Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 21

Liczba wyników na stronie
first rewind previous Strona / 2 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 2 next fast forward last
EN
The article examines the theory and methods of analysing discursive forms of prejudice. Contemporary forms of prejudice are usually sensitive to the norms of political correctness. This is the reason why traditional measures of prejudice do not detect real attitudes. This article shows different approach, based on linguistics (van Dijk's critical discourse analysis, CDA), pragmatics (discriminatory speech acts), critical psychology (discursive social psychology) and social-cognition (linguistic intergroup bias, LIB). All of these perspectives present attitudes in argumentative context and examine intergroup uses of various forms of language. Finally, a case of modern Polish anti-Semitism is presented as a model issue for future application of presented methods.
2
Content available remote Influence of phyllosilicates 2:1 on structure of polymer nanocomposites
63%
EN
Purpose: To verify influence of nanoparticles on structure development. Design/methodology/approach: Injection moulding technologies including conventional and non-conventional ones. Findings: Stiffness of materials reinforced by MMT increased dramatically and expectations of most interesting results were concentrated close to 3 wt% of nano filling. Research limitations/implications: N-CIM technology allows control of development of the structure, limited by parameters of non-conventional injection system (time, pressures etc). Practical implications: PP/MMT nanocomposites are the promising engineering materials with wide range of application for household equipment, agriculture, packaging, medicine, automotive and building engineering. Originality/value: Induced shearing supports splitting of agglomerations, improve dispersion and intercalation of MMT. Better distribution improves significantly the strength.
3
63%
EN
Lightning strike protection is one of the crucial structural demands for aircraft composites addressed to their integrity and durability after a strike. When the lightning strikes a classic composite structure, the generated heat from electrical resistance as well as mechanical impulse resulting from acoustic wave propagation, might cause serious damage. Currently used metallic meshes and foils immersed in composite structures are effective in dissipating lightning charges and generated heat, however, such a solution has numerous disadvantages like increasing mass, problems with adhesion on the metal/polymer interface, complicated manufacturing technology, etc. Therefore, a fully organic conductive composite was developed as an alternative to current solutions. After a lightning strike the developed composite should not only effectively conduct and dissipate the electrical charge and generated heat, but also stop burning, which appears due to very high temperature values in the vicinity of the strike area. In this study, flammability tests were performed for a classic carbon fabric-reinforced composite as well as for the developed conductive polymer and carbon fabric-reinforced composite based on this polymer for comparative purposes, with measurement of the combustion temperature. The obtained results show that the developed composite is characterized by sufficiently low flammability, however, further studies will be focused on further improvement of flame retardancy.
PL
Ochrona odgromowa jest jednym z ważniejszych wymagań strukturalnych stawianych kompozytom lotniczym, odnoszących się do ich integralności oraz trwałości po uderzeniu pioruna. Gdy piorun uderza w klasyczne struktury kompozytowe, ciepło generowane z oporu elektrycznego oraz impuls mechaniczny, wynikający z propagacji fali akustycznej, może spowodować poważne uszkodzenia. Obecnie stosowane metalowe siatki i folie zatopione w strukturach kompozytowych są efektywne w rozpraszaniu ładunków piorunowych i generowanego ciepła, jednak takie rozwiązanie posiada szereg wad, jak wzrost masy, problemy z adhezją na granicy ośrodków metal/polimer, skomplikowana technologia wytwarzania itd. Dlatego został opracowany w pełni organiczny kompozyt przewodzący jako alternatywa dla obecnych rozwiązań. Po uderzeniu pioruna opracowany kompozyt powinien nie tylko efektywnie przewodzić i rozpraszać ładunek elektryczny i generowane ciepło, ale także zatrzymać płonięcie, powstające w wyniku bardzo dużych wartości temperatury w otoczeniu miejsca uderzenia. W niniejszej pracy w celach porównawczych badania palności przeprowadzono dla klasycznego kompozytu wzmacnianego tkaniną węglową oraz opracowanego polimeru i kompozytu wzmacnianego tkaniną węglową na jego bazie z pomiarem temperatury spalania. Otrzymane wyniki wykazały, że opracowany kompozyt charakteryzuje się stosunkowo niską palnością, jednak przyszłe badania będą skupione na dalszej poprawie ognioodporności.
