A New Weighted k-Nearest Neighbor Algorithm Based on Newton¿s Gravitational Force

[EN] The kNN algorithm has three main advantages that make it appealing to the community: it is easy to understand, it regularly offers competitive performance and its structure can be easily tuning to adapting to the needs of researchers to achieve better results. One of the variations is weighting the instances based on their distance. In this paper we propose a weighting based on the Newton's gravitational force, so that a mass (or relevance) has to be assigned to each instance. We evaluated this idea in the kNN context over 13 benchmark data sets used for binary and multi-class classification experiments. Results in F1 score, statistically validated, suggest that our proposal outperforms the original version of kNN and is statistically competitive with the distance weighted kNN version as well.This research was partially supported by CONACYT-Mexico (project FC-2410). The work of Paolo Rosso has been partially funded by the SomEMBED TIN2015-71147-C2-1-P MINECO research project.Aguilera, J.; González, LC.; Montes-Y-Gómez, M.; Rosso, P. (2019). A New Weighted k-Nearest Neighbor Algorithm Based on Newton¿s Gravitational Force. Lecture Notes in Computer Science. 11401:305-313. https://doi.org/10.1007/978-3-030-13469-3_36S3053131140

Current Studies and Applications of Krill Herd and Gravitational Search Algorithms in Healthcare

Nature-Inspired Computing or NIC for short is a relatively young field that tries to discover fresh methods of computing by researching how natural phenomena function to find solutions to complicated issues in many contexts. As a consequence of this, ground-breaking research has been conducted in a variety of domains, including synthetic immune functions, neural networks, the intelligence of swarm, as well as computing of evolutionary. In the domains of biology, physics, engineering, economics, and management, NIC techniques are used. In real-world classification, optimization, forecasting, and clustering, as well as engineering and science issues, meta-heuristics algorithms are successful, efficient, and resilient. There are two active NIC patterns: the gravitational search algorithm and the Krill herd algorithm. The study on using the Krill Herd Algorithm (KH) and the Gravitational Search Algorithm (GSA) in medicine and healthcare is given a worldwide and historical review in this publication. Comprehensive surveys have been conducted on some other nature-inspired algorithms, including KH and GSA. The various versions of the KH and GSA algorithms and their applications in healthcare are thoroughly reviewed in the present article. Nonetheless, no survey research on KH and GSA in the healthcare field has been undertaken. As a result, this work conducts a thorough review of KH and GSA to assist researchers in using them in diverse domains or hybridizing them with other popular algorithms. It also provides an in-depth examination of the KH and GSA in terms of application, modification, and hybridization. It is important to note that the goal of the study is to offer a viewpoint on GSA with KH, particularly for academics interested in investigating the capabilities and performance of the algorithm in the healthcare and medical domains.Comment: 35 page

Understanding dark matter halos with tidal caustics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 181-188).The products of interactions between galaxies with a high mass ratio and low orbital angular momentum are studied. The interactions scatter the material from the smaller galaxy into structures with distinctive dynamics and morphology, including high local densities and a simple density profile related to properties of the participating galaxies. The role of the larger galaxy's tides in creating these structures and their relation to a well-studied class of mathematical objects motivates us to name them "tidal caustics". We study the densities achievable in tidal caustics for a typical merger of this type using an example from the Andromeda galaxy to determine whether they are sufficient to produce a detectable gamma-ray signal from self-interactions in the dark matter component, for likely particle models of dark matter. We find that the expected signal is an order of magnitude too low to be detected with current instruments. We also study the constraints that can be placed on the properties of the participating galaxies by observing the surface brightness profiles of the tidal caustics. We find that the local gravity and gravity gradient of the larger galaxy, and the energy spread and initial phase space density of the smaller galaxy, can be jointly constrained by fitting this profile. The constraints are degenerate but model-independent. We find that measurements of multiple caustics and the velocity of the material in each caustic along the line of sight give information about the orbital angular momentum and the deviations from spherical symmetry in the larger galaxy, though this information is somewhat model-dependent. We discuss the main technical difficulty in fitting the surface brightness profile: determining the inclination angle of the caustic. We demonstrate that a simple model can successfully recover the necessary parameters for some cases, and that a simple modification to this model will improve its success rate.by Robyn Ellyn Sanderson.Ph.D

