- Détails du magazine
- Format
- Magazine
- eISSN
- 2256-0939
- Première publication
- 30 Aug 2012
- Période de publication
- 2 fois par an
- Langues
- Anglais

#### Chercher

- Accès libre

X Baltic-Nordic Agrometrics Conference: Mathematics and Statistics for the Sustainable Development

Pages: 2 - 3

#### Résumé

#### Résumé

Since 2014, there have been admission tests in mathematics for applicants to the Estonian University of Life Sciences for Geodesy, Land Management and Real Estate Planning; Civil Engineering; Hydraulic Engineering and Water Pollution Control; Engineering and Technetronics curricula. According to admission criteria, the test must be taken by students who have not passed the specific mathematics course state exam or when the score was less than 20 points. The admission test may also be taken by those who wish to improve their state exam score. In 2016, there were 126 such applicants of whom 63 took the test. In 2015, the numbers were 129 and 89 and in 2014 150 and 47 accordingly. The test was scored on scale of 100. The arithmetic average of the score was 30.6 points in 2016, 29.03 in 2015 and 18.84 in 2014. The test was considered to be passed with 1 point in 2014 and 20 points in 2015 and 2016. We analyzed test results and gave examples of problems which were solved exceptionally well or not at all.

#### Mots clés

- teaching mathematics
- admission test
- mathematics education
- basic competence in mathematics

- Accès libre

Application of Statistical Methods in the Analysis of Sentence Structure

Pages: 10 - 13

#### Résumé

The goal of this research is to explore sentence structures expressed by parts of speech. Due to a small amount of data, a problem of

#### Mots clés

- sentence structure
- Zipf’s law
- coding

#### Résumé

In this article, common test results over the years 2000 – 2016 are analysed. The test questions for new entrants were based on secondary school mathematics. The students took the test in the first lesson of the higher mathematics course. The test results were analysed by years, by tasks and by specialities, and their differences were found. The test results’ dependence on state-exams score was studied and other types of dependence were looked at.

It was found that the test score has a strong correlation with a state-exam but with high school mathematics mark and with later higher mathematics course marks has very weak correlation. During these 16 years, the questions that have been the most difficult for students have not changed. The highest test scores were found among students who had chosen the most popular specialities (with the highest competition).

#### Mots clés

- common test in mathematics
- teaching mathematics
- basic competence in mathematics

- Accès libre

The Modeling of Nitrogen Mass Transport in CoCr Alloys

Pages: 19 - 26

#### Résumé

The kinetics of plasma nitriding of CoCr alloy below temperatures of nitrides formation and mechanisms of nitrogen penetration are analyzed by proposed kinetic modeling in this article. Proposed nitrogen diffusion model is based on the trapping – detrapping (TD) model and developed taking into account the effect of the concentration dependent diffusivity of nitrogen, nitrogen adsorption on the surface of alloy and surface swelling process. The model indicates the influence of chromium atoms to nitrogen atoms diffusivity. The model consists of time and depth dependent diffusion, which is described by a partial differential equation, and it is solved by using Crank – Nicolson finite difference method. By fitting of experimental nitrogen depth profiles, it is shown that nitrogen diffusion coefficient varies with nitrogen concentration according to Einstein-Smoluchowski relation. Nitrogen depth profiles in plasma nitrided medical grade CoCr alloy (ISO 5831 – 12) at

#### Mots clés

- Crank – Nicolson method
- kinetic modeling
- CoCr plasma nitriding

- Accès libre

Mathematical Estimation of Mobility of Peasants in Vilnius Governorate in the 19^{th} Century

^{th}Century

Pages: 27 - 33

#### Résumé

The article deals with the problem of local mobility of peasants in Vilnius Governorate in the nineteenth century. To solve the problem, statistical-demographical data from the “Memory Books” permanently issued by the Tsarist Russian government was used. Pure demographic data brings little information, unless it is properly mathematically processed. Such processing leads to the discovering of new proportions concerning inhabitants, villages and farmsteads. Such proportions are related to the administrative territorial unit under investigation and show how many people reside in a farmstead and how many farmsteads are comprised in a village. In the course of time, numbers of villages and farmsteads change, and these numbers show the numbers of people taking part in local mobility of inhabitants. The higher are changes in villages and farmsteads, the higher is mobility of inhabitants.

#### Mots clés

- migration
- farmstead
- village

- Accès libre

Fault Diagnosis of Low-Power Three-Phase Induction Motor

Pages: 34 - 41

#### Résumé

An Induction motor reliability survey at an egg processing plant shows that almost 50% of the total motor failures are fan induction motors. Visual investigations of the faulty fan motors show that the main cause of the induction motor failure is air gap eccentricity. In this study, experimental tests are performed on a 1.1kW three-phase induction motor to detect air gap eccentricity and overheating of the induction motor. Heating tests show that end shield housing temperature reaches 100°C with blocked air flow from the fan, which can reduce the lifespan of the bearing. Dimension measurements of the end shield housing show that the dimensions of both tested motors back-end shields are larger than ISO tolerance grade limit. It leads to a loose fit between the housing and bearing, causing air gap eccentricity. Also, both motor back end shield housing has an out-of-round condition leading to an unbalanced magnetic pull. To detect the air gap eccentricity caused by too loose of a fit between housing bore and bearing, current Park’s vector approach is used. To measure three phase current, Hall Effect current transducers, a digital oscilloscope is used and

#### Mots clés

- induction motor
- air gap eccentricity
- Park’s vector
- stator current
- stator winding heating
- bearing housing

- Accès libre

The Characteristics of Extruded Faba Beans (Vicia faba L.)

Pages: 42 - 48

#### Résumé

Faba beans (

#### Mots clés

- faba beans
- extrusion
- protein
- starch
- wheat