Eccentricity Type Research Articles

Accurate Modeling of a Flywheel Motor Considering Vehicle Start-Up Driving Conditions

The eccentricity type for flywheel motors under vehicle start-up driving conditions is very unique. It is difficult to characterize the air-gap function geometrically. Therefore, the existing methods cannot be used to solve the problem of accurate motor modeling in this case. To solve this problem, an accurate modeling method for flywheel motors considering vehicle start-up driving conditions is proposed in this study. First, the model is divided into two submodules corresponding to two different vehicle start-up driving conditions. Then, the change law for the flywheel motor air gap under vehicle start-up driving conditions is analyzed and summarized by using the curve fitting method. Subsequently, the predictive air-gap function is obtained, and an accurate flywheel motor model is established. Finally, accelerating and turning experiments are conducted, and good experimental results are obtained that show that a model adopting the proposed modeling method has high accuracy.

The value of magnetic resonance imaging-based tumor shape features for assessing microsatellite instability status in endometrial cancer.

BackgroundMicrosatellite instability (MSI) status can be used for the classification and risk stratification of endometrial cancer (EC). This study aimed to investigate whether magnetic resonance imaging (MRI)-based tumor shape features can help assess MSI status in EC before surgery.MethodsThe medical records of 88 EC patients with MSI status were retrospectively reviewed. Quantitative and subjective shape features based on MRI were used to assess MSI status. Variables were compared using the Student’s t-test, χ2 test, or Wilcoxon rank-sum test where appropriate. Univariate and multivariate analyses were performed by the logistic regression model. The area under the curve (AUC) was used to estimate the discrimination performance of variables.ResultsThere were 23 patients with MSI, and 65 patients with microsatellite stability (MSS) in this study. Eccentricity and shape type showed significant differences between MSI and MSS (P=0.039 and P=0.033, respectively). The AUC values of eccentricity, shape type, and the combination of 2 features for assessing MSI were 0.662 [95% confidence interval (CI): 0.554–0.770], 0.627 (95% CI: 0.512–0.743), and 0.727 (95% CI: 0.613–0.842), respectively. Considering the International Federation of Gynecology and Obstetrics (FIGO) staging, eccentricity maintained a significant difference in stages I–II (P=0.039), while there was no statistical difference in stages III–IV (P=0.601).ConclusionsIt is possible that MRI-based tumor shape features, including eccentricity and shape type, could be promising markers for assessing MSI status. The features may aid in the preliminary screening of EC patients with MSI.

Analysis and Detection of Rotor Eccentricity in Permanent Magnet Synchronous Machines Based on Linear Hall Sensors

Rotor eccentricity commonly exists in permanent magnet synchronous machines (PMSMs) due to improper assembly, excessive vibration, and continuous operation. Consequently, the unbalanced magnetic pull, introduced by rotor eccentricity, may lead to unfavorable noise, vibration, and even bear damage, which makes the detection of eccentricity meaningful. Although motor current signal analysis is the most popular method to diagnose eccentricity based on the amplitudes of sideband component, it is a big challenge to classify different types of eccentricities and quantify the eccentric ratio due to the spatiotemporal coupling effect. In this article, by installing a set of Hall sensors at stator slots of PMSMs to measure the magnetic flux density in time domain, the static eccentricity and dynamic eccentricity can be easily separated. This article provides a novel complex-analytical model to reveal the single side band modulation effect in air-gap filed due to dynamic eccentricity. Moreover, a diagnosis algorithm based on frequency-adaptive notch filter is designed to identify the eccentricity type and the corresponding degree. The effectiveness of the novel diagnosis method is validated by both simulations and experiments.

Three-body Resonances in the Saturnian System

Abstract Saturn has a dynamically rich satellite system, which includes at least three orbital resonances between three pairs of moons: Mimas–Tethys 4:2, Enceladus–Dione 2:1, and Titan–Hyperion 4:3 mean-motion resonances. Studies of the orbital history of Saturn’s moons usually assume that their past dynamics was also dominated solely by two-body resonances. Using direct numerical integrations, we find that three-body resonances among Saturnian satellites were quite common in the past, and could result in a relatively long-term, but finite capture time (10 Myr or longer). We find that these three-body resonances are invariably of the eccentricity type and do not appear to affect the moons’ inclinations. While some three-body resonances are located close to two-body resonances (but involve the orbital precession of the third body), others are isolated, with no two-body arguments being near resonance. We conclude that future studies of the system’s past must take full account of three-body resonances, which have been overlooked in the past work.

