Fault detection and diagnosis of induction motors using motor current signature analysis and a hybrid FMM-CART model

In this paper, a novel approach to detect and classify comprehensive fault conditions of induction motors using a hybrid fuzzy min-max (FMM) neural network and classification and regression tree (CART) is proposed. The hybrid model, known as FMM-CART, exploits the advantages of both FMM and CART for undertaking data classification and rule extraction problems. A series of real experiments is conducted, whereby the motor current signature analysis method is applied to form a database comprising stator current signatures under different motor conditions. The signal harmonics from the power spectral density are extracted as discriminative input features for fault detection and classification with FMM-CART. A comprehensive list of induction motor fault conditions, viz., broken rotor bars, unbalanced voltages, stator winding faults, and eccentricity problems, has been successfully classified using FMM-CART with good accuracy rates. The results are comparable, if not better, than those reported in the literature. Useful explanatory rules in the form of a decision tree are also elicited from FMM-CART to analyze and understand different fault conditions of induction motors.

Application of the fuzzy min-max neural network to fault detection and diagnosis of induction motors

In this paper, an application of the motor current signature analysis (MCSA) method and the fuzzy min–max (FMM) neural network to detection and classification of induction motor faults is described. The finite element method is employed to generate simulated data pertaining to changes in the stator current signatures under different motor conditions. The MCSA method is then used to process the stator current signatures. Specifically, the power spectral density is employed to extract harmonics features for fault detection and classification with the FMM network. Various types of induction motor faults, which include stator winding faults and eccentricity problems, under different load conditions are experimented. The results are analyzed and compared with those from other methods. The outcomes indicate that the proposed technique is effective for fault detection and diagnosis of induction motors under different conditions.

Understanding macrographia in children with autism spectrum disorders

It has been consistently reported that children with autism spectrum disorders (ASD) show considerable handwriting difficulties, specifically relating to accurate and consistent letter formation, and maintaining appropriate letter size. The aim of this study was to investigate the underlying factors that contribute to these difficulties, specifically relating to motor control.

We examined the integrity of fundamental handwriting movements and contributions of neuromotor noise in 26 children with ASD aged 8-13 years (IQ. >. 75), and 17 typically developing controls. Children wrote a series of four cursive letter l's using a graphics tablet and stylus.

Children with ASD had significantly larger stroke height and width, more variable movement trajectory, and higher movement velocities. The absolute level of neuromotor noise in the velocity profiles, as measured by power spectral density analysis, was significantly higher in children with ASD; relatively higher neuromotor noise was found in bands >3. Hz.

Our findings suggest that significant instability of fundamental handwriting movements, in combination with atypical biomechanical strategies, contribute to larger and less consistent handwriting in children with ASD.

The effect of environmental conditions on performance in timed cycling events

Air temperature, pressure and humidity are environmental factors that affect air density and therefore the relationship between a cyclist’s power output and their velocity. These environmental factors are changeable and are routinely quite different at elite cycling competitions conducted around the world, which means that they have a variable effect on performance in timed events. The present work describes a method of calculating the effect of these environmental factors on timed cycling events and illustrates the magnitude and significance of these effects in a case study. Formulas are provided to allow the calculation of the effect of environmental conditions on performance in a time trial cycling event. The effect of environmental factors on time trial performance can be in the order of 1.5%, which is significant given that the margins between ranked performances is often less than this. Environmental factors may enhance or hinder performance depending upon the conditions and the comparison conditions. To permit the fair comparison of performances conducted in different environmental conditions, it is recommended that performance times are corrected to the time that would be achieved in standard environmental conditions, such as 20 oC, 760 mmHg (1013.25 hPa) and 50% RH.

