Analysis of the Linearity and Shift Invariance Characteristics of the X-Space Magnetic Particle Imaging

Asl, Hamed Jabbari,Kim, Myeong Ok,Yoon, Jungwon American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.8

<P>The x-space reconstruction method for magnetic particle imaging (MPI) is a fast and robust method which provides the possibility for real-time imaging of the magnetic nanoparticle tracers. One limitation of this method is the requirement to utilize the complete MPI signal. The necessary filtering action in the MPI, removes the first harmonic information which affects the linearity and shift invariance (LSI) characteristics of the image. In this paper, LSI properties of the x-space imaging, necessary for medical diagnosis applications, is analyzed. It is shown that filtering the output signal causes an image loss which depends on the trajectory of the drive field where, for a harmonic drive field, its value is constant and can be compensated in 1D imaging. The findings of this paper reveal the importance of the method of applying the driving field in multidimensional x-space in order to keep the LSI properties.</P>

Bidirectional Quasi-Cuk DC/DC Converter with Reduced Voltage Stress on Capacitor and Capability of Changing the Output Polarity

Asl, Elias Shokati,Sabahi, Mehran The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.3

In this paper, a bidirectional topology for quasi-Cuk dc/dc converter with capability of zero-voltage and zero-current-switching (ZVZCS) is proposed. The bidirectional quasi-Cuk (BQ-Cuk) converter has different voltage and current transfer ratio, reduced voltage stress on capacitor and capability of changing the output polarity in comparison with conventional bidirectional Cuk converter. In this paper, steady-state analysis of the quasi-Cuk converter with capability of ZVZCS in turn-on is presented. Then, critical inductances for transient from this operation to two new operations are calculated. Next, besides values designing of used elements, maximum and minimum value of their current and voltage are calculated. Finally, experimental results to verify the accuracy of the proposed converter in different operating modes are presented.

Bounded‐input control of the quadrotor unmanned aerial vehicle: a vision‐based approach

Asl, Hamed Jabbari,Yoon, Jungwon Wiley-Blackwell 2017 Asian journal of control Vol.19 No.3

Histopathology of leech parasitism on Capoeta capoeta gracilis, Squalius cephalus and Carassius auratus

asl, Adel Haghighi Khiabanian,Salimi, Behnam The Korean Society of Fish Pathology 2017 한국어병학회지 Vol.30 No.2

Parasitic leeches could directly (through causing poor growth, anemia and wound in the fish) and indirectly (by predisposition of the fish to secondary bacterial and fungal infections) affects their hosts. In the present study, fishes that were attacked by leeches in natural and experimental environment were studied. Pathologic samples were obtained from damages at the site of leech bite, as well as kidney and liver of the fish. Histopathological examination revealed numerous lesions at the site of leech bite including tissue demolition, detachment at the site of leech bite in the epidermis of epithelial tissue in the skin, destructed nucleus in epithelial cells of the skin plus necrosis in the damaged skin and weak inflammatory penetration to acute necrotic damages along with piercing dermis layer. Pathologic lesions in the kidney included some changes such as proliferation by increasing glomerular cells and membrane cells in capillary vein of the kidney, blood cell necrosis in kidney with infiltration of white blood cells mainly mononuclear and less polymorphonuclear which are the symptoms of anemia due to blood feeding and sucking by leeches. There was also a chronic kidney infection probably originated from another part of body such as skin. Moreover, leeches caused hemorrhagic anemia due to blood consumption of the hosts, which led to observation of immature red blood cells. Also results showed that diseases induced by leeched in fish could be acute or chronic, which depends on size of fish, species of leech and severity of infection.

Effects of internal stresses and intermediate phases on the coarsening of coherent precipitates: A phase-field study

M. Asle Zaeem,H. El Kadiri,M.F. Horstemeyer,M. Khafizov,Z. Utegulov 한국물리학회 2012 Current Applied Physics Vol.12 No.2

Phase stability, topology and size evolution of precipitates are important factors in determining the mechanical properties of crystalline materials. In this article, the CahneHilliard type of phase-field model was coupled to elasticity equations within a mixed-order Galerkin finite element framework to study the coarsening morphology of coherent precipitates. The effects of capillarity, particle size and fraction,compositional strain, and inhomogeneous elasticity on the kinetics and kinematics of coherent precipitates in a binary dual phase crystal admitting a third intermediate stable/meta-stable phase were investigated. The results demonstrated the ability of the model to simulate coarsening under the concomitant action of Ostwald ripening and mismatch elastic strain mechanisms. Using a phenomenological coarsening power law, coarsening rates were determined to depend on precipitate size and volume fraction, compositional strain, and strain mismatch between precipitates and the matrix. Results also showed that the necking incubation time between two neighboring precipitates depends inversely on the precipitate’s initial sizes; however, under fixed volume fraction of precipitates, any increase in the initial sizes of the precipitates mitigates the coarsening. Meanwhile, the compositional strain and the growth of the intermediate stable/meta-stable phase leads to substantial enhancements of precipitate coarsening.

