Application of conversion model for designing hydrodynamic pumps in turbine mode

ArticleThe use of the smallest water resources has been coming again to the centre of interest in recent years. A water engine – turbine, is the heart of these power plants. This is usually the highest expense for the investor, in terms of cost. The effort is therefore to seek investment less demanding alternatives. One of them is the use of hydrodynamic pumps in reverse turbine operation. This paper provides a methodology for conversion of parameters of the smallest power pumps (micro hydro sites) to turbine operation. The conversion model is based on the results of experimental research at the author's workplace and is suitable for pumps with low specific speeds and outputs. The pump design process for turbine mode is complemented by a practical example for a specific deployment site. This example also serves to verify the accuracy of the conversion model

Determination of conversion relations for the use of small hydrodynamic pumps in reverse turbine operation

ArticleIn small - scale hydropower, hydrodynamic pumps used in reverse mode are an important economical alternative to conventional water turbines. E fficient utilisation of these devices however requires taking into account all the specifics of the reverse pump operation and optimise the pump design for maximum utilisation of the hydro - technical potential of the deployment site. The article compares ex isting conversion models, describes initial theoretical assumptions and determines new conversion relations for the design of pumps as turbines (PAT) for the lowest power and specific speed category. The validity of the conversion relations is experimental ly verified on a hydraulic test circuit with a radial centrifugal pump tested in both pump and turbine operation modes. The results of the verification of the new conversion relations proved better correspondence to reality within this category of machines than that reported by the previously used conversion models

Nondestructive Damage Detection Based on Modal Analysis

Three studies of damage identification and localization based on methods using experimentally estimated modal characteristics are presented. The results of an experimental investigation of simple structural elements (three RC-beams and three RC-slabs) obtained in the laboratory are compared with the results obtained on a real structure (a composite bridge – a concrete deck supported by steel girders) in situ.

Damage Evolution During Fatigue in Structural Materials

AbstractEarly stages of damage evolution in cyclic loading are described and discussed. The importance of the role of cyclic plastic strain in damage evolution is emphasized and the relation between stress and strain in cyclic straining is clarified. The principal stages of damage evolution in fatigued crystalline structural material are identified. The basic characteristic and theories of fatigue crack initiation are sketched and confronted with experimental observations. Early fatigue crack growth is characterized and quantitatively described. The relation between the growth of short cracks and fatigue life in the form of Manson-Coffin law is established

CLASSIFICATIONS OF INNOVATIONS: APPROACHES AND CONSEQUENCES

Abstract TABAS, J., BERANOVÁ, M., POLÁK, J.: Classifi cation of innovations: approaches and consequences. Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 2, pp. 399-406 Currently, innovations are perceived as a life blood of businesses. The inevitable fact is that even if the innovations have a potential to transform the companies or all the industries, the innovations are high risky. Even though, the second fact is that in order to companies' development and their survival on the markets, the innovations have become the necessity. In the theory, it is rather diffi cult to fi nd a comprehensive defi nition of innovation, and to settle down a general defi nition of innovation becomes more and more diffi cult with the growing number of domains where the innovations, or possible innovations start to appear in a form of added value to something that already exist. Defi nition of innovation has come through a long process of development; from early defi nition of Schumpeter who has connected innovation especially with changes in products or production processes, to recent defi nitions based on the added value for a society. One of possible approaches to defi ne the content of innovation is to base the defi nition on classifi cation of innovation. In the article, the authors provide the analysis of existing classifi cations of innovations in order to fi nd, respectively in order to defi ne the general content of innovation that would confi rm (or reject) their defi nition of innovation derived in the frame of their previous work where they state that innovation is a change that leads to gaining profi t for an individual, for business entity, or for society, while the profi t is not only the accounting one, but it is the economic profi t. The article is based especially on the secondary research while the authors employ the method of analysis with the aim to confront various classifi cation-based defi nitions of innovation. Then the methods used are especially comparison, analysis and synthesis. added value, classifi cation of innovations, competitive advantage, defi nition of innovation, innovatio

Evaluation of transgenic Prunus domestica L., clone C5 resistance to Plum pox virus

Plum pox virus (PPV) is one of the most devastating diseases of Prunus species. Since few sources of resistance to PPV have been identified, transgene-based resistance offers a complementary approach to developing PPV-resistant stone fruit cultivars. C5, a transgenic clone of Prunus domestica L., containing the PPV coat protein (CP) gene, has been described as highly resistant to PPV in greenhouse tests, displaying characteristics typical of post-transcriptional gene silencing (PTGS). Moreover, C5 trees exposed to natural aphid vectors in the field remained uninfected after 4 years while susceptible transgenic and untransformed trees developed severe symptoms within the first year. In our study, a high and permanent infection pressure of PPV was provided by bud grafting of inoculum in the field trial of clone C5 conducted in the Czech Republic, in which PPV-infected and healthy control trees were used. Moreover, trees with combined inoculations by PPV, ACLSV and PDV were also used in the trial. The presence of the viruses throughout the tree tissues, the relative titre of the viruses and symptoms on C5 trees have been monitored over the years. The resistance stability of C5 clones under permanent infection pressure is discussed.Keywords: PPV, C5, resistance, real-time PC

