The influence of applied heat-treatment on in 718 fatigue life at three point flexural bending

The Inconel alloy 718 is an iron-nickel based superalloy with a working temperature up to 650 °C. Presented phases such as γ\u27\u27 (Ni3Nb), γ\u27 (Ni3Al), and δ (delta – Ni3Nb) are responsible for the alloy\u27s unique properties. The δ – delta phase is profitable when situated at grain boundaries in small quantities due to increasing fatigue life. However, at temperatures close to 650 °C the γ\u27\u27 transforms to δ – delta and causes a decrease in fatigue life. Heat-treatment (800°C/ for 72 hours) and its influence on fatigue life are discussed in this paper. Fatigue tests were carried out at room temperature. After the tests we plotted the S-N curves for both stages. SEM (Scanning Electron Microscopy) fractography was carried out as well

Low and high frequency fatigue tests of nodular cast irons

The paper deals with the comparison of fatigue properties of nodular cast iron at low and high frequency cyclic loading. The specimens from three melts of nodular cast iron with different microstructure and mechanical properties were used for experiments. Fatigue tests were carried out at low and high frequency sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C). Low frequency fatigue tests were carried out using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz; high frequency fatigue tests were carried out using the ultrasonic fatigue testing device KAUP-ZU at frequency f ≈ 20 kHz

Структура полицейских наук в Словакии

The subject. The authors create an instrumental apparatus that saturates existing and emerging data needs in the theory constituting process and thus create preconditions for police practice development.The methodology. The research is based on the content analyses of final research reports, the object of which is police proceedings and the subject is police reality,The purpose. The authors substantiate the following hypothesis. The source of the development of knowledge in police practice and the development of police theory is a permanent solution to the philosophical contradiction between police theory and police practice, with police practice being the defining aspect of this contradictory unity. The need and areas of scientific knowledge of activities in the police proceedings structure are therefore determined by police practice.The main results. By verifying police practice, the authors confirm the necessary obligatory interaction between theory and practice, which is predominantly determined by the achieved research outputs and their acceptance. At the same time, they respect that systematically processed knowledge from applied research can show the character of a theory. In accordance with their knowledge, consisting of a system of knowledge presented by the achieved outputs from scientific research, evaluation and explanation of phenomena registered in the purposeful implementation of activities in the structure of police proceedings (research object). The term police action can be understood as a synthetic term for a holistic grasp of the police activity and its bodies. The activity of police and security authorities means: a special form of professional service for the state, self-governing as well as commercial organizations and, last but not least, citizens. It contains a set of executive, organizational, management and other activities that have the character of official interventions, official acts, other official activities and other measures. They are carried out in accordance with the rule of law and ethical principles of civil democratic society, preventive and, where necessary, repressive methods of police work. Their aim is to protect the fundamental human rights of citizens and society from crime and other anti-social activities. They define the identity of these phenomena through the subject (optics) of research, systematically defining the police reality by the process parameters, their determinants and constructs of specific police activities. In the Slovak Republic, the authors of this paper participate in the performance of tasks related to the constitution of police sciences. The outputs of applied research offer a system of scientific knowledge about police reality. With the dialectical approach, in relation to the examined activities in the structure of police proceedings, they define the reasons related to the assumption of the existence of links among the elements of police reality, or they reveal their objective absence. By identifying systems, the authors create a model of these purposefully implemented activities with properties characterizing their behaviour. At the same time, they respect that the strategic form of the parameters of this model is expressed by the achieved set intentions and goals of certain specific activities. Determining them is a concentrated expression of this will. The basic context in their work (participation in the process of constituting police sciences), determining the meaning and mission, is a specific subject accepted by them. This is the police reality, an objective fact that the theory of police sciences examines and uses to explain existing and emerging objects. Therefore, their activity in the process of constituting police sciences corresponds to changes in social processes. When creating their instruments (conceptual system, categories, theoretical models, forms of thinking), they combine it with the explanation of new approaches related to the development and advancement of policing processes, characterized by openness and possibilities of social control in their purposeful implementation. This confirms that this process forms a system. Its design shows relative stability and closeness. They do not include any inputs in its content, just those that are foreseen and anticipated. In this context, they realize that the interdisciplinary of concepts enriches the view of constituted police science. For the police sciences , the abstractness and generality of statements from other scientific disciplines is not a starting point, but already the result of research into specific systems (disposition of knowledge), significantly contributing to increase effectiveness of their scientific work. In the conditions of the Slovak Republic, the police sciences are constituted as practical, social and security sciences. Therefore, the authors of this paper accept that the theoretical and methodological development of police sciences requires them to be confronted and independently dealt with the current state in the theory and methodology of science in the early 21st century, to be sensitive to the current development of the overall scientific atmosphere and independently and critically. In this process, the meaningfulness of their scientific work is evident. This corresponds to the registered needs for the transfer of scientific knowledge into police practice.Conclusions. From these findings it is clear that in the current stage of development of the Slovak Republic, the process of constituting police sciences forms a structured system with to the point management. Its successful completion is also determined by the results of a constructive discussion, the authors participated in with this presented knowledge.Рассмотрены полицейские науки, которые согласно словацкой доктрине изучают полицейскую деятельность и подразделяются на практические, социальные и науки о безопасности. Отмечено, что деятельность полиции и органов безопасности означает особую форму профессиональной службы в интересах государства, органов местного самоуправления, а также коммерческих организаций и, что не менее важно, граждан. Такая деятельность включает комплекс принудительных, организационных, управленческих и других актов, выраженных в форме официальных действий, решений, мероприятий и других мер. Они должны осуществляться в соответствии с верховенством закона и этическими принципами гражданского демократического общества, посредством превентивных и, при необходимости, репрессивных методов работы полиции

