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Detent force is an inherent problem of permanent magnet linear synchronous machines (PMLSMs). In this paper, a mesh-level design methodology is proposed to minimize the detent force on PMLSMs. The novelty concerns introducing the inverse-based design to shape the mover ends on PMLSMs, allowing for automatically exploring the ideal mover ends configuration without any pre-given template. To this end, the ON/OFF method is used to express the topology of mover ends, metaheuristics algorithms are used to steer the topological evolution. To clarify the proposed method, two typical PMLSMs are adopted as numerical examples. The resulting mover ends produced by the genetic algorithm and immune algorithm are presented, and the convergence of the two algorithms is discussed. The comprehensive numerical results show that the proposed method is universal and practical as the detent force of the two typical PMLSMs can be suppressed to a low level.

The permanent magnet electrodynamic suspension (PMEDS) owns the promising application prospect, due to its simple structure, low cost and reliable load capacity. However, the underdamping of the PMEDS system is still a challenge in engineering applications of transportation. This paper proposes a passive damping method and its implementation structure to improve the underdamping characteristics. This method utilizes the inherent magnetic leakage of on-board magnets technically. The principle of passive damping and its implementation structure is introduced in detail. And the kinetic models of ordinary and improved structure are established based on the topology graph. Besides, the magnetic field and the electromagnetic force involved in the kinetic models are analyzed, and the numerical analysis method of the drag force is verified by the high-speed test rig. Furthermore, the performance of passive damping is verified by finite element method (FEM) and the time-domain response analysis. The results show that the improved damping structure can effectively suppress vibration and improve the dynamic stability of the PMEDS system. It is beneficial to the engineering application of the PMEDS in the future. [ABSTRACT FROM AUTHOR]

Linear flux-switching permanent magnet (LFSPM) machines have high power density and simple robust stator structure,which shows significant potential in long stroke applications. However,linear motors are required to have high thrust density and low thrust ripple in many applications. Therefore,the research on the issues causing the thrust force ripple and corresponding suppression methods are important means to enhance the application potential of the LFSPM machines. Through the finite element analysis (FEA) method,the end effect of LFSPM machine is improved by using different structures of the additional teeth,and the end force is reduced. Based on this,different thrust ripple reduction methods are employed and compared to suppress different thrust ripple components of the LFSPM machine. In the process of comparison,a step (staggered tooth) displacement selection method is given. It shows that each structure can reduce the thrust force ripple while taking into account the average output thrust force. FEA verifies the universality of the proposed method,and it can be used in LFSPM machines with different structures to reduce the thrust force ripple while taking into account the average output thrust.

The virtual equivalent line method for the axial-flux permanent magnet eddy current coupler is proposed in this paper to solve the problem of the difference in the length of the magnetic flux path between the inner radius and outer radius of the axial section of the radial centerline of the magnetic pole. Different from the average radius equivalent method, the virtual equivalent line method adopts the function of variable pole radius instead of the fixed average radius, which establishes a uniform analytical expression of the air gap flux density and can accurately calculate the magnetic flux density at any magnetic pole radius. Furthermore, the end-effect compensation function is obtained. In order to investigate the effectiveness of the proposed method, the results calculated by the analytical method are compared with the finite element method. It is shown that the novel method proposed in this paper is highly consistent with the air gap flux density calculated by the finite element method.

Linear permanent magnet Vernier machines (LPMVMs) is an attractive solution for stroke and direct-drive applications. Several LPMVM topologies have been presented for different applications that operate based on magnetic flux modulation. LPMVMs have some advantages including high force, and torque density at low speeds. This paper introduces a double-excited linear Vernier machine for wave energy conversion. To model the machine, finite element analysis and nonlinear equivalent network model are used. To improve the accuracy of the model and compact the network, a new meshing method is proposed. For better continuity in the output waveforms of the machine, special positioning is utilized. The end-effect is modeled using two separate networks. Finally, the modeling and simulation results are compared with each other and validated experimentally. [ABSTRACT FROM AUTHOR]

In this paper the novel method for analysis of the results of surface topography measurement was presented. The plateau-valley separation approach (PVSA), based on the thresholding of the valley component of the analysed surface texture detail was proposed. Cylindrical topographies with additionally burnished dimples and laser-textured surfaces, measured with a stylus or optical instruments were studied. It was found that the PVSA method can be fairly advantageous in areal surface texture analysis than regular, commonly-used procedures. The effect of the PVSA scheme on values of areal surface topography parameters, from ISO 25178 standards, were also studied in detail.