EN
Purpose: Comparison of tribological properties of coated metal sheets. Design/methodology/approach: Samples were subjected to the variety of tests such as: pencil hardness test, resistance to scratching, bending test (T-test), paint adhesion, determining optimal method of measurement of the coating thickness. Findings: Polyurethane coatings are extremely hard and its strength exceeds strength of organic coating, but polyester coatings have proved to be superior in adhesion to the steel substrate. Micrometer method was found to be one of the best methods of measurement of the coating thickness. Research limitations/implications: Galvanized and coated materials can be successfully implemented for application which are cost effective and will not create a financial burden in the future. Practical implications: Wide range of application for industrial and household. Originality/value: Optimal configuration of the coatings properties in order to create best technological solutions.
PL
Zastosowanie techniki przyrostowej FDM pozwala na wytwarzanie poszczególnych elementów i ich złożeń w oparciu wyłącznie o przygotowany wirtualny model w środowisku CAD. Dzięki temu, technika FDM, jako technika szybkiego prototypowania znalazła szerokie zastosowanie w wielu segmentach przemysłu. Poprawne wykonanie elementu zależy od szeregu parametrów technologicznych, ustawianych przed rozpoczęciem operacji wytwarzania. Niewłaściwe zdefiniowanie tych parametrów może prowadzić do wad wytwarzania, m.in. szczeliny oraz przegrzanie wytwarzanych elementów, co negatywnie wpływa na ich jednorodność i wytrzymałość. W niniejszym artykule opisano wyniki badań eksperymentalnych dla próbek o różnym stopniu wypełnienia przy różnych rodzajach wypełnienia - liniowym i heksagonalnym. Przeprowadzone badania eksperymentalne obejmowały quasi-statyczną próbę rozciągania oraz analizę modalną, na podstawie której określono częstotliwości własne drgań oraz odpowiadające im postacie własne oraz współczynniki tłumienia modalnego. Na podstawie uzyskanych wyników możliwe było opracowanie zaleceń dotyczących parametrów wytwarzania elementów techniką przyrostową FDM.
EN
Using the additive FDM technique allows manufacturing of particular elements and their assemblies basing on a virtual model prepared in the CAD environment only. Owing to this, the FDM technique, as a rapid prototyping technique found wide applicability on many segments of industry. The correct manufacturing of an element depends on series of technological parameters, defined before the beginning of manufacturing operation. Inadequate defining of these parameters may cause the manufacturing defects, e.g. gaps and overheating of manufacturing elements, which influences negatively on their homogeneity and strength. In the following paper the results of experimental studies for specimens with various degrees of filling for various types of filling - linear and hexagonal. The performed studies covered quasi-static tensile tests and the modal analysis, based on which the natural frequencies of vibration as well as accompanying modal shapes and coefficients of modal damping were determined. Based on the obtained results the elaboration of recommendations for the manufacturing parameters using the additive FDM technique was possible.
6
Content available Mikroskopia świetlna i konfokalna
51%
7
Content available remote Morphological aspect of multilaminar PP composite
51%
EN
Purpose: Analyzing and observing the obtained multi-laminar structure of polymer nanocomposites performed by non-conventional technique of injection moulding. Design/methodology/approach: Basing on DOE conventional technique was evolved and fitted out with additional mould externally operated by computer and pressure machine (generating 150 bar hydraulic pressure). Findings: Chosen method brings advantage of final highly developed and reinforced structure during manufacturing. Research limitations/implications: Polymer-layered silicate and silica nanocomposites are nowadays very important engineering materials showing their noticeable impact among composites. Practical implications: Nanocomposites with created layered structure on nano and micro level are undoubtedly high performance engineering materials with promising growth and with continuous interests and developing branch in science and industry. Originality/value: Non-conventional technique allows for the manipulation through reversing of the melted polymer and polymer blends while the cooling phase starts, creating self-reinforced polymer composite.
