Push-Pull Block Puzzles are Hard

This paper proves that push-pull block puzzles in 3D are PSPACE-complete to solve, and push-pull block puzzles in 2D with thin walls are NP-hard to solve, settling an open question by Zubaran and Ritt. Push-pull block puzzles are a type of recreational motion planning problem, similar to Sokoban, that involve moving a `robot' on a square grid with $1 \times 1$ obstacles. The obstacles cannot be traversed by the robot, but some can be pushed and pulled by the robot into adjacent squares. Thin walls prevent movement between two adjacent squares. This work follows in a long line of algorithms and complexity work on similar problems. The 2D push-pull block puzzle shows up in the video games Pukoban as well as The Legend of Zelda: A Link to the Past, giving another proof of hardness for the latter. This variant of block-pushing puzzles is of particular interest because of its connections to reversibility, since any action (e.g., push or pull) can be inverted by another valid action (e.g., pull or push).Comment: Full version of CIAC 2017 paper. 17 page

4-Holes in point sets

We consider a variant of a question of Erdos on the number of empty k-gons (k-holes) in a set of n points in the plane, where we allow the k-gons to be non-convex. We show bounds and structural results on maximizing and minimizing the number of general 4-holes, and maximizing the number of non-convex 4-holes. In particular, we show that for n >= 9, the maximum number of general 4-holes is ((pi)(4)); the minimum number of general 4-holes is at least 5/2 n(2) - circle minus(n); and the maximum number of non-convex 4-holes is at least 1/2 n(3) - circle minus(n(2) logn) and at most 1/2 n(3) - circle minus(n(2)). 2014 (c) Elsevier B.V. All rights reserved.Postprint (author’s final draft

Relaxed Disk Packing

Motivated by biological questions, we study configurations of equal-sized disks in the Euclidean plane that neither pack nor cover. Measuring the quality by the probability that a random point lies in exactly one disk, we show that the regular hexagonal grid gives the maximum among lattice configurations.Comment: 8 pages => 5 pages of main text plus 3 pages in appendix. Submitted to CCCG 201

ACCOUNTING FOR PRIVATISATION IN BANGLADESH: TESTING WORLD BANK CLAIMS

The World Bank and the IMF have encouraged many less developed countries (LDCs) to pursue privatisation policies. Development economists and World Bank reports claim this facilitates development by improving controls within enterprises and external regulation of financial markets acting on external accounting reports. This paper questions these beliefs. It compares the post-privatisation performance of companies in Bangladesh examined in a World Bank report with the authors' own research on the same companies. The World Bank report reported that the success of the privatisations established the case for more. In the research reported here, only one of the privatised companies was judged a commercial success, though the unavailability and dubious accuracy of accounting reports prevented any definitive assessment. Above all, the paper questions the narrow criteria adopted by the World Bank report - namely profitability - and the neglect of employment conditions, trade union and individual rights; social returns; and financial transparency and accountability to external constituents. Our evidence suggested that privatisation has not increased returns to society: privatised companies' contributions to state revenue declined in real terms and as a proportion of value added. Transparent external reports failed to materialise as required by law and there was evidence of untoward transactions affecting minority shareholders, creditors, and tax collecting institutions. Internal controls may have become more commercial but at the cost of declining employment, wages, quality of working life, and employee rights. The World Bank claims rest upon efficiency benefits trickling down to all but the effects of privatisation may have been a redistribution of power and wealth to the new owners. This paper argues that the IMF, the World Bank, and Western capitalist states have not provided the technical infrastructure and organisational capacity to execute their neo-liberal privatisation agenda, which rests on dubious socio-economic assumptions. Our unfavourable evaluation of privatisation in Bangladesh is not unique. It has been happening again and again around the world. © 2003 Published by Elsevier Science Ltd

A contingency framework of enterprise governance in the UK: A value-based management approach

