## Search results

### Search results

Number of results: 93
items per page: 25 50 75
Sort by:

## The mathematical skills of third graders. A subjective selection from the research

### Abstract

Over the past few years, a great deal of research has been conducted concerning the mathematical skills of children after the first stage of education. In my report, I present a selection of results from this research in order to illustrate the most typical didactical effects of the style in which mathematical education is performed in our schools. Comparing some detailed results from research in a number of chosen fields, I also try to assess whether or not, and how, the level of schoolchildren’s skills has changed in the recent years.
Go to article

## Simultaneous Analysis of Vibrations and Noise in the Task of Minimizing Vibroacoustic Activity of Machines

### Abstract

Simultaneous propagation of vibrations and noise has an important role in the task of minimizing vibroacoustic hazards on the station of operator of the construction machinery. In many cases vibrations transferred by the construction are processed to noise in different points of the machine. As a result, they may increase the level of noise at the workplace. The paper presents the proposition of a simple estimation of noise and vibration propagation paths of the machine. On the basis of the analysis of hydraulic excavator an effectiveness of a proposed procedure was shown. This procedure helps to minimize the transfer of vibrations of power unit in selected frequency ranges which led to the change of overall noise level in operator’s cab about 5 dB.
Go to article

## Simultaneous Analysis of Noise and Vibration of Machines in Vibroacoustic Diagnostics

### Abstract

The article is a continuation of the authors’ elaboration (Dąbrowski, Dziurdź, 2016). The aim of this continuation is to prove that a proposed way of modelling and using the coherent analysis to filter nonlinear disturbances is a useful technique in vibroacoustic diagnostics. The thesis was proved by solving the task of diagnosing the damage of the gear of the car gearbox on the basis of the measurement of mechanical vibrations and the noise in the engine chamber.
Go to article

## Synthesis and CAD of permanent magnet DC brushless motors

### Abstract

The paper presents an algorithm and software for the optimal design of permanent magnet brushless DC motors. Such motors are powered by DC voltage sources via semiconductor switches connected to the motor phase belts. The software is adjusted to the design of motors with NdFeB high energy density magnets. An attention has been given to issues important in the design of the motors, i.e., permanent magnet selection, structure of magnetic circuit, and armature windings. Particularly, precision of calculation of the permanent magnet operating point, visualization of selection process of the winding belts, and magnetic circuit dimensioning have been investigated. The authors have been trying to make the equations more specific and accurate than those presented in the literature. The user software interface allows changes in the magnetic circuit dimensions, and in the winding parameters. It is possible to examine simultaneously the influence of these changes on the calculation results. The software operates both with standard and inverted (outer rotor) motor structure. To perform optimization, a non-deterministic method based on the evolution strategy (ž + λ) - ES has been used.
Go to article

## Rola wyobraźni w procesie twórczym a zagrożenia współczesnego świata

### Abstract

We wszystkich obszarach aktywności twórczej wyobraźnia, jest niezbędnym elementem w życiu i funkcjonowaniu człowieka. W wielu sytuacjach życiowych jest ona nieodłącznym elementem wykorzystywanym w sposób mniej lub bardziej świadomy. Pozwala tworzyć wyobrażenia, które nie mają odpowiedników w żadnym z wrażeń, stanowiąc podstawę twórczości wszelkiej aktywności człowieka. Wyobraźnia jest naturalnym przedłużeniem wzroku, specyficzną zdolnością do wywoływania obrazów, pobudzającą do twórczego myślenia i działania. W dzisiejszych czasach człowiek nieustannie bombardowany jest coraz większą ilością dźwięków i obrazów, które „zagłuszają” naturalny rozwój wyobraźni. Szybki postęp technologiczny, którego jesteśmy świadkami, nie pozostaje bez wpływu na rozwój twórczego myślenia, tworzy bariery ograniczające człowieka.
Go to article

## Spitsbergen, Polish Polar Station in Hornsund Maps in the scale of 1:5000 and 1:500

### Abstract

Works connected with execution of geodesic and photogrammetric surveys and with setting up maps in the scale of 1:5000 of environs of the Polish Polar Station on the Isbjörnhamna Bay and in the scale of 1:500 of the area covered with buildings of the Station are discussed.
Go to article

## Pressure drop related to flow maldistribution in a model minichannel plate heat exchanger

### Abstract

The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 μm, 571 μm, 750 μm, and 823 μm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.
Go to article