General Framework for Network Throughput Maximization in Sink-Based Energy Harvesting Wireless Sensor Networks

Mehrabi, Abbas,Kim, Kiseon IEEE Computer Society 2017 IEEE TRANSACTIONS ON MOBILE COMPUTING Vol.16 No.7

<P>Due to the advancement in energy harvesting wireless sensor networks (EH-WSNs), the data collection from one-hop stationary sensor nodes using a path-constrained mobile sink has become one of the challenging issues. Toward the throughput improvement, we propose a general framework for network throughput maximization (NTM) problem by optimizing practically feasible parameters. For each proposed scenario, a mixed integer linear programming (MILP) optimization model is introduced for the problem formulation. Due to the NP-Hardness of the MILP models, we design two efficient algorithms namely as ODSAA and ODAA for two practically implementable scenarios. Having a preknowledge about the deployed location of nodes, the proposed algorithms run centrally by sink and find the sub-optimal solutions within a reasonable computation time. Furthermore, under the uniform distribution of energy harvesting, we find out two threshold points on, respectively, energy harvesting mean and battery capacity of nodes after which the network throughput reaches a stable point. Finally, simulations are conducted on a different set of node deployments, which the results confirm that the proposed algorithms significantly improve the data throughput collected by sink and also the theoretical thresholds provide a confidence interval of 90 percent.</P>

Maximizing Data Collection Throughput on a Path in Energy Harvesting Sensor Networks Using a Mobile Sink

Mehrabi, Abbas,Kiseon Kim IEEE 2016 IEEE transactions on mobile computing Vol.15 No.3

<P>In energy harvesting wireless sensor networks (EH-WSNs), maximizing the data collection throughput is one of the most challenging issues. In this paper, we consider the problem of data collection on a pre-specified path using a mobile sink which has a fixed-mobility pattern. As a generalization of the previous works, we propose an optimization model for the problem which incorporates the effective and heterogeneous duration of sensors' transmission in each time slot. To improve the network throughput, a simple condition is proposed which determines the maximum number of available time slots to each sensor node. Accordingly, the proposed condition specifies the constant velocity of the mobile sink. The NP-Hardness of the problem under the proposed condition is proved and an online centralized algorithm with less complexity is designed to handle the problem. Its complexity is in polynomial order and is easily scalable to the networks with large number of sensor nodes. Furthermore, we address the effect of increase in time slot period on the total amount of collected data which has not been yet exploited well. Finally, through extensive simulations on different set of deployed nodes, we observe that the proposed algorithm significantly increases the network throughput when the travelled distance by sink per time slot is reduced down to the adjusted point.</P>

Experimental study of the influence of pad angle on the thermal performance of a direct evaporative cooling system

Mehrabi M.,Goudarzi K.,Farahani S. Davoodabadi 대한설비공학회 2023 International Journal of Air-Conditioning and Refr Vol.31 No.1

One of the most important parts of direct evaporative cooling systems is the cooling pad. Pads vary in materials and construction features. The parameters studied in the performance of the pads are air speed, pad thickness, geometrical characteristics, and its configuration and the provided water flow rate. The performance of the pads is usually determined through saturation efficiency, pressure drop, temperature drop and humidity increase in the treated air, evaporation and water consumption, cooling capacity, coefficient of performance, and heat and mass transfer coefficients. Since the geometry and how to place the pad in the evaporative cooling system is one of the most important issues related to the performance of such systems, the present work experimentally investigates the amount of cooling and evaporation of the direct evaporative cooling system under 5 different angles of placement of the cellulose pad in relation to the vertical position. It includes angles of , , , , and in 5 different air speeds, 2 different inlet water flow rates, 2 inlet air temperatures, and 2 different inlet water temperatures. Results show that the lowest output temperature, highest air relative humidity, highest coefficient of performance (about 12% more than ), highest saturation efficiency, and highest evaporation rate are obtained in the case of a of cooling pad placement angle.

Impact noise radiated by collision of two spheres: Comparison between numerical simulations, experiments and analytical results

K. Mehraby,H. Khademhosseini Beheshti,M. Poursina 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Impact is very common source of noise in the industries. The impacts can be visible, such as forging, and can be invisible, such as impacts due to clearance of hinges. As a result of this generality, the control of impact noise needs more attention. Reduction of this tiresome noise needs enough perception about the impact. A study of this noise sources presents difficult problems both theoretically and experimentally. This is partly due to the many complex interconnected mechanical phenomena that occur and partly due to the fact that usual steady-state techniques of analysis cannot be applied. In such complex problems numerical techniques can help to acousticians. To gain some insight into this source of sound, in this paper collision of two steel spheres are studied with finite element method (FEM). Then the FEM results were compared with experiments to show authority of this numerical method to simulate impact noises. FEM results show that if the vibrational modes are excited by impact, the vibrational modes can be as effective as rigid body motion.