Condition assessment of timber utility poles based on a hierarchical data fusion model

This paper proposes a novel hierarchical data fusion technique for the non-destructive testing (NDT) and condition assessment of timber utility poles. The new method analyzes stress wave data from multisensor and multiexcitation guided wave testing using a hierarchical data fusion model consisting of feature extraction, data compression, pattern recognition, and decision fusion algorithms. The researchers validate the proposed technique using guided wave tests of a sample of in situ timber poles. The actual health states of these poles are known from autopsies conducted after the testing, forming a ground-truth for supervised classification. In the proposed method, a data fusion level extracts the main features from the sampled stress wave signals using power spectrum density (PSD) estimation, wavelet packet transform (WPT), and empirical mode decomposition (EMD). These features are then compiled to a feature vector via real-number encoding and sent to the next level for further processing. Principal component analysis (PCA) is also adopted for feature compression and to minimize information redundancy and noise interference. In the feature fusion level, two classifiers based on support vector machine (SVM) are applied to sensor separated data of the two excitation types and the pole condition is identified. In the decision making fusion level, the Dempster–Shafer (D-S) evidence theory is employed to integrate the results from the individual sensors obtaining a final decision. The results of the in situ timber pole testing show that the proposed hierarchical data fusion model was able to distinguish between healthy and faulty poles, demonstrating the effectiveness of the new method.

The effect of laser power density on the fatigue life of laser-shock-peened 7050 aluminium alloy

Laser shock peening (LSP) is an innovative surface treatment method that can result in significant improvement in the fatigue life of many metallic components. The process produces very little or no surface profile modification while producing a considerably deeper compressive residual stress layer than traditional shot peening operations. The work discussed here was designed to: (a) quantify the fatigue life improvement achieved by LSP in a typical high strength aircraft aluminium alloy and (b) identify any technological risks associated with its use. It is shown that when LSP conditions are optimal for the material and specimen configuration, a —three to four times increase in fatigue life over the as-machined specimens could be achieved for a representative fighter aircraft loading spectrum when applied at a representative load level. However, if the process parameters are not optimal for the material investigated here, fatigue lives of LSP treated specimens may be reduced instead of increased due to the occurrence of internal cracking. This paper details the effect of laser power density on fatigue life of 7050-T7451 aluminium alloy by experimental and numerical analysis.

Effects of the density on compressive properties in cellular aluminum produced by the sintering method

The cellular aluminum materials with relative densities of 0.1"-'0.25 were fabricated by the sintering method and effects of the density on mechanical properties of the cellular aluminum were investigated by compressive tests. The cellular aluminum exhibited a plateau region with a nearly constant flow stress. The stress in the plateau region increased with increasing relative density, on the other hand, the densification strain decreased with increasing relative density. Observation of the deformed cells revealed that the cell walls were bent. Besides, the stress in the plateau region was proportional to 1.9 power of the density. These suggest that plastic collapse is dominated by bending of the cell walls for the cellular aluminum produced by the sintering method.

Photoreceptor topography and spectral sensitivity in the common brushtail possum (Trichosurus vulpecula)

Marsupials are believed to be the only non-primate mammals with both trichromatic and dichromatic color vision. The diversity of color vision systems present in marsupials remains mostly unexplored. Marsupials occupy a diverse range of habitats, which may have led to considerable variation in the presence, density, distribution, and spectral sensitivity of retinal photoreceptors. In this study we analyzed the distribution of photoreceptors in the common brushtail possum (Trichosurus vulpecula). Immunohistochemistry in wholemounts revealed three cone subpopulations recognized within two spectrally distinct cone classes. Long-wavelength sensitive (LWS) single cones were the largest cone subgroup (67-86%), and formed a weak horizontal visual streak (peak density 2,106 ± 435/mm2) across the central retina. LWS double cones were strongly concentrated ventrally (569 ± 66/mm2), and created a "negative" visual streak (134 ± 45/mm2) in the central retina. The strong regionalization between LWS cone topographies suggests differing visual functions. Short-wavelength sensitive (SWS) cones were present in much lower densities (3-10%), mostly located ventrally (179 ± 101/mm2). A minority population of cones (0-2.4%) remained unlabeled by both SWS- and LWS-specific antibodies, and may represent another cone population. Microspectrophotometry of LWS cone and rod visual pigments shows peak spectral sensitivities at 544 nm and 500 nm, respectively. Cone to ganglion cell convergences remain low and constant across the retina, thereby maintaining good visual acuity, but poor contrast sensitivity during photopic vision. Given that brushtail possums are so strongly nocturnal, we hypothesize that their acuity is set by the scotopic visual system, and have minimized the number of cones necessary to serve the ganglion cells for photopic vision.