In this paper, the performance of Variable Reluctance Linear Resolver (VR-L-Resolver) with overlapping and non-overlapping windings is investigated by a novel parametric Magnetic Equivalent Circuit (MEC). The proposed MEC is capable of modeling various VR-L-Resolvers with arbitrary geometry and adjustable accuracy by changing the number of considered flux tubes. This technique is more suitable for modeling, analysis, and optimizing of the mentioned resolvers thanks to its flexibility and shorter processing time compared to the Finite Element Method (FEM). Moreover, it has the potential to model both healthy and faulty conditions by a unique model. Therefore, the resolver with two windings configurations under healthy and faulty cases are analyzed in this paper to study their performance. In faulty case, the inter-turn and asymmetrical air-gap faults are considered, and the position error is calculated for both cases. Finally, the MEC results are validated by 2D-FEM and experimental results to show the effectiveness of the proposed model. In general, applying a novel MEC-based modeling technique for the resolver sensitivity analysis, under mentioned faults and various windings configurations, is the main paper novelty. [ABSTRACT FROM AUTHOR]

This paper presents a new structure of Permanent Magnet Flux-Switching Linear Motor (PM-FSLM) with a simple low weight modular primary and acceptable thrust ripple production. A flexible Magnetic Equivalent Circuit (MEC) is applied for modeling the proposed machine, which is capable to analyze the performance of different structures of PM-FSLMs. The saturation and end-effect phenomena are considered by a nonlinear permeability function and virtual zones at both ends of the machine, respectively. The machine operation under dynamic load is also investigated and its specifications are obtained. The proposed PM-FSLM has more power capability, lower current un-symmetry, and simpler mover structure compared to other ones, which can be mentioned as its benefits. Finally, the results of the proposed method are validated by the Finite Element Method (FEM) to show the effectiveness of the proposed MEC technique in terms of accuracy and processing time. The introduced linear machine and the proposed analysis method with adjustable accuracy are the paper novelties, which are presented in this work for the first time. [ABSTRACT FROM AUTHOR]

This paper proposes a Magnetic Equivalent Circuit (MEC) method to model the Ladder-Secondary-Linear Induction Machines (LS-LIMs), where the model accuracy can be determined as desired. This method makes it much easier to change parameters of motor include poles and slots number as well as its dimension than the Finite Element Method (FEM). The end-effect phenomenon is considered in the model by two virtual zones with arbitrary length at the both exit and entrance ends of the primary for saturable LS-LIMs. The proposed MEC method also makes it possible to investigate the motor performance under different secondary structures (two types), bars material and their width. Finally, FEM and experimental results are given to evaluate the accuracy of the proposed method, and simulation time is compared with 2D-FEM. In a general overview, modeling the end-effect and saturation phenomena, analyzing the impacts of different secondary structures and bars width on the performance of motor are studied by the suggested MEC method in the present work. • A flexible MEC-based method for Ladder secondary Linear Machine based on MEC method. • Determining the accuracy level of model as desired. • Performance analysis under various secondary sheets. • Performance analysis under various secondary bars width. • Performance analysis under various secondary bars material. [ABSTRACT FROM AUTHOR]

This paper deals with the modelling of traction linear induction motors (LIMs) for public transportation. The magnetic end effect inherent to these motors causes an asymmetry of their phase impedances. Thus, if the LIM is supplied from the three-phase symmetrical voltage, its phase currents become asymmetric. This effect must be taken into consideration when simulating the LIMs’ performance. Otherwise, when the motor phase currents are assumed to be symmetric in the simulation, the simulation results are in error. This paper investigates the LIM performance, considering the end-effect induced asymmetry of the phase currents, and presents a comparative study of the LIM performance characteristics in both the voltage and the current mode.