An Analytical Approach for Fast Recovery of the LSI Properties in Magnetic Particle Imaging

Jabbari Asl, Hamed,Yoon, Jungwon Hindawi Publishing Corporation 2016 International journal of biomedical imaging Vol.2016 No.-

<P>Linearity and shift invariance (LSI) characteristics of magnetic particle imaging (MPI) are important properties for quantitative medical diagnosis applications. The MPI image equations have been theoretically shown to exhibit LSI; however, in practice, the necessary filtering action removes the first harmonic information, which destroys the LSI characteristics. This lost information can be constant in the <I>x</I>-space reconstruction method. Available recovery algorithms, which are based on signal matching of multiple partial field of views (pFOVs), require much processing time and<I> a priori</I> information at the start of imaging. In this paper, a fast analytical recovery algorithm is proposed to restore the LSI properties of the <I>x</I>-space MPI images, representable as an image of discrete concentrations of magnetic material. The method utilizes the one-dimensional (1D) <I>x</I>-space imaging kernel and properties of the image and lost image equations. The approach does not require overlapping of pFOVs, and its complexity depends only on a small-sized system of linear equations; therefore, it can reduce the processing time. Moreover, the algorithm only needs<I> a priori</I> information which can be obtained at one imaging process. Considering different particle distributions, several simulations are conducted, and results of 1D and 2D imaging demonstrate the effectiveness of the proposed approach.</P>

Robust image-based control of the quadrotor unmanned aerial vehicle

Jabbari Asl, Hamed,Yoon, Jungwon Springer-Verlag 2016 Nonlinear dynamics Vol.85 No.3

Stable Assist-as-Needed Controller Design for a Planar Cable-Driven Robotic System

Hamed Jabbari Asl,윤정원 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

Robot-assisted rehabilitation systems have shown promising advantages over traditional therapist-basedmethods. The type of the controller has an important role in the efficiency of such systems. In this regard, thispaper presents a new assist-as-needed (AAN) controller for 4-cable planar robots. The main purpose is to designa bounded-input AAN controller with an adjustable assistance level and a guaranteed closed-loop stability. Theproposed controller involves the advantages of both the model-based and non-model-based AAN controllers, and inthis way can increase the efficiency of rehabilitation. The controller aims to follow a desired trajectory by allowingan adjustable tracking error, which enables the human subject to freely move the target limb inside this error area. This feature of the controller gives an important advantage over the existing model-based controllers. The controlleralso compensates for the dynamic modeling uncertainties of the system through an adaptive neural network. Theadaptive term includes a forgetting factor to adjust the assistance level of neural network term. The stability of theclosed-loop system is analysed, and the uniformly ultimately bounded stability is proven. The effectiveness of theproposed control scheme is validated through simulations conducted for gait rehabilitation.

Some general aspects of a gas-solid fluidized bed using digital image analysis

Mahdi Salehi-Asl,Saeed Azhgan,Salman Movahedirad 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.2

Digital image analysis (DIA) was used to achieve some information related to aspect ratio of the bubbles, bed expansion fluctuations and the emulsion area at different gas velocities and different bed heights. All experiments were done in a pseudo-2D gas-solid fluidized bed. Variations of the bubble fraction at different gas velocities and different bed heights were investigated. It was found that when the excess gas velocity increases, the dimensionless bed height increases linearly with slope of about 0.4 for LLDPE particles. To validate the analysis, the bubble diameter achieved by DIA results in this work was compared with the bubble diameter correlation presented by Shen et al. Bubble aspect ratio in different heights of the bed was extracted through image analysis, and it was observed that the bubble aspect ratio first increases with the bed height and near the freeboard becomes flattened. Results of the experiments show that the emulsion phase becomes more expanded at higher excess gas velocities. As demonstrated by the analysis results, by increasing the bed height, bubble fraction parameter is decreased.

Evaluation of Friction Strength Loss in Endplate Moment Connections with Skewed Beam

Masoud Hoseinzadeh Asl,Mahsa Saeidzadeh,Seyedbabak Momenzadeh 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.6

This paper investigates the behaviour of skewed beam to column connections with endplates. The skewed moment connection results in torsional moment at the column face. The torsional moment causes to additional shear stress at the end plate surface, which will be combined with the shear stress due to the connection shear force. Since the endplate moment connection is a friction bolted connection, the increased shear stress at the connection face can lead to the frictional force loss and possible slippage of the end plate. In order to study the eff ect of skewed beam to column endplate connection on the ratio of friction force of the connection, 132 non-linear fi nite element models of beams with 10°, 20°, 30° and 45° of deviation are investigated. The results show that the beams with deviation angle of 45° have considerable loss in frictional force at the end plate. For the smaller deviation angles, adding one or two rows of bolts is an eff ective method to reduce the frictional force loss of the skewed beams with small deviation.