Structural dynamics branch research and accomplishments

Summaries are presented of fiscal year 1989 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center. Highlights from the branch's major work areas include aeroelasticity, vibration control, dynamic systems, and computation structural methods. A listing of the fiscal year 1989 branch publications is given

Particle dynamics modeling of vibrating granular beds

Particle dynamics modeling is done to study the behavior of granular beds subjected to vibrations imposed by a plane boundary which oscillates sinusoidally about a zero mean speed. Significant differences between the lower and higher shaking acceleration regions are found for the granular temperature and solids fraction depth profiles, which characterize the effectiveness of the boundary in fluidizing the beds. When higher accelerations are applied, the temperature is maximum at the vibrating floor and attenuates through the depth, while the solids fraction profiles exhibit a maximum at some intermediate depth. At lower acceleration values, most of the mass is located near the bottom, and fluidization occurs on the top, where a high temperature and low solids fraction is found, Simulation results are in good agreement with the kinetic theory predictions of Richman et al. in the higher acceleration regions and quantitatively consistent with the experimental data of Hunt et al. in the lower accelerations. Diffusion coefficients, computed using both the velocity autocorrelation function and the Einstein relation, are in agreement with each other and with the theoretical predictions of Savage. Critical conditions to produce a convective flow and associated segregation phenomena in a frictional bed are carefully investigated. The cell size, friction coefficient, agitation amplitude and acceleration are found to be the crucial factors. The first observation in simulation of an arching movement near the bottom of a large cell is also reported

Migration of an intruder particle in a boundary driven shear flow

This study reports on three-dimensional, discrete element simulations of a single large spherical intruder in a Couette shear flow composed of uniform sized particles. The simulation results are useful in providing a numerical reproduction of the experiments for size segregation and mixing. This in turn has a major importance in many industries which are concerned with handling of particles and powders, such as pharmaceutical manufacturing, agriculture, chemical and mineral processing. Discrete element simulations are carried out using the soft sphere model of Walton, et. al., which provides a method for obtaining the information at a macroscopic level from multi-body collisions within each computational step. A granular shearing flow is induced by allowing the upper and lower bumpy walls to move with the same constant speed in opposite directions. The wall particles are in square arrangements and have the same size as the regular flow particles. The typical transport properties of this flow are characterized by the depth profile of granular temperature, mean velocity and granular pressure which are related to the wall roughness, shear gap height and particle inelasticity measured by a constant normal restitution coefficient. By means of autocorrelation and spectral analysis, the vortex-like structure of velocity field has been revealed, which coincides with the results from the wavelet analysis. In the micro-gravity study case, an intruder with different size ratio has been added in the uniform shear flow described above. It has been observed to migrate away from the walls and finally become trapped in the central area with a small fluctuation around the equilibrium location. The amplitude of the fluctuation has a relation with the intruder size ratio. Computations indicated that the intruder\u27s motion is induced by the depth distribution of granular pressure which is higher near the moving boundary and lower in the center of the gap. The differences of the normal pressure on the depth profile could be represented by the fluctuation of net force on both sides of the intruder. Also, the circulation pattern in the velocity field may enhance this trend. Simulations of the annular shear cell device shows us that the motion of the intruder is very sensitive to gravity. Similar to the experimental studies, the intruder will eventually migrate to the top of the shear flow with a velocity proportional to the size ratio. A further investigation also revealed that the migration of the intruder may have a relation with the pattern of the velocity field in the cross-section of the shear direction

OREGAMI: Software Tools for Mapping Parallel Computations to Parallel Architectures

