Theory of micropolar gyroelastic continua

This paper is devoted to the dynamic modeling of micropolar gyroelastic continua and explores some of the modeling and analysis issues related to them. It can be considered as an extension of the previous studies on equivalent continuum modeling of truss structures with or without angular momentum devices. Assuming unrestricted or large attitude changes for the axes of the gyros and utilizing the micropolar theory of elasticity, the energy expressions and equations of motion for undamped micropolar gyroelastic continua are derived. Whereas the micropolar gyroelastic continuum model with extra coefficients and degrees of freedom is primarily developed to account for the asymmetric stress–strain analysis in the gyroelastic continua, it also proves to be beneficial for a more comprehensive representation of the actual gyroelastic structure. The dynamic equations of the general gyroelastic continua are reduced to the case of one-dimensional gyroelastic beams. Simplified micropolar beam torsion and bending theories are used to derive the governing dynamic equations of micropolar gyroelastic beams from Hamilton’s principle. A finite element model corresponding to the micropolar gyrobeams is built in MATLAB\({^{\circledR}}\) and is used in numerical examples to study the spectral and modal behavior of simply supported micropolar gyroelastic beams.     

Body orientation estimation with the ensemble of logistic regression classifiers

Multimedia Tools and Applications - Orientation of human body is an important feature that can be used for behavioral analysis in surveillance systems. This cue contains useful information such as...     

Distinct element analysis and experimental evaluation of the Heckel analysis of bulk powder compression

In a number of powder processing operations such as dosing, compaction and tabletting, the behaviour of bulk powders subjected to compression is of great interest. Single particle mechanical properties obviously affect the bulk behaviour and there have been a number of attempts to establish relationships between the two scales of single particle and bulk deformation. A widely used approach, particularly in the pharmaceutical industries, is the Heckel analysis where the applied load and bulk deformation are used to infer the yield stress of individual particles. However, it is difficult to analyse this process rigorously and to ascribe any significance to the parameters quantified in the Heckel analysis because the individual particles are not loaded uniformly in the bed. It is therefore of great interest to elucidate what exactly the Heckel analysis does provide. The most appropriate approach for this purpose is the use of the Distinct Element Method (DEM) to simulate the bulk deformation based on single particle properties. Our analysis shows that there is a critical ratio of Young's modulus to the yield stress of individual particles (E/σ_y)_c, above which the Heckel analysis does reflect the effect of the yield stress, but below which it in fact reflects the effect of Young's modulus. Heckel's parameter is numerically equal to the yield stress of particles only for a certain value of E/σ_y. For ratios higher than this value, Heckel's parameter can even exceed the yield stress of the individual particles. Therefore the Heckel analysis does not have general validity and should be used with caution.     

Effect of granulation scale-up on the strength of granules

Granulation is commonly used to enlarge particle size to impart desirable characteristics and functionality to the granules. In this work, the effect of operating scale of the granulator on the physical properties of granules is analysed. Three scaling up rules of constant tip speed, constant shear stress and constant Froude number have been evaluated using 1, 5 and 50 l Cyclomix high shear mixer granulators, calcium carbonate powder and Polyethylene glycol (PEG) as binder. The strength of granules produced in different granulator scales is analysed by side crushing test. The results indicate that the condition of constant tip speed for scale-up produces granules with relatively similar strength. When the condition of constant shear stress is used to scale-up the granulator, the granules produced in 5 and 50 l have relatively similar strength, but 1 l produces much weaker granules than those of 5 and 50 l. Work has also been carried out to analyse the flow field of granules in the granulator to provide a better insight into the velocity and stress profiles as a function of equipment scale. Positron Emission Particle Tracking (PEPT) analysis shows that under constant shear stress condition macroscopic flow field of 1 l and 5 l granulators are different, a feature which could affect the final structure of the agglomerates. The PEPT results are used to describe the velocity gradient in the Distinct Element Method (DEM) simulation of the agglomerate deformation under bulk shearing. DEM modelling of microscopic interactions in agglomerate behaviour within a shearing bed shows that flow conditions of 1 l granulator make the agglomerate with a higher elongation factor and lower packing fraction, indicating that the agglomerate would be weaker. This feature has also been observed experimentally.     

An Iontronic Multiplexer Based on Spatiotemporal Dynamics of Multiterminal Organic Electrochemical Transistors

The seamless integration of electronics with biology requires new bio-inspired approaches that, analogously to nature, rely on the presence of electrolytes for signal multiplexing. On the contrary, conventional multiplexing schemes mostly rely on electronic carriers and require peripheral circuitry for their implementation, which imposes severe limitations toward their adoption in bio-applications. Here, a bio-inspired iontronic multiplexer based on spatiotemporal dynamics of organic electrochemical transistors (OECTs), with an electrolyte as the shared medium of communication, is shown. The iontronic system discriminates locally random-access events with no need of peripheral circuitry or address assignment, thus deceasing significantly the integration complexity. The form factors of OECTs that allow for intimate biointerfacing as well as the electrochemical nature of the communication medium, open new avenues for unconventional multiplexing in the emerging fields of bioelectronics, wearables, and neuromorphic computing or sensing.     

