Integrated urban evolutionary modeling

Cellular automata models have proved rather popular as frameworks for simulating the physical growth of cities. Yet their brief history has been marked by a lack of application to real policy contexts, notwithstanding their obvious relevance to topical problems such as urban sprawl. Traditional urban models which emphasize transportation and demography continue to prevail despite their limitations in simulating realistic urban dynamics. To make progress, it is necessary to link CA models to these more traditional forms, focusing on the explicit simulation of the socio-economic attributes of land use activities as well as spatial interaction. There are several ways of tackling this but all are based on integration using various forms of strong and loose coupling which enable generically different models to be connected. Such integration covers many different features of urban simulation from data and software integration to internet operation, from interposing demand with the supply of urban land to enabling growth, location, and distributive mechanisms within such models to be reconciled. Here we will focus on developin

Image Labeling on a Network: Using Social-Network Metadata for Image Classification

Large-scale image retrieval benchmarks invariably consist of images from the Web. Many of these benchmarks are derived from online photo sharing networks, like Flickr, which in addition to hosting images also provide a highly interactive social community. Such communities generate rich metadata that can naturally be harnessed for image classification and retrieval. Here we study four popular benchmark datasets, extending them with social-network metadata, such as the groups to which each image belongs, the comment thread associated with the image, who uploaded it, their location, and their network of friends. Since these types of data are inherently relational, we propose a model that explicitly accounts for the interdependencies between images sharing common properties. We model the task as a binary labeling problem on a network, and use structured learning techniques to learn model parameters. We find that social-network metadata are useful in a variety of classification tasks, in many cases outperforming methods based on image content.Comment: ECCV 2012; 14 pages, 4 figure

An error bound analysis for M-DPSK in frequency-selective Rayleigh fading channel with diversity reception

A theoretical upper bound is presented to calculate the error probability for raised cosine filtered M-ary differential phase-shift keying (RC M-DPSK) in frequency-selective Rayleigh fading channels. This analysis also allows the use of postdetection maximal-ratio diversity combining. The effect of delay spread and filter roll-off are also considered in the formulation. The irreducible error probabilities for 2, 4, 8 and 16-DPSK are compared with first and second order diversity reception. The numerical results show similar irreducible error performances for 4 and 8-DPSK with both performing better compared to B-DPSK and 16-DPSK. When diversity is applied, the performance of 4-DPSK is superior to that of other levels. The irreducible error performance of 4, 8 and 16-DPSK is shown to be better than B-DPSK in frequency selective fading channels

XUV-driven mass loss from extrasolar giant planets orbiting active stars

Upper atmospheres of Hot Jupiters are subject to extreme radiation conditions that can result in rapid atmospheric escape. The composition and structure of the upper atmospheres of these planets are affected by the high-energy spectrum of the host star. This emission depends on stellar type and age, which are thus important factors in understanding the behaviour of exoplanetary atmospheres. In this study, we focus on Extrasolar Giant Planets (EPGs) orbiting K and M dwarf stars. XUV spectra for three different stars – ∊ Eridani, AD Leonis and AU Microscopii – are constructed using a coronal model. Neutral density and temperature profiles in the upper atmosphere of hypothetical EGPs orbiting these stars are then obtained from a fluid model, incorporating atmospheric chemistry and taking atmospheric escape into account. We find that a simple scaling based solely on the host star’s X-ray emission gives large errors in mass loss rates from planetary atmospheres and so we have derived a new method to scale the EUV regions of the solar spectrum based upon stellar X-ray emission. This new method produces an outcome in terms of the planet’s neutral upper atmosphere very similar to that obtained using a detailed coronal model of the host star. Our results indicate that in planets subjected to radiation from active stars, the transition from Jeans escape to a regime of hydrodynamic escape at the top of the atmosphere occurs at larger orbital distances than for planets around low activity stars (such as the Sun)

E-books at the University of Hong Kong libraries: current status, issues and the future

E-books are now nothing new to staff and students of the University of Hong Kong (HKU), the oldest university in Hong Kong and one of the leading tertiary institutions in the Asia-Pacific Region. E-books from netLibrary and other Web-based e-books vendors found their presence in the library website at the beginning of this century and almost at the same time, library staff began engaging in the production of electronic versions of printed books. The University of Hong Kong Libraries (HKUL) has been aggressive in building up its e-book collection and as of end of June 2005, the number of e-books in the library collection amounted to more than 918,000, nearly all of which can be accessed online by registered borrowers. On the other hand, e-book production has become an operational priority of HKUL and it is now actively partnering with sister institutions in book digitization projects. This paper provides an up-to-date account of the provision of e-books at HKUL, including size and compoistion of the collection, usage as well as projects currently undeertaken in book digitization. In addition, the issues that HKUL has been facing in dealing with e-books, namely budgetary implications, copyright restrictions, consortia purchasing, access, bibliographic control, usage tracking and promotion, will be addressed to. Finally, the paper concludes with a projection of the future of e-books at HKUL.published_or_final_versionUniversal digital libraries: universal access to information, the 1st International Conference on Universal Digital Library, ICUDL2005