Radiation from an axially slotted antenna coated with eccentric layer of inhomogeneous medium embedded in metamaterial

The gain properties of an axially slotted cylindrical antenna coated with eccentric layer of inhomogeneous material placed in different metamaterials have been investigated. The slot is assumed to be infinitesimally thin such that it can excite TE mode only. The radiated fields in region filled by inhomogeneous material are written in terms of modified Bessel and Hankel functions of non-integer order and the eccentricity is mathematically incorporated by employing Graf’s addition theorem. Numerical results to describe the radiation characteristics of antenna are presented and discussed while taking different profiles for the inhomogeneity, values of the eccentricity parameter, operating frequency, and type of host medium. It is observed that the radiation pattern can be controlled, from isotropic (omnidirectional) to directive one, by selecting suitable choice of the inhomogeneity profile and value of the eccentricity parameter. Another interesting feature of the antenna is found when it is embedded in zero index medium, in that case the exponent of the profile function ψ(κρ) has direct relationship with the number of main lobes in the radiation pattern.

Stability and load-carrying capacity of short open-section composite columns under eccentric compression loading

This paper presents the results of a study investigating the eccentric compression loading of thin-walled composite profiles with Z, channel and top-hat sections. The buckling, post-buckling and limit state of the profiles are investigated. The primary objective of the study was to determine the effect of load eccentricity and profile section type on the stability and load-carrying capacity of the profiles. The thin-walled profiles made of CFRP by the autoclave technique were subjected to static compression over the full range of loading until final failure. At the same time, the compressed profiles were examined by nonlinear numerical analysis with the finite element method using the commercial simulation software ABAQUS®. Damage initiation in the composite material was analysed using the Hashin criteria and a progressive damage model. Numerical models were validated by experimental tests. Obtained numerical and experimental results show a high agreement.

Performance of Topological Perception in the Myopic Population

ABSTRACT Purpose: Discriminating objects’ topological property (TP) is a primitive function of visual representation, which is reported to be associated with magnocellular (M) visual pathway, temporal lobe (TL), and superior colliculus (SC)-pulvinar subcortical pathway. Previous studies have shown that M pathway and TL were affected in high myopia (HM) subjects. The study was accordingly designed to explore whether topological perception performance was abnormal in HM subjects. Methods: 30 mildly myopic, 25 moderately myopic, 35 highly myopic, and 20 emmetropic subjects were enrolled. All participants underwent a comprehensive ophthalmological assessment including automated refraction, intraocular pressure, Humphrey 10–2 standard automated perimetry, ocular fundus photography and swept-source optical coherence tomography. Defined by differences in hole, TP and non-TP discrimination with letters “E”, “S”, “P”, “d” as stimuli in the central and peripheral regions was performed using the MATLAB 2017 software. d-primes extracted from the software were analyzed within each group. The correlation of peripheral TP/non-TP deficit with spherical equivalent (SE), axial length (AL) and average peripapillary retinal nerve fiber layer (RNFL) thickness was performed. Results: The patterns of topological perception performance were similar among the groups. TP discrimination peripherally was significantly better than that centrally in the mild myopia (P < .001), moderate myopia (P < .001), high myopia (P < .001) and emmetropia groups (P = .001). In the peripheral region, TP d-prime scores were significantly better than non-TP d-prime scores (all P < .001). The main and interaction effects of eccentricity and stimulus type were statistically significant(P < .05). There was no statistically significant correlation between peripheral TP/non-TP deficit and SE, AL or average RNFL thickness (P > .05). Conclusions: The current study first showed that patterns of topological perception among the myopic population were similar and not affected by the severity of myopia.

