Aerodynamic Design Optimization with Consistently Discrete Sensitivity Derivatives Via the Incremental Iterative Method

In this study which involves advanced fluid-flow codes, an incremental iterative formulation (also known as the delta or correction form), together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently available. Iterative methods for solving these equations in the standard form are generally unsatisfactory due to an ill-conditioned coefficient matrix; this problem is overcome when these equations are cast in the incremental form. The methodology is successfully implemented and tested using an upwind cell-centered finite-volume formulation applied in two dimensions to the thin-layer Navier-Stokes equations for external flow over an airfoil. In three dimensions this methodology is demonstrated with a marching-solution algorithm for the Euler equations to calculate supersonic flow over the High-Speed Civil Transport configuration (HSCT 24E). The sensitivity derivatives obtained with the incremental iterative method from a marching Euler code are used in a design-improvement study of the HSCT configuration that involves thickness, camber, and planform design variables

Fault Tolerant Real Time Dynamic Scheduling Algorithm For Heterogeneous Distributed System

Fault-tolerance becomes an important key to establish dependability in Real Time Distributed Systems (RTDS). In fault-tolerant Real Time Distributed systems, detection of fault and its recovery should be executed in timely manner so that in spite of fault occurrences the intended output of real-time computations always take place on time. Hardware and software redundancy are well-known e ective methods for faulttolerance, where extra hard ware (e.g., processors, communication links) and software (e.g., tasks, messages) are added into the system to deal with faults. Performances of RTDS are mostly guided by eciency of scheduling algorithm and schedulability analysis are performed on the system to ensure the timing constrains. This thesis examines the scenarios where a real time system requires very little redundant hardware resources to tolerate failures in heterogeneous real time distributed systems with point-to-point communication links. Fault tolerance can be achieved by..

Operating system fault tolerance support for real-time embedded applications

Tese de doutoramento em Electrónica Industrial (ramo de conhecimento em Informática Industrial)Fault tolerance is a means of achieving high dependability for critical and highavailability systems. Despite the efforts to prevent and remove faults during the development of these systems, the application of fault tolerance is usually required because the hardware may fail during system operation and software faults are very hard to eliminate completely. One of the difficulties in implementing fault tolerance techniques is the lack of support from operating systems and middleware. In most fault tolerant projects, the programmer has to develop a fault tolerance implementation for each application. This strong customization makes the fault-tolerant software costly and difficult to implement and maintain. In particular, for small-scale embedded systems, the introduction of fault tolerance techniques may also have impact on their restricted resources, such as processing power and memory size. The purpose of this research is to provide fault tolerance support for real-time applications in small-scale embedded systems. The main approach of this thesis is to develop and integrate a customizable and extendable fault tolerance framework into a real-time operating system, in order to fulfill the needs of a large range of dependable applications. Special attention is taken to allow the coexistence of fault tolerance with real-time constraints. The utilization of the proposed framework features several advantages over ad-hoc implementations, such as simplifying application-level programming and improving the system configurability and maintainability. In addition, this thesis also investigates the application of aspect-oriented techniques to the development of real-time embedded fault-tolerant software. Aspect- Oriented Programming (AOP) is employed to modularize all fault tolerant source code, following the principle of separation of concerns, and to integrate the proposed framework into the operating system. Two case studies are used to evaluate the proposed implementation in terms of performance and resource costs. The results show that the overheads related to the framework application are acceptable and the ones related to the AOP implementation are negligible.Tolerância a falhas é um meio de obter-se alta confiabilidade para sistemas críticos e de elevada disponibilidade. Apesar dos esforços para prevenir e remover falhas durante o desenvolvimento destes sistemas, a aplicação de tolerância a falhas é normalmente necessária, já que o hardware pode falhar durante a operação do sistema e falhas de software são muito difíceis de eliminar completamente. Uma das dificuldades na implementação de técnicas de tolerância a falhas é a falta de suporte por parte dos sistemas operativos e middleware. Na maioria dos projectos tolerantes a falhas, o programador deve desenvolver uma implementação de tolerância a falhas para cada aplicação. Esta elevada adaptação torna o software tolerante a falhas dispendioso e difícil de implementar e manter. Em particular, para sistemas embebidos de pequena escala, a introdução de técnicas de tolerância a falhas pode também ter impacto nos seus restritos recursos, tais como capacidade de processamento e tamanho da memória. O propósito desta tese é prover suporte à tolerância a falhas para aplicações de tempo real em sistemas embebidos de pequena escala. A principal abordagem utilizada nesta tese foi desenvolver e integrar uma framework tolerante a falhas, customizável e extensível, a um sistema operativo de tempo real, a fim de satisfazer às necessidades de uma larga gama de aplicações confiáveis. Especial atenção foi dada para permitir a coexistência de tolerância a falhas com restrições de tempo real. A utilização da framework proposta apresenta diversas vantagens sobre implementações ad-hoc, tais como simplificar a programação a nível da aplicação e melhorar a configurabilidade e a facilidade de manutenção do sistema. Além disto, esta tese também investiga a aplicação de técnicas orientadas a aspectos no desenvolvimento de software tolerante a falhas, embebido e de tempo real. A Programação Orientada a Aspectos (POA) é empregada para segregar em módulos isolados todo o código fonte tolerante a falhas, seguindo o princípio da separação de interesses, e para integrar a framework proposta com o sistema operativo. Dois casos de estudo são utilizados para avaliar a implementação proposta em termos de desempenho e utilização de recursos. Os resultados mostram que os acréscimos de recursos relativos à aplicação da framework são aceitáveis e os relativos à implementação POA são insignificantes