KINETIKA ADSORPSI LOGAM BERAT Cr(VI) DENGAN ADSORBEN PASIR YANG DILAPISI BESI OKSIDA

Adsorption into iro-oxide coated sand is an interesting alternative for removal of dissolved Cr(VI) in aqueous solution waste industry due to the material characteristics, the availability this material in Indonesia and economic considerations. Many adsorption experiments based on equilibrium research and less of them based on kinetics adsorption research. The objective of this work was to study the appropriate kinetic model for adsorption dissolved Cr(VI) in aqueous solution and the kinetic adsorption dependency upon temperature. The experiment was carried out in a stirred batch flask. Iron-oxide coated sand was contacted with Cr(VI) solution at constant temperature. Sample was drawn at certain times and the remaining heavy metal concentration was measured by Atomic Absorption Spectrophotometer (AAS). The results showed that the pseudo-first-order model was the most appropriate model for explaining the adsorption of Cr(VI) solution into iron-oxide coated. The results also indicated that temperature had significant effect to the rate constant of pseudo-first-order adsorption model ( k1) and maximum capacity of adsorption (qe). Keywords : iron oxide coated sand, adsorption, kinetic model

Run Generation Revisited: What Goes Up May or May Not Come Down

In this paper, we revisit the classic problem of run generation. Run generation is the first phase of external-memory sorting, where the objective is to scan through the data, reorder elements using a small buffer of size M , and output runs (contiguously sorted chunks of elements) that are as long as possible. We develop algorithms for minimizing the total number of runs (or equivalently, maximizing the average run length) when the runs are allowed to be sorted or reverse sorted. We study the problem in the online setting, both with and without resource augmentation, and in the offline setting. (1) We analyze alternating-up-down replacement selection (runs alternate between sorted and reverse sorted), which was studied by Knuth as far back as 1963. We show that this simple policy is asymptotically optimal. Specifically, we show that alternating-up-down replacement selection is 2-competitive and no deterministic online algorithm can perform better. (2) We give online algorithms having smaller competitive ratios with resource augmentation. Specifically, we exhibit a deterministic algorithm that, when given a buffer of size 4M , is able to match or beat any optimal algorithm having a buffer of size M . Furthermore, we present a randomized online algorithm which is 7/4-competitive when given a buffer twice that of the optimal. (3) We demonstrate that performance can also be improved with a small amount of foresight. We give an algorithm, which is 3/2-competitive, with foreknowledge of the next 3M elements of the input stream. For the extreme case where all future elements are known, we design a PTAS for computing the optimal strategy a run generation algorithm must follow. (4) Finally, we present algorithms tailored for nearly sorted inputs which are guaranteed to have optimal solutions with sufficiently long runs

LES of additive and non-additive pulsatile flows in a model arterial stenosis

Transition of additive and non-additive pulsatile flows through a simple 3D model of arterial stenosis is investigated by using a large eddy simulation (LES) technique. We find in both the pulsatile cases that the interaction of the two shear layers, one of which separates from the nose of the stenosis and the another one from its opposite wall, causes recirculation in the flow downstream of the stenosis where the nature of the transient flow becomes turbulent. The strength of this recirculation is found to be quite high from the non-additive pulsations when the flow Reynolds numbers, Re ≥ 1500, for which both the pressure and shearing stresses take on an oscillating form at the post-stenotic region. Potential medical consequences of these results are discussed in the paper. In addition, some comparisons of the non-additive pulsatile results are given with those of both the additive pulsatile and steady flows. The capability of using LES to simulate the pulsatile transitional flow is also assessed, and the present results show that the smaller (subgrid) scales (SGS) contributes about 78% energy dissipation to the flow when the Reynolds number is taken as 2000. The level of SGS dissipation decreases as the Reynolds number is decreased. The numerical results are validated with the experimental data available in literature where a quite good agreement is found

Electric fields as a means of controlling thin film flow over topography

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Gravity-driven, steady-state flow of a thin liquid film over a substrate containing topography in the presence of a normal electric field is investigated. The liquid is assumed to be a perfect conductor and the air above it an ideal dielectric. The Navier-Stokes equations are solved using a new depth-averaged approximation that is capable of analysing film flows with inertia, with the flow coupled to the electric field via a Maxwell normal stress term that results from the solution of Laplace’s equation for the electric potential above the film. The latter is solved analytically using separation of variables and Fourier series. The coupled solver is used to analyse the interplay between inertia and electric field effects for flow over onedimensional step and trench topographies and to predict the effect of an electric field on three-dimensional Stokes flow over a two-dimensional trench topography. Sample results are given which investigate the magnitude of the electric fields needed to suppress free surface disturbances induced by topography in each of the cases considered.This study is funded by the European Union via Marie Curie Action Contract MEST-CT-2005-020599