Cyclic Plastic Response and Damage in Materials for High Temperature Applications

In this contribution, the methods allowing to study the sources of cyclic stress and early fatigue damage at room and elevated temperatures are presented and used to reveal details of the mechanisms of cyclic plastic straining and fatigue damage evolution in austenitic steels and nickel superalloys.Анализ кривых гистерезиса показывает, что при различной температуре имеют место характерные изменения зависимости между циклическими пластическими деформациями и напряжениями в нержавеющей стали и суперсплавах. Соответствующее изменение микрорельефа поверхности при мягком нагружении зафиксировано с помощью сканирующей и томографической электронной микроскопии с высоким разрешением. Проанализированы механизмы локализации циклической деформации, образования поверхностного микрорельефа, инициирования усталостных трещин и роста коротких трещин.Аналіз кривих гістерезису показує, що за різних температур відбуваються характерні зміни залежності між циклічними пластичними деформаціями і напруженнями в нержавіючій сталі і суперсплавах. Відповідні зміни мікрорельєфу поверхні за м’якого навантаження зафіксовано за допомогою сканувальної і томографічної електронної мікроскопії з високим розділенням. Проаналізовано механізми локалізації циклічної деформації, утворення поверхневого мікрорельєфу, ініціювання тріщин від утомленості і росту коротких тріщин

Plane waves in a relativistic homogeneous and isotropic elastic continuum

Propagation of gravitational and acoustic plane waves in a flat universe filled with a general relativistic, homogeneous and isotropic, spatially flat continuum is studied. The continuum is described by analogues of nonrelativistic characteristics, namely energy per particle, pressure and Lame coefficients, and considered in the comoving proper-time gauge. For all modes with the given wave covector, differential equations governing the time dependence of the amplitudes are derived. In particular, longitudinal acoustic waves are described, in analogy with the nonrelativistic theory, by two coupled first-order equations. As an example, plane waves in a stiff ultrarigid continuum are considered.Comment: 12 pages, 1 figure; section 4 extended, minor changes elsewhere, author adde

Snakes Represent Emotionally Salient Stimuli That May Evoke Both Fear and Disgust

Humans perceive snakes as threatening stimuli, resulting in fast emotional and behavioral responses. However, snake species differ in their true level of danger and are highly variable in appearance despite the uniform legless form. Different snakes may evoke fear or disgust in humans, or even both emotions simultaneously. We designed three-step-selection experiments to identify prototypical snake species evoking exclusively fear or disgust. First, two independent groups of respondents evaluated 45 images covering most of the natural variability of snakes and rated responses to either perceived fear (n = 175) or disgust (n = 167). Snakes rated as the most fear-evoking were from the family Viperidae (Crotalinae, Viperinae, and Azemiopinae), while the ones rated as the most disgusting were from the group of blind snakes called Typhlopoidea (Xenotyphlopinae, Typhlopinae, and Anomalepidinae). We then identified the specific traits contributing to the perception of fear (large body size, expressive scales with contrasting patterns, and bright coloration) and disgust (thin body, smooth texture, small eyes, and dull coloration). Second, to create stimuli evoking a discrete emotional response, we developed a picture set consisting of 40 snakes with exclusively fear-eliciting and 40 snakes with disgust-eliciting features. Another set of respondents (n = 172) sorted the set, once according to perceived fear and the second time according to perceived disgust. The results showed that the fear-evoking and disgust-evoking snakes fit mainly into their respective groups. Third, we randomly selected 20 species (10 fear-evoking and 10 disgust-evoking) out of the previous set and had them professionally illustrated. A new set of subjects (n = 104) sorted these snakes and confirmed that the illustrated snakes evoked the same discrete emotions as their photographic counterparts. These illustrations are included in the study and may be freely used as a standardized assessment tool when investigating the role of fear and disgust in human emotional response to snakes

Media reporting: facts, nothing but facts?

This IRIS Special examines the principles of accuracy, objectivity and fairness in news and current affairs coverage by European media organisations. The issue is explored from a number of perspectives, including from that of media organisations, the Council of Europe, the European Court of Human Rights, member states, and judicial and regulatory bodies. It also includes chapters on a number of Council of Europe member states, discussing the regulatory framework that impacts upon this issue, including national legislation, case law, regulatory codes, and regulatory enforcement