22 pagesThe mapping problem in message-passing parallel processors involves the assignment of tasks in a parallel computation to processors and the routing of inter-task messages along the links of the interconnection network. We have developed a unified set of software tools called OREGAMI for automatic and guided mapping of parallel computations to parallel architectures in order to achieve portability and maximal performance from parallel systems. Our tools include a description language which enables the programmer of parallel algorithms to specify information about the static and dynamic communication behavior of the computation to be mapped. This information is used by the mapping algorithms to assign tasks to processors and to route communication in the network topology. Two key features of our system are (a) the ability to take advantage of the regularity present in both the computation structure and the interconnection network and (b) the desire to balance the user's knowledge and intuition with the computational power of efficient combinatorial algorithms

Transport processes in directional solidification and their effects on microstructure development

The processing of materials with unique electronic, mechanical, optical and thermal properties plays a crucial role in modern technology. The quality of these materials depend strongly on the microstructures and the solute/dopant fields in the solid product, that are strongly influenced by the intricate coupling of heat and mass transfer and melt flow in the growth systems. An integrated research program is developed that include precisely characterized experiments and detailed physical and numerical modeling of the complex transport and dynamical processes. Direct numerical simulation of the solidification process is carried out that takes into account the unsteady thermo-solutal convection in the vertical Bridgman crystal growth system, and accurately models the thermal interaction between the furnace and the ampoule by appropriately using experimentally measured thermal profiles. The flow instabilities and transitions and the nonlinear evolution following the transitions are investigated by time series and flow pattern analysis. A range of complex dynamical behavior is predicted with increasing thermal Rayleigh number. The route to chaos appears as: steady convection → transient mono-periodic → transient bi-periodic → transient quasiperiodic → transient intermittent oscillation-relaxation → stable intermittent oscillation-relaxation attractor;The spatio-temporal dynamics of the melt flow is found to be directly related to the spatial patterns observed experimentally in the solidified crystals. The application of the model to two phase Sn-Cd peritectic alloys showed that a new class of tree-like oscillating microstructure develops in the solid phase due to unsteady thermo-solutal convection in the liquid melt. These oscillating layered structures can give the illusion of band structures on a plane of polish. The model is applied to single phase solidification in the Al-Cu and Pb-Sn systems to characterize the effect of convection on the macroscopic shape and disorder in the primary arm spacing of the cellular/dendritic freezing front. The apparently puzzling experimental observation of higher disorder in the weakly convective Al-Cu system than that in the highly convective Pb-Sn system is explained by the numerical calculations

A four-equation two-phase flow model for sodium boiling simulation of LMFBR fuel assemblies

A three-dimensional numerical model for the simulation of sodium boiling transients has been developed. The model uses mixture mass and energy equations, while employing a separate momentum equation for each phase. Thermal equilibrium on the saturation line between coexisting phases is assumed.The four governing equations are supplemented by a number of constitutive relations, addressing the interphase and intraphase exchanges, as well as the fluid-solid interactions. It should be noted that this four-equation two-phase flow model requires only one interfacial relation, i.e., the momentum exchange, compared to the six-equation model which needs two additional relations, describing the mass and energy exchanges. Consequently, the relatively high degree of uncertainty currently associated with the interfacial exchange phenomena is considerably reduced.From a numerical point of view, the basic approach in this work is a semi-implicit method, in which pressure pulse propagation and local effects characterized by short characteristic times are treated implicitly, while convective transport and diffusion heat transfer phenomena, associated with longer time constants, are handled explicitly. The method remains tractable and efficient in multidimensional applications.Simulation of a number of experiments has yielded very encouraging results. The numerical method and the constitutive relations have performed well, especially so in light of the extreme severity of the conditions involving sodium boiling

