Wyniki wyszukiwania

Filtruj wyniki

  • Czasopisma
  • Autorzy
  • Słowa kluczowe
  • Data
  • Typ

Wyniki wyszukiwania

Wyników: 82
Wyników na stronie: 25 50 75
Sortuj wg:

Abstrakt

Kończące się zasoby paliw kopalnych, a także niestabilność produkcji energii ze źródeł odnawialnych powodują, że zrównoważone zarządzanie produkcją i zużyciem energii stanowi jedno z naczelnych wyzwań XXI wieku. Wiąże się ono również z zagrożeniami stanu środowiska przyrodniczego m. in. wskutek negatywnego wpływu energetyki na klimat. W takiej sytuacji jednym ze sposobów poprawy efektywności gospodarki energetycznej – zarówno w skali mikro (energetyka rozproszona), jak i makro (system elektroenergetyczny), mogą być innowacyjne rozwiązania technologiczne umożliwiające magazynowanie energii. Ich skuteczna implementacja pozwoli na jej gromadzenie w okresach nadprodukcji i wykorzystanie w sytuacjach niedoboru. Wyzwania te są nie do przecenienia – przed współczesną nauką staje konieczność rozwiązywania różnego rodzaju problemów związanych z magazynowaniem między innymi z zastosowaną technologią czy sterowaniem/zarządzaniem magazynami energii. Technologie magazynowania ciepła, nad którymi są prowadzone prace badawcze dotyczące zarówno magazynów opartych na medium takim jak woda, jak i magazynów wykorzystujących przemiany termochemiczne czy też materiały zmiennofazowe. Dają one szerokie możliwości zastosowania i poprawy efektywności systemów energetycznych zarówno w skali makro, jak i mikro. Oczywiście właściwości technologiczne oraz parametry ekonomiczne mają wpływ na zastosowanie wybranej technologii. W artykule przedstawiono porównanie magazynów czy sposobów magazynowania ciepła oparte na różnych materiałach z określeniem ich parametrów pracy czy kosztów eksploatacji.
Przejdź do artykułu

Abstrakt

The article presents the possibility of using the Cobb-Douglas production function for planning in a turbulent environment. A case study was carried out – the Cobb-Douglas function was used to examine the condition of the Polish hard coal mining industry and the progress which has been made after undertaking certain activities aimed at increasing the competitiveness of coal companies over recent years. Only the correct and confirmed identification of the causes of irregularities in the production process can allow for the introduction of effective remedies. The effectiveness of the solutions proposed by the author has been confirmed thanks to the simulation during which the impact of the proposed production strategy on the parameters of the CD function was examined. Three variants of production functions models were created and production productivity rates and marginal substitution rates were determined. The results enabled the verification of the progress of restructuring as well as identification of the origin of the observed problems and comparison of the current state with the results of analyses carried out in previous years. Scenarios of possible trend developments for the factors introduced into the function model in order to present remedial measures that could improve the process of hard coal extraction were created. The scenarios were created using the ARIMA class models. Which scenario is the most favourable was determined. A computer program, created by the author, for optimising the level and use of labor resources at the level of the entire coal company has been presented.
Przejdź do artykułu

Abstrakt

In the Fugleberget catchment area (Spitsbergen, Hornsund Fiord region) the growing season lasted 95 days, with growth beginning under the snow. In this time shoots of moss Calliergon stramineum reached a mean length of 19 mm and mean biomass of 0.593 mg dry weight. Annual primary production of moss communities amounts to 220-270 g dry weight per square meter per year. In the first year of destruction the dead plant material lost 30-45% of its initial value, after 10 years only ca 25% of the initial amount of organic matter was left.
Przejdź do artykułu

Abstrakt

This study investigated changes in the real-time measured levels of milk β-hydroxybutyrate according milk yield, lactation number and status of reproduction in dairy cows. A total of 378 cows were selected. According to their reproductive status the cows were classified as belonging to the following groups: Fresh (1 – 44 days after calving. n=43). Open (45 – 65 days after calving. n=78), Inseminated (1 – 35 days after insemination. n=133). Pregnant (35 – 60 days after insemination and pregnant (relatively pregnant) (n=124). The cows were milked with DeLaval milking robot (DeLaval Inc., Tumba, Sweden) in combination with a Herd Navigator (Lattec I/S. Hillerød. Denmark) analyser. We observed that milk β-hydroxybutyrate (BHB) had a tendency of increasing with an increase of lactation number. The average BHB in multiparous cows was 11.111% higher in comparison with primiparous cows (p<0.001). We found higher BHB concentration in the multiparous cows in all reproduction status groups (p<0.001). A strong positive statistically significant (p<0.001) relationship has been found between BHB and the average milk yield within all groups of primiparous cows although we found a statistically unreliable coefficient of correlation (from -0.202 to 0.057) between highest milk yield and BHB in primiparous and multiparous cows.
Przejdź do artykułu

