Some relations of subsequences in permutations to graph theory with algorithmic applications

A thesis submitted to the Faculty d£ Science of the University of the Witwatersfand in fulfillment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 1977.The representation of some types of graphs as permutations, is utilized in devising efficient algorithms on those graphs. Maximum 'cliques in permutation graphs and circle graphs are found, by searching for a longest ascending or descending subsequence in their representing permutation. The correspondence between n-noded binary trees and the set SSn of stack-sortable permutations, forms the basis of an algorithm for generating and indexing such trees. The-relations between a graph and its representing p ermutation, are also employed in the proof of theorems concerning properties of subsequences in this permutation. In particular, expressions for the average lengths of the longest ascending and descending subsequence a in a random member of SSn , and the average number of inversions in such a permutation, are derived using properties of binary trees. Finally, a correspondence between the set SSn , and the set of permutations of order n With no descending subsequence of length 3, is demonstrated

Superpatterns and Universal Point Sets

An old open problem in graph drawing asks for the size of a universal point set, a set of points that can be used as vertices for straight-line drawings of all n-vertex planar graphs. We connect this problem to the theory of permutation patterns, where another open problem concerns the size of superpatterns, permutations that contain all patterns of a given size. We generalize superpatterns to classes of permutations determined by forbidden patterns, and we construct superpatterns of size n^2/4 + Theta(n) for the 213-avoiding permutations, half the size of known superpatterns for unconstrained permutations. We use our superpatterns to construct universal point sets of size n^2/4 - Theta(n), smaller than the previous bound by a 9/16 factor. We prove that every proper subclass of the 213-avoiding permutations has superpatterns of size O(n log^O(1) n), which we use to prove that the planar graphs of bounded pathwidth have near-linear universal point sets.Comment: GD 2013 special issue of JGA

Permafrost saline water and Early to mid-Holocene permafrost aggradation in Svalbard

Deglaciation in Svalbard was followed by seawater ingression and deposition of marine (deltaic) sediments in fjord valleys, while elastic rebound resulted in fast land uplift and the exposure of these sediments to the atmosphere, whereby the formation of epigenetic permafrost was initiated. This was then followed by the accumulation of aeolian sediments, with syngenetic permafrost formation. Permafrost was studied in the eastern Adventdalen valley, Svalbard, 3–4 km from the maximum up-valley reach of post-deglaciation seawater ingression, and its ground ice was analysed for its chemistry. While ground ice in the syngenetic part is basically fresh, the epigenetic part has a frozen freshwater–saline water interface (FSI), with chloride concentrations increasing from the top of the epigenetic part (at 5.5 m depth) to about 15 % that of seawater at 11 m depth. We applied a one-dimensional freezing model to examine the rate of top-down permafrost formation, which could be accommodated by the observed frozen FSI. The model examined permafrost development under different scenarios of mean average air temperature, water freezing temperature and degree of pore-water freezing. We found that even at the relatively high air temperatures of the Early to mid-Holocene, permafrost could aggrade quite fast down to 20 to 37 m (the whole sediment fill of 25 m at this location) within 200 years. This, in turn, allowed freezing and preservation of the freshwater–saline water interface despite the relatively fast rebound rate, which apparently resulted in an increase in topographic gradients toward the sea. The permafrost aggradation rate could also be enhanced due to non-complete pore-water freezing. We conclude that freezing must have started immediately after the exposure of the marine sediment to atmospheric conditions.</p

Efficient Processing of Spatial Joins Using R-Trees

Abstract: In this paper, we show that spatial joins are very suitable to be processed on a parallel hardware platform. The parallel system is equipped with a so-called shared virtual memory which is well-suited for the design and implementation of parallel spatial join algorithms. We start with an algorithm that consists of three phases: task creation, task assignment and parallel task execu-tion. In order to reduce CPU- and I/O-cost, the three phases are processed in a fashion that pre-serves spatial locality. Dynamic load balancing is achieved by splitting tasks into smaller ones and reassigning some of the smaller tasks to idle processors. In an experimental performance compar-ison, we identify the advantages and disadvantages of several variants of our algorithm. The most efficient one shows an almost optimal speed-up under the assumption that the number of disks is sufficiently large. Topics: spatial database systems, parallel database systems

Utility of human life cost in anaesthesiology cost-benefit decisions

The United States (US) aviation industry provides a potentially useful mental model for dealing with certain cost-benefit decisions in aesthesiology. The Federal Aviation Administration (FAA), the national aviation authority of the United States, quantifies a price for the value of a human life based on the U.S. Department of Transportation’s (DOT) value of a statistical life (VSL) unit. The current VSL is around $9.6 million, indexed to grow with consideration given to inflation and wage changes from the 2016 baseline of$9.4 million [1]. To illustrate the concept, if the FAA estimates that 100 people are likely to die in the future given the current practice standards then the monetary cost of this loss will be $940 million. The FAA uses this estimated monetary value as an official reference point in its regulatory decisions, and the agency publishes in detail how it derives the estimated value. When proposing new regulations, the FAA bases its decisions on comparisons of the human life cost associated with the existing regulation versus the alternative cost that the industry stakeholders will incur subsequent to the adoption of the regulation. In this example, if the cost incurred by the industry is more than the$940 million cost then the FAA will not adopt the proposed regulation and hence will not require the industry to undertake this cost

The influence of the cultural climate of the training environment on physicians' self-perception of competence and preparedness for practice

<p>Abstract</p> <p>Background</p> <p>In current supervisory practice, the learning environment in which the training of specialist registrars (SpRs) takes place is important. Examples of such learning environments are the hospital settings and/or geographical locations where training occurs. Our objective was to investigate whether the cultural climate of different learning environments influences physicians' perceived level of competence and preparedness for practice.</p> <p>Methods</p> <p>An electronic questionnaire was sent to an equal group of paediatricians who had trained in clinical settings located in Europe and the Caribbean. 30 items (Likert scale 1–4 = totally disagree-totally agree) were used to measure the level of preparedness of the respondents in 7 physician competencies.</p> <p>Results</p> <p>42 participants were included for analysis. The distribution of participants in both groups was comparable. The overall perception of preparedness in the Caribbean group was 2.93 (SD = 0.47) and 2.86 (SD = 0.72) in the European group. The European group felt less prepared in the competency as manager 1.81 (SD = 1.06) compared to their Caribbean counterparts 2.72 (SD = 0.66). The difference was significant (p = 0.006).</p> <p>Conclusion</p> <p>The training in the different environments was perceived as adequate and comparable in effect. The learning environment's cultural climate appeared to influence the physician's perception of their competencies and preparedness for clinical practice.</p

Towards energy aware cloud computing application construction

The energy consumption of cloud computing continues to be an area of significant concern as data center growth continues to increase. This paper reports on an energy efficient interoperable cloud architecture realised as a cloud toolbox that focuses on reducing the energy consumption of cloud applications holistically across all deployment models. The architecture supports energy efficiency at service construction, deployment and operation. We discuss our practical experience during implementation of an architectural component, the Virtual Machine Image Constructor (VMIC), required to facilitate construction of energy aware cloud applications. We carry out a performance evaluation of the component on a cloud testbed. The results show the performance of Virtual Machine construction, primarily limited by available I/O, to be adequate for agile, energy aware software development. We conclude that the implementation of the VMIC is feasible, incurs minimal performance overhead comparatively to the time taken by other aspects of the cloud application construction life-cycle, and make recommendations on enhancing its performance