Isocyanurate based fluorinated polyurethane dispersion for anti-graffiti coatings

Fluorinated polyurethane dispersions (FPUDs) were synthesized using HDI isocyanurate, polyester polyol and DMPA with varying concentrations of trifluoro ethanol (TFE) in the range of 0–9 wt%. Further FPUDs were characterized by FT-IR and ¹H NMR for structural elucidation. Effects of trifluoro ethanol on the dispersion were evaluated by particle size analyzer. It was observed that with increase in TFE, particle size increases. Topography and contact angle were studied by atomic force microscopy (AFM) and goniometer, respectively. To gain more insight into the formation of roughness, power spectral density (PSD) analysis was carried out. It was found that with increase in TFE content, surface roughness increases due to migration of fluorinating agent on the coating substrate and consequently water repellency increases. Nano indentation of coating revealed that fluorinated coating possesses less stiffness and elastic modulus, due to the presence of fluorine on the coating. Further, coatings were analyzed for thermal properties by thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) which shows the enhancement in thermal stability and glass transition temperature with increase in TFE content. Anti-graffiti test was carried out which showed improved resistance with increasing fluorine content.     

Mobile agent based approach for QoS routing

A mobile agent based on-demand quality of service (QoS) unicast routing scheme for supporting multimedia applications is proposed that considers bandwidth, delay and packet loss as QoS metrics for feasible path computation. A mobile agent is employed to find multiple QoS paths and select a best path among them to preserve resources so as to increase call success ratio and network bandwidth utilisation as well as adapt to network dynamics. The scheme is simulated in various network scenarios (sparse and dense networks) to verify performance and operation effectiveness, and compared with RSVP-based QoS routing by using an internet routing protocol. The results demonstrate significant improvements in call success ratio and network bandwidth utilisation compared with RSVP-based QoS routing, both in case of sparse and dense networks. Benefits of the agent-based scheme are adaptability, flexibility, and support for component-based software engineering features such as software reuse, customisation and maintainability     

Fish bone structure based data aggregation and routing in wireless sensor network: multi-agent based approach

Wireless sensor networks (WSNs) are constrained by limited node (device) energy, low network bandwidth, high communication overhead and latency. Data aggregation alleviates the constraints of WSN. In this paper, we propose a multi-agent based homogeneous temporal data aggregation and routing scheme based on fish bone structure of WSN nodes by employing a set of static and mobile agents. The primary components of fishbone structure are backbone and ribs connected to both sides of a backbone. A backbone connects a sink node and one of the sensor nodes on the boundary of WSN through intermediate sensor nodes. Our aggregation scheme operates in the following steps. (1) Backbone creation and identifying master centers (or nodes) on it by using a mobile agent based on parameters such as Euclidean distance, residual energy, backbone angle and connectivity. (2) Selection of local centers (or nodes) along the rib of a backbone connecting a master center by using a mobile agent. (3) Local aggregation process at local centers by considering nodes along and besides the rib, and delivering to a connected master center. (4) Master aggregation process along the backbone from boundary sensor node to the sink node by using a mobile agent generated by a boundary sensor node. The mobile agent aggregates data at visited master centers and delivers to the sink node. (5) Maintenance of fish bone structure of WSN nodes. The performance of the scheme is simulated in various WSN scenarios to evaluate the effectiveness of the approach by analyzing the performance parameters such as master center selection time, local center selection time, aggregation time, aggregation ratio, number of local and master centers involved in the aggregation process, number of isolated nodes, network lifetime and aggregation energy. We observed that our scheme outperforms zonal based aggregation scheme.     

Wheel Based Event Triggered Data Aggregation and Routing in Wireless Sensor Networks: Agent Based Approach

Event triggered data aggregation and routing minimizes the amount of energy and bandwidth required to transmit the data from the event affected area. This paper proposes a Wheel based Event Triggered data aggregation and routing (WETdar) scheme in Wireless Sensor Networks (WSNs) by employing a set of static and mobile agents. A wheel with spokes is constructed by WSN nodes around an event node (a sensor node where an event occurs). Gathering and aggregation of the information is performed along the spokes of a wheel in Spoke Aggregator (SA) nodes and sent to an event node, which routes to a sink node. Spoke generation and identification of SA nodes along the spokes is performed by using a mobile agent, based on parameters such as Euclidean distance, residual energy, spoke angle and connectivity. Mobile agent and its clones discover multiple paths to a sink node from an event node. The scheme is simulated in various WSN scenarios to evaluate the effectiveness of the approach. The performance parameters analyzed are number of SAs, SA selection time, aggregation time, aggregation energy, energy consumption, number of isolated nodes and network life time. We observed that proposed scheme outperforms as compared to the existing aggregation scheme.     

WiGriMMA: A Wireless Grid Monitoring Model Using Agents

The complexity, heterogeneity, device mobility and the unpredictable user behavior demands proper automation of monitoring activity in the wireless Grid to enable the user needs. Since the wireless devices can dynamically join/leave the Grid, and its state may be affected by various parameters (like the battery power, signal strength, the number of jobs submitted to it, device mobility, etc.) leading to overload state, it is essential to monitor the devices so that long term resource planning can be achieved. This paper proposes a Wireless Grid Monitoring Model using Agents (WiGriMMA) that monitor the device mobility and state, communicates the state to Grid information server (GIS), provides the resource availability information, controls the selfish users and the device state so that the device is not overloaded. The model is simulated to test its operation effectiveness considering the performance parameters such as resource availability, resource stability, device state, job execution rate, user behavior and agent overhead. The results show that the proposed WiGriMMA performs better than the existing Grid monitoring model (GridView) in terms of the resource availability, device states and the job execution rate.     