8
Content available remote Non-conventionally obtained polymer nanocomposites with different nano-clay ratios
51%
EN
Purpose: Aim of work has been concentrated on investigation of nanocomposites, as promising engineering materials, basing on polymers and organo-modified silicates as nano fillers. Design/methodology/approach: Conventional injection molding process additionally equipped with external computer controlled manipulation system for inducing the shear rates. Findings: Evidently reinforced structures at 3 and 5 wt % of nano-clay content inside polymer matrix for different processing settings related to higher shearing time. Research limitations/implications: Application of nano platelet together with developed injection molding technique brought satisfying mechanical results and development of morphology in the shape of gradient composition. Practical implications: Reinforced nanocomposites are promising materials with high strength and stiffness and with low cost of raw materials (97 wt% of polypropylene and 3 wt% of 2:1 phyllosilicate). Originality/value: Wide application of polymer nanocomposites as materials with ameliorates properties render them high potential materials.
EN
Purpose: This work was performed in the aim of exploring non-conventional injection moulding technique and to study the effect of processing thermomechanical treatment on the morphology and properties of polymer-polymer composites. Design/methodology/approach: Multilayered highly oriented skin regions induced by high shearing of the melt were obtained during non-conventional injection moulding process. Structure development has been observed in the polarized light microscope and by scanning electron microscopy. The fracture energy has been calculated from notched bar specimens. Findings: The processing variables (melt temperature, stroke time and number) are determinant of the fracture energy of the neat PP. Higher setting of these processing variables gives enhanced fracture energy (25% higher). Immiscible polymer blend of PP/PC processed by melt manipulation techniques show improved fracture toughness compared to neat PP. Addition of MAP to PP/PC did not affect the fracture energy for low setting of the processing variables, but significantly decreased it for high adjustments. The fracture energy of nanoclay reinforced PP is the double of the neat PP, for both melt temperature settings. Lower values of fracture energy have been obtained for polymer-polymer composite of PP/PC reinforced with nanoparticles (3-fold lower). Research limitations/implications: Further work contains research of different materials’ ratio, as well different polymer-polymer compositions (e.g., PP/PS and PP/LCP). Other mechanical properties will be assessed. Practical implications: The improvement of mechanical response is sharply apparent by use of SCORIM technique and by the use of nanoparticles reinforcement. Originality/value: This polymer processing technology is promising route for morphology manipulation and improvement on the mechanical properties of polymer systems. Research studies on processing-structure-properties relationships of polymer-polymer composites and nanocomposites moulded by melt manipulation techniques are scarce.
PL
W pracy przedstawiono wyniki badań materiałów kompozytowych o osnowie stopów magnezu EN-MCMgAl9Zn1 wzmacniane cząstkami Al2O3 o wielkości 0,5 i 2 mikrometry oraz udziale objętościowym cząstek ceramicznych 50%, wytworzonych metodą prasowania w stanie ciekłym. Przedstawiono wyniki badań metalograficznych oraz rentgenowskiej analizy fazowej otrzymanych kompozytów.
EN
In this work investigation results of magnesium alloy EN-MCMgAl9Zn1 matrix composite materials were presented. For these materials strengthening processes by ceramics particles of Al2O3 with size 0,5 and 2 micrometres has occured. Strengthening processes have occured thanks to squeeze casting and fraction of hard particles was 50%. In this paper also results of light metallography, hardness and qualitative diffraction rentgenography were presented.
EN
In this paper, the criticality of the self-heating effect accompanying the fatigue process of polymeric composites is studied by monitoring various physical parameters, which reflects degradation progress in a direct or indirect way. The occurring self-heating effect, resulted from the mechanical energy dissipation due to the viscoelastic nature of a polymeric matrix of composites, under certain loading conditions, may dominate the fatigue process, causing significant intensification of degradation and thermal failure at temperature often higher than the glass-transition temperature. The aim of this study is to determine the critical values of the self-heating temperature, which exceeding results in damage initiation and, in consequence, intensive degradation and failure. Additionally, performed tests enable evaluation of sensitivity of particular techniques as well as obtaining more accurate results with physical justification. Following the obtained results, the critical value of a self-heating temperature, at which domination of the fatigue process by the self-heating effect is observed, is at a level of 65–70 °C. Information about the obtained critical values has a great importance both during the design stage of composite structures subjected to cyclic loading as well as their further operation.
