Spanning spiders and light-splitting switches

AbstractMotivated by a problem in the design of optical networks, we ask when a graph has a spanning spider (subdivision of a star), or, more generally, a spanning tree with a bounded number of branch vertices. We investigate the existence of these spanning subgraphs in analogy to classical studies of Hamiltonicity

Optimal Multi-TDMA Scheduling in Ring Topology Networks

A scheduling algorithm will be proposed for wireless ring topology networks, utilizing time division multiple access (TDMA) with possible simultaneous operation of nodes. The proposed algorithm finds the optimal schedule to minimize the turnaround time for messages in the network. The properties of the algorithm are mathematically analyzed and proven, and practical test results are also provided

A radiographic study of ossification in the spine and limbs of the human fetus

Until recently relatively little has been known about factors which affect growth and development in early life. and which have a fundamental influence on later adult life. Thus pre- and postnatal growth and development must be studied as a continuum for they have a profound effect on ultimate physical and mental development. However, legal and ethical problems governing the availability of human fetal material diminish the prospects for assembling large comprehensive surveys. Because of this, there is often inaccuracy and inconsistency in many reports of human fetal development and, in particular, the study of certain regions has been considerably neglected. Ossification of the human fetal spine and limbs is one such example. The initial purpose of the present study was an attempt to increase knowledge in an area where there appears to be substantial gaps. [Continues.

Multidimensional image analysis of cardiac function in MRI

Cardiac morphology is a key indicator of cardiac health. Important metrics that are currently in clinical use are left-ventricle cardiac ejection fraction, cardiac muscle (myocardium) mass, myocardium thickness and myocardium thickening over the cardiac cycle. Advances in imaging technologies have led to an increase in temporal and spatial resolution. Such an increase in data presents a laborious task for medical practitioners to analyse. In this thesis, measurement of the cardiac left-ventricle function is achieved by developing novel methods for the automatic segmentation of the left-ventricle blood-pool and the left ventricle myocardium boundaries. A preliminary challenge faced in this task is the removal of noise from Magnetic Resonance Imaging (MRI) data, which is addressed by using advanced data filtering procedures. Two mechanisms for left-ventricle segmentation are employed. Firstly segmentation of the left ventricle blood-pool for the measurement of ejection fraction is undertaken in the signal intensity domain. Utilising the high discrimination between blood and tissue, a novel methodology based on a statistical partitioning method offers success in localising and segmenting the blood pool of the left ventricle. From this initialisation, the estimation of the outer wall (epi-cardium) of the left ventricle can be achieved using gradient information and prior knowledge. Secondly, a more involved method for extracting the myocardium of the leftventricle is developed, that can better perform segmentation in higher dimensions. Spatial information is incorporated in the segmentation by employing a gradient-based boundary evolution. A level-set scheme is implemented and a novel formulation for the extraction of the cardiac muscle is introduced. Two surfaces, representing the inner and the outer boundaries of the left-ventricle, are simultaneously evolved using a coupling function and supervised with a probabilistic model of expertly assisted manual segmentations

On gradual regime switching models: A generalisation of Hamilton's method of time-series analysis.

The class of Markov Switching time series models, introduced by Professor James Hamilton, is nearly twenty years old. Despite this, relatively little work has been done on allowing gradual transitions between the regimes of the model. Almost all of the published work relates to modelling a transition between two regression lines rather than incorporating it into a time series model. We decided to approach the problem from two directions. First, we wanted to look at Filtered Telegraph signals (Filtered Markov processes) and consider their suitability for time series analysis. Secondly, we wished to extend the existing Regime Switching models to allow a gradual transition between regimes. In our work on the Filtered Markov process we present a method for obtaining moments for a signal with any number of regimes, rather than the usual two. This enables us to find the stationary, transient and conditional moments of the signal. We include an expression for the covariance of two observations from a signal, obtained using the conditional moments. While considering how to fit a Filtered Markov process we identify several new methods that can be used for estimating the parameters of a sample from the Beta distribution where the observations have been contaminated by noise. We also include extensive tables of the percentiles of the estimators for each of the methods. We also present a new algorithm that utilises the Filtered Markov process to generate random Beta variates. Finally we take a more practical approach, introducing some simple models that, while useful in their own right, could also be used to bridge the gap between the two-regime Markov switching model and the Filtered Markov process. These Ladder models are then applied to several data sets to explore the problems faced by gradual switching models and collect evidence of their suitability

Systems Analysis of Hydrologic Problems

Introduction: Increasing national and international interest in water resources in recent years has stimulated much new activity and progress in hydrology. It is now generally recognized that the science of hydrology is basic to an understanding of water resources problems and to planning for water resources development. Accompanying this demand upon the science of hydrology is an urgent need for improved education at the university level. In resopnse to this need for improved education, the First International Seminar for Hydrology Professors was held at Urbana, Illinois, in July 1969. The Second International Seminar was held at Logan, Utah, during August 2-14, 1970, and was a continuation of the program to acquaint hydrology professors with modern concepts and technologies. The major overall objective of the second seminar was to emphasize the systems approach as applied to hydrology, in which the various fundamental hydrologic processes and their interrelationships were studied and examined. Because of the need to apply new concepts and technologies to the development and utilization of the limited supply of water resources throughout the world, hydrologic programs in our colleges and universities generally require much improvement, particularly with reference to the application of systems concepts and methods. Accordingly, the specific objectives of the Seminar were as follows: 1. To impress upon hydrology professors the improtance of the systems approach to the science of hydrology, and to acquaint them with the fundamental and basic concepts of the the hydrologic system. 2. To present concepts for defining or describing the hydrologic system in terms of particular management objectives. 3. To examine various techniques for monitoring the hydrologic system, including the design of monitoring networks in terms of particular objectives. 4. To acquaint the participants with several methods of modeling hydrologic systems, and to provide them with experiences which demonstrate the utility of modeling for (a) examining various system interrelationships and sensitivies; and (b) maximizing particular objective functions subject to given external contraints and production functions

