The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics. Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points. Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.
W porządkowaniu liniowym obiektów wielocechowych najpopularniejszą metodą doprowadzania danych do porównywalności jest transformacja zmiennych do przedziału [0;1] z jednoczesną zamianą destymulant na stymulanty. W tym przekształceniu wykorzystuje się zaobserwowane najmniejsze i największe wartości zmiennych. Jeżeli występują wartości odstające, lub rozkład zmiennej jest bardzo asymetryczny to w efekcie mamy do czynienia ze sztucznym ważeniem tej zmiennej. Przy asymetrii prawostronnej zmienna sztucznie zyskuje na zaznaczeniu, a przy lewostronnej – traci. W pracy zaproponowano nową, iteracyjną metodę porządkowania obiektów wielocechowych, która pozwala na ominięcie omówionej niedogodności metody klasycznej. Dalsze pozycje w rankingu wyznacza się kolejno, po jednej w każdej iteracji, a przyporządkowany obiekt jest eliminowany ze zbioru, w którym poszukujemy obiektu następnego w kolejności. Taka procedura wymagała również zaproponowania nowego sposobu wyznaczania wskaźnika agregatowego.
The paper deals with the effect of microstructure diversified by means of variable cooling rate on service properties of AlSi7Mg cast alloy refined traditionally with Dursalit EG 281, grain refining with titanium-boron and modified with sodium and a variant of the same alloy barbotage-refined with argon and simultaneously grain refining with titanium-boron and modified with strontium. For both alloy variants, the castings were subject to T6 thermal treatment (solution heat treatment and artificial aging). It turned out that AlSi7Mg alloy after simultaneous barbotage refining with argon and grain refining with titanium-boron and modified with strontium was characterised with lower values of representative microstructure parameters (SDAS – secondary dendrite arm spacing, λE, lmax) and lower value of the porosity ratio compared to the alloy refined traditionally with Dursalit EG 281 and grain refining with titanium-boron and modified with sodium. The higher values of mechanical properties and fatigue strength parameters were obtained for the alloy simultaneously barbotagerefined with argon and grain refining with titanium-boron and modified with strontium.
The cooling rate is one of the main tools available to the process engineer by means of which it is possible to influence the crystallisation process. Imposing a desired microstructure on a casting as early as in the casting solidification phase widens significantly the scope of technological options at disposal in the process of aluminium-silicon alloy parts design and application. By changing the cooling rate it is possible to influence the course of the crystallisation process and thus also the material properties of individual microstructure components. In the study reported in this paper it has been found that the increase of cooling rate within the range of solidification temperatures of a complex aluminium-silicon alloy resulted in a decrease of values of the instrumented indentation hardness (HIT) and the instrumented indentation elastic modulus (EIT) characterising the intermetallic phase occurring in the form of polygons, rich in aluminium, iron, silicon, manganese, and chromium, containing also copper, nickel, and vanadium. Increased cooling rate resulted in supersaturation of the matrix with alloying elements.
The paper presents results of metallographic examination of faults occurring in the course of founding thin-walled cast-iron castings in furan resin sand molds. A non-conformance of the scab type was Observed on surface of the casting as well as sand buckles and cold shots. Studied the chemical composition by means of a scanning electron microscope in a region of casting defects: microanalysis point and microanalysis surface. Around the observed defects discloses high concentration of oxides of iron, manganese and silicon. A computer simulation of the casting process has been carried out with the objective to establish the cause of occurrence of cold shots on casting surface. The simulation was carried out with the use of NovaFlow & Solid program. We analyzed the flowing metal in the mold cavity. The main reason for the occurrence of casting defects on the surface of the casting was gating system, which caused turbulent flow of metal with a distinctive splash stream of liquid alloy.