Motor Current Signature Analysis for the Air Gap Eccentricity Detection In the Squirrel Cage Induction Machines

The classical diagnosis approaches, deeply spread in the industrial environment, are based on the Fourier analysis of the steady-state current, the basis of the proposed methodology consist of analysing the current demanded by the machine during the connection process (startup transient); the objective is to extract the characteristic evolution during the transient of some harmonic components created by the fault; this evolution is caused by the dependence of these components on the slip (s). In this paper the induction motor under dynamic and mixed eccentricity type is modeled with high precision using (CMC) approach.

The influence of hygrothermal environments on the stress concentration in unidirectional composite lamina

In this paper, the stress analysis of unidirectional composite lamina, containing aligned broken fibers and exposed to hygrothermal conditioning, is investigated. The governing equations are derived based on the modified shear-lag model and a proper micromechanic rule are used to consider the effect of temperature and moisture content on stress concentration factor (SCF) in composite materials. The results show that the SCF has been less affected by low temperature and moisture content while the hot/wet conditions have significant effect on it. At the high operational temperature levels, specifically near to the glass transition temperature and saturation state, it can be observed that the results are in a good agreement with the original shear lag model. The SCF decreases exponentially by increasing the fiber volume fraction in both in dry and hygrothermal conditions. Moreover, the effect of crack eccentricity and crack-tip matrix type on SCF has been evaluated in hygrothermal conditions.

Terrestrial planet formation under migration: systems near the 4:2:1 mean motion resonance

In this work, we extensively investigate the formation of near 4:2:1 mean motion resonances (MMRs) configuration by performing two sets of N-body simulations. We model the eccentricity damping, gas drag, type I and type II planetary migration of planetesimals, planetary embryos and giant planets in the first sets. For the simulations of giant planets with type II migration, the massive terrestrial planets, with a mass up to several Earth masses, are likely produced in the systems. We further show that by shepherding and/or scattering mechanisms through Jovian planet's type II migration, the terrestrial planets and giant planets in the systems can be evolved into a near 4:2:1 MMRs. Moreover, the models are applicable to the formation of Kepler-238 and 302 systems. In the second set, we study the 4:2:1 MMRs formation in the terrestrial planetary systems, where the planets undergo type I migration and eccentricity damping. By considering type I migration, $\sim$ 17.1\% of the simulations indicate that terrestrial planets are evolved into 4:2:1 MMRs. However, this probability should depend on the initial conditions of planets. Hence, we conclude that both type I and type II migration can play a crucial role in close-in terrestrial planet formation.

소프트 콘택트렌즈 착용자의 피팅 상태에 따른 각막 이심률과 곡률반경과의 상관관계

Purpose. Because of a recent increase in use of soft contact lens at younger ages, in the present study, the correlation between corneal eccentricity and radius of curvature and fitting types of contact lens was investigated. Methods. The study evaluated the fitting status of targets through lens centration, push-up test, dynamic lag test and static lag test of lenses usually worn by 49 men and women (98eyes) in their 20s to 30s who put on soft contact lenses. After evaluation, the subjects were classified into 3 categories by fitting status(steep, aligment and flat). The radius of corneal curvature in the naked eyes was measured by using keratometer. Moreover the corneal eccentricity in the nasal side, temporal side, superior side and inferior side was measured by using the device capable of measuring the corneal eccentricity. Results. The radius of corneal curvature and corneal eccentricity of soft lenses worn by subjects were higher in the order of steep fitting and flat fitting, and the higher average corneal curvature radius and corneal eccentricity is intend to be more steep fitting(p=0.051, p=0.052). The corneal eccentricity showed a tendency to nasal fitting type at the higher eccentricity and temporal fitting type at the smaller eccentricity, statistically significant difference was observed(p<0.05). The study showed there were low correlation that nasal and temporal side at steep fitting, superior side at normal fitting and 4side(nasal, temporal, superior, inferior) at flat fitting, therefore when the corneal eccentricity changed the radius of corneal curvature also changed. The corneal eccentricity and the radius of corneal curvature showed statistically significant difference at 4side and each fitting types(p<0.05). Conclusions. The results of this study, the fitting status, of wearer are based on radius of corneal curvature and corneal eccentricity, and if lens fitting would be done considering that, it seems to be useful in a soft contact lens prescription.