Aiming at the problem of structure parameters design of Halbaeh permanent magnetic array working on wall-climbing robots, an experimental study on adsorption force calculation was carried out. Adsorption force of ideal array was calculated firstly as a basis for followup correction methods. Then the optimal magnetization direction of each module in a full-symmetric discrete array was analyzed and the loss of adsorption force caused by discretization was calculated with Fourier analysis method. A simplified correction model of the end-effect was proposed for rapid calculation, by studying a method on distribution of magnetic induction on the reference line instead of global integration, and the calculation formula of adsorption force was modified considering the end-effect caused by the change of structure parameters. The test results indicate that the computed adsorption force basically tallies with measured force, with the average relative error less than 3.3%. [ABSTRACT FROM AUTHOR]

This paper deals with the modelling of traction linear induction motors (LIMs) for public transportation. The magnetic end effect inherent to these motors causes an asymmetry of their phase impedances. Thus, if the LIM is supplied from the three-phase symmetrical voltage, its phase currents become asymmetric. This effect must be taken into consideration when simulating the LIMs' performance. Otherwise, when the motor phase currents are assumed to be symmetric in the simulation, the simulation results are in error. This paper investigates the LIM performance, considering the end-effect induced asymmetry of the phase currents, and presents a comparative study of the LIM performance characteristics in both the voltage and the current mode. [ABSTRACT FROM AUTHOR]

Abstract Chitin oligosaccharides, composed of homogeneous β(1 → 4)-linked N -acetyl-D-glucosamine (GlcNAc) sequences, is a well-known elicitor of plant immune defense, and also occur as structural elements of chitosan and nodulation (Nod) factor. Detailed microstructure characterization is required for understanding the function mode of these bioactive molecules. Herein, experimental conditions for detection and elucidation of the 1H NMR resonances of amide groups in chitin oligosaccharides are presented. The binary mixture of 70% H 2 O: 30% DMSO‑ d 6 was found to be the optimal solvent for amide proton measurements in homogeneous GlcNAc sequences, facilitating differentiation of the local chemical microenvironments of all four amide groups of the chitin tetrasaccharide. Experimental evidence that anomeric end-effect triggers amide proton resonance differentiation at the adjacent residue has potential to provide important insights into the solution structure of chitin and other amino sugars containing GlcNAc sequences. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Surface‐mounted permanent magnet (SPM) machines are preferred for high‐speed aerospace applications over induction and switched reluctance machines, since they combine the advantages of high torque density and efficiency. Also, in aerospace applications, where low rotor weight and inertia are essential requirements, a permeable hollow shaft is proposed to replace the need for rotor back‐iron and reduce the overall rotor weight. For rotor mechanical integrity, a retaining sleeve is commonly used, leading to thicker magnetic airgap. Furthermore, when permeable rotor endcaps are applied, an increase of the magnetic end leakage occurs, i.e. end‐effect. In this study, the influence of the rotor endcaps on the mechanical and electromagnetic performance of a high‐speed SPM machine is investigated through 3D‐finite element analyses. Also, different endcap thickness and different rotor shaft materials are investigated and compared in this work. Finally, a prototype of the SPM machine under study has been manufactured and tested. The comparison between simulation and experimental results is presented and discussed. [ABSTRACT FROM AUTHOR]

Magnetic levitation technology has become the great candidate to provide ultraprecision motion in vacuum environment due to its characteristics, e.g., non-contact, frictionless, and unlimited stroke, etc. This paper presents the design, modeling, analysis, and control of a 6 Degrees-Of-Freedom (DOF) maglev positioning system, and the proposed system is able to achieve a planar motion of 50 mm × 50 mm while the levitation height is up to 4 mm. In this work, the model of eddy current damping for moving Halbach Permanent Magnet (PM) array is analytically established to predict the damping force in operating of the maglev positioning system. Furthermore, the magnetic field end-effect is analyzed in the maglev system, where two guidelines are provided to ideally avoid the model error due to end-effect during the design of the maglev system. To control the maglev positioning system to achieve good planar tracking performance, the system identification is carried out for x and y -axes, and a simple PID controller is designed and optimized according to the specifications characterizing on the closed-loop performance of the maglev system. Finally, the experiments are conducted on the maglev prototype to demonstrate the positioning performance, and the results show that the maximal static positioning error is less than 200 nm with the Root Mean Square Error (RMSE) around 60 nm. [ABSTRACT FROM AUTHOR]