Bone density and neuromuscular function in older competitive athletes depend on running distance

UNLABELLED: Individuals who are involved in explosive sport types, such as 100-m sprints and long jump, have greater bone density, leg muscle size, jumping height and grip strength than individuals involved in long-distance running. INTRODUCTION: The purpose of this study is to examine the relationship between different types of physical activity with bone, lean mass and neuromuscular performance in older individuals. METHODS: We examined short- (n = 50), middle- (n = 19) and long-distance (n = 109) athletes at the 15th European Masters Championships in Poznań, Poland. Dual X-ray absorptiometry was used to measure areal bone mineral density (aBMD) and lean tissue mass. Maximal countermovement jump, multiple one-leg hopping and maximal grip force tests were performed. RESULTS: Short-distance athletes showed significantly higher aBMD at the legs, hip, lumbar spine and trunk compared to long-distance athletes (p ≤ 0.0012). Countermovement jump performance, hop force, grip force, leg lean mass and arm lean mass were greater in short-distance athletes (p ≤ 0.027). A similar pattern was seen in middle-distance athletes who typically showed higher aBMD and better neuromuscular performance than long-distance athletes, but lower in magnitude than short-distance athletes. In all athletes, aBMD was the same or higher than the expected age-adjusted population mean at the lumbar spine, hip and whole body. This effect was greater in the short- and middle-distance athletes. CONCLUSIONS: The stepwise relation between short-, middle- and long-distance athletes on bone suggests that the higher-impact loading protocols in short-distance disciplines are more effective in promoting aBMD. The regional effect on bone, with the differences between the groups being most marked at load-bearing regions (legs, hip, spine and trunk) rather than non-load-bearing regions, is further evidence in support of the idea that bone adaptation to exercise is dependent upon the local loading environment, rather than as part of a systemic effect.

Greater association of peak neuromuscular performance with cortical bone geometry, bone mass and bone strength than bone density : a study in 417 older women

BACKGROUND: We evaluated which aspects of neuromuscular performance are associated with bone mass, density, strength and geometry. METHODS: 417 women aged 60-94years were examined. Countermovement jump, sit-to-stand test, grip strength, forearm and calf muscle cross-sectional area, areal bone mineral content and density (aBMC and aBMD) at the hip and lumbar spine via dual X-ray absorptiometry, and measures of volumetric vBMC and vBMD, bone geometry and section modulus at 4% and 66% of radius length and 4%, 38% and 66% of tibia length via peripheral quantitative computed tomography were performed. The first principal component of the neuromuscular variables was calculated to generate a summary neuromuscular variable. Percentage of total variance in bone parameters explained by the neuromuscular parameters was calculated. Step-wise regression was also performed. RESULTS: At all pQCT bone sites (radius, ulna, tibia, fibula), a greater percentage of total variance in measures of bone mass, cortical geometry and/or bone strength was explained by peak neuromuscular performance than for vBMD. Sit-to-stand performance did not relate strongly to bone parameters. No obvious differential in the explanatory power of neuromuscular performance was seen for DXA aBMC versus aBMD. In step-wise regression, bone mass, cortical morphology, and/or strength remained significant in relation to the first principal component of the neuromuscular variables. In no case was vBMD positively related to neuromuscular performance in the final step-wise regression models. CONCLUSION: Peak neuromuscular performance has a stronger relationship with leg and forearm bone mass and cortical geometry as well as proximal forearm section modulus than with vBMD.