Report of the IEEE Workshop on Measurement and Modeling of Computer Dependability

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNASA Langley Research Center / NASA NAG-1-602 and NASA NAG-1-613ONR / N00014-85-K-000

Traffic Steering in Radio Level Integration of LTE and Wi-Fi Networks

A smartphone generates approximately 1, 614 MB of data per month which is 48 times of the data generated by a typical basic-feature cell phone. Cisco forecasts that the mobile data traffic growth will remain to increase and reach 49 Exabytes per month by 2021. However, the telecommunication service providers/operators face many challenges in order to improve cellular network capacity to match these ever-increasing data demands due to low, almost flat Average Revenue Per User (ARPU) and low Return on Investment (RoI). Spectrum resource crunch and licensing requirement for operation in cellular bands further complicate the procedure to support and manage the network. In order to deal with the aforementioned challenges, one of the most vital solutions is to leverage the integration benefits of cellular networks with unlicensed operation of Wi-Fi networks. A closer level of cellular and Wi-Fi coupling/interworking improves Quality of Service (QoS) by unified connection management to user devices (UEs). It also offloads a significant portion of user traffic from cellular Base Station (BS) to Wi-Fi Access Point (AP). In this thesis, we have considered the cellular network to be Long Term Evolution (LTE) popularly known as 4G-LTE for interworking with Wi-Fi. Third Generation Partnership Project (3GPP) defined various LTE and Wi-Fi interworking architectures from Rel-8 to Rel-11. Because of the limitations in these legacy LTE Wi-Fi interworking solutions, 3GPP proposed Radio Level Integration (RLI) architectures to enhance flow mobility and to react fast to channel dynamics. RLI node encompasses link level connection between Small cell deployments, (ii) Meeting Guaranteed Bit Rate (GBR) requirements of the users including those experiencing poor Signal to Interference plus Noise Ratio (SINR), and (iii) Dynamic steering of the flows across LTE and Wi-Fi links to maximize the system throughput. The second important problem addressed is the uplink traffic steering. To enable efficient uplink traffic steering in LWIP system, in this thesis, Network Coordination Function (NCF) is proposed. NCF is realized at the LWIP node by implementing various uplink traffic steering algorithms. NCF encompasses four different uplink traffic steering algorithms for efficient utilization of Wi-Fi resources in LWIP system. NCF facilitates the network to take intelligent decisions rather than individual UEs deciding to steer the uplink traffic onto LTE link or Wi-Fi link. The NCF algorithms work by leveraging the availability of LTE as the anchor to improvise the channel utilization of Wi-Fi. The third most important problem is to enable packet level steering in LWIP. When data rates of LTE and Wi-Fi links are incomparable, steering packets across the links create problems for TCP traffic. When the packets are received Out-of-Order (OOO) at the TCP receiver due to variation in delay experienced on each link, it leads to the generation of DUPlicate ACKnowledgements (DUP-ACK). These unnecessary DUP-ACKs adversely affect the TCP congestion window growth and thereby lead to poor TCP performance. This thesis addresses this problem by proposing a virtual congestion control mechanism (VIrtual congeStion control wIth Boost acknowLedgEment -VISIBLE). The proposed mechanism not only improves the throughput of a flow by reducing the number of unnecessary DUPACKs delivered to the TCP sender but also sends Boost ACKs in order to rapidly grow the congestion window to reap in aggregation benefits of heterogeneous links. The fourth problem considered is the placement of LWIP nodes. In this thesis, we have addressed problems pertaining to the dense deployment of LWIP nodes. LWIP deployment can be realized in colocated and non-colocated fashion. The placement of LWIP nodes is done with the following objectives: (i) Minimizing the number of LWIP nodes deployed without any coverage holes, (ii) Maximizing SINR in every sub-region of a building, and (iii) Minimizing the energy spent by UEs and LWIP nodes. Finally, prototypes of RLI architectures are presented (i.e., LWIP and LWA testbeds). The prototypes are developed using open source LTE platform OpenAirInterface (OAI) and commercial-off-the-shelf hardware components. The developed LWIP prototype is made to work with commercial UE (Nexus 5). The LWA prototype requires modification at the UE protocol stack, hence it is realized using OAI-UE. The developed prototypes are coupled with the legacy multipath protocol such as MPTCP to investigate the coupling benefits

