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Fault diagnosis of low-power three-phase induction motor
2016
Gedzurs, A., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Engineering
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 Matlab software to process the measurement data. Results show that Park’s vector approach can be used to detect the air gap eccentricity caused by too loose a fit between bearing and housing. Therefore, the Park’s vector approach can be used to diagnose air gap eccentricity and analyse the type of the air gap eccentricity.
Afficher plus [+] Moins [-]Do social networks have effects on the risk attitude of commercial poultry farmers? Evidence from Southwest Nigeria
2017
Obayelu, O.A., University of Ibadan (Nigeria) | Olowe, O.O., University of Ibadan (Nigeria) | Faleye, T.G., University of Ibadan (Nigeria)
Poultry production decision setting is full of risk and imperfect information. Attitude towards risk is a measure of farmers’ willingness to take risks which is an important determinant in their production decisions. Strong social capital emanating from social networks can lead to efficient risk management strategies, thereby minimizing risks faced by the farmers. Therefore, the effects of social capital on the risk attitude of small-scale commercial poultry farmers in Oyo state were assessed. Data were collected from two hundred small-scale farmers and analysed using descriptive and inferential statistics, factorial analysis, multinomial logit and a two-stage least square. Results showed that 52.5%, 37.5% and 10% of the poultry farmers were risk averse, risk neutral and risk preferring, respectively. About 31.4% and 68.6% of the female and male farmers respectively were risk averse. Close to a fifth, a quarter and two-thirds of the risk averse, risk neutral and risk takers respectively contributed 21-30% of the decisions in the associations. Fourteen percent of the farmers belonged to homogeneous groups. The choice of being risk averse was affected by marital status, educational level, family size, percentage spent on poultry income and aggregate social capital. There was no reverse causality between risk attitude and social capital.
Afficher plus [+] Moins [-]Financial literacy of rural population as a determinant of saving behaviour in Kazakhstan
2017
Gaisina, S., Hochschule Stralsund (Germany). Business School | Kaidarova, L., Innovative Eurasian Univ., Pavlodar (Kazakhstan). Faculty of Economics
In rural Kazakhstan, the credit and insurance services are limited and the state support is weak. The main goal of this study is to contribute to the literature on financial literacy in emerging economies, namely, the effect of financial literacy on saving rates of rural population. Being well educated not always means to be financial literate and make efficient decisions regarding one’s own finance. People with a lower formal education level but with better experience in consuming financial products could be better prepared for making financial decisions including those related to savings. In this paper other socio-economic determinants of saving rates were taken into account, such as an income level, family size and an employment status. This research was carried out in Pavlodar region of Kazakhstan, and the data collection took place in spring 2014. In total, 405 households were surveyed. Results of the analysis show that if a respondent gives at least one correct answer, it positively affects the saving rates as well as one can observe that the higher the financial literacy level, the higher are the saving rates. Availability of state supported financial education programs for rural people will significantly contribute to the financial literacy improvement.
Afficher plus [+] Moins [-]Growth and yield of 15-year plantations of pine, spruce and birch in agricultural land
2017
Daugaviete, M., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Lazdins, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Lazdina, D., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Makovskis, K., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Daugavietis, U., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
The growth data and the potential returns from 15-year-old plantations of pine Pinus sylvestris L. (6 trial sites), spruce Picea abies Karst L. (9 trial sites) and silver birch Betula pendula Roth (13 trial sites), established in abandoned agricultural lands in a variety of soil types (sod calcareous, anthrosols, podzolic, podzols, gley, podzolic gley, alluvial), using the planting density 2,500 and 3,300 and also 5,000 trees/ha are analysed. For tree plantations in agricultural soils (alluvial sod-gley, gley-sod podzolic, sod-podzolic gley, typic podzol) at the survival of 80-98% the stock volume for 15-year pine is as high as 102-155 m**3haE−1 with the volume growth 5.72-8.94 m**3haE−1 per year; the same indices for spruce in agricultural soils (gley sod-calcareous, sodpodzolic, cultivated, sod-podzolic gley, alluvial sod-gley, base-unsaturated brown) are 75-98 m**3haE−1 and 10.26-15.76 m**3haE−1, respectively. For 15-year plantation birch the mentioned indices may vary from 61 to 169 m**3haE−1 and from 7.54 to 29.82 m**3haE−1 per year. The lowest volume growth (4.66 m**3haE−1 per year) is for birch in heavy clay soil (gleyic sod-podzolic), the highest (29.72-29.82 m**3haE−1 per year) – in cultivated soils and pseudogley soil. Plantation cultivation of pine, spruce and birch in agricultural lands may by the age of 15 years yield with a profit such forest products as pulpwood, fire wood and woody biomass. The gross income gained from first commercial thinnings of plantation pine, utilizing pulpwood, fire wood and logging residue biomass, may vary from 679-2267 EUR haE−1, for spruce the same indices are 1644-3272 EUR haE−1, for birch - 683-2188 EUR haE−1.
