Congestion prevention in broadband wireless access systems: An economic approach

While the demand for mobile broadband wireless services continues to increase, radio resources remain scarce. Even with the substantial increase in the supported bandwidth in the next generation broadband wireless access systems (BWASs), it is expected that these systems will severely suffer from congestion, due to the rapid increase in demand of bandwidth-intensive multimedia services. Without efficient bandwidth management and congestion control schemes, network operators may not be able to meet the increasing demand of users for multimedia services, and hence they may suffer an immense revenue loss. In this paper, we propose an admission-level bandwidth management scheme consisting of call admission control (CAC) and dynamic pricing. The main aim of our proposed scheme is to provide monetary incentives to users to use the wireless resources efficiently and rationally, hence, allowing efficient bandwidth management at the admission level. By dynamically determining the prices of units of bandwidth, the proposed scheme can guarantee that the number of connection requests to the system are less than or equal to certain optimal values computed dynamically, hence, ensuring a congestion-free system. The proposed scheme is general and can accommodate different objective functions for the admission control as well as different pricing functions. Comprehensive simulation results with accurate and inaccurate demand modeling are provided to show the effectiveness and strengths of our proposed approach.     

The transposition median problem is NP-complete

During recent years, the genomes of more and more species have been sequenced, providing data for phylogenetic reconstruction based on genome rearrangement measures, where the most important distance measures are the reversal distance and the transposition distance. The two main tasks in all phylogenetic reconstruction algorithms are to calculate pairwise distances and to solve the median of three problem. While the reversal distance problem can be solved in linear time, the reversal median problem has been proven to be NP-complete. The status of the transposition distance problem is still open, but it is conjectured to be more difficult than the reversal problem. This, in turn, also suggests that the transposition median problem is NP-complete. However, this conjecture could not yet be proven. We have now succeeded in giving a non-trivial proof for the NP-completeness of the transposition median problem.     

Energetic ion loss detector on the Alcator C-Mod tokamak

A scintillator-based energetic ion loss detector has been successfully commissioned on the Alcator C-Mod tokamak. This probe is located just below the outer midplane, where it captures ions of energies up to 2 MeV resulting from ion cyclotron resonance heating. After passing through a collimating aperture, ions impact different regions of the scintillator according to their gyroradius (energy) and pitch angle. The probe geometry and installation location are determined based on modeling of expected lost ions. The resulting probe is compact and resembles a standard plasma facing tile. Four separate fiber optic cables view different regions of the scintillator to provide phase space resolution. Evolving loss levels are measured during ion cyclotron resonance heating, including variation dependent upon individual antennae.     

High performance computing algorithms for land cover dynamics using remote sensing data

Global and regional land cover studies need to apply complex models on selected subsets of large volumes of multi-sensor and multi-temporal data sets that have been derived from raw instrument measurements using widely accepted pre-processing algorithms. The computational and storage requirements of most of these studies far exceed what is possible on a single workstation environment. We have been pursuing a new approach that couples scalable and open distributed heterogeneous hardware with the development of high performance software for processing, indexing and organizing remotely sensed data. Hierarchical data management tools are used to ingest raw data, create metadata and organize the archived data so as to automatically achieve computational load balancing among the available nodes and minimize input/output overheads. We illustrate our approach with four specific examples. The first is the development of the first fast operational scheme for the atmospheric correction of Landsat Thematic Mapper scenes, while the second example focuses on image segmentation using a novel hierarchical connected components algorithm. Retrieval of the global Bidirectional Reflectance Distribution Function in the red and near-infrared wavelengths using four years (1983 to 1986) of Pathfinder Advanced Very High Resolution Radiometer (AVHRR) Land data is the focus of our third example. The fourth example is the development of a hierarchical data organization scheme that allows on-demand processing and retrieval of regional and global AVHRR data sets. Our results show that substantial reductions in computational times can be achieved by the high performance computing technology.     

Mixing of low-dose cohesive drug and overcoming of pre-blending step using a new gentle-wing high-shear mixer granulator

The objective of this study was to examine the influence of drug amount and mixing time on the homogeneity and content uniformity of a low-dose drug formulation during the dry mixing step using a new gentle-wing high-shear mixer. Moreover, the study investigated the influence of drug incorporation mode on the content uniformity of tablets manufactured by different methods. Albuterol sulfate was selected as a model drug and was blended with the other excipients at two different levels, 1% w/w and 5% w/w at impeller speed of 300?rpm and chopper speed of 3000?rpm for 30?min. Utilizing a 1?ml unit side-sampling thief probe, triplicate samples were taken from nine different positions in the mixer bowl at selected time points. Two methods were used for manufacturing of tablets, direct compression and wet granulation. The produced tablets were sampled at the beginning, middle, and end of the compression cycle. An analysis of variance analysis indicated the significant effect (p?相似文献   

Framing a new discourse on petromodernity: the global petroleumscape and petroleum modernism*

The concept of the Global Petroleumspace is an analytical tool which engages the roles which different oil actors play in the development of new urban ideas and built forms. Coined by Hein, this concept contributes to enriching our understanding of globalization, modernity, and architectural history and their impacts on space through time. Petroleum is modern industry’s fuel par excellence. For much of the world, it is the arrival of petroleum on the local scene that introduces modernity with its attendant spaces, forms, materials, and discourses. To frame this new discourse on urban development and petromodernity, three events were organized: ‘Petroleumscape Roundtable’ held as part of the 17th IPHS Conference at TU Delft, ‘Petroleum Modernism Symposium’, organized at the Illinois Institute of Technology, and ‘The Global Petroleumscape Conference’ held at the Faculty of Architecture at TU Delft. This article briefly recounts and reflects upon the scholarly discussions which took place at these events, in order to outline an emergent discourse on petroleum’s imbrication in architecture and planning.     

Periodic autoregressive conditional duration

We propose an autoregressive conditional duration (ACD) model with periodic time-varying parameters and multiplicative error form. We name this model periodic autoregressive conditional duration (PACD). First, we study the stability properties and the moment structures of it. Second, we estimate the model parameters, using (profile and two-stage) Gamma quasi-maximum likelihood estimates (QMLEs), the asymptotic properties of which are examined under general regularity conditions. Our estimation method encompasses the exponential QMLE, as a particular case. The proposed methodology is illustrated with simulated data and two empirical applications on forecasting Bitcoin trading volume and realized volatility. We found that the PACD produces better in-sample and out-of-sample forecasts than the standard ACD.     

Investigations on High Amylose Corn Starch Films. Part 3: Stress Strain Behaviour

By autoclaving a watery high amylose corn starch suspension, homogenous and isotrope films were obtained with different processing parameters. The films were used for investigations on the stress strain behavior. A systematical dependence on the water content and the relationship between native lipids and the starch chains was observed. Especially for films obtained from defatted corn starch, a clear transition was obtained, depending on the water content, from a brittle behavior far below the glass transition temperature T_G with a very high Youngsmodulus to a ductile failure behavior above T_G. The results led to a microscopical model for the native high amylose corn starch films, which in addition outlines the very interesting possibility of controlling in detail changes of the macroscopic stress strain behavior through variations on a molecular scale.