Topological minors of cover graphs and dimension

We show that posets of bounded height whose cover graphs exclude a fixed graph as a topological minor have bounded dimension. This result was already proven by Walczak. However, our argument is entirely combinatorial and does not rely on structural decomposition theorems. Given a poset with large dimension but bounded height, we directly find a large clique subdivision in its cover graph. Therefore, our proof is accessible to readers not familiar with topological graph theory, and it allows us to provide explicit upper bounds on the dimension. With the introduced tools we show a second result that is supporting a conjectured generalization of the previous result. We prove that $(k+k)$-free posets whose cover graphs exclude a fixed graph as a topological minor contain only standard examples of size bounded in terms of $k$.Comment: revised versio

Airport Deregulation and Airline Competition

Liberalisation has affected all parts of the air travel industry, with airports as well as airlines increasingly run on commercial lines. This paper models interactions between airports and airlines to show that, for example, the potential benefits to passengers of increased competition between airlines may be (more than) absorbed by the unregulated airports through which they travel, and that effecting airport competition in one country may lead to the majority of the gains going abroad. The policy conclusion is that the (de)regulation of airlines and associated services should be fully co-ordinated and internationally coherent. Keywords: Airports, airlines, competition, deregulation

Airport Deregulation and Airline Competition

Liberalisation has affected all parts of the air travel industry, with airports as well as airlines increasingly run on commercial lines. This paper models interactions between airports and airlines to show that, for example, the potential benefits to passengers of increased competition between airlines may be (more than) absorbed by the unregulated airports through which they travel, and that effecting airport competition in one country may lead to the majority of the gains going abroad. The policy conclusion is that the (de)regulation of airlines and associated services should be fully co-ordinated and internationally coherent. Keywords: Airports, airlines, competition, deregulation

Short arc reduction of radar altimetry computer program

The Air Force Geophysics Laboratory computer program SARRA (Short Arc Reduction of Radar Altimetry) has been used for geoid determination with altimetric observations from the GEOS-3 satellite. An important feature of SARRA is the simultaneous recovery of the orbit parameters and the surface coefficients as defined by covariance function weights. Orbits good to approximately 20 meters are adequate for precise geoid determinations by virtue of the orbital adjustment in the reductions. Altimetric data over a portion of the North Atlantic Ocean have been processed to derive the regional geoid and gravity field. Analyses of altimeter residuals resulting from the short arc adjustment show that the residuals can be used to define the neglected higher order geoidal undulations with high fidelity and continuity

Analysing of supervision skills of juvenile justice workers

There is evidence that the style of supervision by juvenile justice workers can make a difference to the likelihood that young people under supervision will re-offend. This study aimed to examine the style of supervision offered by juvenile justice workers and how this relates to re-offending patterns by clients. It provides information about what goes on in worker/client interviews and what works best in fostering reduced recidivism.More specifically the aim was to gather information about the nature of micro-skills which are used by youth justice workers in the supervision of offenders on probation parole and other community based orders, how clients respond to the use of those micro-skills and how the use of the skills relates to client outcomes such as recidivism.The research was conducted in collaboration with the Department of Juvenile Justice in NSW. Forty-seven workers participated in the study. The next 5 clients allocated to the workers from the time of volunteering from the study were then selected for each of the workers. The workers were then asked to invite the research officers who were working on the project to observe the next interview they conducted with any one of the five clients who were allocated to them. Eighty-nine interviews were observed however an additional 39 were also observed as part of the pilot study for this project. They are included in the analysis and results reported on in this paper. In total 128 interviews were observed. Eighty interviews were also conducted with clients following the observation and 78 interviews were conducted with workers following the observations and interviews with the clients.Two year recidivism data is available for 117 of the observations. Eleven of the interviews were conducted in remote areas of NSW during 2011 and the recidivism data for those interviews is not yet available

On the problem of network monopoly

We introduce a new regulatory concept: the independent profit-maximising agent, as a model for regulating a network monopoly. The agent sets prices on cross-network goods taking either a complete, or arbitrarily small, share of the associated profit. We examine welfare and profits with and without each agent type under both network monopoly and network duopoly. We show that splitting up the network monopoly (creating network duopoly) may be inferior for both firm(s) and society compared with a network monopoly "regulated" by an agent and that society always prefers any of the four agent regimes over network monopoly and network duopoly

Network Regulation Using an Agent

This paper introduces a new regulatory concept: the independent profit-maximising regulatory agent, as a possible model for regulating network industries where complex demand interdependencies, in particular demand complementarities, make traditional methods of regulation difficult. We derive a simple theoretical network model with differentiated demands and explore alternative competitive and regulatory strategies. We show that the employment of an independent profit-maximising agent may offer a partial solution to the problem of network regulation, yielding outcomes which involve all parties pursuing their own interests yet are relatively desirable to both firms and society

On the Economics of Integrated Ticketing

In this paper we explore alternative pricing and regulatory strategies within a simple transport network with Cournot duopoly and differentiated demands. We show that whilst firms always prefer to offer integrated ticketing, a social planner will not. With integrated ticketing, the firms always prefer complete collusion but there is not a uniform ranking of some of the less collusive regimes. Society generally prefers the less collusive regimes to complete collusion but prefers some collusion to independent pricing

Boolean Dimension, Components and Blocks

We investigate the behavior of Boolean dimension with respect to components and blocks. To put our results in context, we note that for Dushnik-Miller dimension, we have that if $\dim(C)\le d$ for every component $C$ of a poset $P$, then $\dim(P)\le \max\{2,d\}$; also if $\dim(B)\le d$ for every block $B$ of a poset $P$, then $\dim(P)\le d+2$. By way of constrast, local dimension is well behaved with respect to components, but not for blocks: if $\text{ldim}(C)\le d$ for every component $C$ of a poset $P$, then $\text{ldim}(P)\le d+2$; however, for every $d\ge 4$, there exists a poset $P$ with $\text{ldim}(P)=d$ and $\dim(B)\le 3$ for every block $B$ of $P$. In this paper we show that Boolean dimension behaves like Dushnik-Miller dimension with respect to both components and blocks: if $\text{bdim}(C)\le d$ for every component $C$ of $P$, then $\text{bdim}(P)\le 2+d+4\cdot2^d$; also if $\text{bdim}(B)\le d$ for every block of $P$, then $\text{bdim}(P)\le 19+d+18\cdot 2^d$.Comment: 12 pages. arXiv admin note: text overlap with arXiv:1712.0609