Upper domination and upper irredundance perfect graphs

Let β(G), Γ(G) and IR(G) be the independence number, the upper domination number and the upper irredundance number, respectively. A graph G is called Γ-perfect if β(H) = Γ(H), for every induced subgraph H of G. A graph G is called IR-perfect if Γ(H) = IR(H), for every induced subgraph H of G. In this paper, we present a characterization of Γ-perfect graphs in terms of a family of forbidden induced subgraphs, and show that the class of Γ-perfect graphs is a subclass of IR-perfect graphs and that the class of absorbantly perfect graphs is a subclass of Γ-perfect graphs. These results imply a number of known theorems on Γ-perfect graphs and IR-perfect graphs. Moreover, we prove a sufficient condition for a graph to be Γ-perfect and IR-perfect which improves a known analogous result. © 1998 Elsevier Science B.V. All rights reserved

ELECTRICITY INFRASTRUCTURE PLANNING: EVALUATING SOLAR POTENTIAL ASSESSMENTS FOR INFORMAL SETTLEMENTS USING GRASS AND FREELY AVAILABLE DATA

Informal settlements, also known as slums or shanty towns, are characterised by rapid and unstructured expansion, poorly constructed buildings, and in some cases, they are on disputed land. Such settlements often lack basic services, such as electricity. As a result, informal settlement dwellers turn to hazardous alternative sources of energy, such as illegal electricity connections and paraffin. Solar power is a clean and safe alternative. However, informal settlements are often located on undesirable land on the urban fringe where the topography may hinder the use of solar energy. The high density of dwellings could also be a hindrance. Therefore, the solar potential needs to be assessed before any implementations are planned. Solar potential assessment functionality is generally available in geographic information system (GIS) products. The nature, cost and accessibility of datasets required for the assessment vary significantly. In this paper, we evaluate the results of solar potential assessments using GRASS (Geographic Resources Analysis Support System) for a number of different datasets. The assessments were done for two informal settlements in the City of Tshwane (South Africa): Alaska, which is nestled on a hill; and Phomolong, a densely populated settlement with a rather flat topography. The results show that solar potential assessments with open source GIS software and freely available data are feasible. This eliminates the need for lengthy and bureaucratic procurement processes and reduces the financial costs of assessing solar potential for informal settlements

Audit of antenatal care at a community health centre in Tshwane North subdistrict, Gauteng province

Objective: Few studies document the level of compliance with antenatal care protocols in primary health care in South Africa. The aim of this study was to conduct an audit of antenatal care at a community health centre in Tshwane North subdistrict in order to measure the level of compliance of maternity staff with antenatal care protocols. This study was part of a larger study on a quality improvement initiative in primary health care.Design and setting: A retrospective cross-sectional descriptive study was undertaken of women attending antenatal care at the study clinic. Data were collected through a review of the women’s antenatal cards using criteria from the Guidelines for maternity care in South Africa and the basic antenatal care (BANC) checklist. In addition, qualitative interviews of maternity staff were undertaken in order to investigate reasons for  noncompliance with the maternity care guidelines.Results: The overall rate of compliance of nurses was 85.1%. This is less than optimal. The response (decision-making and interpretation)  component of compliance was only 57.6%. This represents a significant missed opportunity in terms of quality of antenatal care. Important  protocols, such as that pertaining to the prevention of mother-to-child transmission (PMTCT) of human immunodeficiency virus, were also not carried out correctly. The response to PMTCT protocols was 50% only, another significant opportunity missed. Administrative factors, patient-related factors and deficiencies in the knowledge and skills of nurses were identified and documented as reasons for noncompliance.Conclusion: The study has provided a detailed picture of the situation with regard to non-compliance with the maternity care guidelines in a primary health care facility. Therefore, these data are very important in terms of quality assurance of maternity services in primary health care

LANDFORM PERCEPTION ACCURACY IN SHADED RELIEF MAPS: A REPLICATION STUDY CONFIRMS THAT NNW LIGHTING IS BETTER THAN NW AGAINST THE RELIEF INVERSION EFFECT

Relief inversion effect is a perceptual phenomenon that leads to an inverted perception of convex and concave shapes. This perceptual inversion occurs in scenes where the shading/shadows act as the main depth cue. In visuospatial displays, such as shaded relief maps, the positioning of the shadows in the northern slopes, thus when light source placed broadly in south, mislead the cognitive system based on the ‘light from above prior’ assumption (Mamassian and Goutcher 2001). Thus, assuming the light must come from above, our mind creates an illusion, and we perceive the landforms incorrectly. To judge the 3D spatial relationships in terrain representations correctly, the relief inversion effect must be avoided. Cartographic convention against this effect is to place the light source at northwest (NW), whereas a recent study demonstrated that north-north-west (NNW), or even north yields more precise results (Biland and Çöltekin, 2016). Since this finding goes against decades of convention, to establish its validity further, we attempted replicating the results with a different sample in South Africa. In this paper, we present our findings, which broadly confirm that the NNW (or also N) is better than NW against the relief inversion effect

Distributed agents for online spatial searches

As the availability and utilisation of online data blossoms, automated online searches—whether to answer a simple question, seek specific sensor readings, or investigate research in a particular domain—have raised a number of issues. Simple search tools do not access the deep web of services and online forms, and cannot handle knowledge domain-specific search problems, but specialist search tools can have a narrow domain and applicability. Some online tools circumvent these problems by putting more filter controls into the hands of users, but this leads to more complex interfaces which can raise usability barriers. A distributed approach, where specialised search agents act autonomously to find contextualised information, can provide a useful compromise between a simple, general search interface and specialist searches. This paper outlines work in progress on design and use of specialist search agents, with a case study to find public transportation bus stops within a spatial region. The approach is demonstrated with a proof of concept web interface, developed to interpret a text query to find and show bus stop locations within a named boundary by coordinating multiple online search agents. Search agents were designed to follow a common model to allow for future development of agent types, including specialist agents used in the case study to search standard open web services and extract spatial features

Perfect graphs of strong domination and independent strong domination

AbstractLet γ(G), i(G), γS(G) and iS(G) denote the domination number, the independent domination number, the strong domination number and the independent strong domination number of a graph G, respectively. A graph G is called γi-perfect (domination perfect) if γ(H)=i(H), for every induced subgraph H of G. The classes of γγS-perfect, γSiS-perfect, iiS-perfect and γiS-perfect graphs are defined analogously. In this paper we present a number of characterization results on the above classes of graphs. For example, characterizations of K4-free γSiS-perfect graphs and triangle-free γiS-perfect graphs are given. Moreover, the strong dominating set and independent strong dominating set problems as well as the weak dominating set and independent weak dominating set problems are shown to be NP-complete on a class of graphs. Several problems and conjectures are proposed