LIPIcs, Volume 261, ICALP 2023, Complete Volume

LIPIcs, Volume 261, ICALP 2023, Complete Volum

Symmetries in Quantum Mechanics

Symmetry and quantum mechanics are two of the most fundamental probes we have of nature. This collection of eleven papers discusses new quantum phenomena in atoms, galaxies, and people (quantum cognition), which is a testimonial to the breadth of the influence of symmetry and quantum mechanics. The book represents an international effort of researchers from educational and research institutions in nine countries, including India, Finland, France, Mexico, Norway, Russia, Spain, Turkey, and the United States. The papers can be divided into four broad categories: Fundamentals of quantum systems, including a new derivation of the uncertainty principle from optimal stochastic control theory, a new model of energy transfer between atoms with no wave function collapse, a new asymmetric optical micro-device with the remarkable property of showing a current with no applied voltage, and a model of quantum cognition to predict the effect of irrelevant information on decision making. 2. Algebraic methods in quantum mechanics, describing an elegant derivation of hydrogen atom Stark effect matrix elements, and a new group theoretical method for the computation of radiative shifts. Teleportation and scattering, including a method to improve the information transfer in teleportation, and the use of permutation symmetry to compute scattering cross sections. Cosmology, including scalar-tensor theory applied to inflation, the characterization of new Levi-Cevita space-times, and a comprehensive analysis of gravitational dispersion forces

Markov-Gibbs Random Field Approach for Modeling of Skin Surface Textures

Medical imaging has been contributing to dermatology by providing computer-based assistance by 2D digital imaging of skin and processing of images. Skin imaging can be more effective by inclusion of 3D skin features. Furthermore, clinical examination of skin consists of both visual and tactile inspection. The tactile sensation is related to 3D surface profiles and mechanical parameters. The 3D imaging of skin can also be integrated with haptic technology for computer-based tactile inspection. The research objective of this work is to model 3D surface textures of skin. A 3D image acquisition set up capturing skin surface textures at high resolution (~0.1 mm) has been used. An algorithm to extract 2D grayscale texture (height map) from 3D texture has been presented. The extracted 2D textures are then modeled using Markov-Gibbs random field (MGRF) modeling technique. The modeling results for MGRF model depend on input texture characteristics. The homogeneous, spatially invariant texture patterns are modeled successfully. From the observation of skin samples, we classify three key features of3D skin profiles i.e. curvature of underlying limb, wrinkles/line like features and fine textures. The skin samples are distributed in three input sets to see the MGRF model's response to each of these 3D features. First set consists of all three features. Second set is obtained after elimination of curvature and contains both wrinkle/line like features and fine textures. Third set is also obtained after elimination of curvature but consists of fine textures only. MGRF modeling for set I did not result in any visual similarity. Hence the curvature of underlying limbs cannot be modeled successfully and makes an inhomogeneous feature. For set 2 the wrinkle/line like features can be modeled with low/medium visual similarity depending on the spatial invariance. The results for set 3 show that fine textures of skin are almost always modeled successfully with medium/high visual similarity and make a homogeneous feature. We conclude that the MGRF model is able to model fine textures of skin successfully which are on scale of~ 0.1 mm. The surface profiles on this resolution can provide haptic sensation of roughness and friction. Therefore fine textures can be an important clue to different skin conditions perceived through tactile inspection via a haptic device

New Trends in Lithium Niobate

The present volume “New Trends in Lithium Niobate: From Bulk to Nanocrystals” contains the materials of a Special Issue of the MDPI journal Crystals dedicated to the memory of Prof. Dr. Ortwin F. Schirmer and provides a new synopsis of his research focusing on LiNbO3. It also includes recent developments, exemplifying the continued interest in this outstanding ferroelectric, non-linear optical and holographic crystal as a workhorse for testing and realizing new ideas and applications.This book starts with reviews on intrinsic and extrinsic crystal defects in LiNbO3 of single-crystal, thin-film or nano-powder forms, studied by various optical, magnetic resonance and nuclear methods, clarifying in particular the reasons for the suppression of anion vacancy formation upon thermal reduction, mechano-chemical processing or irradiations of various types. The reviews are followed by research papers on the experimental and theoretical investigation of small polarons, together with recent results on the properties of Li(Nb,Ta)O3 mixed crystals. Among the various contributions dealing with nonlinear optical applications, papers on device development, entangled photon pair generation and thin films on the Lithium Niobate On Insulator (LNOI) platform can also be found