A study of guided wave propagation in timber pole using spectral finite element method

Timber is one of the most widely used structural material all over the world. Round timbers can be seen as a structural component in historical buildings, jetties, short span bridges and also as piles for foundation and poles for electrical and power distribution. To evaluate the current condition of these cylindrical type timber structures, guided wave has a great potential. However, the difficulties associated with the guided wave propagation in timber materials includes orthotropic behaviour of wood, moisture contents, temperature, grain direction, etc. In addition, the effect of fully or partially filled surrounding media, such as soil, water, etc. causes attenuation on the generated stress wave. In order to investigate the effects of these parameters on guided wave propagation, extensive numerical simulation is required to conduct parametric studies. Moreover, due to the presence of multi modes in guided wave propagation, dispersion curves are of great importance. Even though conventional finite element method (FEM) can determine dispersion curves along with wave propagation in time domain, it is highly computationally expensive. Furthermore, incorporating orthotropic behaviour and surrounding media to model a thick cylindrical wave (large diameter cylindrical structures) make conventional FEM inefficient for this purpose. In contrast, spectral finite element method (SFEM) is a semi analytical method to model the guided wave propagation which does not need fine meshes compared to the other methods, such as FEM or finite difference method (FDM). Also, even distribution of mass and stiffness of structures can be obtained with very few elements using SFEM. In this paper, the suitability of SFEM is investigated to model guided wave propagation through an orthotropic cylindrical waveguide with the presence of surrounding soil. Both the frequency domain analysis (dispersion curves) and time domain reconstruction for a multi-mode generated input signal are presented under different loading location. The dispersion curves obtained from SFEM are compared against analytical solution to verify its accuracy. Lastly, different numerical issues to solve for the dispersion curves and time domain results using SFEM are also discussed.

Synthesis, structure and spectral properties of dithiocarbamato bridged dirhenium(III,II) complexes: a combined experimental and theoretical study

Sodium salts of dimethyldithiocarbamate, diethyldithiocarbamate and pyrrolidinedithiocarbamate react with the multiply bonded paramagnetic dirhenium(III,II) complex Re₂(μ-O₂CCH₃)Cl₄(μ-dppm)₂, 1 (dppm = Ph₂PCH₂PPh₂) in refluxing ethanol to afford the paramagnetic substitution products of the type Re₂(η²-S,S)₂(μ-S,S)(μ-Cl)₂(μ-dppm), where S,S represents the dithiocarbamato ligands [S,S = S₂CNMe₂, 4(L_Me); S₂CNEt₂, 4(L_Et) and S₂CN(CH₂)₄, 4(L_Pyr)]. These are the first examples of dirhenium complexes that contain bridging dithiocarbamato ligand along with the dppm ligand. These complexes have very similar spectral (UV-Vis, IR, EPR) and electrochemical properties which are also reported. The identity of 4(L_Et) has been established by single-crystal X-ray structure determination (Re-Re distance 2.6385 (9) Å) and is shown to have edge-shared bioctahedral structure. The electronic structure and the absorption spectra of the complexes are scrutinized by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses.

Implementation of dual stack technique for reducing leakage and dynamic power

This paper deals with proposal of a new dual stack approach for reducing both leakage and dynamic powers. The development of digital integrated circuits is challenged by higher power consumption. Thecombination of higher clock speeds, greater functional integration, and smaller process geometries has contributed to significant growth in power density. Scaling improves transistor density and functionality ona chip. Scaling helps to increase speed and frequency of operation and hence higher performance. As voltages scale downward with the geometries threshold voltages must also decrease to gain the performance advantages of the new technology but leakage current increases exponentially. Today leakage power has become anincreasingly important issue in processor hardware and software design. It can be used in various applications like digital VLSI clocking system, buffers, registers, microprocessors etc. The leakage power increases astechnology is scaled down. In this paper, we propose a new dual stack approach for reducing both leakage and dynamic powers. Moreover, the novel dual stack approach shows the least speed power product whencompared to the existing methods. All well known approach is “Sleep” in this method we reduce leakage power. The proposed Dual Stack approach we reduce more power leakage. Dual Stack approach uses theadvantage of using the two extra pull-up and two extra pull-down transistors in sleep mode either in OFF state or in ON state. Since the Dual Stack portion can be made common to all logic circuitry, less number of transistors is needed to apply a certain logic circuit.The dual stack approach shows the least speed power product among all methods. The Dual Stack technique provides new ways to designers who require ultra-low leakage power consumption with much less speedpower product.