12
Content available remote Mechanical approach of PP/MMT polymer nanocomposite
51%
EN
Purpose: Paper summarizes and focus on investigation of PP/MMT nanocomposite in mechanical and statistical approach. Design/methodology/approach: Research has been performed basing on design of experiment. Findings: Considerable predominance of PP + nanoclay mixture in the increment of absorption of energy is found; Level of absorbed energy, required to break the specimens during fracture test is two times higher after structure reinforcement by nanoparticles. Research limitations/implications: Non-conventional injection moulding gives us possibility to control orientation level and develop morphology and it is limited due to non-conventional injection system limitation (pressure, time etc). Practical implications: PP/MMT nanocomposites are the materials with promising future wide range of application also in the specific branches like car and aircraft industries. Originality/value: Nanocomposites obtained in experiment obtaining allow to achieve shish-kebab structure, reinforce skin/core structure and improve mechanical behaviour
13
Content available remote Polymer composite strengthening by developed injection moulding technique
51%
EN
Purpose: This work presents method of mechanical strengthening of nanoreinforced polymer and immiscible polymer blends of polypropylene (PP) and polycarbonate (PC) obtained by non-conventional injection moulding technique. Design/methodology/approach: Melt manipulation of solidifying polymer inside mould cavity has been used for improving fracture toughness of polymer composites and nanocomposites. Findings: Improvement of mechanical properties, especially for nanocomposites, has been obtained due to different processing conditions and ratios of particular components. Research limitations/implications: Nanocomposites of polymer blends and montmorillonite were moulded by direct injection moulding according to melt temperature and stroke time-number combination included in design of experiments. Practical implications: Comparison of analyzed composites brought satisfying results proving advantage of implicated method and composites ratio as well. Originality/value: Non conventional injection moulding method and their influence on strengthening polymer composites and nanocomposites is promising technology with multi-applicable character.
EN
Purpose: Investigation of microstructure of polymer nanocomposites subjected to high shear rates during solidification phase. Design/methodology/approach: Injection moulding technique combined with specially designed mould gives possibility to manipulate solidifying polymer or polymer's mixture inside cavity mould. Findings: Significant increment of fracture energy depending of applied conditions including melt temperature and time of shearing of polymer blend. Research limitations/implications: Obtained nanocomposites contain better mechanical properties comparing to polymer composites and application of SCORIM technique brought satisfying and improved results comparing to conventional methods. Practical implications: Implicated advanced technique to conventional injection moulding gives high performance material with good increased toughness and nanoplatteled particles, uniformly distributed, thanks to the applied technique, inside matrix well reinforce final products. Originality/value: SCORIM technique is rarely used technology and has influence on creation and development of morphology of processed materials.
EN
The article examines Polish-Jewish youth encounters as a sociological phenomenon, revealing the processes of approaching collective memories of both groups. The authors presents data collected during Polish-Jewish meetings, as well as qualitative analysis of letters and 'difficult questions' written by young Poles and Jews. The main issues of Polish and Jewish collective memories are shaped by the adult discourse, that strongly influences the youth inter-group discourse. However, the main differences that underlie most of the 'difficult questions' in Polish-Jewish dialogue are based on the different ways of approaching the past: individualised and emotional among young Jews, but collectivist, depersonalised and rather neutral among young Poles. These differences show, that not only the content, but also the form (pragmatics) of collective memory has to be studied by the sociologist in order to understand the role of history in inter-ethnic relations.