Unbalanced Magnetic Force Mitigation and Torque Ripple Reduction in Eccentric Switched Reluctance Motors Using Flux Leakages

—In this article, a comprehensive method is introduced to redress eccentricity fault consequences. Two main effects of eccentricity faults include considerable increase in unbalanced magnetic force and torque ripple. Dependency of unbalanced magnetic force and torque ripple on eccentricity fault level is shown, and the possibility of compensating them via controlling currents in facing poles is proved. These objectives are accomplished through a novel converter that controls currents in poles of every phase such that one pole is responsible for nullifying unbalanced magnetic force and the facing pole is in charge of torque ripple reducing. The control algorithm is analyzed in details and through finite-element method and MATLAB/Simulink (The MathWorks, Natick, Massachusetts, USA) is implemented on a 6/4 switched reluctance motor with 30% eccentricity fault level. The proposed strategy samples the flux leakage as the index both for occurrence and criterion for compensation of unbalanced magnetic force. The suggested method is designed such that there is no need to detect eccentricity fault direction, location, and type, which makes it cost effective and practical for a wide range of switched reluctance motors and applications.

Diagnosis of Eccentric Rotor in Synchronous Machines by Analysis of Split-Phase Currents—Part II: Experimental Analysis

This work shows a method to quantify rotor eccentricities in synchronous machines by exploiting the unbalance caused in the split-phase currents. The paper first develops a machine model comprehensive of eccentricities and parallel circuits in the stator, by using symmetrical components. Then, the model is used for formal calculation of the unbalanced currents. Finally, the equations are reversed to obtain eccentricity degrees from current measurements. Practical formulas are given for fault assessment, only requiring machine line voltage and synchronous reactance. The method can be applied on load. This paper provides full details of the theory underlying the method. The theory also clarifies some aspects about split-phase currents, not deepened before. It is proven that the air gap flux modulation due to eccentricities, acting through additional 2(p ±1) -pole flux waves in 2p-pole machines, stimulates additional currents, which circulate in the stator and turn into 2(p ±1)-pole rotating space vectors in the complex domain. Vector trajectories have shape and amplitude dictated by eccentricity type and degree, respectively. This study is limited to 2p-pole machines with p ≥ 2. The theory is corroborated by simulations of a practical 1950-kVA generator in this paper. Experimental proofs and simulations of a laboratory 17-kVA machine are provided in a sequel of this paper.

Diagnosis of Eccentric Rotor in Synchronous Machines by Analysis of Split-Phase Currents—Part I: Theoretical Analysis

This work shows a method to quantify rotor eccentricities in synchronous machines by exploiting the unbalance caused in the split-phase currents. The paper first develops a machine model comprehensive of eccentricities and parallel circuits in the stator, by using symmetrical components. Then, the model is used for formal calculation of the unbalanced currents. Finally, the equations are reversed to obtain eccentricity degrees from current measurements. Practical formulas are given for fault assessment, only requiring machine line voltage and synchronous reactance. The method can be applied on load. This paper provides full details of the theory underlying the method. The theory also clarifies some aspects about split-phase currents, not deepened before. It is proven that the air gap flux modulation due to eccentricities, acting through additional 2(p ±1) -pole flux waves in 2p-pole machines, stimulates additional currents, which circulate in the stator and turn into 2(p ±1)-pole rotating space vectors in the complex domain. Vector trajectories have shape and amplitude dictated by eccentricity type and degree, respectively. This study is limited to 2p-pole machines with p ≥ 2. The theory is corroborated by simulations of a practical 1950-kVA generator in this paper. Experimental proofs and simulations of a laboratory 17-kVA machine are provided in a sequel of this paper.

Dynamic simulation of eccentric squirrel cage induction motors by including saturable reluctances of individual teeth

This study proposes an analytic model for three-phase squirrel cage induction motors (SCIMs) under general eccentricity fault with variable degree, including static, dynamic and mixed eccentricities. After defining general air gap function, the air gap length within each slot pitch is assumed to be constant and equal to its length at the centre of the slot pitch by approximation. Then, by using modified winding function theory, analytic equations are obtained for the motor inductances. A novel technique is introduced to calculate saturable reluctances of individual teeth in every simulation step. These reluctances are added to the model by proper increment of the air gap length in front of each tooth. Consequently, dynamic simulation of SCIMs with any eccentricity type and degree and with the effect of the teeth saturable reluctances is made possible in the frame of a single Matlab code. It is shown that by adding the teeth reluctances, the amplitudes of the side-band harmonics around the fundamental line current, as the eccentricity fault indices, are reduced towards the corresponding harmonic amplitudes obtained by experiments. Finally, the proposed method is extended to include axial asymmetries.

