Computing Delay-Constrained Least-Cost Paths for Segment Routing is Easier Than You Think

With the growth of demands for quasi-instantaneous communication services such as real-time video streaming, cloud gaming, and industry 4.0 applications, multi-constraint Traffic Engineering (TE) becomes increasingly important. While legacy TE management planes have proven laborious to deploy, Segment Routing (SR) drastically eases the deployment of TE paths and thus became the most appropriate technology for many operators. The flexibility of SR sparked demands in ways to compute more elaborate paths. In particular, there exists a clear need in computing and deploying Delay-Constrained Least-Cost paths (DCLC) for real-time applications requiring both low delay and high bandwidth routes. However, most current DCLC solutions are heuristics not specifically tailored for SR. In this work, we leverage both inherent limitations in the accuracy of delay measurements and an operational constraint added by SR. We include these characteristics in the design of BEST2COP, an exact but efficient ECMP-aware algorithm that natively solves DCLC in SR domains. Through an extensive performance evaluation, we first show that BEST2COP scales well even in large random networks. In real networks having up to thousands of destinations, our algorithm returns all DCLC solutions encoded as SR paths in way less than a second

Performance Analysis of Quantization-Based Approximation Algorithms for Precomputing the Supported QoS

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Holistic Study of Thermal Management in Direct Liquid Cooled Data Centres: from the Chip to the Environment

The IT (Information Technology) infrastructure power consumption constitutes a large portion of global electricity consumption and a large proportion of this energy is to maintain an acceptable thermal environment for the IT equipment. Therefore, it is important to understand and improve the thermal and energy management of data centres for lower cost and higher sustainability. Toward this goal, Direct Contact Liquid Cooled (DCLC) servers, where liquid loop heat exchangers are attached to the CPU, were proposed to study the use of chiller-less energy efficient data centre. Thirty Sun Fire V20z servers in a data centre rack have their CPUs water cooled with the remaining components air cooled, together with a rear door heat exchanger to capture this air heat flow. The heat generated by the servers is ultimately transferred to the environment using an Air Handling Unit (AHU). The AHU was fitted with a water spray system to increase the heat transfer capacity. The designed DCLC system was tested and characterised in terms of power consumption and thermal performance. The design successfully provided stable inlet coolant temperature (±1℃) to the IT despite the variation in the IT workload and environmental conditions. Activating the spray reduced the thermal resistance of the AHU heat exchanger (HE) by 50%. However, the power consumption and pressure drop across the HE was increased. The flow distribution and the coolant pumping configurations of centralised (where the coolant is pumped by two central pumps connected in series) and distributed (where small pumps inside the servers are activated) was investigated. The EPANET software was used to analyse the flow and showed that the servers in the top of the rack receive a higher flow rate (by approximately 30%) than the servers in the bottom of the rack. This resulted in a variation in the CPU temperatures of different servers. Optimisation analysis proposed increasing the manifolds size to improve the flow rate and reduce the flow maldistribution. In the distributed pumping case, the CPUs temperature showed to be 2℃ higher compared with the central pumping case for the high IT workload. The rack inlet temperature was tested in the range of the ASHRAE W4 envelope in terms of CPU temperatures, power consumption and computational efficiency. Increasing the coolant inlet temperature resulted in high energy saving in the AHU, while the rack energy consumption increases marginally in idle operation and considerably more in high IT workloads. This results in an improvement in the energy effectiveness of 17% but a deterioration in the computational efficiency of 4%. Finally, a parallel study was carried out to investigate the droplet evaporation over heated surfaces which ultimately be used in studying sprays in the AHU or in direct on chip cooling via evaporation. A novel experimental design was proposed to track the lifetime of any droplet size that span the surface tension to gravitydominated regimes. A theoretical model was also proposed to predict the droplet lifetime based on the initial contact angle, contact radius and the receding contact angle. The model predicted the droplet evaporation over hydrophobic surfaces with good accuracy of an error less than 4% while under estimated the evaporation with hydrophilic surfaces

Optimal filter design for power converters regulated by FCS-MPC in the MEA

For the DC electrical power distribution system onboard more electric aircraft, the voltage quality of DC bus is of a great concern since there could be significant harmonics distortions when feeding different power electronics loads. This problem can be potentially addressed by introducing a dc filter to the point-of-load converters regulated by the finite control set model predictive control (FCS-MPC). To optimize this filter, Genetic Algorithm (GA) is utilized for searching the optimal design which guarantees a low mass and low power losses. Different from the conventional filter design methods, the proposed method treats LC as design variables which need to be optimised while ensuring the output power quality. First, relations among variables, operation conditions and constraints are built based on commercial data and circuit simulations. Then, the design and optimization are developed with these relations and a Pareto-front is finally given by GA. After that, the best design is obtained by an index integrating two objectives. Lastly, the design approach is verified by experiment where an FCS-MPC regulated converter was used as a particular example fed by three different LC filters