EN
The self-heating effect occurring during the cyclic loading of polymers and polymeric composites may initiate accelerated thermally induced fatigue processes, which causes a rapid increase in the self-heating temperature at a location of stress concentration and, as a consequence, sudden structural degradation. Therefore, it is essential to investigate this process and determine the criticality of the self-heating effect, i.e. the critical value of temperature which initiates accelerated degradation processes. In this paper, an aspect of microcrack formation and development was considered as an indicator which reflects the degradation degree of a structure. Microscopic observation of microcrack development at progressive temperature values was chosen due to its high sensitivity to the initiation of fracture processes among applied measurement techniques to evaluate structural degradation during fatigue tests. Appropriate image processing techniques as well as quantitative measures to describe microcrack development enable evaluation of the criticality of the self-heating effect using this approach and comparison of the obtained results with those obtained by other measurement techniques. The specified critical value of self-heating temperature allows determination of a safe temperature range for heavily loaded structures made of polymeric composites, which can be helpful both during the design stage as well as at the operating stage of composite structures.
PL
Efekt samorozgrzania, powstający podczas cyklicznych obciążeń polimerów i kompozytów polimerowych, może zainicjować przyspieszone indukowane termicznie procesy zmęczeniowe, co powoduje szybki wzrost temperatury samorozgrzania w miejscu koncentracji naprężeń i w konsekwencji nagłą degradację strukturalną. Dlatego istotne jest zbadanie tego procesu i określenie krytyczności efektu samorozgrzania, tj. krytycznej wartości temperatury, która inicjuje przyspieszone procesy degradacji. W artykule aspekt formowania i rozwoju mikropęknięć uwzględniono jako czynnik, który odzwierciedla stopień degradacji struktury. Obserwacja mikroskopowa rozwoju mikropęknięć przy narastających wartościach temperatury została wybrana dzięki wysokiej wrażliwości na inicjację procesów zniszczenia spośród technik pomiarowych stosowanych do oceny degradacji strukturalnej podczas testów zmęczeniowych. Odpowiednie techniki przetwarzania obrazów oraz miary ilościowe do opisu rozwoju mikropęknięć pozwoliły na ocenę krytyczności efektu samorozgrzania, wykorzystując takie podejście, oraz na porównanie otrzymanych wyników z wynikami uzyskanymi z wykorzystaniem innych technik pomiarowych. Wyznaczona wartość krytyczna temperatury samorozgrzania pozwoliła na określenie bezpiecznego przedziału temperaturowego dla silnie obciążanych struktur wykonanych z kompozytów polimerowych, co może być pomocne zarówno na etapie projektowania, jak i podczas eksploatacji struktur kompozytowych.
17
Content available remote Microstructure and mechanical properties of Polypropylene/Polycarbonate blends
51%
EN
Purpose: Researches, which are presented in this paper, consider the effect of chosen different weight ratios polycarbonate blended in a polypropylene matrix (PP/PC) at variable injection moulding conditions and its effect on the microstructure, and also on fracture and flexural properties. Design/methodology/approach: Composites contain between 0 and 30 wt% of polycarbonate and changes at constant rate of 10wt%. Specimens were produced with advantage of melt manipulation technology, further called as non-conventional injection moulding technique (SCORIM). Then, the results were compared with conventional injection moulding, as a result of comparison structure development and mechanical behaviour. Fracture and flexural tests were done on universal testing machine-Instron. The structure sample appearance was observed in polarized light microscope. Findings: PC addition influence on energy absorption and flexural modulus. There are also visible microstructure changes. The SCORIM technique have a significant influence on mechanical properties. Higher settings of those processing variables give higher values of energy at break and flexural modulus. Research limitations/implications: Further work contains research of termomechanical indices to establish straightforward connection between mechanical properties and processing set-ups. Other mechanical properties will be assessed. Practical implications: The improvement of mechanical response is clearly visible by using SCORIM technique and increasing a percentage polycarbonate volume. Originality/value: The Shear Controlled Injection Moulding technique is based on the in-mould shear melt manipulation during the solidification phase. This technology is very important for morphology manipulation and the improvement on the mechanical polymer system properties.