The feature extraction of marine vessel-radiated noise (MVRN) under the complex ocean background is explored. To this end, a hybrid approach is presented based on the analysis of MVRN in subspaces of intrinsic mode functions (IMF) extracted using the improved empirical mode decomposition (IEMD) and measuring complexity. The restriction of the end-effect is an important problem when employing the EMD algorithm. In this study, first, to reduce the end-effects, an IEMD algorithm based on the correlation expansion model is proposed. Then, a comparative study of IEMD, classic EMD (CEMD), and EMD by other expansion methods are conducted on several signals. Next, IEMD, CEMD, and variational mode decomposition (VMD) algorithms are utilized to extract a group of IMFs for three types of MVRN. Later, one obtained IMF from each method that contains the most dominant information is selected. Lastly, two statistical complexity measures (i.e., permutation entropy (PE) and slope entropy (SlopEn)) are used as the features of the chosen IMF to improve the underwater signal separability and stability. Experimental results indicate that the suggested approach (IEMD-PE/SlopEn) can effectively extract the feature information of underwater signals. Additionally, it has a better ability to discriminate between various kinds of MVRN. • Investigation of issues due to end-effects in classic empirical mode decomposition (CEMD) algorithm. • Providing an improved EMD (IEMD) by a novel strategy for signal expansion at boundaries and end-effects minimization. • Permutation entropy (PE) and slope entropy (SlopEn) are introduced into the hybrid feature extraction of marine vessel noise combined with IEMD. [ABSTRACT FROM AUTHOR]

There is a special phenomenon in linear arc-shaped motor and linear induction motor with finite- length primary. Their no-load rotating ( translational ) speeds exceed the so-called synchronous speed. With a simplified single-sided linear induction motor( SLIM) as the research object,the mathematical model of the motor was established by using Maxwell's equations. Air gap and end region magnetic field distribution considering dynamic longitudinal end effect was calculated. A physical quantity"Equivalent electromagnetic pole pitch"considering the dynamic longitudinal end effects was proposed and correction coefficients corresponding to mechanical pole pitch with different number of poles was given. Finally,the rationality of the analytical method and validity of correction coefficients were verified by finite element method( FEM) simulation software and prototype testing. It can be concluded that no-load speed does not exceed the synchronous speed calculated by"Equivalent electromagnetic pole pitch"and just exceeds the synchronous speed calculated by mechanical pole pitch. It has some informative values to the theoretical research and development of linear induction motor. [ABSTRACT FROM AUTHOR]

Abstract: The Ramakrishnan–Cappiello method is based on the injection of an incompressible nonwetting phase at successively higher pressures (or flow-rates), and measuring the velocity (or injection pressure), while eliminating end-effects. Many enhanced oil recovery processes involve injection of a compressible nonwetting phase for which the velocity through the medium increases by decompression. Here, exact and perturbation expressions for decompression corrections are given along with Padé approximants of density and viscosity for CO2. We compute an increase of 1, 4 and 11% for liquid, supercritical, and gaseous CO2 relative permeability for previously conducted experiments. [Copyright &y& Elsevier]

The authors examine the effect of pressure gradient on gas-oil relative permeability in horizontal and vertical immiscible displacement. The experiments are conducted on a core from lower Dalan formation in the South Pars oilfield of Iran, in constant pressure, unsteady-state condition, and different pressure gradients. The Toth method is used for calculating the relative permeability and plotting proper curves. Data analysis and the effect of pressure gradient on gas-oil relative permeability are investigated. Results show that relative permeability curves are affected by pressure gradient and this effect is much prominent at low pressures due to end-effect phenomena. The dependence of relative permeability curves on pressure gradient is correlated as a function of dimensionless capillary number. The accuracy of this correlation for relative permeability prediction is examined and a new method is introduced to minimize the end-effect phenomena on relative permeability curves. [ABSTRACT FROM PUBLISHER]

