Abstract:Nowadays electric and electronic equipments are produced on a large scale, for example, personal computers. Therefore, more and more waste is recycled. To increase the strength properties of recycled materials, they are reinforced with various types of fillers such as natural. Over the last few years, fillers from tuffs of volcanic origin have been gaining in popularity. It is characterized by a low mass, high hardness, high matrix adhesion, which allow for uniform distribution of particles in the volume of the material. In this paper, composites based on recycled polystyrene waste with tuff microparticles in mass weight of 10% and 20% were produced by injection moulding. The basic mechanical properties at room temperature (+24°C) -24 and +80°C were evaluated. The aim of the study was to demonstrate the possibility of using the mineral filler particles as compatibilizer for recycled polystyrene waste of poor quality.
Abstract:The paper presents a method of optimizing Quantitative Learner’s Motivation Model with the use of genetic algorithm. It is focused on optimizing the formula for prediction of learning motivation by means of different weights for three values: interest, usefulness in the future and satisfaction. For the purpose of this optimization, we developed a C++ library that implements a genetic algorithm and an application in C# which uses that library with data acquired from questionnaires enquiring about those three elements. The results of the experiment showed improvement in the estimation of student’s learning motivation.
Abstract:The tests were conducted on a wheel/axle press-fit joint model, which consisted of a shaft and a sleeve. Macrographic observations were demonstrated fretting wear on the shaft surface with and without coatings. In the case of the uncoated shaft, wear around the entire circumference of the axle seat was visible in the form of a peculiar ring of a specific width. The coated shaft surface was distinguished by a considerably smaller number of visible traces of wear. Wear was observed around the entire circumference of the axle seat, was spaced at random, and insignificantly sized areas each time. Micrographic observations with the use of a scanning microscope demonstrated that fretting was primarily comprised of the build-up of the material from both surfaces joined together. In addition to the build-up, surface micro-abrasion, micropits and microcracks are observed, albeit to a lesser extent.
Abstract:Certain crane operations – hoisting/lowering the payload connected to a slewing jib – require a nonlinear description to take Euler and Coriolis forces into account, the impacts of which should already be minimised at the stage of selection of the system parameters and mechanism structure. Optimal sets of parameters for the crane mechanisms thus obtained were optimised for the full range of slewing motion. It is demonstrated that the selection of the geometric dimensions of the structural elements of the hoisting mechanisms, i.e. the slewing system and counterbalances, enables the horizontal track error load to be minimised whilst the forces acting on the mechanism and inducing its vertical movement can be reduced. Thus, for the assumed lifting capacity and distance jaunt we get the structure of the crane mechanism that guarantees the minimal consumption of energy.
Abstract:The mechanical properties of manufactured composites based on polyoxymethylene (Tarnoform 300) were determined. POM composites reinforced with ultra-high molecular weight silicon, thermoplastic polyurethane, and special chalk in order to reduce abrasiveness and aramid fibres were manufactured. The basic mechanical properties (tensile strength (σM), modulus of elasticity (Et), strain at break (εB), flexural modulus (Ef) and flexural stress at 3.5% strain (σs)) were evaluated at three temperatures -20, 20 and 80°C. The density and Charpy impact of the produced composites were examined. In order to make reference to the effects of reinforcement and determine the characteristics of their microstructure SEM, images were taken.
Abstract:The aim of the paper is to prove two theorems on the existence and uniqueness of mild and classical solutions of a semilinear functional-differential evolution second order equation together with nonlocal initial conditions. The theory of strongly continuous cosine families of linear operators in a Banach space is applied. The paper is based on publications [1–12] and is a generalization of paper [7].
Abstract:Modern data centres consume large amounts of power resulting in high levels of carbon dioxide emission. The data centre is a virtual environment in which the workload is performed by virtual machines. A widely used technique to decrease data centre power consumption is to consolidate the virtual machines using a minimal number of physical servers. The authors propose a two-stage method to solve the virtual machine consolidation problem in cloud data centres. The proposed method is programmed in C# to evaluate it and to perform modelling using Google cluster-usage traces. The proposed method enables powering off nearly fifty percent of the previously selected physical servers by using an acceptable number of migrations of virtual machines.
Abstract:This article presents a modern method of calculating the exponential function exp(x) based on the CORDIC iterative algorithm. The proposed solution is implemented in the form of a single iterative equation, which results in the simplification of the electronic version of this algorithm, thus reducing the cost of the device. It is important to point out that the accuracy of the calculation of the analysed function is not lost.
Abstract:This paper discusses the principle of constructing an evolutionary model for the parametric optimisation of electromagnetic instruments with solid-state valves. To illustrate the method, a triple voltage scheme was selected – this converts variable voltage into constant voltage and at the same time, triples the amplitude. Valve operation was modelled according to the ideal key diagram; the considered resistance was that of an open valve.
Abstract:Many methods are used to obtain functional polymer foams. This review focuses on reactive extrusion of poly(ethylene terephthalate). This process is based on the reaction between PET and the appropriate blowing agent. The next step is the creation of foam by closing gas cells in the polymer matrix. This method of modification allows material with higher molecular weight to be obtained and, therefore, higher melt strength. The use of different chemical modifiers and their concentration influences properties of created foam. The enhanced features of foamed PET allow it to be used in many areas of application such as transport, construction or general industry. Another big advantage of this technique is the possibility of using recycled materials as the source of PET.
