Performance of electromagnetic communication in underwater wireless sensor networks

Underwater wireless sensor networks (WSNs) composed of a number of sensor nodes that are deployed to conduct a collaborative monitoring task. Wireless signals are used for communication between the sensor nodes. Acoustic signals are the dominant signals used as a wireless communication medium in underwater WSNs due to the relatively low absorption in the underwater environments. Acoustic signals face a lot of challenges such as ambient noise, manmade noise, limited bandwidth, multipath and low propagation speed. Some of these challenges become more severe in shallow water environment where a high level of ambient and mankind noise, turbidity and multipath propagation are available. Therefore, electromagnetic signals can be applied as an alternative communication signal for underwater WSNs in the shallow water. In this project, the performance of EM communication in underwater WSNs is investigated for the shallow water environment. Theoretical calculations and practical experiments are conducted in fresh and seawater. It is shown that signals propagate for longer ranges in freshwater comparing to seawater. Theoretical results show that attenuation of electromagnetic communication in seawater is much higher than in fresh water. The attenuation is increasing with the increasing of frequency. In addition, velocity of the signal is increasing as the frequency is increasing while loss tangent is decreasing as the frequency increasing. Based on practical experiments, freshwater medium permits short ranges EM communication that does not exceed 25.1 cm for 2.4 GHz frequency. On the other hand, communication in seawater is very difficult to achieve for the same high frequency. Path loss exponent was estimated for freshwater environment based on logdistance path loss model. The estimation was achieved through a comparison between theoretical calculations and practical measurements. The path loss exponent for EM communication in fresh water was estimated to be in the range of 2.3 to 2.4

High temperature optical absorption investigation into the electronic transitions in sol–gel derived C12A7 thin films

Optical absorption into 6 mm thick sol–gel derived films, annealed at 1300 °C of 12CaO·7Al2O3 calcium aluminate binary compound on MgO〈100〉 single crystal substrates was studied at temperatures ranging from room temperature to 300 °C. Experimental data were analysed in both Tauc and Urbach regions. The optical band gap decreased from 4.088 eV at 25 °C to 4.051 eV at 300 °C, while Urbach energy increased from 0.191 eV at 25 °C to 0.257 eV at 300 °C. The relationship between the optical band gap and the Urbach energy at different temperatures showed an almost linear relationship from which the theoretical values of 4.156 and 0.065 eV were evaluated for the band gap energy and Urbach energy of a 12CaO·7Al2O3 crystal with zero structural disorder at 0 K

Building Educational Presence in Second Life: An Exploratory Study

Second Life ® (SL) as the exemplar of virtual worlds has become a new platform for simulating real-life experiences and interactions. Businesses, universities, hospitals, governmental organizations, and individuals participate in SL for a variety of activities and experiences. Increasing participation in range of activities has made SL a suitable environment for creativity and innovation in the web-based delivery of services. However, there is little knowledge about the process of creating systems/presence in this new environment. This paper explores the unique aspects of systems development for educational purposes in SL using a case study approach. Multiple cases have been analyzed to investigate the process of systems development in SL projects and contrasted with existing information system development approaches. Contributions to education and research are discussed

A Theory of Cheap Control in Embodied Systems

We present a framework for designing cheap control architectures for embodied agents. Our derivation is guided by the classical problem of universal approximation, whereby we explore the possibility of exploiting the agent's embodiment for a new and more efficient universal approximation of behaviors generated by sensorimotor control. This embodied universal approximation is compared with the classical non-embodied universal approximation. To exemplify our approach, we present a detailed quantitative case study for policy models defined in terms of conditional restricted Boltzmann machines. In contrast to non-embodied universal approximation, which requires an exponential number of parameters, in the embodied setting we are able to generate all possible behaviors with a drastically smaller model, thus obtaining cheap universal approximation. We test and corroborate the theory experimentally with a six-legged walking machine. The experiments show that the sufficient controller complexity predicted by our theory is tight, which means that the theory has direct practical implications. Keywords: cheap design, embodiment, sensorimotor loop, universal approximation, conditional restricted Boltzmann machineComment: 27 pages, 10 figure

Enhancing Analysts’ Mental Models for Improving Requirements Elicitation: A Two-stage Theoretical Framework and Empirical Results