18
Content available remote Polymer nanocomposites reinforced with montmorillonite
51%
EN
Purpose: Light microscope with polarized light has been used for observation layered zone, visible thanks to polarization of the light, inside polymer-polymer composites and nanocomposites Aim of work has been concentrated on investigation of nanocomposites as promising engineering materials, basing on composition of polypropylene and montmorillonite as reinforcement in the shape of nanoparticles of 2:1 silicate. Design/methodology/approach: Conventional and non-conventional injection molding process has been used for obtaining nanocomposites. In non-conventional process has been used the special mold for inducing the shear rates, additionally equipped with external computer to control melt manipulation of solidifying polymer inside mold cavity Findings: Highly developed structure consisted of multilayer zone between skin and core mainly responsible for reinforcement and improvement of fracture toughness of polymer composites and nanocomposites Research limitations/implications: Nanocomposites of polymer blends and montmorillonite were moulded by direct injection moulding according to melt temperature and stroke time-number combination included in design of experiments. Practical implications: Application of special injection moulding technique provides to structure development and gives possibility to create multilayer zone, which strengthen material. Besides strengthening obtaining of such nanocomposites is cheap thanks to application of low cost injection moulding technique and not expensive polyolefines with developed structure, without using additional fillers (e.g. compatybilizers). Originality/value: Very wide application of polymer composites and nanocomposites as engineering materials used for various industries like building engineering, automotive and aerospace
19
Content available remote Computer aided image analysis of nanocomposites microstructures
51%
EN
Purpose: Scanning electron microscopy and light microscopy with polarization has been used for observation cross sectioned samples of nanocomposites with developed layered region, visible in the polarized light; Purpose of this work was to focus on investigation of nanocomposites, with polyolefin matrix and nanometric 2:1 silicate reinforcement, as future engineering materials, Design/methodology/approach: Process of injection molding has been used to manufacture nanocomposites; conventional mold equipped with special hydraulic pressure system and connected to external computer for controlling flow movements inside mold cavity Findings: Layered region, with medium thickness of layer equal to 200 microns, obtained due to the melt manipulation of polymer, improved fracture toughness of investigated nanocomposites; nanoparticles located in the matrix make llalom-like crack propagation extending fracture due to bypassing parallely oriented nanoclay tactoids Research limitations/implications: Specimen shape used in the experiment is rectangular and obtained data of investigated specimens approve very good reinforcement along specimen, application of mre complicated shapes may perturb uniform distribution of nanoparticles in the matric and affect mechanical properties Practical implications: Application developed injection moulding technique and nanomaterials gives possibility to obtain layered region with raised toughness and simultaneously obtain cheaply nanocomposites, thanks to economical technology of manufacturing and commercially available polyolefins at low price Originality/value: Accordingly to increment of plastic market and its upward tendency, wide range of products and applications (and still increasing) in different sectors including medical, household appliances, furniture, automotive, aerospace, electronics and buildings.
EN
Purpose: In this paper the result of laser surface feeding or remelting is discussed. The remelted layers which were formed on the surface of the investigated hot work steel were examined and analyzed metallographically and analyzed using a hardness testing machine. The resistance research has been done on the CSM Instruments. Design/methodology/approach: In this paper the results of laser treatment techniques applied in metal surface technology are presented and discussed. There is presented laser treatment with feeding or remelting of hot work tool steel X40CrMoV5-1 with ceramic powders especially - Al2O3 and Si3N4, as well as results of laser remelting influence on structure and properties of the surface of the hot work steel, carried out using the high power diode laser (HPDL). Findings: On the basis of the wear abrasion tests carried out on hot work tool steel it could be found that each of those specimens is characterized by different resistance for the same powders and the power of the laser beam. The metallographic investigations on light microscope show that during feeding or remelting the hot work tool steel with the ceramic powder layer in the whole range of the laser power values used 1.2-2.3 kW the obtained bead face is characteristic of the high roughness, multiple pores, irregularity. Practical implications: The resistance to abrasive wear is a practical aim of this work as well as improvement of hardness as a very important properties for practical use. It is necessary to continue the research to determine feeding or remelting parameters for demanded properties of hot work tool steels surface layers. Originality/value: Laser feeding or remelting by using HPDL laser (High Power Diode Laser) and selected ceramic powders can be very attractive for industries.
first rewind previous Strona / 2 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.