Investigating accessibility indicators for feedback from a travel to a land use model

Activity locations such as work locations or leisure facilities are not uniformly distributed geographically. Also, the travel access to different locations is not uniform. It is plausible to assume that locations with easier access to other activity locations are more attractive than locations with less access. In consequence, urban simulation models such as UrbanSim use accessibility measures, such as ``number of jobs with 30 minutes by car', for several of their submodels. A problem, however, is that accessibility variables are not easy to compute within UrbanSim, for two reasons: 1) UrbanSim does not contain a travel model, and in consequence is not able to compute by itself the congestion effects resulting from land use decisions 2) The travel times are fed back from the travel model in the form of zone-to-zone travel time matrices. As is well known, such matrices grow quadratically in the number of zones. This limits the number of attributes that can be passed, for example different values for different times-of-day and/or for different activity purposes. These issues could be solved within UrbanSim, but only with considerable implementation effort. For that reason, it is important to consider how accessibility measures could be fed back from a travel model to UrbanSim. The present study will look at the question in how far location-based accessibility measures that are computed in the travel model and then fed back to UrbanSim could be used for this purposes. Those accessibility measures are no longer measures belonging to pairs of locations, but just belong to one location; a typical representative is a logsum term. In consequence, the number of entries now grows linearly in the number of locations, allowing much more freedom both in the number of considered locations and in the number of attributes that could be attached to every location that is considered in this way. This paper will address issues such as different spatial resulutions of such accessibility measures, comparisons between different accessibility measures, and computing times.

CCi digital futures 2014: the Internet in Australia

This report presents findings from the third survey of the Australian component of the World Internet Project. The survey was conducted in late 2013. This research is a project of the ARC Centre of Excellence for Creative Industries and Innovation at the Swinburne Institute for Social Research, Swinburne University of Technology. This report provides an overview of the study, presenting a broad picture of the Internet in Australia, with comparisons to our earlier 2007, 2009 and 2013 studies, and to the international findings of our partners in the World Internet Project. At the end of each section we have added some further analysis, examining aspects of the Australian data in more detail, and providing some international context using results from the findings of our international research partners. &nbsp

Conceiving the impossible and the mind-body problem

Las intuiciones basadas en la perspectiva de la primera persona fácilmente nos pueden inducir a error sobre lo que es y no es concebible. Este punto usualmente se presenta como apoyo de posiciones reduccionistas comunes sobre el problema mente-cuerpo, pero considero que se puede separar de tal perspectiva. Me parece que la fuerte apariencia de contingencia en la relación entre el funcionamiento del organismo físico y la mente consciente –una apariencia que depende directa o indirectamente de la perspectiva de la primera persona– tiene que ser una ilusión. En otras palabras, creo que hay una conexión necesaria en ambas direcciones entre lo físico y lo mental, pero que no puede descubrirse a priori. La opinión sedivide fuertemente entre la credibilidad de algún tipo de reduccionismo funcionalista, y no examinaré mis razones para ubicarme en el lado antireduccionista de este debate. Mi lectura del asunto es que nuestra falta de habilidad para obtener una concepción inteligible de la relación mente-cuerpo es un signo de la  inadecuación de nuestros conceptos actuales, y que se requiere algún grado de desarrollo.The Intuitions based on the first-person perspective can easily mislead us about what is and is not conceivable. This point is usually made in support of familiar reductionist positions on the mind-body problem, but I believe it can be detached from that approach. It seems to me that the powerful appearance of contingency in the relation between the functioning of the physical organism and the conscious mind –an appearance that depends directly or indirectly on the first person– perspective must be an illusion. In other words, I believe that there is a necessary connection in both directions between the physical and the mental, but that it cannot be discovered a priori. Opinion is strongly divided on the credibility of some kind of functionalist reductionism, and I won’t go through my reasons for being on the antireductionist side of that debate. My reading of the situation is that our inability to come up with an intelligible conception of the  relation between mind and body is a sign of the inadequacy of our present concepts, and that some development is needed

The Meaning of Equality

There are many different kinds of equality, and some of the most pressing moral and political problems concern the priorities among them

Investigating accessibility indicators for feedback from a travel to a land use model

Activity locations such as work locations or leisure facilities are not uniformly distributed geographically. Also, the travel access to different locations is not uniform. It is plausible to assume that locations with easier access to other activity locations are more attractive than locations with less access. In consequence, urban simulation models such as UrbanSim use accessibility measures, such as ``number of jobs with 30 minutes by car', for several of their submodels. A problem, however, is that accessibility variables are not easy to compute within UrbanSim, for two reasons: 1) UrbanSim does not contain a travel model, and in consequence is not able to compute by itself the congestion effects resulting from land use decisions 2) The travel times are fed back from the travel model in the form of zone-to-zone travel time matrices. As is well known, such matrices grow quadratically in the number of zones. This limits the number of attributes that can be passed, for example different values for different times-of-day and/or for different activity purposes. These issues could be solved within UrbanSim, but only with considerable implementation effort. For that reason, it is important to consider how accessibility measures could be fed back from a travel model to UrbanSim. The present study will look at the question in how far location-based accessibility measures that are computed in the travel model and then fed back to UrbanSim could be used for this purposes. Those accessibility measures are no longer measures belonging to pairs of locations, but just belong to one location; a typical representative is a logsum term. In consequence, the number of entries now grows linearly in the number of locations, allowing much more freedom both in the number of considered locations and in the number of attributes that could be attached to every location that is considered in this way. This paper will address issues such as different spatial resulutions of such accessibility measures, comparisons between different accessibility measures, and computing times

Equivalence of glass transition and colloidal glass transition in the hard-sphere limit

We show that the slowing of the dynamics in simulations of several model glass-forming liquids is equivalent to the hard-sphere glass transition in the low-pressure limit. In this limit, we find universal behavior of the relaxation time by collapsing molecular-dynamics data for all systems studied onto a single curve as a function of $T/p$, the ratio of the temperature to the pressure. At higher pressures, there are deviations from this universal behavior that depend on the inter-particle potential, implying that additional physical processes must enter into the dynamics of glass-formation.Comment: 4 pages, 4 figure

The essence of Biot waves in an oscillator with two degrees of freedom

In poroelastic media, i.e., porous structures whose pores contain fluid, a kind of waves can be observed that does not occur in elastic media, the so-called slow P-waves or Biot waves, which may be perceived as opaque when first encountered. In this paper, we pursue two goals: firstly, we want to provide a simple explanatory model of these waves and, secondly, we want to prepare the reader for Biot’s seminal paper. We discretize a finite poroelastic waveguide by Galerkin’s method to arrive at a mechanical system with 2 degrees of freedom and solve the eigenvalue problem of free oscillations. This oscillator representation (ODE) is simpler than the wave representation (PDE) while maintaining salient features of poroelastodynamics and offering a different perspective. In fact, an oscillation is a standing wave with wave velocity and wave length being related to frequency and domain length. In this reduced model, slow P-waves, when they exist, correspond to an oscillation with large phase shift and fast P-waves to an oscillation with small phase shift. The intended audience are engineering or physics graduate students with basic knowledge of linear oscillations, linear differential equations and some understanding of biphasic media