Research has extensively documented the importance of accurate system requirements in avoiding project delays, cost overruns, and system malfunctions. Requirement elicitation (RE) is a critical step in determining system requirements. While much research on RE has emerged, a deeper understanding of three aspects could help significantly improve RE: 1) insights about the role and impacts of support tools in the RE process, 2) the impact of using support tools in multiple stages of the RE process, and 3) a clear focus on the multiplicity of perspectives in assessing RE outcomes. To understand how using support tools could improve RE, we rely on the theoretical lens of mental models (MM) to develop a dynamic conceptual model and argue that analysts form mental models (MMs) of the system during RE and these MMs impact their outcome performance. We posit that one can enhance analysts’ MMs by using a knowledge-based repository (KBR) of components and services embodying domain knowledge specific to the target application during two key stages of RE, which results in improved RE outcomes. We measured the RE outcomes from user and analyst perspectives. The knowledge-based component repository we used in this research (which we developed in collaboration with a multi-national company) focused on insurance claim processing. The repository served as the support tool in RE in a multi-period lab experiment with multiple teams of analysts. The results supported the conceptualized model and showed the significant impacts of such tools in supporting analysts and their performance outcomes at two stages of RE. This work makes multiple contributions: it offers a theoretical framework for understanding and enhancing the RE process, develops measures for analysts’ mental models and RE performance outcomes, and shows the process by which one can improve analysts’ RE performance through access to a KBR of components at two key stages of the RE process

Microwave-promoted solvent free one-pot synthesis of triazolo[1,2-a] indazole-triones catalyzed by silica-supported La0.5Ca 0.5CrO3 nanoparticles as a new and reusable perovskite-type oxide

Microwave assisted solvent free synthesis of triazolo[1,2-a]indazole-1,3,8-triones through one-pot three-component reaction of dimedone, phenyl urazole and aromatic aldehydes is presented. The reaction process was catalyzed by La0.5Ca0.5CrO3 and silica-supported La0.5Ca0.5CrO3 nanoparticles as new perovskite-type catalysts. The nano catalyst was studied by XRD, SEM and IR characterization tools. Some advantages of the proposed approach include high yield, being eco-friendly, procedure convenience and reusability of the catalyst.               KEY WORDS: One-pot reaction, Triazolo[1,2-a]indazole trione, Perovskite oxide, Nano catalyst, Microwave, Solvent-free Bull. Chem. Soc. Ethiop. 2018, 32(2), 239-248.DOI: https://dx.doi.org/10.4314/bcse.v32i2.

Artifact paths removal algorithm for ultra-wideband channels

Ultra-wideband (UWB) is a promising technology for achieving high data rate communications. When UWB channel measurements are conducted, channel impulse responses (CIRs) are extracted from measured UWB waveforms using CLEAN deconvolution algorithm. However, artifact paths that represent unreal received multipath components (MPCs) are generated during this process. These artifact paths are registered as part of the measured CIRs representing a reflected signal from a scatterer. In reality, these paths do not represent a real scattering environment and this affects accurate channel modeling. Therefore, removal of the artifact paths is important to conserve better and have a more real scattering environment. In this work, an algorithm was developed to remove artifact paths from measured CIRs. The algorithm development was achieved based on the concept of geometric elliptical modeling applied to wideband channels, where the effective path in each ellipse is utilized to represent the channel response of the ellipse. Several UWB channel measurements were conducted to obtain the measured UWB waveforms. In addition, the characteristics of the UWB channels were analyzed in terms of CIRs properties and their stationarity regions. The algorithm performance was evaluated by comparing the single-template CLEAN CIRs with the CIRs result from the application of the developed algorithm on single-template CLEAN CIRs. Results showed that the developed algorithm can successfully remove the artifact paths. Besides that, an enhancement in the received power was achieved. For a specific measured channel, the received power enhancement obtained was more than 5%. The algorithm is beneficial for enhancing accuracy of CIRs extracted from a single-template CLEAN algorithm. Consequently, more accurate channel characteristics are gained leading to improved channel modelling and different parameter extractions

Study algicidial activity of 6 species (of) seaweed from Persian Gulf on growth (of) Cochlodinium polykrikoides