Afficher plus [+] Moins [-]Mathematics education problems and attempts to solve them in nowadays Lithuanian school
2017
Malaukyte, I., Aleksandras Stulginskis Univ., Akademija, Kaunas reg. (Lithuania). Centre of Mathematics, Physics and Information Technology
The decreasing number of the Lithuanian residents has strong impact on the educational system: the number of pupils is decreasing, the schools are getting closed. School is considered to be the provider of educational services, so it is necessary to search, how to preserve and attract clients – pupils. The growing competition induces search for distinctiveness among the schools. According to the theory of generations of William Strauss and Neil Howe, now we have to educate representatives of generation Z, who do not like violence, restrictions, want to be distinctive and are open to the world of technologies. The teacher faces the challenge when s/he wants to convey mathematical skills to these pupils. The profile teaching followed by training based on individual curricula provided more choices for the pupils. This freedom led to the dead-end of mathematical literacy and forced to return to a compulsory national final exam of Mathematics and to change the indexes for the persons entering studies of the first cycle and integrated studies. In the article, mathematics achievements and situation in schools in Lithuania as well as the measures taken to improve mathematical literacy in the country are described.
Afficher plus [+] Moins [-]Application of statistical methods in the analysis of sentence structure
2016
Piaseckiene, K., Siauliai Univ. (Lithuania). Faculty of Technology, Physical and Biomedical Sciences
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 sparse data has arisen, which was solved by recording the annotated sentences and considering a “framework” of a sentence made up from a verb and a noun, which was conditionally called a code. The code of a sentence is created by changing each word of a sentence by a symbol (letter or number) that encodes one or other property of that word as a constituent of the sentence. Zipf’s law describes sentences, encoded like that, rather well. If we ‘learn’ well to identify and analyze (annotate, translate, etc.) sentences of the simplest structure, we can automatically process quite a large part of text sentences. It is possible to identify at least 17% of sentences consisting of the simplest structure.
Afficher plus [+] Moins [-]Common diagnostic test results over the years
2016
Aruvee, E., Estonian Univ. of Life Sciences, Tartu (Estonia). Inst. of Technology
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).
Afficher plus [+] Moins [-]The modeling of nitrogen mass transport in CoCr alloys
2016
Petraitiene, A., Aleksandras Stulginskis Univ., Akademija, Kauno reg. (Lithuania). Centre of Mathematics, Physics and Information Technologies
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 T = 400 °C for 1, 4 and 20 hours calculated on the basis of this model are in good agreement with experimental nitrogen profiles. Furthermore, the swelling process is showed and analysed, derived the dependency of swelling rate on nitriding duration – the swelling rate is inversely proportional to the square root of nitriding duration. The obtained diffusion coefficient value and the swelling process rates satisfy the experimental data form Ref. The derived model explains physical processes during plasma nitriding and allows obtaining nitrogen depth profiles for any requisite nitriding duration.
Afficher plus [+] Moins [-]Mathematical estimation of mobility of peasants in Vilnius Governorate in the 19th century
2016
Kanisauskas, V., Siauliai Univ. (Lithuania). Faculty of Technology, Physical and Biomedical Sciences
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.
Afficher plus [+] Moins [-]Trends of Lithuanian cultural landscapes in the recreational territorial system of the Southeast Baltic Sea region
2018
Abromas, J., Klaipeda Univ. (Lithuania) | Grecevicius, P., Klaipeda Univ. (Lithuania) | Jankauskaite, A., Klaipeda Univ. (Lithuania) | Piekiene, N., Klaipeda Univ. (Lithuania)
1991-2017 the Southeast coast of the Baltic Sea area, Lithuania, Latvia and Kaliningrad Region of the Russian coastal habitats was very intense, often chaotic variety of recreational facilities and areas of privatization and urbanization. These processes significantly influenced the character of the recreational landscape of Palanga, Jurmala and other resorts and coastal areas, as well as the expression of the urban structure and architecture of seaside towns, Ventspils, Liepaja, Giruliai, Melnragė, Karklė, Šventoji, Curonian Spit and other settlements. After a quarter of a century, some tendencies of the recreational environment and the evolution of the cultural landscape identity can be noticed. Recently, several projects for the improvement of recreational infrastructure and architectural environments have been implemented in Lithuania with the assistance of the European Union Structural Funds. Unfortunately, the results of the projects are not always positive. The planning of coastal settlements is often overlooked by good long-term planning experience. This article analyses the impact of changes in the quality of the Lithuanian recreational territorial system in the South-Eastern Baltic and the region’s recreational potential. Palanga resort areas dominated by architectural chaos and recreational quality of the environment tended to deteriorate; especially experts poorly assessed the central Basanavičiaus Street. The changes in cultural landscapes are influenced by a whole range of methodological and practical factors: insufficiently effective research and modelling methods, unjustified privatization of state property, huge flows of individual automobiles, and faults in the formation of recreational greenery. Based on the research of the recreational system of the coastal region of the long-term seaside, it can be concluded that in recent years the quality of the environment of many coastal zones of Lithuania has lost important qualitative components, deteriorated the quality of public spaces and increased urban and architectural chaos
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