An investigation on process of seeded granulation in a continuous drum granulator using DEM

Numerical simulation of wet granulation in a continuous granulator is carried out using Discrete Element Method (DEM) to discover the possibility of formation of seeded granules in a continuous process with the aim of reducing number of experimental trials and means of process control. Simple and scooped drum granulators are utilized to attain homogenous seeded granules in which the effects of drum rotational speed, particles surface energy, and particles size ratio are investigated. To reduce the simulation time a scale-up scheme is designed in which a dimensionless number (Cohesion number) is defined based on the work of cohesion and gravitational potential energy of the particles. Also a mathematical/numerical method along with a MATLAB code is developed by which the percentage of surface coverage of each granule is predicted precisely. The results show that use of continuous granulator for seeded granulation is promising provided that a high level of shear is considered in the granulator design, i.e. using baffles inside drum granulators is essential for producing seeded granules. It is observed that the optimum surface energy for seeded granulation in scooped granulator (used in this study) with rotational speed of 50 rpm is 3 J/m², which is close to the value predicted by the concept of Cohesion number. It is also shown that increasing the seed/fine size ratio enhances the seeded granulation both quantitatively (60% increase in seeds surface coverage) and qualitatively (more homogeneous granules).     

A hybrid evolutionary approach to segmentation of non-stationary signals

Automatic segmentation of non-stationary signals such as electroencephalogram (EEG), electrocardiogram (ECG) and brightness of galactic objects has many applications. In this paper an improved segmentation method based on fractal dimension (FD) and evolutionary algorithms (EAs) for non-stationary signals is proposed. After using Kalman filter (KF) to reduce existing noises, FD which can detect the changes in both the amplitude and frequency of the signal is applied to reveal segments of the signal. In order to select two acceptable parameters of FD, in this paper two authoritative EAs, namely, genetic algorithm (GA) and imperialist competitive algorithm (ICA) are used. The proposed approach is applied to synthetic multi-component signals, real EEG data, and brightness changes of galactic objects. The proposed methods are compared with some well-known existing algorithms such as improved nonlinear energy operator (INLEO), Varri?s and wavelet generalized likelihood ratio (WGLR) methods. The simulation results demonstrate that segmentation by using KF, FD, and EAs have greater accuracy which proves the significance of this algorithm.     

An efficient online secondary path estimation for feedback active noise control systems

In practical cases for active noise control (ANC), the secondary path has usually a time varying behavior. For these cases, an online secondary path modeling method that uses a white noise as a training signal is required to ensure convergence of the system. The modeling accuracy and the convergence rate are increased when a white noise with a larger variance is used. However, the larger variance increases the residual noise, which decreases performance of the system and additionally causes instability problem to feedback structures. A sudden change in the secondary path leads to divergence of the online secondary path modeling filter. To overcome these problems, this paper proposes a new approach for online secondary path modeling in feedback ANC systems. The proposed algorithm uses the advantages of white noise with larger variance to model the secondary path, but the injection is stopped at the optimum point to increase performance of the algorithm and to prevent the instability effect of the white noise. In this approach, instead of continuous injection of the white noise, a sudden change in secondary path during the operation makes the algorithm to reactivate injection of the white noise to correct the secondary path estimation. In addition, the proposed method models the secondary path without the need of using off-line estimation of the secondary path. Considering the above features increases the convergence rate and modeling accuracy, which results in a high system performance. Computer simulation results shown in this paper indicate effectiveness of the proposed method.     

Frontal face modeling using morphing-based averaging and Low-rank decomposition

Multimedia Tools and Applications - Head pose variations are a major problem in face recognition. Many advanced methods exist for synthesizing frontal face images with head pose variations. These...     

Super-quasi-orthogonal space-time trellis codes for four transmit antennas

We introduce a new family of space-time trellis codes that extends the powerful characteristics of super-orthogonal space-time trellis codes to four transmit antennas. We consider a family of quasi-orthogonal space-time block codes as building blocks in our new trellis codes. These codes combine set partitioning and a super set of quasi-orthogonal space-time block codes in a systematic way to provide full diversity and improved coding gain. The result is a powerful code that provides full rate, full diversity, and high coding gain. It is also possible to maintain a tradeoff between coding gain and rate. Simulation results demonstrate the good performance of our new super-quasi-orthogonal space-time trellis codes.