Low and high frequency fatigue tests of nodular cast irons

The paper deals with the comparison of fatigue properties of nodular cast iron at low and high frequency cyclic loading. The specimens from three melts of nodular cast iron with different microstructure and mechanical properties were used for experiments. Fatigue tests were carried out at low and high frequency sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C). Low frequency fatigue tests were carried out using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz; high frequency fatigue tests were carried out using the ultrasonic fatigue testing device KAUP-ZU at frequency f ≈ 20 kHz

Influence of laser surface hardening on corrosion properties of Al-Zn-Si cast alloy

This work is focused on the effect of the laser surface treatment (laser power 50 and 80 W) on microstructure and corrosion properties of self-hardened AlZn10Si8Mg cast alloy used for engine and vehicle constructions. The electrochemical impedance spectroscopy (EIS) technique and Nyquist plots in a 1M NaCl test solution at 20 °C were carried out. A detailed corrosion study showed that corrosion resistance samples with laser layer were marginally less; probably the presence of chloride ions significantly damaged the Al2O3 film and caused the formation of NaAlO2

Fatigue behaviour of synthetic nodular cast irons

The paper shows the influence of charge composition on microstructure, fatigue properties and failure micromechanisms of nodular cast irons. The additive of metallurgical silicon carbide (SiC) in analysed specimens increases the content of ferrite in the matrix, decreases the size of graphite and increases the average count of graphitic nodules per unit of area. Consequently, the mechanical and fatigue properties of nodular cast iron are improved. The best fatigue properties (fatigue strength) were reached in the melt which was created by 60 % of steel scrap and 40 % of pig iron in the basic charge with SiC additive

Influence of laser surface hardening on corrosion properties of Al-Zn-Si cast alloy

This work is focused on the effect of the laser surface treatment (laser power 50 and 80 W) on microstructure and corrosion properties of self-hardened AlZn10Si8Mg cast alloy used for engine and vehicle constructions. The electrochemical impedance spectroscopy (EIS) technique and Nyquist plots in a 1M NaCl test solution at 20 °C were carried out. A detailed corrosion study showed that corrosion resistance samples with laser layer were marginally less; probably the presence of chloride ions significantly damaged the Al2O3 film and caused the formation of NaAlO2

Preventive Effects of Flavonoids on Alloxan-Induced Diabetes Mellitus in Rats

The aim of the present study was the evaluation of possible protective effects of quercetin and chrysin in experimental alloxan-induced diabetes in rats. Alloxan was injected at a single dose of 60 mg/kg (into the tail vein) for diabetes induction. Quercetin (50 and 100 mg/kg; orally) and chrysin (50 and 100 mg/kg; orally) were administered daily for 3 days prior and 7 days after alloxan injection. Alloxan induced a significant increase of glycaemia (p p p p < 0.01). On the other hand, glycosuria was increased in all groups of animals receiving alloxan. We suggest that the protective effect of the used flavonoids in experimental diabetes mellitus may be related to their antioxidative/chelatory properties. Increased glycosuria indicated that inhibition of renal glucose reabsorption may also play a role in the hypoglycaemic effect of both flavonoids

Two-loop QED radiative corrections to the decay pi0 -> e+ e- : The virtual corrections and soft-photon bremsstrahlung

This paper is devoted to the two-loop QED radiative corrections to the decay pi0 -> e+ e-. We compute the virtual corrections without using any approximation and we take into account all the relevant graphs with the inclusion of those omitted in the previous approximative calculations. The bremsstrahlung is then treated within the soft photon approximation. We concentrate on the technical aspects of the calculation and discuss in detail the UV renormalization and the treatment of IR divergences within the dimensional regularization. As a result we obtain the O(alpha^3 p^2) contribution in closed analytic form. We compare the exact two-loop results with existing approximative calculations of QED corrections and find significant disagreement in the kinematical region relevant for the KTeV experiment.Comment: 48 pages plus 4 appendices (72 pages total), 26 figures; v3: new chapter 9 with phenomenological discussion added, references added, minor typos corrected; coincides with the journal versio