Empty Squares in Arbitrary Orientation Among Points

This paper studies empty squares in arbitrary orientation among a set $P$ of $n$ points in the plane. We prove that the number of empty squares with four contact pairs is between $\Omega(n)$ and $O(n^2)$, and that these bounds are tight, provided $P$ is in a certain general position. A contact pair of a square is a pair of a point $p\in P$ and a side $\ell$ of the square with $p\in \ell$. The upper bound $O(n^2)$ also applies to the number of empty squares with four contact points, while we construct a point set among which there is no square of four contact points. These combinatorial results are based on new observations on the $L_\infty$ Voronoi diagram with the axes rotated and its close connection to empty squares in arbitrary orientation. We then present an algorithm that maintains a combinatorial structure of the $L_\infty$ Voronoi diagram of $P$, while the axes of the plane continuously rotates by $90$ degrees, and simultaneously reports all empty squares with four contact pairs among $P$ in an output-sensitive way within $O(s\log n)$ time and $O(n)$ space, where $s$ denotes the number of reported squares. Several new algorithmic results are also obtained: a largest empty square among $P$ and a square annulus of minimum width or minimum area that encloses $P$ over all orientations can be computed in worst-case $O(n^2 \log n)$ time.Comment: 39 pages, 11 figure

A Discrete Optimization Model to Minimize Organ Recovery Time Using Heuristic Algorithms

This study proposes a discrete optimization model to minimize the organ recovery time in an Organ Procurement Organization (OPO) by grouping its associated hospitals and transplant centers into several clusters, based on their available organ recovery groups. Typically, the OPO covers a relatively large geographical area to recover organs from donors and deliver them to the recipients. Organs and/or tissues need to be transplanted within their viable time. Therefore, a discrete optimization model is proposed, based on the -median approach to identify optimal locations of the organ recovery groups to recover the organs within a desired time interval. Three heuristic solution approaches, such as Multi-start Fast Interchange (MFI), Simulated Annealing (SA), and Lagrangian Relaxation Algorithm (LRA), are applied to solve the -median clustering problems. Numerical examples are tested to identify a better solution approach in terms of a set of key performance indicators, such as elapse time, Silhouette index, and objective function value. The experimental results indicate that the MFI approach is effective finding an initial solution in the shortest possible time. To find a non-dominant optimal solution, the LRA outperformed the initial solution. In the future, the experimental results will be compared with real data to ensure the effectiveness of the proposed model

The Guidelines of Material Design and Process Control on Hybrid Fiber Metal Laminate for Aircraft Structures

Fiber metal laminate (FML) is a hybrid material system that consists of thin metal sheets bonded into a laminate with intermediate thin fiber reinforced composite layers. The aerospace industry has recently increased their use of FMLs due to the considerable weight reduction and consequent benefits for critical load-carrying locations in commercial aircraft, such as upper fuselage skin panels. All FML materials and their processes should be qualified through enough tests and fabrication trials to demonstrate reproducible and reliable design criteria. In particular, proper surface treatment technologies are prerequisite for achieving long-term service capability through the adhesive bonding process. This chapter introduces a brief overview of design concept, material properties and process control methodologies to provide detailed background information with engineering practices and to help ensure stringent quality controls and substantiation of structure integrity. The guidelines and information found in this chapter are meant to be a documentation of current knowledge and an application of sound engineering principles to the FML part development for aerospace usage