Gravity Field Refinement by Radial Basis Functions from In-situ Satellite Data

In this thesis, an integrated approach is developed for the regional refinement of global gravity field solutions. The analysis concepts are tailored to the in-situ type character of the observations provided by the new satellite missions CHAMP, GRACE, and GOCE. They are able to evaluate data derived from short arcs of the satellite's orbit and, therefore, offer the opportunity to use regional satellite data for the calculation of regional gravity field solutions. The regional character of the approach will be realized at various stages of the analysis procedure. The first step is the design of specifically tailored space localizing basis functions. In order to adapt the basis functions to the signal content to be expected in the gravity field solution, they will be derived from the covariance function of the gravitational potential. To use the basis functions in gravity field modeling, they have to be located at the nodal points of a spherical grid; therefore investigations will be performed regarding a suitable choice of such a nodal point distribution. Another important aspect in the regional gravity field analysis approach is the downward continuation process. In this context, a regionally adapted regularization will be introduced which assigns different regularization matrices to geographical areas with varying signal content. Regularization parameters individually determined for each region take into account the varying frequency behavior, allowing to extract additional information out of a given data set. To conclude the analysis chain, an approach will be described that combines regional solutions with global coverage to obtain a global solution and to derive the corresponding spherical harmonic coefficients by means of the Gauss-Legendre quadrature method. The capability of the method will be demonstrated by its successful application to real data provided by CHAMP and GRACE and to a simulation scenario based on a combination of GRACE and GOCE observations.Verfeinerungen des Gravitationsfeldes mit radialen Basisfunktionen aus in-situ Satellitendaten In der vorliegenden Arbeit wird ein ganzheitliches Konzept für die regionale Verfeinerung globaler Gravitationsfeldmodelle entwickelt. Die dazu verwendeten Analyseverfahren sind dem in-situ Charakter der Beobachtungen der neuen Satellitenmissionen CHAMP, GRACE und GOCE angepasst. Sie beruhen auf kurzen Bahnbögen und ermöglichen somit die Berechnung regionaler Gravitationsfeldmodelle aus regional begrenzten Satellitendaten. Der regionale Charakter des Ansatzes wird dabei auf verschiedenen Ebenen des Analyseprozesses realisiert. Der erste Schritt ist die Entwicklung angepasster orts-lokalisierender Basisfunktionen. Diese sollen das Frequenzverhalten des zu bestimmenden Gravitationsfeldes widerspiegeln; sie werden daher aus der Kovarianzfunktion des Gravitationspotentials abgeleitet. Um die Basisfunktionen für die Schwerefeldmodellierung zu verwenden, müssen sie an den Knotenpunkten eines sphärischen Gitters angeordnet werden. Daher werden Untersuchungen durchgeführt, welche Punktverteilung für diese Aufgabe besonders geeignet ist. Einen wichtigen Aspekt bei der regionalen Gravi-tationsfeldanalyse stellt der Fortsetzungsprozess nach unten dar. In diesem Zusammenhang wird ein regional angepasstes Regularisierungsverfahren entwickelt, das verschiedene Regularisierungsmatrizen für regionale Gebiete mit unterschiedlichem Schwerefeldsignal ermöglicht. Individuell angepasste Regularisierungsparameter berücksichtigen den variierenden Signalinhalt, wodurch erreicht wird, dass zusätzliche Informationen aus einem gegebenen Datensatz extrahiert werden können. Schließlich wird ein Ansatz vorgestellt, der regionale Lösungen mit globaler Überdeckung zu einer globalen Lösung zusammenfügt und die zugehörigen sphärischen harmonischen Koeffizienten mit Hilfe der Gauss-Legendre-Quadratur berechnet. Die Leistungsfähigkeit des beschriebenen Ansatzes wird durch eine erfolgreiche Anwendung auf die Echtdatenanalyse aus Daten der Satellitenmissionen CHAMP und GRACE und auf ein Simulationsszenario aus einer Kombination simulierter GRACE- und GOCE-Beobachtungen verdeutlicht