Plastic pollution in the ocean

Plastic pollution in the ocean was first reported by scientists in the 1970s, yet in recent years it has drawn tremendous attention from the media, the public, and an increasing number of scientists spanning diverse fields, including polymer science, environmental engineering, ecology, toxicology, marine biology, and oceanography. In the oceans, the threat to marine life comes in various forms, such as overexploitation and harvesting, dumping of waste, pollution, alien species, land reclamation, dredging and global climate change. The extremely visible nature of much of this contamination is easy to convey in shocking images of piles of trash on coastlines, marine mammals entangled in fishing nets, or seabird bellies filled with bottle caps, cigarette lighters, and colourful shards of plastic. Even without these images, anyone who has visited a beach has certainly encountered discarded cigarette butts, broken beach toys left behind, or pieces of fishing gear or buoys that have washed ashore

Data communication network at the ASRM facility

The main objective of the report is to present the overall communication network structure for the Advanced Solid Rocket Motor (ASRM) facility being built at Yellow Creek near Iuka, Mississippi. This report is compiled using information received from NASA/MSFC, LMSC, AAD, and RUST Inc. As per the information gathered, the overall network structure will have one logical FDDI ring acting as a backbone for the whole complex. The buildings will be grouped into two categories viz. manufacturing critical and manufacturing non-critical. The manufacturing critical buildings will be connected via FDDI to the Operational Information System (OIS) in the main computing center in B 1000. The manufacturing non-critical buildings will be connected by 10BASE-FL to the Business Information System (BIS) in the main computing center. The workcells will be connected to the Area Supervisory Computers (ASCs) through the nearest manufacturing critical hub and one of the OIS hubs. The network structure described in this report will be the basis for simulations to be carried out next year. The Comdisco's Block Oriented Network Simulator (BONeS) will be used for the network simulation. The main aim of the simulations will be to evaluate the loading of the OIS, the BIS, the ASCs, and the network links by the traffic generated by the workstations and workcells throughout the site

Analysis of adaptive algorithms for an integrated communication network

Techniques were examined that trade communication bandwidth for decreased transmission delays. When the network is lightly used, these schemes attempt to use additional network resources to decrease communication delays. As the network utilization rises, the schemes degrade gracefully, still providing service but with minimal use of the network. Because the schemes use a combination of circuit and packet switching, they should respond to variations in the types and amounts of network traffic. Also, a combination of circuit and packet switching to support the widely varying traffic demands imposed on an integrated network was investigated. The packet switched component is best suited to bursty traffic where some delays in delivery are acceptable. The circuit switched component is reserved for traffic that must meet real time constraints. Selected packet routing algorithms that might be used in an integrated network were simulated. An integrated traffic places widely varying workload demands on a network. Adaptive algorithms were identified, ones that respond to both the transient and evolutionary changes that arise in integrated networks. A new algorithm was developed, hybrid weighted routing, that adapts to workload changes

Status and projections of the NAS program

NASA's Numerical Aerodynamic Simulation (NAS) Program has completed development of the initial operating configuration of the NAS Processing System Network (NPSN). This is the first milestone in the continuing and pathfinding effort to provide state-of-the-art supercomputing for aeronautics research and development. The NPSN, available to a nation-wide community of remote users, provides a uniform UNIX environment over a network of host computers ranging from the Cray-2 supercomputer to advanced scientific workstations. This system, coupled with a vendor-independent base of common user interface and network software, presents a new paradigm for supercomputing environments. Background leading to the NAS program, its programmatic goals and strategies, technical goals and objectives, and the development activities leading to the current NPSN configuration are presented. Program status, near-term plans, and plans for the next major milestone, the extended operating configuration, are also discussed

Qucs modelling and simulation of analog/RF devices and circuits (Chapter 6)

Trends in compact device modeling and analog circuit simulation point towards a growing interest among the modeling community in the standardization of Verilog-A as an equation based modeling language for compact semiconductor device model and circuit macromodel development. . This chapter introduces the principles of compact device modeling with equation-defined devices and VerilogA models. For completeness circuit macromodel principles and construction are also included. It also describes the use of the different types of equation based models in analog and RF circuit simulation. Throughout the text the properties of a range of analog and RF circuits with different levels of complexity are introduced and their performance investigated with the “Quite universal circuit simulator” (Qucs) and its related software package QucsStudio. All the device and circuit modeling techniques introduced in this chapter form part of the standard features implemented in Qucs and QucsStudio

Single-Phase Photovoltaic-Inverter Operation Characteristic in Distributed Generation System

Single-phase grid tied inverter is one among types of inverters widely used in photovoltaic (PV) generation system due to the advantages they offer. This chapter describes model and simulation of such inverter in operation as distributed generation in electrical power system. Power characteristics including power quality, grid interaction behavior and load sharing that are important aspects in their operation as grid connected inverter will be simulated and analyzed. The role of current or voltage control and associated mechanism in photovoltaic inverter such as photovoltaic I-V characteristic, maximum power point tracker (MPPT), and other mechanism that involves in power flow and load sharing control are described. Further, some observation and measurement from a 5-kWp laboratory scale grid interconnected photovoltaic plant that employ single phase photovoltaic inverter will be presented. The load sharing behavior between photovoltaic plant and utility grid during supplying both linear and non linear load that connected on their point of common coupling. In addition, observation and measurement results of power quality parameter behavior during photovoltaic inverter operation along extremely density variation of photovoltaic produced energy that comes from the atmospheric condition will be presented. Keywords: single phase PV Inverter, distributed generatio

Comparative study of networks using packet and circuit switching within a single network

During the last couple of years, in addition to voice, other types of communications network services are becoming increasingly important. These are interactive data, facsimile, slow scan image, and bulk data. Typically, these services are delivered by separate networks using various kinds of switching technology, such as packet, circuit, or message switching. Recently, much of the focus has been on the integration of all types of communication services within the same switch or network, especially within the telephony and business industry. Integration of the communication services is being realized by integrating packet and circuit switching within the same switch or network. The overall goal of this thesis is to present the key aspects of the integration of circuit and packet switching within the same switch/network

Performance Study of Shared Versus Nonshared Bandwidth on a Packet-Switched Network

In wide area computer data communications, many networks have evolved by satisfying increased user demands in the most expedient manner. In some cases, new users’ demands are satisfied by installing a new link, rather than sharing the links that are already in place. This research investigates the differences in performance between using a dedicated link for each source destination pair (nonshared bandwidth) and using a single link to be used by all source destination pairs (shared bandwidth). Simulation models are developed for a wide area network using shared bandwidth, and a wide area network using nonshared bandwidth. The quality of service offered by each network is based on its responsiveness and productivity. Responsiveness will be measured in terms of average end to end delay of packet transmission, and productivity will be measured in terms of percent bandwidth utilization. The networks are modeled under a common set of operating assumptions and system environment. This allows for accurate comparison of packet delay and bandwidth utilization. Two variable input parameters are used in the simulation: intensity of input traffic load, and amount of link capacity. Provided that the intensity of the input traffic load remains below the network saturation level, it is shown that the shared system clearly outperforms the nonshared system. This result occurs for both a uniform and a nonuniform traffic load destination distribution