Simulation of superelastic SMA helical springs

Reza Mehrabi,Mohammad Reza Karamooz Ravari 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.1

Shape memory alloy (SMA) helical springs have found a large number of different applications in industries including biomedical devices and actuators. According to the application of SMA springs in different actuators, they are usually under tension and torsion loadings. The ability of SMAs in recovering inelastic strains is due to martensitic phase transformation between austenite and martensite phases. Stress or temperature induced martensite transformation induced of SMAs is a remarkable property which makes SMA springs more superior in comparison with traditional springs. The present paper deals with the simulation of SMA helical spring at room temperature. Three-dimensional phenomenological constitutive model is used to describe superelastic behavior of helical spring. This constitutive model is implemented as a user subroutine through ABAQUS STANDARD (UMAT), and the process of the implementation is presented. Numerical results show that the developed constitutive model provides an appropriate approach to captures the general behavior of SMA helical springs.

Characterisation of Melt Spun Ni-Ti Shape Memory Ribbons’ Microstructure

Kambiz Mehrabi,Mihael Brunˇcko,Albert C. Kneiss,Miodrag ˇColiˇc,Dragoslav Stamenkovic,Janko Ferˇcec,Ivan Anžel,Rebeka Rudolf 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.3

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires,self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the micro-structure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sec-tions of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

Revenue Maximization in Scheduling of Electric Vehicles Considering the Capacity of Parking Lots

Abbas Mehrabi,Hyoyoung Jung,Saransh Malik,Kiseon Kim 한국통신학회 2016 한국통신학회 학술대회논문집 Vol.2016 No.1

2D magneto-mechanical vibration analysis of a micro composite Timoshenko beam resting on orthotropic medium

Mojtaba Mehrabi,Mehdi Mohammadimehr,Fatemeh S. Mousavinejad 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.1

In the present study, the free vibration analysis of a size-dependent micro composite Timoshenko beam model reinforced by various distributions of carbon nanotubes under temperature changes and two-dimensional magnetic field is investigated based on modified strain gradient theory. Also, the effects of environment are simulated by orthotropic elastic foundation and it is assumed that the material properties are temperature-dependent. Mathematical formulations are obtained using Hamilton's principle and the governing equations of motion are derived based on energy approach and variation method. These equations are solved using semi-analytical and numerical methods such as Navier's type solution, finite element method and generalized differential quadrature method for various boundary conditions. The obtained results of this study are compared with the other previous researches and there is a good agreement between them. The main purpose of this work is the comparison of various solution methods on the problem outputs. Thus, the results are compared together and the effects of solution approach on the dimensionless natural frequencies is developed. Moreover, the effects of length-to-thickness ratio, magnetic field, temperature changes, elastic foundation and carbon nanotubes volume fractions on the dimensionless natural frequencies are studied. The results of this article demonstrate that the micro composite Timoshenko beam reinforced by FG-O and FG-X CNTs have lowest and highest dimensionless natural frequency, respectively. It is investigated that the dimensionless natural frequency enhances by increasing the magnetic field in x and z-directions.

A fuzzy virtual temperature sensor for an irradiative enclosure

Dalileh Mehrabi,Morteza Mohammadzaheri,Ali Firoozfar,Mohammadreza Emadi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

This paper presents the idea of virtual temperature sensors for irradiative enclosures. Such a virtual sensor is an algorithm which receives the temperature of a number of points on surfaces of an enclosure and estimates the temperature of another point (or a number of other points) within enclosure. This paper proposes a data-driven method based on fuzzy inference systems to develop temperature virtual sensing algorithms. The proposed method is validated on an experimental setup exhibiting excellent estimation accuracy with no need to thermo-physical properties of the enclosure. In this research, the designed and validated algorithm estimates the temperature of a single point; however, the methodology can be evidently extended to multiple points.

Evaluation of Genetic Diversity of Aegilops tauschii Accessions Using Morphological Characters

Mansouri, Sajjad,Mehrabi, Ali Ashraf,Kahrizi, Danial 한국작물학회 2013 Journal of crop science and biotechnology Vol.16 No.3

A collection of sixty-three accessions of Ae. tauschii belonging to different eco-geographical regions were used to evaluate its genetic diversity by 15 morphological characters. The data recorded were analyzed on all accessions using multivariate analyses. Principal component analysis (PCA) indicated that first six principal components with eigenvalues more than 1 explained 77.2% of the variability amongst accessions. Through cluster analysis according to Euclidian distance and UPGMA method, accessions divided into three groups. Knowledge of genetic diversity in Aegilops species provides different levels of information which is important in the management of germplasm resources.