lag (TPL) generalized thermoelasticity theory. In presence of magnetic field and due to the rotating behavior of the cylinder, the governing equations are redefined for generalized thermoelasticity with thermal time delay. In order to obtain the stress, displacement and temperature field, the field functions are expressed in terms of modified Bessel functions in Laplace transformed domain. When the outer radius of hollow cylinder tends to infinity, the corresponding results are discussed. Finally an appropriate Laplace transform inversion technique is adopted.     

Force-field parametrization based on radial and energy distribution functions

We propose a novel force-field-parametrization procedure that fits the parameters of potential functions in a manner that the pair distribution function (DF) of molecules derived from candidate parameters can reproduce the given target DF. Conventionally, approaches to minimize the difference between the candidate and target DFs employ radial DFs (RDF). RDF itself has been reported to be insufficient for uniquely identifying the parameters of a molecule. To overcome the weakness, we introduce energy DF (EDF) as a target DF, which describes the distribution of the pairwise energy of molecules. We found that the EDF responds more sensitively to a small perturbation in the pairwise potential parameters and provides better fitting accuracy compared to that of RDF. These findings provide valuable insights into a wide range of coarse graining methods, which determine parameters using information obtained from a higher-level calculation than that of the developed force field. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.     

椭球粒子声辐射力计算及分析

针对水下椭球粒子,以声散射理论为基础,采用分波序列的方法,建立了椭球粒子声辐射力的理论计算模型。进而根据声辐射力计算公式,以刚性椭球粒子和液体椭球粒子为例,计算并分析不同Bessel波束作用下椭球粒子的轴向声辐射力函数特征。数值仿真计算结果表明,对于刚性椭球粒子,扁平椭球粒子相对于细长椭球粒子更有助于激发负声辐射力；对于液体椭球粒子,细长椭球粒子相对于扁平椭球粒子更加容易产生负声辐射力；对于不同介质的椭球粒子,不同的入射波束激发的负声辐射力的效果也存在明显的差异。该结果为复杂的尺寸和介质粒子声操控技术提供了理论的可行性。     

Bio-silica incorporated barium ferrite composites: Evaluation of structure,morphology, magnetic and microwave absorption traits

A series of bio-silica incorporated barium-ferrite-composites with the composition of (x)Bio-SiO₂:(80-x)γ-Fe₂O₃:(20)BaO, where x = 0, 1, 2, and 3 wt% were prepared using the modified solid-state reaction method. The influence of different bio-silica (extricated from sintered rice husk) contents on the surface morphologies, structures, and magnetic characteristics of these composites were assessed. The relative complex permittivity and permeability were resolved using the Nicholson-Ross-Weir strategy in the frequency range of 8–13 GHz. Meanwhile, the reflection loss was estimated through the transmission/reflection line theory to assess the MW absorption properties of the composites. Incorporation of the bio-silica in the barium ferrite composites generated a new hexagonal phase (Ba₃Fe₃₂O₅₁) and a tetragonal phase (BaFeSi₄O₁₀) which led to a decrease in the saturation magnetization and significant shift in the MW frequency absorption peak positions.