Volume 2 Issue 2
Authors: Sadia Sultana; Amran Hossen Bhuiyan; Nahida Akter; Bellal Hossain; Humayun Kabir; Mahbuba Yeasmin
Abstract: Continuous power supply is very important issue in the purpose of the application of wireless sensor networks. But in the power system of WSN, the battery has a very limited lifetime and is not replaced yet by any other continuous power system. Many researchers are performing several analyses about the energy harvesting circuit of WSNs power system. In this paper, such approach was also performed, with radio frequencies used as input power of energy harvesting circuit for wireless sensor networks. RF energy harvesting technology is not new, but it is able to harvest a minute amount of energy which is not sufficient to continuous power to the node of WSN. In this work, an optimization of the voltage doublers stages in an energy conversion module for Radio Frequency (RF) energy harvesting system at 950 MHz band is presented. Advanced design system (ADS) simulator was used to design a 10-stage voltage multiplier RF energy harvesting circuit, which produces approximately 5 Volt at 0 dBm and maximum 36.489 Voltage. Two 10 stage voltage multipliers were designed and the Agilent diode HSMS-2850 and HSMS-2822 were compared, and finally, it was confirmed that the HSMS-2850 works much better than HSMS-2822 diode. The proposed system can be used to power low power sensors in sensor networks ultimately in place of batteries.
Keywords: Wireless Sensor Networks (WSNs); Radio Frequency (RF); Ambient Energy; Harvesting; Voltage Multiplier
Authors: Oleg Sytnik
Abstract: The problem of estimating Doppler shifts and delays of signals modulated by pseudorandom sequences is discussed. It is shown that signals reflected from slow-moving targets hidden among optically opaque wreckages contain some information on targets in the variations of the full phase of a signal over the period that exceeds considerably the pseudorandom oscillation period. For example, these variations in the full phase may result from breathing and heartbeat of those who survived after man-made or natural disasters. Non-correlated and correlated types of noise lead to the errors in a thin structure of code sequences. In this paper a quasi-optimal receiver with non-coherent discriminators is proposed. The receiver has the two parallel channels which are synchronized by phase with a sounding signal. The receiver synthesis procedure, its operating conditions and its characteristics are fully considered. The synthesis is based on the modified non-linear filtering methods. This theory has been used to build the signal processing algorithm. The synthesis procedure consists of two steps. At the first step, an assumption is made that signal frequency has no shift and the base structure of the signal processing algorithm has been obtained. At the second step, the assumption that the structure of the algorithm remains unchanged is made, and using the theory of signal filtering the filter in the control loop for shifted frequencies is designed. It is shown that the sequences of combined estimates of the frequencies shifts and the signal delay can be used as a model of a dynamic Kalman filter.
Keywords: Coherent Radar; Pseudorandom Sequences; Non-Linear Filtering; Non-Correlated and Correlated Noise; Slow-Moving Targets; Optically Opaque Wreckages; Quasi-Optimal Receiver
Authors: S. Haddad; A. Othmane; L. Mora
Abstract: Engineering the surface chemistry of a material so that it can interface with cells is an extraordinarily demanding task. The surface of a cell is composed of thousands of different lipids, proteins and carbohydrates, all intricately (and dynamically) arranged in three dimensions on multiple length scales. This complexity presents both a challenge and an opportunity to chem¬ists working on bioactive interfaces. In this paper, polyurethane (PU) films, modified with an antithrombin-heparin complex (ATH), are used as substrates for endothelial cell attachment and growth. These processes and the corresponding surface fonctionnalization are characterized using Cyclic Voltammetry (CV), contact angle measurement and Atomic Force Microscopy (AFM). It is observed that the addition of a small amount of heparin and AT additives onto the polymer surface results in a considerable change in the surface characteristics, and it is found that PU films that were modified with the ATH complex are able to greatly enhance the adhesion and proliferation of endothelial cells (ECs).
Keywords: Polyurethane; Heparin; Antithrombin; Endothelial Cells
Authors: Ko-Ming Chiu; Jing-Sin Liu; Shih-Rong Yang
Abstract: Wireless sensor network (WSN) technology is widely used in environment monitoring, health care, surveillance systems and unmanned space or planet exploration. To collect the exploration data, controllable mobility such as mobile robot called data mules can be used to help complete data gathering missions using the same sensors. This study focuses on data gathering by a mobile robot in a WSN, also referred to as a robot routing problem. It is formulated as a Traveling Salesman Problem with Neighborhoods (TSPN). Basing on the need of practical applications, a two-phase method, a clustering-based parallel genetic algorithm with migration (CBPGA), is proposed as a TSPN route computing and optimizing scheme that allows simultaneously searching of the order and locations of waypoints of clusters. The first phase of the method consists of a Euclidean-distance based clustering algorithm that assigns the nodes to clusters, and the second phase routes these clusters by planning the data collection points in the common intersection area of each cluster and the order to visit them using a genetic algorithm (GA). A travel cost reduction scheme by finding the closest waypoint in a cluster according to the visiting order is used to further shorten the path length. Simulation studies are conducted to evaluate the performance of CBPGA, by comparing it with other solutions to TSPN in WSN with identical or random sensing radii. To reveal the relative performance of each solution scheme, the effect of clustering, the role of GA and parallelism, and the integration of CBPGA in data-gathering route design are highlighted.
Keywords: Data Collection; Traveling Salesman Problem with Neighborhoods (TSPN); Clustering; Genetic Algorithm