Broadcasting

In 1999, the Commonwealth Government referred the Broadcasting Services Act and related legislation to the Productivity Commission for inquiry and report within twelve months. The inquiry stems from the Government’s commitment under the Competition Principles Agreement to review legislation for its anticompetitive effects and covers the Broadcasting Services Act 1992 (including the 1998 digital conversion amendments), Broadcasting Services (Transitional Provisions and Consequential Amendments) Act 1992, Radio Licence Fees Act 1964 and the Television Licence Fees Act 1964. The Commission was to advise on practical courses of action to improve competition, efficiency and the interests of consumers in broadcasting service.broadcasting - digital television - media ownership - legislation - licensing - radio - television - tv - spectrum - airwaves - cultural diversity - local contect - radiofrequency - public interest - competition principles agreement - media - news - indigenous broadcasting - audiovisual - film - spectrum management - narrowcaster - analog - analogue - digital - cross-media - audience - sport - convergence - programs - programming - standards

NSSDC Conference on Mass Storage Systems and Technologies for Space and Earth Science Applications, volume 1

Papers and viewgraphs from the conference are presented. This conference served as a broad forum for the discussion of a number of important issues in the field of mass storage systems. Topics include magnetic disk and tape technologies, optical disks and tape, software storage and file management systems, and experiences with the use of a large, distributed storage system. The technical presentations describe, among other things, integrated mass storage systems that are expected to be available commercially. Also included is a series of presentations from Federal Government organizations and research institutions covering their mass storage requirements for the 1990's

A Dynamic Risk Management Framework for Water and Environmental Sustainability

The risks and vulnerabilities facing reservoir systems in river basins shift dynamically over time and space. These risks involve regime changes and shifts, throughout which one observes the transition of water availability from prolonged dry periods to prolonged wet periods. Ensuring reliability of water supply under these hydrological regime shifts involves understanding how these regime shifts can be identified, characterized, and quantified. This dissertation describes a dynamic risk management (DRM) framework for water management at the basin level whose main features are (1) a system of updating risk assessments and policy recommendations on a yearly basis, where the risk assessments themselves are multi-year projections for the purposes of long-term planning into the future, and (2) integration of water supply and water demand variables into a quantitative hydrological risk assessment and streamflow regime identification tool. The DRM framework expounded in this dissertation will be split into four parts. The first part is extending streamflow records using tree-ring chronology-based paleo-reconstruction techniques. Longer streamflow records have the advantage of containing more information about the past hydrological behavior than the much shorter observed records do. Chapter 2 details a novel streamflow reconstruction approach for river basins in which the streamflow gauges are organized as a network, in which one streamflow gauge feeds into another one downstream. The method is applied to reconstructing streamflow for eighteen streamflow gauges in the Upper Missouri River Basin (UMRB). The second part of the DRM system, discussed in chapter 3, introduces a set of metrics for identifying and quantifying hydrological regimes in streamflow records. The metrics developed here are applied to the streamflow reconstructions developed in chapter 2. A thorough analysis of the specific hydrological behavior identified along with a spatial analysis of the intensity of those hydrological phenomena as they appear in the UMRB, are presented. The third part of DRM is covered in Chapter 4, v which is a review of the entire history of the evolution of water policy and water consumption in the Delaware River Basin, specifically for the three reservoirs that serve New York City in this watershed, as a means of better understanding the demand side of water management and the factors that influence it. Finally, chapter 5 covers the fourth and final part of the DRM framework for the purposes of this dissertation, which is a constrained scenario-analysis model for determining the feasible demand space for future water management and water release policies. The constraints placed on this model are probabilistic constraints based on controlling the manifestation of risk factors to the reservoir system; namely, droughts and spills. The demand space is a set of water demand/release values that satisfy all constraints simultaneously while satisfying the needs of ecosystems and societies that demand on the water coming from the reservoir system

View on 5G Architecture: Version 2.0

The 5G Architecture Working Group as part of the 5GPPP Initiative is looking at capturing novel trends and key technological enablers for the realization of the 5G architecture. It also targets at presenting in a harmonized way the architectural concepts developed in various projects and initiatives (not limited to 5GPPP projects only) so as to provide a consolidated view on the technical directions for the architecture design in the 5G era. The first version of the white paper was released in July 2016, which captured novel trends and key technological enablers for the realization of the 5G architecture vision along with harmonized architectural concepts from 5GPPP Phase 1 projects and initiatives. Capitalizing on the architectural vision and framework set by the first version of the white paper, this Version 2.0 of the white paper presents the latest findings and analyses with a particular focus on the concept evaluations, and accordingly it presents the consolidated overall architecture design