Earth Resources: A continuing bibliography with indexes

This bibliography lists 475 reports, articles and other documents introduced into the NASA scientific and technical information system between January 1 and March 31, 1984. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economical analysis

Integrated Online Media Management Systems For Media Centers: A Model For Selection And Effective Use

The researcher proposed to advice in the selection of an Integrated Online Library System (IOLS) for use in the 103 school media centers in the Palm Beach County Schools, Florida. This was accomplished by evaluating the two finalists of those vendors who answered the district\u27s Request for Proposal (RFP). Of the five vendors who responded to the RFP. CLSI and SIRSI were selected as the systems most likely to meet the needs of the media centers of the school district. An overview and definition of IOLS was first discussed. This overview then related itself to the needs of the school district as presented in the RFP. A selection criteria was then designed from previous research on the subject to help find the ideal system. The history and development of an Integrated Online Library System was important in seeing where the systems have originated in contrast to the systems in the Eighties to the also revealed the present time. Literature IOLS principles of operation. The Request for Proposal reflected the needs assessment discussed over several years of committee meetings of representatives from various schools. The committees explored IOLS automated options and compared these options. The RFP outlined the system requirements. Thoughts on staff attitudes while planning for a system were also considered. Each system was evaluated with the criteria outlined in the RFP. The background and capabilities of both systems were explored. This exploration took place where by the benchmark tests, on-site demonstrations systems were in use daily, conferences with the vendors, systems. And reading literature reviews on both systems. Evaluation guidelines and criteria were found in library resources. The functions required for terminal access requirements, process for data conversion, vendor background and reliability, contained in these library resources. And the cost were contained in these library resources. The results of this study culminated in the official recommendation of the SIRSI to be purchased by the district\u27s school board. It was the expectation of the author of this document to see the purchase of the recommended system by the school board and have it implemented in all the schools in the district within a three year period following the submission of the recommendation

Summary of results from the Tandem Mirror Experiment (TMX)

This report summarizes results from the successful experimental operation of the Tandem Mirror Experiment (TMX) over the period October 1978 through September 1980. The experimental program, summarized by the DOE milestones given in Table 1-1, had three basic phases: (1) an 8-month checkout period, October 1978 through May 1979; (2) a 6-month initial period of operation, June through November 1979, during which the basic principles of the tandem configuration were demonstrated (i.e., plasma confinement was improved over that of a single-cell mirror); and (3) a 10-month period, December 1979 through September 1980, during which the initial TMX results were corroborated by additional diagnostic measurements and many detailed physics investigations were carried out. This report summarizes the early results, presents results of recent data analysis, and outlines areas of ongoing research and data analysis which will be reported in future journal publications

Crop identification and area estimation through the combined use of satellite and field data for county Durham, northern England

This thesis investigates the use of combined field and satellite data for crop identification and area estimation in County Durham, Northeast England. The satellite data were obtained by the Thematic Mapper (TM) sensor onboard Landsat-5 on 31 May 1985. The TM data were geometrically corrected to the British National Grid and the county boundaries were digitized in order to apply the methodology used in this study on a county basis. The field data were obtained by applying a stratified random sampling strategy. The area was subdivided into five main strata and forty four 1km(_^2) sample units were randomly chosen and fully surveyed by the author using a pre-prepared questionnaire. The field area measurements were taken and the final hectarage estimates were obtained for each crop. The research demonstrated the ability of Landsat-TM data to discriminate between agricultural crops in the study area. Results obtained emphasised that satellite data can be used for identification of agricultural crops over large geographic areas with small field sizes and different environmental and physical features. A land-cover classification system appropriate to the study area was designed. Using the Landsat-TM data, the study produced a classification map of thirteen land-cover types with more than 80% accuracy. The classification accuracy was assessed quantitatively by using the known land-use information obtained from the sample units visited during the field survey. The study analysed the factors which influenced the degree of separability between different agricultural crops since some crops were more clearly identified than others. Using a double sampling method based on the combination of both Landsat- TM and field data in regression analysis, a hectarage estimate was produced for each crop type in County Durham. The results obtained showed that the regression estimator was always more efficient than the field estimator. Crop area estimated by regression reduced the imprecision in all strata and was more efficient in some strata than others. This indicated that a gain in precision was achieved by using Landsat- TM in conjunction with the field data. The results illustrated that stratification based on an environmental criterion was an efficient approach as far as the the application of agricultural remote sensing in County Durham is concerned. The stratified approach allowed each stratum to be analysed separately, thereby lessening the reliance on cloud free imagery for the whole county on any given date. Furthermore, the results obtained by this study suggest that it is possibile to link remote sensing data with existing county based information systems on agricultural and land-use