Advanced Eccentricity Fault Recognition in Permanent Magnet Synchronous Motors Using Stator Current Signature Analysis

In this paper, a novel index is introduced for static and dynamic eccentricity fault diagnosis in permanent magnet synchronous motors (PMSMs). The proposed index is a linear combination of the energy, shape factor, peak, head angle of the peak, area below the peak, gradient of the peak of the detail signals in wavelet decomposition, and coefficients of the autoregressive model, which are extracted from the stator current signature analysis. Principal component analysis is applied to the features as the linear transform for dimension reduction and elimination of linear dependence between the features. In order to demonstrate the capability of these indexes to estimate eccentricity type and degree, the fuzzy support vector machine is employed as a classifier. Classification of the results indicates that the nominated index can be utilized to detect eccentricity occurrence, recognize its type, and determine its degree precisely. Since extraction of efficient indexes closely depends on precise computation of necessary signals, the time-stepping finite element method is utilized to model the PMSM under eccentricity fault and calculate the stator currents as a proper signal for processing. Simulation results are verified by the experimental results.

이심률 및 각막형상이 자세변화에 의한 토릭소프트렌즈의 회전에 미치는 영향

목적: 렌즈 착용자의 자세가 변했을 때 각막이심률 및 각막형상이 토릭소프트렌즈의 회전 양상에 미치는 영향을 알아보고자 하였다. 방법: 각막난시 -1.00 D의 직난시를 가진 20대 남녀 41안의 이심률을 측정하고 전체난시량에 따라 토릭소프트렌즈를 피팅하였다. 정자세와 누운 자세일 때의 토릭소프트렌즈의 회전을 슬릿램프에 장착된 카메라를 이용하여 촬영하고 분석하였다. 결과: Accelerated stabilization 디자인의 토릭소프트렌즈는 이심률에 관계없이 대부분 누운 방향인 귀쪽으로 회전하였으며 이심률이 큰 경우와 비대칭나비형 각막에서는 코쪽으로 회전하는 경우도 있었다. 렌즈착용 직후 정자세와 누운 자세에서 회전양과 이심률은 상관관계가 없었으나 일정 시간동안 누운 자세로 있는 경우는 이심률이 큰 각막에서 회전양이 더 컸다. 회전속도는 누운 자세로 변화된 직후부터 속도가 감소하였으며, 이심률에 따른 큰 차이는 없었다. 누운 자세로 변화된 직후 대칭나비형과 비대칭나비형의 경우는 타원형 각막에 비해 회전양이 더 크게 증가하였으며 일정 시간이 지난 후에도 마찬가지였다. 누운 자세에서의 렌즈회전속도는 다른 각막형태에 비해 비대칭나비에서 가장 느렸다. 결론: 본 연구를 통하여 자세변화시 토릭소프트렌즈의 회전 양상은 각막이심률 및 각막형상에 의해 영향을 받는다는 것을 알 수 있었다. 따라서 토릭소프트렌즈 피팅 및 디자인 개발 시에 이에 대한 고려가 이루어져야 할 것으로 보인다. Purpose: The present study aimed to investigate the effects of corneal eccentricity and shape on the rotational pattern of toric soft lens by the postural change of lens wearers. Methods: The corneal eccentricity of 41 eyes (aged 20s) having -1.0 D with-the-rule corneal astigmatism (WRCA) was measured, and then toric soft lenses were fitted with the amount of total astigmatism. In lying and straight postures, the rotation of toric soft lenses was recorded by a camera attached to slitlamp and analyzed. Results: Most toric soft lens designed with accelerated stabilization rotated to the temporal direction, which was the lying position direction, regardless of corneal eccentricity, and some lenses rotated to the nasal direction for high corneal eccentricity and corneal type of asymmetric bowtie. There was no correlation between the amount of rotation and corneal eccentricity right after of contact lens wearing in straight and lying posture, however, the amount of rotation was the greater for the cornea with the higher eccentricity after the subjects laying down for some period. The speed of lens rotation started to decrease after the subjects laying down, but the speed was not different according to corneal eccentricity difference. The amount of lens rotation for symmetric and asymmetric bowtie-typed corneas increased more than it for oval-typed cornea, and it was same even with time elapsing. The speed of lens rotation in lying posture was the slowest in asymmetric bowtie-typed cornea compared with other corneal types. Conclusions: From the present study, it was revealed that the rotational pattern of toric soft lens was affected by corneal eccentricity and corneal shape when the wearer's posture changed. Thus, it should be considered for the development of the fitting guideline and the design of toric soft lens.

