In this paper an attempt to determine the relationship between the electrical resistivity and the tensile strength and hardness of cast iron of
carbon equivalent in the range from 3.93% to 4.48%. Tests were performed on the gray cast iron for 12 different melts with different
chemical composition. From one melt poured 6 samples. Based on the study of mechanical and electro-resistive determined variation
characteristics of tensile strength, hardness and resistivity as a function of the carbon equivalent. Then, regression equations were
developed as power functions describing the relationship between the resistivity of castings and their tensile strength and hardness. It was
found a high level of regression equations to measuring points, particularly with regard to the relationship Rm=f(ρ). The obtained
preliminary results indicate the possibility of application of the method of the resistance to rapid diagnostic casts on the production line,
when we are dealing with repeatable production, in this case non variable geometry of the product for which it has been determinated
before a regression equation.
The paper describes the influence of graphite shape, size and amount to electrical properties of different cast irons. Experiments of electrical resistivity measurements were conducted during solidification of four different melts in different time intervals from melt treatment by inoculation and nodularization. Metallographic analyses were made in order to determine the shape, size, distribution and amount of graphite and correlate results with electrical resistivity measurements. It was found out that nodular graphite is giving the lowest electrical resistivity and is decreased during solidification. Electrical resistivity of lamellar cast iron is increased during solidification since lamellas interrupt metal matrix severely There is no significant difference in resistivity of vermicular cast iron from nodular cast iron. Smaller size of graphite and lower amount of graphite and higher amount of metal matrix also decrease resistivity.
A revision of the standard approach to characterization of thin-semiconductor-layer Hall samples has been proposed. Our results show that simple checking of I(V) curve linearity at room temperature might be insufficient for correct determination of bias conditions of a sample before measurements of Hall effect. It is caused by the nonlinear behaviour of electrical contact layers, which should be treated together with the tested layer a priori as a metal-semiconductor-metal (MSM) structure. Our approach was examined with a Be-doped p-type InAs epitaxial layer, with four gold contacts. Despite using full high-quality photolithography a significant asymmetry in maximum differential resistance (Rd) values and positions relative to zero voltage (or current) value was observed for different contacts. This suggests that such characterization should be performed before each high-precision magneto-transport measurement in order to optimize the bias conditions.
While the number of forced migrants moving out of conflict-ridden or otherwise troubled regions into rela-tively stable and safe parts of the world is higher than ever, the countries of destination are increasingly trying to prevent migrants from reaching their territories. Given the scale of forced displacement and current trends of tightening immigration policies, it should be expected that tragedies at the borders, similar to that recently witnessed in Europe, will become the norm rather than the exception and that new discourses and practices will continue to emerge, transforming territorial borders in various parts of the world into highly conflictual and politicised ‘borderspaces’. This article is a contribution to the understanding of borders through a case study of the recent policy of ‘closed doors’ that Poland has adopted towards Russia’s North Caucasus asylum seekers at the country’s eastern border with Belarus, preventing them from entering the territory and claiming protection. It demonstrates that, through the process of ‘bordering’, power is no longer exercised only by the border guards at the crossing point in Terespol from where asylum seekers are being returned and that it is increasingly to be found in social practices that occur on both sides of the border, away from the clearance points. The article examines the various practices of resistance undertaken by the asylum seekers and other actors on several different levels in response to the changed reality at the border. It also analyses the meanings and discourses developed by Polish state actors in order to legitimise restrictive migration policies.
The process of social remitting is complex and multilayered, and involves numerous social actors that at each stage face several choices. By definition, the process of socially remitting ideas, codes of behav-iour and practices starts with the migrants themselves and their social context in the destination country. This paper focuses on the as yet unexplored issue of resistance performed and articulated by migrants confronted with potential change influenced by social remittances and the generalised process of diffu-sion. Faithful to the understanding of social remittances as ultimately a process where individual agency is the crucial determinant, the article follows the ideas, practices and values travelling across the trans-national social field between Britain and various localities in Poland. Resistance to change and new ways of doing things is a continuous dialogical process within one culture’s power field, which is un-derstood here in anthropological terms as a porous, open-ended field of competing meanings and dis-courses. Notions of bifocality, infra-politics of power relations and resistance are an important aspect of remittances and their reinterpretations, and resistance to social remittances by migrants, both in their destinations and in their communities of origin, is a crucial component of the whole process without which our understanding of remittances is incomplete.
The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.