Review of multicast routing mechanisms in mobile ad hoc networks

Frequent interactions among the group members of distributed wireless network environment may be facilitated with the help of Mobile Ad Hoc NETworks (MANETs). Some of the group-oriented applications include disaster management, battlefields, audio/video conferencing, e-commerce, e-education, etc. Group communication demands dynamic construction of efficient and reliable multicast routes under user mobility and varying channel conditions. Multicast routing mechanisms in MANETs have been consistently improved by researchers considering various performance measures such as energy efficient route establishment, packet delivery ratio, quicker and faster proactive route recovery, network life time, reliability, Quality of Service (QoS) based on bandwidth, delays, jitters, and security. The paper focuses on most recent reliable and QoS based multicast routing mechanisms that helps in multimedia communication over MANETs. The mechanisms are considered under different topological routing categories such as mesh, tree, zone and hybrid. We provide an overview of existing multicast routing mechanisms based on routing categories and point to directions for future research and development.     

Decision Tree Assessment of Challenging Technologies for Mission to Europa

The intriguing possibility that conditions exist that could support the evolution of life, as we understand it, in the ice-covered oceans of Europa makes the exploration of that Jovian moon a significant priority in NASA’s solar system explorations. There is a need, therefore, to develop and demonstrate technologies and scientific methodologies that could be used to explore these extreme subice realms with the goal of establishing whether or not some form of life has evolved. A NASA search-for-life mission to Europa would involve site reconnaissance, site selection, landing, deep drilling through ice, small autonomous submersibles traversing the purported sea under the ice, and in-situ life detection. Many advanced technologies not currently available would be required. Identification and rank ordering of enabling technologies in a portfolio that can be developed for a certain specified research and development budget is crucial for mission success. This paper describes the results of utilizing a decision tree methodology and an appropriate optimization process to formalize the technology investment strategy.     

Cognitive Agent Based Critical Information Gathering and Dissemination in Vehicular Ad hoc Networks

Next generation vehicles will have capability of sensing, computing, and communicating capabilities. Different components in a vehicle have to constantly exchange available information with other vehicles on the road and cooperate for the purpose of ensuring safety and comfort using a Vehicular Ad hoc Network (VANET). Critical information like navigation, cooperative collision avoidance, lane-changing, speed limit, accident, obstacle or road condition warnings, etc. play a significant role for safety-related applications in VANET. Such kind of critical information gathering and dissemination is challenging, because of their delay-sensitive nature. This paper proposes an agent based model that consists of heavy-weight static cognitive (based on Belief Desire Intention : BDI) and light-weight mobile agents. Proposed model executes push (gather/store and disseminate) and pull (gather/store) operations on information gathered based on information relevance, criticalness and importance. The simulation results show that BDI based information gathering and dissemination scheme performs better than the reliable broadcast scheme in terms of bandwidth utilization, packet delivery ratio, push latency (information saturation time) and push/pull decision latency.     

Ring Mesh Based Multicast Routing Scheme in MANET Using Bandwidth Delay Product

Quality of Service (QoS) support in Mobile Ad Hoc Networks (MANETs) for group communication necessitates design of reliable networks with multicast support mechanisms. Reliable network connectivity among MANET nodes require high quality links that have much less packet drops and reliable nodes considering node mobility and failures. Reliability of a network can be enhanced by designing an end-to-end network pipe that satisfies the required QoS in terms of in-flight packets from source to a destination as well as by using a path comprising of reliable nodes. In-flight packets may be computed by using bandwidth delay product (BDP) of a network pipe. To meet the QoS requirements of an application, BDP should be maintained stable irrespective of vibrant network conditions. In this paper, we propose a BDP based multicast routing scheme in MANET using reliable ring mesh backbone. The scheme operates in the following sequence. (1) Reliable node pairs are computed based on mobility, remaining battery power and differential signal strength. The node pairs also compute BDP between them. BDP of a reliability pair is assessed using available bandwidth and delay experienced by a packet between them. (2) Backbone ring mesh is constructed using reliable pair nodes and convex hull algorithm. Reliable ring mesh is constructed at an arbitrary distance from the centroid of the MANET area. (3) Multicast paths are found by discovering a path from source to each destination of the group with concatenated set of reliability pairs that satisfy the BDP requirement. (4) The ring mesh maintains high BDP on ring links and can recover in case of node mobility and failures. Results show that there is an improvement in terms of end-to-end delay, packet delivery ratio, control overhead, memory overhead and application rejection ratio as compared to the Enhanced On Demand Multicast Routing Protocol.     

PVA/PMMA polymer blended composite electrospun nanofibers mat and their potential use as an anti-biofilm product

Bacterial infections have increased dramatically due to microbial biofilm formation resulting in chronic pathological conditions in human subjects. Microbial biofilm causes poor drug penetration and antibiotic resistance, which has made site-specific sustained drug delivery the most appropriate option. Our work entails fabrication of ciprofloxacin hydrochloride (CPX) loaded nanofibers using polyvinyl alcohol (PVA) and poly(meth) methacrylate (PMMA) employing electrospinning method to form PVA:PMMA:CPX nanofibers mat. These nanofibers mat were optimized, characterized, and further subjected to anti-biofilm activity. Microscopic images revealed average nanofibers diameter of 243 ± 80 nm with smooth surface morphology. Analytical graphs and thermal analysis confirmed drug encapsulation and drug-polymer compatibility. In vitro studies demonstrated sustained release of CPX for 22 days displaying Hixon Crowell and two-stage desorption kinetics. Anti-biofilm activity showed zones of inhibition 3.0 ± 0.5 cm, 2.8 ± 0.1 cm, 2.9 ± 0.2 cm for Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, respectively which was well above the minimum inhibitory concentration levels of the bacteria forming biofilm. Conclusively, these nanofibers mat have potential to be used as an anti-biofilm product.