The paper concerns evaluation of the coefficient of friction characterising a friction couple comprising a commercial brake disc cast of flake graphite grey iron and a typical brake pad for passenger motor car. For the applied interaction conditions, the brake pressure of 0.53 MPa and the linear velocity measured on the pad-disc trace axis equalling 15 km/h, evolution of the friction coefficient μ values were observed. It turned out that after a period of 50 minutes, temperature reached the value 270°C and got stabilised. After this time interval, the friction coefficient value also got stabilised on the level of μ = 0.38. In case of a block in its original state, stabilisation of the friction coefficient value occurred after a stage in the course of which a continuous growth of its value was observed up to the level μ = 0.41 and then a decrease to the value μ = 0.38. It can be assumed that occurrence of this stage was an effect of an initial running-in of the friction couple. In consecutive abrasion tests on the same friction couple, the friction coefficient value stabilisation occurred after the stage of a steady increase of its value. It can be stated that the stage corresponded to a secondary running-in of the friction couple. The observed stages lasted for similar periods of time and ended with reaching the stabile level of temperature of the disc-pad contact surface.
Image sequences, in particular digital video sequences, are characterised by the features which result in their high potential as measurement data. However, as early as at the stage of visual assessment of digital film images, originating, in particular, from amateur cameras, occurrence of some deformations may be observed, which may highly influence the results of measurements performed using these images; such deformations differ from deformations occurred in the case of static photographic images. It results both, by the method of image recording, using an electronic shutter and interlaced or progressive scanning, as well as the method of file recording and compression. It is worth to notice the systematic nature of such deformations, which highly depend on mutual motions of a camera and recorded objects. The objective of presented research works was to develop the mathematical description of image deformations, as a function of motion parameters. This would allow for adaptation of the camera calibration process to the demands of sequential imaging, as well as for modification of algorithms of measurements using self-calibration, and, as a result, minimisation of deformations. Another objective was to analyse the influence of deformations, typical for digital film images, on the results of measurements performed using these images, by means of series of experiments, which were based on multiple calibration of static and a moving camera, also with the use of a spatial test field. The first part was made by developing formulas based on some geometric relations, using some simplifications. On the stage of experimental research a certain degree of compatibility of experimental results and theoretical assumptions were confirmed.
The paper is an attempt at reviewing the classical theory of externalities and club goods in the new context of flow economy and network relations, as well as the role of human capital connected with high quality surroundings (urban environment), which is a catalysing factor, and allows the formation of new resources and new competitive advantages for cities and busiensses.
State Urban Policy – concept, Institutional scope and structure in integrative management of the development. The management of space, as a common good, closely linked with economic and social development in Poland – meets a number of barriers. One of the major barriers is flawed and inefficient system of spatial planning and the lack of explicit national urban policy. The causes of this situation are manifold and complex. There is a week understanding that spatial planning has regulatory function and that is a main measure of intervention in inefficient – by its nature – market mechanism of real estate development and location of new construction objects. The existing in Poland since 2015 formal document under the title “National City Policy” is in fact the part of cohesion policy. It formulates only very soft policy recommendations concerning spatial development which are identified in different cities and their functional areas, whereas financial measures go separately through sectoral programs. In the article author consider the future place of national urban policy in integrative system of development policy which combine economic, social and build environmental dimensions. Than he analyzes the relationship between national spatial policy and the urban polices at the national and local level. Finally he presents some general conclusions and recommendations. According to the author, because of complexity of the issues and challenges, the detailed formulation of state urban policies and its implementation must lie within the competence of a strong governmental institution (responsible for research, monitoring and evaluation, elaboration of visions and scenarios in a broad global context). The primary partner in the state urban policy, co-responsible for its success, should be adequately, provincial and local governments. Through the cooperation of state and territorial authorities, is the most strongly manifested multilevel model of “public governance”. The special role belongs to the local authorities due to their assigned competence in creation of local by law in respect of land use and building allocation. Efficient urban policy must have two dimensions; horizontal and territorial. Horizontal domain should belong to the state (national planning, passing the law, systemic intervention, etc.). Territorial dimension should belong first of all to local urban policies but formulated and implemented within the framework and measures defined by national spatial policy and operational state urban policies.