THREE ESSAYS IN SUSTAINABLE DEVELOPMENT

The first chapter derives an empirically testable set of propositions on the determinants of environmental aid as a non-market solution for trans-border pollution. The donor country balances environmental benefits against the social costs of aid which results from possible erosion of competitiveness in the export market. Using the panel data for environmental aid from OECD countries to China, it is shown that trade competition significantly reduces types of environmental aid that enhance the competitiveness of China. As the scope of environmental aid that improves China's energy efficiency is limited by trade competition, the change in composition of bilateral environmental aid may reflect a means by which a solution to the trans-border pollution issue can be found. The second chapter shows that the dynamic properties of the pollution-income relationship under an optimal pollution tax depends on three key factors, namely the degree of temporal and inter-temporal flexibility in consumption and the elasticity of substitution among production inputs. This paper derives general conditions for eluding the limits to growth showing that they require rather stringent assumptions which the existing literature has failed to identify. Finally, the third chapter examines environmentally sustainable growth with reference to climate change assuming two final outputs and two factors of production, accounting for both pollution flow and stock effects. If the elasticity of marginal utility of consumption is greater than one, an optimal pollution tax ensures sustainable growth without any further government intervention. Otherwise, either a high temporal elasticity of substitution in production or consumption is required for sustainability. Even a suboptimal pollution tax may allow sustainable development provided the tax time profile meets certain conditions that are developed and described in this paper

On the impossibility of sustainable growth in a manufacturing based economy

This paper investigates a possibility of sustainable growth in a multi-output endogenous growth framework where the capital accumulation takes place mainly through the production of the dirty manufactured goods. It is shown that in a closed economy, economic growth is not environmentally sustainable, even under an optimal pollution tax unless the consumption elasticity of substitution between clean and dirty goods approaches infinity as in a small open economy which exports dirty goods. There exists a minimal threshold level of the ratio of clean to dirty capital that ensures sustainable growth in a closed economy

The Effects of Extremely Low-Frequency Magnetic Fields on Reproductive Function in Rodents

Extremely low-frequency electromagnetic fields (ELF-EMF) are defined as those having frequencies up to 300 Hz, representing a non-ionising radiation having photon energy too weak to interact with biomolecular systems. Exposure to low-frequency electric field and magnetic field (MF) generally results in negligible energy absorption in the body. However, it is well established that ELF-MF induces biologic effects in various cellular functions. ELF-MF acting as a co-inducer can potentiate weak mutagenic signalling. The concern about possible adverse effects on human health of long-term exposure to ELF-MFs, especially at frequencies of 50 or 60 Hz generated from power lines and electric devices, has been increasing. Conversely, long-term effects of chronic exposure have been excluded from the scope of the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) because of insufficient consistent scientific evidence to fix the thresholds for such possible biological effects. The results regarding the adverse effects of ELF-MF on human or animal reproductive functions are contradictory or inconclusive. Overall conclusion of epidemiologic studies on ambient residential MF exposure consistently failed to establish a link between human adverse reproductive outcomes and chronic maternal or paternal exposure to low-frequency MFs. In animal studies, there is no compelling evidence for a causal relationship between disturbed prenatal development and ELF-MF exposure. Testicular spermatogenesis progresses through a complexly regulated cellular process involving mitosis and meiosis; this process seems to be vulnerable to external stressors, such as heat, MF exposure or chemical and physical agents. Exposure to ELF-MF did significant risk impaired implantation or the foetal development in animal studies. However, there is some consistency in the increase of minor skeletal alterations in animal experiments. The evidence derived from recent studies in male mice demonstrates that ELF-MF exposure is involved with an increase in the frequency of apoptosis in spermatogenic cells. Those results suggest that exposure to MF is related to possible cytogenetic effects on testicular germ cells and therefore may negatively affect reproduction. This chapter intends to present an overview on the effects of ELF-EMF exposure on the reproductive function and a plausible mechanism in rodent species

Relaxation of superfluid turbulence in highly oblate Bose-Einstein condensates

We investigate thermal relaxation of superfluid turbulence in a highly oblate Bose-Einstein condensate. We generate turbulent flow in the condensate by sweeping the center region of the condensate with a repulsive optical potential. The turbulent condensate shows a spatially disordered distribution of quantized vortices and the vortex number of the condensate exhibits nonexponential decay behavior which we attribute to the vortex pair annihilation. The vortex-antivortex collisions in the condensate are identified with crescent-shaped, coalesced vortex cores. We observe that the nonexponential decay of the vortex number is quantitatively well described by a rate equation consisting of one-body and two-body decay terms. In our measurement, we find that the local two-body decay rate is closely proportional to $T^2/\mu$, where $T$ is the temperature and $\mu$ is the chemical potential.Comment: 7 pages, 9 figure