An accurate estimation of flux linkage characteristics is very important during the preliminary design stage and high-performance control of linear switched reluctance motor (LSRM). In this paper, longitudinal and transversal end-effects of a double-side LSRM are studied using analytical method and finite element analysis (FEA). The estimation discrepancy introduced by both end-effects is presented respectively by investigating their sensitivities to machine parameters, such as excitation level, translator position, and stack length. [ABSTRACT FROM AUTHOR]

In this study, simulation of field-oriented control of a linear induction motor fed by matrix converter was conducted. End-effect in the linear induction motor which occurs due to the structure has been taken into consideration. The matrix converter and the linear induction motor with end-effect have been modelled in Matlab/Simulink. With the constructed simulation model and because end-effect in the linear induction motor has been taken into account, results in accordance with actual conditions have been obtained. Use of matrix converter in the linear induction motor drive system has brought advantages of the matrix converter to the drive system. Negative reflection of the end-effect to the performance of vector control, in a conventional manner, of the linear induction motor has been shown by the obtained results. Subsequently, this negative reflection has been compensated with a new approach to improve the control performance, and for both cases results were given in comparison. The results demonstrate the effectiveness of the proposed control technique. [ABSTRACT FROM AUTHOR]

Abstract: Stress, strain and modulus are regularly used to characterize material properties of tissue samples. However, when comparing results from different studies it is evident the reported material properties, particularly failure strains, vary hugely. The aim of our study was to characterize how and why specimen length and cross-sectional area (CSA) appear to influence failure stress, strain and modulus in fascicles from two functionally different tendons. Fascicles were dissected from five rat tails and five bovine foot extensors, their diameters determined by a laser micrometer, and loaded to failure at a range of grip-to-grip lengths. Strain to failure significantly decreased with increasing in specimen length in both rat and bovine fascicles, while modulus increased. Specimen length did not influence failure stress in rat tail fascicles, although in bovine fascicles it was significantly lower in the longer 40mm specimens compared to 5 and 10mm specimens. The variations in failure strain and modulus with sample length could be predominantly explained by end-effects. However, it was also evident that strain fields along the sample length were highly variable and notably larger towards the ends of the sample than the mid-section even at distances in excess of 5mm from the gripping points. Failure strain, stress and modulus correlated significantly with CSA at certain specimen lengths. Our findings have implications for the mechanical testing of tendon tissue: while it is not always possible to control for fascicle length and/or CSA, these parameters have to be taken into account when comparing samples of different dimensions. [ABSTRACT FROM AUTHOR]

This article investigates the static characteristics of both doubly-salient brushless machines having magnets in stator, namely the flux-switching permanent magnet machine (three-phase topology) and doubly-salient permanent magnet machines (including three-phase and two-phase structures), especially taking the influence of end-effect into account. The structures and operating principles are described first, and then the end-effect in the stator permanent magnet machines is investigated by a 3-D calculation, and a leakage factor reflecting end-effect is defined to modify the 2-D predicted results. The proposed approach is validated experimentally for the prototype machines. [ABSTRACT FROM AUTHOR]

Abstract: Comb-drive structures consisting of two opposing parallel arrays of microcantilevers are commonly adopted in many designs of MEMS. This work studies pull-in instability of comb-drive structures in which two opposing arrays have different bending rigidities. Based on a simplified spring model, it is verified that equilibrium deflections of all intermediate microcantilevers in the arrays are negligibly small prior to the onset of instability, and non-negligible deflections of the end microcantilevers cause a significant end-effect on pull-in instability of the comb-drive array. With this concept, the critical value for instability of the comb-drive arrays is estimated, with or without the end-effect, for varying bending rigidity ratios. Compared to the results without the end-effect, the end-effect is found to lower the critical interaction coefficient for instability, and the reduction in the critical value for instability increases with decreasing bending rigidities of the end microcantilevers. These results for varying bending rigidity ratios indicate the significance of the end design on the instability of comb-drive structures. In particular, the results obtained by the present method are in good agreement with some known experimental data available in the literature and the exact results obtained by iteration numerical method for the spring model. [Copyright &y& Elsevier]