Harmful algal blooms resulting in red discoloration of coastal waters in the Persian Gulf, Iran were first observed in January 2007. The species responsible for the bloom, which was identified as Cochlodinium polykrikoides, coincided with massive aquatic organisms’ mortalities in the Persian Gulf. The effects of water soluble extract (0.2, 0.6, 0.8 and 1.6 g L-1) from 6 species of marine macroalgae; Ulva lactuca, Enthromorpha intistialis, Colpomenia sinuosa, Sargassum illicifolium, Gracilaria corticat and Hypnea valentiea , fresh thallus (2.5 and 5.0 g L-1) and macroalgal culture medium filtrate from 3species of marine macroalgae; E.intistialis, C.sinuosa, and H.valentiea on growth of Cochlodinium polkrikoides (Dinoflagellate) were investigated for 15 days in co-culture under controlled laboratory conditions. The results clearly showed that the growth of C. polkrikoides was significantly inhibited by the water-soluble extracts of seaweed at relatively all concentrations in contrast to control with any seaweeds extract (p<0.05). The growth inhibition of C. polykrikoides was significantly higher in co-culture with fresh thallus of E.intistialis, C.sinuosa and H.valentiea (p<0.05). In macroalgal culture medium filtrate the highest growth inhibition of C. polykrikoides was obtained in co-culture with E.intistialis and was significantly higher than the other macroalgal culture medium filtrate of seaweeds(p<0.05). Therefore, we could conclude that using the tested seaweeds either as an extract or in co-culture with fresh thallus could be used as an alternative to biological control of C. polykrikoides

The dynamic elastic response to impulse synchronisation of composite prosthetic energy storing and returning feet

In this research, it is proven that perfect synchronisation between the input impulse (human effort) and the ground reaction impulse/impact can result in a phenomenon called the dynamic elastic response to impulse synchronisation with favourable consequences to the behaviour of the energy storing and returning foot. An energy storing and returning composite prosthetic foot was first used in elite competition at the 1988 Paralympic Games. Since its introduction, the prostheses have proven to be a source of controversy. In 2008, it was concluded that the athletes who use such technology when running are in advantageous position when compared to able-bodied athletes. However, these findings have since been disputed. There still remain unanswered questions regarding the level of contribution of energy storing and returning feet in the performance of amputee athletes. A series of investigations have previously been conducted to study the dynamic characteristics of a number of energy storing and returning composite prosthetic feet. It was found that if a sinusoidal input impulse, with a frequency close to one of the energy storing and returning feet’s natural frequencies, could be applied, it can make the energy storing and returning foot susceptible to resonance, which, in the case of bending mode, if sustained can lead to a gain in height or increased velocity

Prognostic value of mean platelet volume in patients undergoing elective percutaneous coronary intervention

Objective: We sought to determine the role of mean platelet volume (MPV) for predicting long-term outcomes of elective percutaneous coronary intervention (PCI). Methods: On the basis of retrospective cohort study, we collected characteristics of 680 patients undergoing elective PCI from October 2005 to August 2010. The patients who had preoperative MPV were assessed for developing major adverse cardiac events (MACE) during 1-year follow- up. They were categorized into two groups including MPV <9.6 fL (n=89) and MPV �9.6 fL (n=92). Data were analyzed using t-test, chi-square test, Pearson correlation, receiver operating characteristic (ROC) curve and logistic regression. Results: One-hundred eighty one patients (26.6) met inclusion criteria. The MACE was observed in 29 patients (16); and its rate in low- and high-MPV groups was 11.2 and 20.7, respectively (p=0.084). MPV was significantly higher in the patients with left ventricular ejection fraction (LVEF) <40 compared with that of �40 (p<0.001). There were a significant and negative correlation between MPV and platelet count (r=-0.305, p<0.001), and significant and positive correlations between MPV and platelet distribution width (PDW) and platelet large cell ratio (P-LCR) (r=0.615, p<0.001 and r=0.913, p<0.001; respectively). The best MPV cut-off point was 9.25 fL; the sensitivity and specificity were 79 and 38, respectively. Elevated MPV was the best predictor of MACE at 1-year follow-up (OR=11.359, 95 CI 2.481-51.994, p=0.002). Conclusion: The results indicate that preoperative MPV is an independent predictor of the MACE at 1-year follow-up in the patients undergoing elective PCI. Moreover, it may be useful for risk stratification in such cases. © 2015 by Turkish Society of Cardiology