scholarly journals Mathematical model for knowledge testing

2008 ◽  
Vol 48 ◽  
Author(s):  
Aleksandras Krylovas ◽  
Natalja Kosareva

There is a mathematical model for obtaining test responses probability distribution proposed. This enables to formulate recomendations for selection of test items for different groups of tested population accordingto their attainment level.

2020 ◽  
Vol 28 (2) ◽  
Author(s):  
Vanya Ivanova ◽  
◽  
Gergana Petkova

Idioms are metaphorical expressions that cannot be translated literally. They are widely used in English because they make everyday speech more interesting and entertaining for native speakers. It is assumed that there are about twenty-five thousand idiomatic expressions in English and one of the most common thematic areas for idioms is colour. Idiomatic expressions are a fun way to enhance the vocabulary and cultural knowledge of learners of English. However, mastering these expressions cause difficulties for students not only because their meaning is not deductible from the meanings of the words comprising it, but also due to the different meaning of colours in the cultures around the world. For instance, purple is usually connected with aristocracy, affluence, and piousness across the globe but in Thailand and Brazil it is the colour of bereavement. In this article we have described an approach to check the acquisition of idiomatic expressions and facilitate their long-term retention by using online practice tests. These tests are designed by the teacher and taken by students on their personal computers or mobile phones at their own convenience. Furthermore, specifically developed criteria for test construction are listed together with typical test questions based on them. Examples of test items are presented to illustrate the process of test creation. Finally, an appendix of a selection of the most widely used idiomatic expressions with colours is compiled.


Author(s):  
I.P. POPOV

The starting mode for the train is the most difficult. An effective method of pulling is the selection of coupling clearances. In this case, the cars are set in motion sequentially and the inert mass, as well as the static friction force immediately at the moment of starting, are minimal. This method has two significant drawbacks - a small fixed value of the gaps in the couplings and the shock nature of the impulse transfer. These disadvantages can be avoided by using elastically deformable couplings. The aim of this work is to construct a mathematical model of "easy" starting of a train with elastic couplings. The softening of the train start-off mode is essentially due to the replacement of the simultaneous start-off of the sections with alternate ones. To exclude longitudinal vibrations of the composition, after reaching the maximum tension of the coupling, the possibility of its harmonic compression should be mechanically blocked.


2018 ◽  
Vol 19 (11) ◽  
pp. 41-44
Author(s):  
Marek Kwietniewski ◽  
Tadeusz Bil

The McPherson column name comes from the inventor of this Earle S. MacPherson solution, which was first manufactured at the Ford plant in 1949. This is one of the most commonly used types of front suspension in popular passenger cars. The advantage of this type of suspension is a compact construction, but the disadvantage is. The influence of the damping motion on the position of the steering wheel may result in an unintentional change of direction of travel. At the same time, there is a slight additional tilt of the wheels when the "spring" movement. In the proposed solution, partial elimination of this type of incorrectness is proposed by changing the type of connection of the steering rod end to the steering wheels of the vehicle. The introduced change consists in replacing one of the spherical joints in these joints into two rotary joints. Such a change introduces a mathematical model describing the behavior of the suspension under the influence of the depreciation of additional parameters. Proper selection of these parameters allows for significant reduction of unnecessary direction changes during driving. The described model of the structure of the mechanism allows to analyze the influence of all its dimensions on the selected parameters of the behavior of the wheels during the ride, resulting from the movement of the suspension and steering.


2021 ◽  
pp. 68-72
Author(s):  
Il'ya A. Meshchikhin ◽  
Sergej S. Gavryushin

As part of the development of monitoring systems for the operation of technical objects, the problem of improving the quality of monitoring systems for the loaded state is considered. Based on the analysis of the mathematical model of the structure and its loading, a methodology for the selection of measuring instruments was developed. The urgency of the problem of calculating substantiation of the choice of key points of the structure is shown, at which it is possible to measure deformations for the subsequent restoration of the existing loads with maximum accuracy. An approach based on the envelope method for determining the rational composition of measuring instruments for restoring the loads acting on the structure is stated.


2020 ◽  
Vol 22 (3) ◽  
pp. 132-139
Author(s):  
A. V. Denisov ◽  
M. D. Stepanov ◽  
N. A. Haraldin ◽  
A. V. Stepanov ◽  
A. I. Borovkov ◽  
...  

Abstract. In the work, a review of scientific articles on the behavior of tissues and organs of the human body under local mechanical effects on it, as well as a description of the physico-mechanical properties of biological materials. The selection of mechanical behavior for each biological material as part of a mathematical model of the human torso was carried out, its finite element model was created, validation experiments were modeled using data presented in the literature. An original calculation model of a human torso with a tuned interaction of organs with each other was developed. Contact interaction parameters are determined. The developed computational model of a human torso was verified based on data from open sources for an experiment with mechanical action by a cylindrical impactor. An algorithm for processing pressure and acceleration graphs has been implemented in order to obtain tolerance curves. A specialized modular program has been created for the automated processing of calculation results and the output of the main results. 42 numerical tests were carried out simulating the entry of a steel ball into each of 21 zones for power engineers of 40 and 80 J. According to the results of the tests for each organ, pressure and acceleration tolerance curves were obtained, animations of the behavior of organs under shock were created, visualization of the pressure field propagation in organs was obtained torso.


2009 ◽  
Vol 46 (04) ◽  
pp. 993-1004
Author(s):  
S. Ma ◽  
M. Molina

We introduce a class of discrete-time two-sex branching processes where the offspring probability distribution and the mating function are governed by an environmental process. It is assumed that the environmental process is formed by independent but not necessarily identically distributed random vectors. For such a class, we determine some relationships among the probability generating functions involved in the mathematical model and derive expressions for the main moments. Also, by considering different probabilistic approaches we establish several results concerning the extinction probability. A simulated example is presented as an illustration.


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