Abstract: The glycosaminoglycan hyaluronan is involved in a diverse range of physiological and diseases processes and comprises repeated disaccharide units of N-acetyl-d-glucosamine (GlcNAc) and d-glucuronic acid (GlcA). A molecular description of the solution conformation of HA is required to account for this biology, which is best attained using nuclear magnetic resonance (NMR). NMR studies of the polymer, however, are frustrated by resonance overlap arising from the highly degenerate structure. In contrast, end-effects in oligosaccharides can produce some chemical shift dispersion, giving the possibility that their conformational properties can be measured and extrapolated to models of the polymer. We report the complete resolution and assignment of 1H, 13C and 15N nuclei in hyaluronan oligosaccharides with seven different naturally occurring terminal rings. At 900MHz, all 1H nuclei in the hexasaccharide GlcA-β-(1→3)-GlcNAc-β-(1→4)-GlcA-β-(1→3)-GlcNAc-β-(1→4)-GlcA-β-(1→3)-GlcNAc-OH were uniquely resolved and the two central rings were found to be a good model for the polymer environment. These assignments now allow resolved, unambiguous structural restraints to be acquired on this oligosaccharide and extrapolated to models for the solution conformation of the polymer. [Copyright &y& Elsevier]

In this paper, the influence of occurrence of surface texture features on the values of surface topography parameters calculated after the application of various data processing techniques was presented. Different types of surface topographies were considered, as follows: cylinder liners, some with additionally burnished dimples, turned, ground, milled, laser-textured, composite, ceramic, or isotropic in general. The effects of feature size on the areal form removal, noise suppressions, or end-effect reducing in surface texture measurements were studied. The variations of the ISO 25178 standard surface topography parameters were taken into consideration in detail. It was assumed that some of the feature sizes, distributions, and densities have a substantial impact on the values of surface topography parameters calculated after applications of regular (commonly used) algorithms and procedures, defined as basic operations, provided for raw surface texture data obtained directly from the measurement process. In the end, some of the practical applications for receiving the relevant values of surface topography parameters were proposed. [ABSTRACT FROM AUTHOR]

Relative permeability is a key determinant of how a reservoir simulation model performs. Although laboratory measurement techniques for two-phase relative permeability are well-established, but still the difficulties and uncertainties persist. The present study aims to investigate the effect of several parameters, including pressure difference, end-effects, interpretation techniques (analytical and numerical), and mineral dissolution, on the unsteady-state gas-water relative permeability curves. For this purpose, a number of precisely planned experiments were carried out on two subsurface anhydrite dolomite samples collected from a well-known gas reservoir in south Iran. In summary, the measured gas relative permeability (k rg) was underestimated at low injection pressures mainly due to the capillary end-effect and a significantly low volume of brine production in compare to the considerable volume that was retained at the end face. Moreover, despite the end-effect was overcame at high injection pressures, but significantly high k rg values were recorded at water saturations close to the residual value and the measurements were corrected considering a gas slippage factor at the endpoint. Furthermore, greater wetting phase relative permeability (k rw) values were driven from numerical (history matching) interpretation of the results compared with the analytical approach that could be due to the automatic end-effect correction by the numerical techniques where the capillary pressure is accounted for. Finally, to investigate the effect of anhydride dissolution on overestimation of the measured gas relative permeability, the interaction of NaCl brine with anhydride was reviewed using the Computed Tomography (CT) images taken before and after the test. • Relative permeability measurement varies against several parameters. • The injection pressure and end-effect are crucial for valid krg measurement. • Numerical technique provides a more precise krw compare to the analytical one. • Anhydrite dissolution originates overestimation of the measured krg. [ABSTRACT FROM AUTHOR]