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Corporate governance (CG) has recently received much attention because of the wave of financial scandals in the early 2000s and the more recent global financial crisis. CG reforms, including laws, codes and listing rules have been established to protect shareholders’ rights and restore investors’ confidence in the capital market. These reforms have largely contributed to the evolution of internal and external governance mechanisms that are aimed at mitigating agency conflicts between managers and shareholders. However, overemphasis has been placed on the monitoring and control dimensions of governance, which may hinder entrepreneurial activities, obscure business prosperity and contribute to a narrow perspective on CG. It has been argued that there is a need to broaden CG beyond compliance (conformance) to a set of rules and laws, to include the performance aspects of governance that focus on strategy and value creation. In other words, governance should not only focus on monitoring managerial performance to ensure accountability to shareholders, but also on mechanisms that motivate management to optimise shareholders’ wealth. Enterprise governance (EG) framework has been introduced to keep the balance between the conformance and performance dimensions of governance. However, few studies address the possible tension between conformance and performance. Moreover, there is no agreement among these studies on the relationship between conformance and performance in the governance context. Arguably, Value-based Management (VBM) is an appropriate approach to address the issue of EG. VBM adopts value creation as an overall objective, develops a strategy that contributes to value creation and integrates it into decision-making. In this way, VBM can act as an effective mechanism for motivating management to maximise shareholder wealth, which works in parallel with other CG mechanisms, to mitigate agency conflicts resulting from the separation between ownership and management. This study aims to develop a contingency framework of EG through operationalising the conformance using CG and performance using corporate entrepreneurship (CE). This framework examines the inter-relationships between VBM, compliance with the Combined Code on Corporate Governance (CCCG), CE and the ultimate effect on organisational performance. More specifically, the study empirically examines the effect of compliance with the CCCG on CE, and whether VBM can achieve a balance between compliance with the CCCG and CE, should a conflict exist. The study also examines whether a fit between contingency variables (company size, agency conflicts, uncertainty, strategy and decentralisation), VBM, compliance with the CCCG codes and CE is associated with organisational performance. To achieve the aim of this study a cross-sectional survey, based on a questionnaire, is conducted to identify the level of VBM implementation, contextual and organisational factors in the large and medium quoted companies in the UK. The questionnaire targets the Chief Financial Officers (CFOs) in these companies as key informants. In addition, a content analysis of the annual reports of the sampled companies is undertaken to measure the level of compliance with the CCCG. Financial data (e.g. organisational performance) have been obtained from the DataStream, Fame and Thomson One Banker databases. Partial Least Squares Structural Equation Modelling (PLS-SEM) is adopted for data analysis and hypotheses testing. The results suggest that VBM implementation is positively associated with agency conflicts, low cost strategies and decentralisation. Compliance with the CCCG is positively associated with agency conflicts and company size. CE is positively associated with company size, uncertainty and differentiation strategies. In addition, the fit between compliance with the CCCG and contingency factors significantly predicts the marketbased performance. The fit between CE and the contingency factors significantly predict the perceived performance. However, the results regarding the effect of VBM on organisational performance are mixed. While VBM has no significant direct effect on the market-based performance, VBM has indirect positive effect on the market-based performance acting through compliance with the CCCG as an intervening variable. VBM is significantly associated with compliance with the CCCG but not with CE. No evidence is found for negative association between compliance with the CCCG and CE. The results support a large number of the proposed relationships between the contingency factors, VBM, compliance with the CCCG and CE. The results also suggest that using both compliance with the CCCG and CE as intervening variables in the relationship between VBM and organisational performance contributes to explaining the mixed results in the VBM literature. In terms of the EG framework, VBM does not keep a balance between conformance and performance. VBM emphasises the compliance with the CCCG (conformance) at the expense of CE (performance). The results did not provide significant evidence of a conflict between compliance with the CCCG and CE, the area which lacks empirical evidence. This study contributes to the literature at different levels. At the theoretical level, this study develops a theoretical model that links a performance management system (PMS), i.e. VBM, to CG practices and CE. This model attempts to bridge the gap between different disciplines, including management accounting, CG and entrepreneurship. Furthermore, combining both the contingency theory and the agency theory lenses contributes to the development of a comprehensive model of EG. At the methodological level, unlike previous studies, this study measures VBM practices on a continuum, rather than categories. Multiple data collection methods are used, and a powerful statistical technique (PLS-SEM) is adopted for data analysis. At the empirical level, the study is conducted in the UK. Though it is different from the US in many aspects, very few studies have been conducted in this context in many research areas such as VBM, CG and CE.This study is supported by the Egyptian Ministry of Higher Education and the Egyptian Cultural Bureau in London

Ununfoldable Polyhedra with Convex Faces

Unfolding a convex polyhedron into a simple planar polygon is a well-studied problem. In this paper, we study the limits of unfoldability by studying nonconvex polyhedra with the same combinatorial structure as convex polyhedra. In particular, we give two examples of polyhedra, one with 24 convex faces and one with 36 triangular faces, that cannot be unfolded by cutting along edges. We further show that such a polyhedron can indeed be unfolded if cuts are allowed to cross faces. Finally, we prove that ``open'' polyhedra with triangular faces may not be unfoldable no matter how they are cut.Comment: 14 pages, 9 figures, LaTeX 2e. To appear in Computational Geometry: Theory and Applications. Major revision with two new authors, solving the open problem about triangular face