Study of free-piston Stirling engine driven linear alternators

The analysis, design and operation of single phase, single slot tubular permanent magnet linear alternator is presented. Included is the no-load and on-load magnetic field investigation, permanent magnet's leakage field analysis, parameter identification, design guidelines and an optimal design of a permanent magnet linear alternator. For analysis of the magnetic field, a simplified magnetic circuit is utilized. The analysis accounts for saturation, leakage and armature reaction

High frequency losses in induction motors, part 2

The following subject areas are covered: high frequency losses in induction motors; stray losses in induction motors; and high frequency time harmonic losses in induction motors

Observations on Reproduction, Aestivation and Polymor-phism in the snail, Limicolaria Martensiana (Smith) from the Queen Elizabeth National Park, Uganda

Volume: 2

The history of Algorithmic complexity

This paper provides a historical account of the development of algorithmic complexity in a form that is suitable to instructors of mathematics at the high school or undergraduate level. The study of algorithmic complexity, despite being deeply rooted in mathematics, is usually restricted to the computer science curriculum. By providing a historical account of algorithmic complexity through a mathematical lens, this paper aims to equip mathematics educators with the necessary background and framework for incorporating the analysis of algorithmic complexity into mathematics courses as early on as algebra or pre-calculus

The history of Algorithmic complexity

This paper provides a historical account of the development of algorithmic complexity in a form that is suitable to instructors of mathematics at the high school or undergraduate level. The study of algorithmic complexity, despite being deeply rooted in mathematics, is usually restricted to the computer science curriculum. By providing a historical account of algorithmic complexity through a mathematical lens, this paper aims to equip mathematics educators with the necessary background and framework for incorporating the analysis of algorithmic complexity into mathematics courses as early on as algebra or pre-calculus

Residential Segregation, Neighborhood Social and Physical Context in Obesity Disparities in Hispanic Preschoolers: A Conceptual Model

During the last decade, there has been a significant inclusion in obesity prevention studies from individual characteristics to household factors then neighborhood factors. The study of place in the context of early childhood obesity studies has been limited to the food and physical built environment. With the persistent disparities in the prevalence of childhood obesity, and Hispanic minorities being increasingly affected, there is a need to reexamine existing models and develop new model conceptual frameworks to examine the role of place and residential segregation in the context of race, ethnicity, social position, and socioeconomic disparities. In the context of place as a relational space linked to where young children live, play and learn, this paper conceptualizes the role of the neighborhood social and physical factors as well as organizational, household and/or individual factors as mediators of the correlation between residential segregation and obesity in Hispanic preschoolers. In the model, we also attempted to include the role of policies and programs in moderating the negative effects of racial residential segregation and resource inequalities and their interactions with the multiple factors that may contribute to childhood obesity. Recommendations for future research need are identified

High order difference schemes using the Local Anisotropic Basis Function Method

Mesh-free methods have significant potential for simulations in complex geometries, as the time consuming process of mesh-generation is avoided. Smoothed Particle Hydrodynamics (SPH) is the most widely used mesh-free method, but suffers from a lack of consistency. High order, consistent, and local (using compact computational stencils) mesh-free methods are particularly desirable. Here we present a novel framework for generating local high order difference operators for arbitrary node distributions, referred to as the Local Anisotropic Basis Function Method (LABFM). Weights are constructed from linear sums of anisotropic basis functions (ABFs), chosen to ensure exact reproduction of polynomial fields up to a given order. The ABFs are based on a fundamental Radial Basis Function (RBF), and the choice of fundamental RBF has small effect on accuracy, but influences stability. LABFM is able to generate high order difference operators with compact computational stencils (4th order with 25 nodes, 8th order with 60 nodes in two dimensions). At domain boundaries (with incomplete support) LABFM automatically provides one-sided differences of the same order as the internal scheme, up to 4th order. We use the method to solve elliptic, parabolic and mixed hyperbolic-parabolic PDEs, showing up to 8th order convergence. The inclusion of hyperviscosity is straightforward, and can effectively provide stability when solving hyperbolic problems. LABFM is a promising new mesh-free method for the numerical solution of PDEs in complex geometries. The method is highly scalable, and for Eulerian schemes, the computational efficiency is competitive with RBF-FD for a given accuracy. A particularly attractive feature is that in the low order limit, LABFM collapses to SPH, and there is potential for Arbitrary Lagrangian-Eulerian schemes with natural adaptivity of resolution and accuracy.Comment: Accepted manuscript: 28 pages, 23 figures. Accepted in J. Comput. Phys. 10th May 202

Thermomechanical processing of 34CrNiMo6 steel for Large Scale Forging

This work simulated the thermo-mechanical processing of large-scale forging product made of 34CrNiMo6 steel to evaluate the effect of different processing condition parameters and cooling rates on the variation of microstructure and the final mechanical properties. Through this investigation we tried to achieve the required mechanical properties for deep sea applications, which were a minimum Charpy impact value of 38J at temperature of -20 °C according to ABS specifications and a minimum surface hardness of 302 HB according to First Subsea specification design. Initially, a series of single and multi-hit plane strain compression tests were performed to evaluate the hot-deformed microstructure in thermo-mechanical processing, with particular attention paid to the effect of austenitising temperature and deformation conditions of temperature, strain and strain rate. The exponential law, power law and hyperbolic sine law types of Zener–Hollomon equations were utilised to calculate the hot activation energy of deformation (Qdef). In addition the constitutive equations were used for modelling and generalising the DRV and DRX flow curves of 34CrNiMo6 steel, using the method proposed by Avrami. Secondly, a heat treatment process using different austenitising temperatures and different cooling rates was also investigated to achieve the required aims, in which many tests were performed through controlling the temperatures, soaking times, and cooling rates to study the effect of the heat treatment parameters on the grain size and transformation behaviour of austenite. Additionally, to attempt to refine the austenite grain size and to increase the austenite phase percentage within the microstructure, multiple heat treatment paths were also used. A double normalizing, double quenching, and single tempered process were used in all possible combinations to investigate their influence on the final microstructure in an attempt to identify the most effective heat treatment cycle with an effective sequence for the heat treatment operations

Performance of Anti-Lock Braking Systems Based on Adaptive and Intelligent Control Methodologies

Automobiles of today must constantly change their speeds in reaction to changing road and traffic circumstances as the pace and density of road traffic increases. In sophisticated automobiles, the Anti-lock Braking System (ABS) is a vehicle safety system that enhances the vehicle's stability and steering capabilities by varying the torque to maintain the slip ratio at a safe level. This paper analyzes the performance of classical control, model reference adaptive control (MRAC), and intelligent control for controlling the (ABS). The ABS controller's goal is to keep the wheel slip ratio, which includes nonlinearities, parametric uncertainties, and disturbances as close to an optimal slip value as possible. This will decrease the stopping distance and guarantee safe vehicle operation during braking. A Bang-bang controller, PID, PID based Model Reference Adaptive Control (PID-MRAD), Fuzzy Logic Control (FLC), and Adaptive Neuro-Fuzzy Inference System (ANFIS) controller are used to control the vehicle model. The car was tested on a dry asphalt and ice road with only straight-line braking. Based on slip ratio, vehicle speed, angular velocity, and stopping time, comparisons are performed between all control strategies. To analyze braking characteristics, the simulation changes the road surface condition, vehicle weight, and control methods. The simulation results revealed that our objectives were met. The simulation results clearly show that the ANFIS provides more flexibility and improves system-tracking precision in control action compared to the Bang-bang, PID, PID-MRAC, and FLC