Thrust ripple analysis for improved modular tubular permanent magnet synchronous linear motor

Various technologies have ever been developed to minimize the detent force of linear motors. Although the traditional modular structure can effectively reduce the detent force, the width of the flux barrier and the number of units severely limit its application. To solve these, this paper proposes a new modular type of tubular permanent magnet synchronous linear motor (TPMSLM), which consists of two identical unit motors. For simplification, a subdomain analytical method of the unit motor is firstly established, and its accuracy is verified by a comparison with that of the finite element method. Using the two approaches, the important parameters of the motor are analyzed. A modified two-unit modular TPMSLM is also proposed through the star vectograms of the electromotive force, which achieves thrust performance similar to the traditional three-unit modular TPMSLM with a smaller axial size. Moreover, to make full use of the volume of the flux barrier, end teeth are added at both ends of the unit motors. The simulation results indicate that a reasonable end tooth structure can not only reduce the magnetic leakage phenomenon of the end but also effectively improve the thrust of the motor.

Heterogeneous origami-architected materials with variable stiffness

Origami, the ancient art of paper folding, has shown its potential as a versatile platform to design various reconfigurable structures. The designs of most origami-inspired architected materials rely on a periodic arrangement of identical unit cells repeated throughout the whole system. It is challenging to alter the arrangement once the design is fixed, which may limit the reconfigurable nature of origami-based structures. Inspired by phase transformations in natural materials, here we study origami tessellations that can transform between homogeneous configurations and highly heterogeneous configurations composed of different phases of origami unit cells. We find that extremely localized and reprogrammable heterogeneity can be achieved in our origami tessellation, which enables the control of mechanical stiffness and in-situ tunable locking behavior. To analyze this high reconfigurability and variable stiffness systematically, we employ Shannon information entropy. Our design and analysis strategy can pave the way for designing new types of transformable mechanical devices.

Combined Attenuation Zones of Combined Layered Periodic Foundations

Layered periodic foundations (LPFs) with identical unit cells have been proposed as a type of seismic metamaterials due to the unique dynamic characteristic of attenuation zones. However, it is difficult to design attenuation zones with both comparatively low starting frequencies and large bandwidths for traditional LPFs with identical unit cells. In this paper, combined layered periodic foundations (CLPFs) are proposed by combining two traditional LPFs with different unit cells in tandem. Combined attenuation zones of the CLPFs are identified by investigating the frequency response functions of the CLPFs. The generation mechanism of the combined attenuation zones was studied by varying the configuration of CLPFs. The results show that the combined attenuation zones are the union of attenuation zones of the two traditional LPFs. To verify the efficiency of CLPFs, the seismic responses of a four-story frame structure with CLPF are simulated. The present work is very helpful for the design of CLPFs with attenuation zones with a low starting frequency and large bandwidth.

Dependencies for Determining the Thermal Conductivity of Moist Capillary-Porous Materials

A method of determining the effective thermal conductivity of moist capillary-porous materials has been proposed, in which calculations are carried out while taking into account all components of the system (solid, liquid and gas) at once. The method makes it easy to take into account the way water is distributed in the pore space of the material, either as isolated inclusions (drops) or as a continuous component, depending on the moisture content of the material. In the analysis of heat transport in moist capillary-porous materials, the theory of generalized conductivity is used and the structure of moist material is modeled using an ordered geometric structure consisting of identical unit cells in the form of a cube. An equation is obtained for calculating the effective conductivity of capillary-porous materials with isolated and continuous liquid inclusions, with adiabatic and isothermal division of the unit cell. The proposed method is compared to the previously proposed method of determining the effective thermal conductivity of moist materials, in which the three-component system is gradually reduced to a binary system, showing disadvantages of this method compared to the currently proposed. It has been shown that the proposed formulas grant the possibility of a sufficiently accurate prediction of experimental results using the experimental results of the thermal conductivity of moist aerated concrete.

Erratum to: Effectiveness Analysis of a Two Non-Identical Unit Standby System with Switching Device and Proviso of Rest

International Journal of Mathematical, Engineering and Management Sciences, 4(6), 1496–1507, 2019. https://dx.doi.org/10.33889/IJMEMS.2019.4.6-118.

Effectiveness Analysis of a Two Non-Identical Unit Standby System with Switching Device and Proviso of Rest

This paper deals with two-unit cold standby system with switching device and proviso of rest. The system consists of two non-identical units which are connected in parallel redundancy. Initially, the first unit is in operative mode and second is kept in cold standby mode. There is also a proviso for rest for the first unit after a random time from its starting operation. For operation and repair, priority is always given to first unit. A switching device is used to shift the failed unit to repair mode. If the switching device is found non-operational then priority is given to it for repair provided that system is in functional mode. The effectiveness of the proposed system has been carried out by determining various reliability characteristics of the proposed model.

On Values Approximation of Some Special Type Hypergeometric Functions with Irrational Parameters

In this paper we investigate arithmetic nature of the values of generalized hypergeometric functions and their derivatives. To solve the problem one often makes use of Siegel’s method. The first step in corresponding reasoning is, using the pigeonhole principle, to construct a functional linear approximating form, which has high order of zero at the origin of the coordinates.A hypergeometric function is defined as a sum of a power series whose coefficients are the products of the values of some rational function. Taken with the opposite sign, the zeroes of a numerator and a denominator of this rational function are called parameters of the corresponding generalized hypergeometric function. If the parameters are irrational it is impossible, as a rule, to employ Siegel’s method. In this case one applies the method based on the effective construction of the linear approximating form.Additional difficulties arise in case the rational function numerator involved in the formation of the coefficients of the hypergeometric function under consideration is different from the identical unit. In this situation even the availability of the effective construction of approximating form does not enable achieving an arithmetic result yet. In this paper we consider just such a case. To overcome difficulties arisen here we consider the values of the corresponding hypergeometric function and its derivatives at small points only and impose additional restrictions on parameters of the function.