如何通过测量复摆的周期计算转动惯量

本文给出一种简约可行的方法,用来计算不规则物体绕任意轴转动时的转动惯量,同时,亦可定出质心轴位置.本文讨论的内容对教学有意义.     

Schröder iteration functions associated with a one-parameter family of biquadratic polynomials

Schröder iteration functions, a generalization of the Newton–Raphson method to determine roots of equations, are generally rational functions which possess some critical points, free to converge to attracting cycles. These free critical points, however, satisfy some higher-degree polynomial equations which we solve analytically. Then, with the help of microcomputer plots, we examine the Julia sets of the Schröder functions and the orbits of all their free critical points associated with a particular one-parameter family of quartic polynomials, by walking in their dynamic and parameter spaces. This examination takes place in the complex plane as well as on the Riemann sphere.     

Growth technology and X-ray investigation results of CuFeSe2 crystal modifications

The growth technologies of CuFeSe₂ monocrystals from melt and GTR methods were developed. The existence of two polytypes of tetragonal (primitive and inverse-type) lattices with slightly different parameters and one modification of spinel-type pseuodocubic lattice was established from X-ray investigations.     

A unified periodical boundary conditions for representative volume elements of composites and applications

An explicit unified form of boundary conditions for a periodic representative volume element (RVE) is presented which satisfies the periodicity conditions, and is suitable for any combination of multiaxial loads. Starting from a simple 2-D example, we demonstrate that the “homogeneous boundary conditions” are not only over-constrained but they may also violate the boundary traction periodicity conditions. Subsequently, the proposed method is applied to: (a) the simultaneous prediction of nine elastic constants of a unidirectional laminate by applying multiaxial loads to a cubic unit cell model; (b) the prediction of in-plane elastic moduli for [±θ]_n angle-ply laminates. To facilitate the analysis, a meso/micro rhombohedral RVE model has been developed for the [±θ]_n angle-ply laminates. The results obtained are in good agreement with the available theoretical and experimental results.     

Sedimentation rate of erythrocyte from physics prospective

The European Physical Journal E - A two-dimensional multiphase cellular automaton (CA) model is proposed for the prediction of growth kinetics and microstructural evolution during peritectic...     

Low-velocity impact of rectangular foam-filled fiber metal laminate tubes

Applied Mathematics and Mechanics - Through theoretical analysis and finite element simulation, the low-velocity impact of rectangular foam-filled fiber metal laminate (FML) tubes is studied in...     

Chemical bias of electrochemical and photoelectrochemical water splitting using a hydrogel separator

Resorcinol-formaldehyde hydrogels are shown to be adequate separators in electrochemical and photoelectrochemical water splitting cells. Combined with concentrated buffer electrolytes, they allow the maintenance of relatively stable pH gradients between basic anolytes and acidic catholytes. The water splitting potential at a current density of 3.0 mA/cm² applied between two Pt electrodes and a pH bias of 8.1 units retained a value of 2.7 V for several hours. Using iron foam/hematite as photoanode and Pt as cathode, the water splitting photocurrents at an applied potential of 1.23 V reached values of 0.40 and 0.06 mA/cm² in the presence and absence, respectively, of this chemical bias.     

Zeolitic imidazolate framework-67 (ZIF-67) rhombic dodecahedrons as full-spectrum light harvesting photocatalyst for environmental remediation

The inferior utilization efficiency of light is the main obstacle to the practical application of traditional photocatalysts such as TiO₂ and ZnO. In this regard, the development of novel photocatalysts with the capability of harvesting full spectrum light (from ultraviolet (UV) to near-infrared (NIR)) energy is a promising solution for solar energy conversion and environmental remediation. Here, we report the discovery of a single material that can harvest UV, visible (VIS), and NIR radiations to decompose heavy metal contaminants in aqueous solution. Zeolitic imidazolate framework-67 (ZIF-67) rhombic dodecahedrons were synthesized through a facile solution approach and employed in the reduction of Cr(VI) under UV−VIS−NIR pulsed laser irradiation, which was generated from the fundamental, second and third harmonics of Nd:YAG laser, respectively. The nanostructures showed efficient Cr(VI) reduction under UV, VIS and NIR laser irradiation and the measured reduction efficiency (%) was 71.22%, 69.52%, and 40.79%, respectively after 120 min. A possible explanation for the photocatalytic activity in Cr(VI) reduction was proposed. This is the first study of its kind where pulsed laser and ZIF-67 rhombic dodecahedrons capable of harvesting full spectrum light energy have been employed for the removal of Cr(VI) from water. The extraordinary capacity of harvesting full-spectrum light and long-term stability make ZIF-67 a potential photocatalyst for environmental remediation.     

A quantitatively controllable mesoscopic reliability model of an interdependent public transit network considering congestion,time-delay interaction and self-organization effects

Nonlinear Dynamics - This paper establishes a multi-parameter controlling cascading failures (CFs) model for measuring interdependent public transit network (PTN) reliability under mesoscopic...     

MOFs-derived hierarchical porous carbon confining the monodisperse Ni and defective WOx for efficient and stable hydrogenolysis of cellulose to ethylene glycol

The one-pot catalytic conversion of cellulose into ethylene glycol (EG) is an attractive way of biomass utilization. However, low-cost, efficient, and stable catalysts are the premise and research challenges of industrial application. Herein, the magnetic recyclable W–Ni@C catalyst was synthesized by in-situ pyrolysis of Ni-MOFs impregnated with ammonium metatungstate. Compared with the Ni-W bimetallic catalysts prepared by the impregnation method and the sol–gel method, the W–Ni@C catalyst for cellulose hydrogenolysis reaction can achieve a higher ethylene glycol yield (67.1% vs 43.3% and 42.6%) and 100% of cellulose conversion rate. The uniformly dispersed Ni nanoparticles and abundant defective WO_x were formed in a reductive atmosphere generated in pyrolysis of Ni-MOFs, which was indispensable for the hydrogenolysis of cellulose into EG. Besides, the hierarchical porous carbon derived from organic ligands in Ni-MOFs reduces the mass transfer resistance while confining Ni nanoparticles and WO_x to prevent their leaching, effectively enhancing the stability of the W–Ni@C catalyst. Therefore, the remarkable catalytic performance, the simple and effective recovery method as well as satisfying stability would make W–Ni@C become a promising catalyst for the conversion of cellulose to EG.

Graphical abstract