A discrete event simulation for utility accrual scheduling in uniprocessor environment

This research has focused on the proposed and the development of an event based discrete event simulator for the existing General Utility Scheduling (GUS) to facilitate the reuse of the algorithm under a common simulation environment. GUS is one of the existing TUF/UA scheduling algorithms that consider the Time/Utility Function (TUF) of the executed tasks in its scheduling decision in a uniprocessor environment. The scheduling optimality criteria are based on maximizing accrued utility accumulated from execution of all tasks in the system. These criteria are named as Utility Accrual (UA). The TUF/ UA scheduling algorithms are design for adaptive real time system environment. The developed GUS simulator has derived the set of parameter, events, performance metrics and other unique TUF/UA scheduling element according to a detailed analysis of the base model

Exceptional Points of Degeneracy in Periodic Coupled Waveguides and the Interplay of Gain and Radiation Loss: Theoretical and Experimental Demonstration

We present a novel paradigm for dispersion engineering in coupled transmission lines (CTLs) based on exceptional points of degeneracy (EPDs). We develop a theory for fourth-order EPDs consisting of four Floquet-Bloch eigenmodes coalescing into one degenerate eigenmode. We present unique wave propagation properties associated to the EPD and develop a figure of merit to assess the practical occurrence of fourth-order EPDs in CTLs with tolerances and losses. We experimentally verify for the first time the existence of a fourth EPD (the degenerate band edge), through dispersion and transmission measurements in microstrip-based CTLs at microwave frequencies. In addition, we report that based on experimental observation and the developed figure of merit, the EPD features are still observable in structures that radiate (leak energy away), even in the presence of fabrication tolerances and dissipative losses. We investigate the gain and loss balance regime in CTLs as a mean of recovering an EPD in the presence of radiation and/or dissipative losses, without necessarily resorting to Parity-Time (PT)-symmetry regimes. The versatile EPD concept is promising in applications such as high intensity and power-efficiency oscillators, spatial power combiners, or low-threshold oscillators and opens new frontiers for boosting the performance of large coherent sources

An adaptive reliable multicast protocol in ad hoc networks

Multicasting is an essential service for ad-hoc wireless networks. In multicast communication, many reliable multicast schemes were studied in order to overcome packet losses in the network. This paper describes our effort to build a Source Tree Reliable Multicast protocol for ad-hoc networks (STRM). STRM provides the delivery of an ordered contiguous sequence of data packets from one sender to many receivers in an ad-hoc network. It is designed to support applications based on bulk data transfer, like files, images and software packages. The core to its support of node mobility, and also what makes the protocol unique, is the dynamic selection of a sub set of 1-hop neighbors from the sender as its Forward Servers (FSs). The key idea behind selecting this sub set 1-hop neighbors is to forward the retransmit lost data packets that needed by some receivers to achieve higher throughput and to receive the ACK packet from receivers to avoid the ACK-implosion problem inherent in any reliable multicast scheme. Finally, simulation results show that the protocol has high delivery ratio and low end-to-end delay comparing with ReMHoc protocol

A discrete event modeling and simulation of wave division multiplexing unidirectional slotted ring metropolitan area network

Problem statement: The lack of uniformity in the choice of simulation platforms for optical WDM networks stands behind the difficulty of developing a common simulation environment. Correlating WDM unidirectional slotted ring network to Discrete Event Simulation (DES) encompassing event definition, time advancing mechanism and scheduler has yet to be developed. Approach: The study focused on the proposed and the development of an event based discrete simulator for the WDM unidirectional slotted ring network to facilitate the reuse of the protocol modules under a common simulation environment. The proposed network architecture implemented for the developed simulator employs a separate wavelength as the control information channel. This control information enabled the nodes to monitor their access to the transmission media. Each node was equipped with a tunable transmitter and fixed receiver for data communication. Access nodes were equipped with a fixed transmitter and fixed receiver for the control information exchange. The developed simulator had derived the use of dividing the wavelength into slots. Nodes used these slots to transmit fixed size packets. Slots can be reused by the access node after receiving packets by the deployment of the spatial reuse scheme, thus enhancing the bandwidth utilization. The developed simulator had derived the set of the parameters, events, performance metrics and other unique WDM simulator elements according to a detailed analysis of the base model. Results: The network delay and packet loss were investigated and compared to a benchmark of the modeled domain. Successful deployment of the developed simulator was proven by the generated results. Conclusion: Extensive performance analysis of WDM unidirectional slotted ring network can be deployed using the developed simulator with low computational overheads. Further enhancements were to extend the developed simulator for bidirectional slotted ring supporting fairness control and considering both uniform and non-uniform traffic

Enhanced dynamic bandwidth allocation proportional to queue length with threshold value for VBR traffic

In Asynchronous Transfer Mode (ATM) network, Variable Bit Rate (VBR) service category has been defined to support any application for which the end-system can benefit from statistical multiplexing, by sending information at a variable rate, and can tolerate or recover from a potentially small random loss ratio. Due to its burst characteristic, bandwidth allocation strategy is necessary in order to share the network resources with other traffics fairly. The implementation of proposed approaches; heuristic, Unused Buffer Reallocation (UnBR) and Higher-priority Queue Sharing (HQS), in bandwidth strategy perform better improvement if compare to the proposed strategy. In addition, we observed that a bandwidth strategy did not always perform well, hence, suitable strategies should be chosen depending on the different conditions in order to fulfill its network demand

TiO2 nanotubes with ultrathin walls for enhanced water splitting

We demonstrate, for the first time, the synthesis of titania nanotubes with ultrathin (3–5 nm) wall thickness. As revealed by the incident photon-to-current collection efficiency (IPCE) and electrochemical impedance spectroscopy measurements, the ultrathin walls, less than the charge carrier diffusion length, were essential to ensure fast and efficient charge carrier collection.Qatar National Research Fund, a member of Qatar Foundation NPRP Grant no. 6-569-1-11

Laparoscopic Sleeve Gastrectomy: 2 cm versus 6 cm Distance from the Pylorus

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Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-is(neopentyloxy)-3-(neopentyloxycarbonyl)- 1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO2 NWs) and subsequent squeegee method to apply TiO2 NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm2. The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO2 NWs/TiO2 NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually

A discourse on the potential of crowdfunding and Islamic finance in the agricultural sector of East Java, Indonesia

Literature evidence on the transformation transpires agriculture sector in East Java for the last 5 to 10 years. The contribution of the agricultural sector towards East Java gross domestic product (GDP) in 2008 recorded at 16.55%, however, shrinks to 13.75% in 2015. This statistic shows the regressed contribution of the agriculture sector in comparison to other economic sectors. One common view that linked to shrinking in credit composition is due to the lack of credit accessibility for the sector. Given that, this paper attempts to propose a viable financing model to develop the agricultural sector in East Java known as Integrated Agricultural Land Crowdfunding Model (IALCM) using Islamic financing instruments through a crowdfunding platform. This model is expected to offer farmers in East Java to meet theirliquidity constraints and the Indonesian government to accelerate social entrepreneurship innovation with conceivable recommendations forthe development of agricultural sector in East Jav