Risk Factors for Cerebral Embolization After Carotid Artery Stenting With Embolic Protection

Meta-analyses of randomized trials have shown an increased risk of periprocedural stroke after carotid artery stenting (CAS) compared with carotid endarterectomy, which may differ in specific patient subgroups. Knowledge of risk factors for cerebral embolic lesions during CAS may impact treatment decisions for the individual patient, but these factors have not been extensively studied. We aimed to identify factors predictive for cerebral ischemic lesions during embolic protected CAS. Preprocedural and postprocedural diffusion-weighted magnetic resonance imaging was performed for evaluation of new cerebral ischemic lesions in 728 (86.9%) of 837 consecutive patients undergoing CAS with cerebral embolic protection. Multivariable logistic regression analyses were performed to identify factors predictive for embolic lesions. New ischemic lesions were found in 32.8% of patients. Age, hypertension, lesion length, lesion eccentricity, and aortic arch type III were significantly associated with new ischemic lesions; calcified lesions were negatively associated. In 25% of these patients embolic lesions were also found in the contralateral hemisphere. Predictive factors for contralateral lesions were age, >50% stenosis of the contralateral internal carotid artery, and an aortic arch type II, with a trend for aortic arch type III. Age, hypertension, lesion morphology, and aortic arch type were predictive for procedural-related cerebral embolic lesions during embolic protected CAS. Age, significant contralateral carotid stenosis, and complex aortic arch type were predictive for bilateral ischemic lesions. The clinical implications of ischemic lesions are not yet fully understood.

AN IMPROVED ANALYTICAL MODEL FOR SALIENT POLE SYNCHRONOUS MACHINES UNDER GENERAL ECCENTRICITY FAULT

This paper develops a more precise analytical model for calculating salient pole synchronous machine (SPSM) inductances in case of general eccentricity including static, dynamic and mixed eccentricities. The developed method is based on the modifled winding function approach (MWFA) which accurately considers variable air gap function and leads to pure analytical expressions of inductances. Available analytical techniques, based on MWFA, approximate the air gap function and simplify the geometrical model of SPSM, whereas, in this study, the in∞uence of the openings between the rotor salient poles has been taken into account by using an efiective form of rotor pole shoes. Using this technique, ∞ux fringing efiect is considered. By taking into account machine geometry, type of windings connection and ∞ux fringing efiect, this method is able to model most of the important features of an eccentric SPSM. The developed analytical expressions can calculate time varying inductances of SPSMs with any eccentricity type and degree in the frame of a single program. Simulation results for static eccentricity are compared with experimental tests on a laboratory generator to verify accuracy of the proposed model.

A Novel Technique for the Computation of Inductances of Salient Pole Machines under Different Eccentricity Conditions

In this article, comprehensive analytical equations are developed to compute time-varying inductances of salient pole machines with any eccentricity type and degree in a unified technique. For this purpose, the inverse air-gap function of the eccentric salient pole machine has been defined, and its indefinite integral has then been determined. The derived analytical expressions, unlike the previous proposals, take into account all the harmonics of the inverse of the air-gap function without any development in Fourier series. The presented method eliminates the need for inexact analytical equations, numerical differentiations, and huge lookup tables, which are common in the modified winding function approach. Theoretical fundamentals and experimental results that validate the proposed technique are presented.