Abstrakt

Jeden z najistotniejszych obszarów decyzyjnych przedsiębiorstwa dotyczy zarządzania kapitałem obrotowym. Przedsiębiorstwa energetyczne zajmujące się wytwarzaniem energii elektrycznej i ciepła stanowią głównych odbiorców węgla energetycznego, dlatego ich decyzje w zakresie kształtowania poziomu zapasów są głównym czynnikiem determinującym harmonogramy dostaw węgla. Decyzje te zależą od wymagań prawnych oraz możliwości technicznych, a także aspektów ekonomicznych. Sezonowość zużycia węgla w połączeniu z kosztami wynikającymi z wcześniejszego zakupu oraz kosztami utrzymywania zapasów stanowią bezpośrednią przyczynę kształtowania harmonogramów dostaw węgla w sposób przypominający parabolę. Wśród uczestników rynku węgla (energetyka, górnictwo, przewoźnicy) istnieje rozbieżność oczekiwań w zakresie harmonogramów dostaw. Celem niniejszego artykułu jest przedstawienie koncepcji kształtowania cen węgla energetycznego i transportu na rynku polskim, zakładającej zastosowanie bodźca cenowego, powodującego równomierne dostawy w ciągu roku. W artykule przedstawiono wybrane treści teoretyczne z zakresu logistyki węgla oraz zarządzania kapitałem obrotowym w przedsiębiorstwie, zidentyfikowano oczekiwania uczestników rynku węgla energetycznego w zakresie kształtowania harmonogramów dostaw oraz motywy, jakimi w tym zakresie kierują się odbiorcy węgla z energetyki zawodowej i ciepłownictwa. Przedstawiona koncepcja sezonowości cen węgla energetycznego i transportu na rynku polskim w zamierzeniu autorów powinna być przedmiotem dalszej dyskusji w pracach naukowych i eksperckich.
Przejdź do artykułu

Abstrakt

The region’s development potential is a set of endogenous features that determine the growth of the local economy. It supports the development of knowledge, innovation and eff ective competition on global markets. The publication argues that saturation with potential may not be enough to cause economic growth. The distribution of potential is also important: concentration is its catalyst. The study proposes a method for measuring the concentration of potential. It has also been shown that the size of the regional economy depends on the distribution of potential in the region.
Przejdź do artykułu

Abstrakt

The main purpose of this article is to present an author’s methodology of production levelling and to show the impact of levelling on the time during which the product passes through the process and on staff performance. The article presents the analysis of literature concerning the method of improving the production process, especially taking production levelling into consideration. The authors focussed on the definition and methodologies of production levelling. A diagram of interrelations showing determinants and efficiency measures of production levelling as well as an author’s production levelling methodology have been presented. An example of the implementation of production levelling in one of the departments of a company manufacturing surgical instruments has also been shown. Analysis of the current state, stages of implementation and end effects have been presented. Attention was focussed on the time during which the product passes through the process and on staff performance.
Przejdź do artykułu

Abstrakt

The Silurian Pelplin Formation is a part of a thick, mud-prone distal fill of the Caledonian foredeep, which stretches along the western margin of the East European Craton. The Pelplin Formation consists of organic carbon- rich mudstones that have recently been the target of intensive investigations, as they represent a potential source of shale gas. The Pelplin mudstones host numerous calcite concretions containing authigenic pyrite and barite. Mineralogical and petrographic examination (XRD, optical microscopy, cathodoluminoscopy, SEM-EDS) and stable isotope analyses (δ13Corg, δ13C and δ18O of carbonates, δ34S and δ18O of barite) were carried out in order to understand the diagenetic conditions that led to precipitation of this carbonate-sulfide-sulfate paragenesis and to see if the concretions can enhance the understanding of sedimentary settings in the Baltic and Lublin basins during the Silurian. Barite formed during early diagenesis before and during the concretionary growth due to a deceleration of sedimentation during increased primary productivity. The main stages of concretionary growth took place in yet uncompacted sediments shortly after their deposition in the sulfate reduction zone. This precompactional cementation led to preferential preservation of original sedimentary structures, faunal assemblages and early- diagenetic barite, which have been mostly lost in the surrounding mudstones during burial. These components allowed for the reconstruction of important paleoenvironmental conditions in the Baltic and Lublin basins, such as depth, proximity to the detrital orogenic source and marine primary productivity. Investigation of the concretions also enabled estimation of the magnitude of mechanical compaction of the mudstones and calculation of original sedimentation rates. Moreover, it showed that biogenic methane was produced at an early-diagenetic stage, whereas thermogenic hydrocarbons migrated through the Pelplin Formation during deep burial.
Przejdź do artykułu

Abstrakt

This paper examines highly paid academics – or “top earners” – employed across universities in ten European countries based on a large-scale international survey data of the academic profession. It examines the relationships between salaries and academic behaviors and productivity, as well as the predictors of being an academic top earner. While in the Anglo-Saxon countries the university research mission traditionally pays off at an individual level, in Continental Europe it pays off only in combination with administrative and related duties. Seeking future financial rewards through research does not seem to be a viable strategy in Europe – but seeking satisfaction in research through solving research puzzles is also getting difficult, with the growing emphasis on “relevance” and “applicability” of research. Thus both the traditional “investment motivation” and “consumption motivation” for research are ever-harder to be followed, with policy implications. The primary data come from 8,466 usable cases. This paper examines change processes in Western Europe and in Poland (in a European context) and its main reference point is American higher education scholarship; it is, on the theoretical plane, the founder of the conceptual frameworks to study academic salaries, and, in practical terms, the US science systems heavily draws on European scientific talents.
Przejdź do artykułu

Abstrakt

The article presents research on the relationship between mining and used resources on the example of Gliśno gravel pit. As regards to resources, the following issues were analyzed: employees’ working time, time of running machines, fuel consumption and electricity consumption. The aim of the publication is to examine the dependencies that exist between the analyzed variables. KPI’s (Key Performance Indicators) were calculated for individual resources. The analysis presented in the publication contains data from 2008-2014.
Przejdź do artykułu

Abstrakt

Experiments have been carried out on the influence exerted by Aroclor 1254 upon the photosynthetic production of organic 14C by an assemblage of marine Antarctic diatoms (Thalassiosira sp. 48%, Nitzschia sp. 21%, Chaetoceros sp. 15% and Corethron iriophilum 10%). Samples of various numbers of cells per cm3 of water have been used. Incorporation of 14C02 by the diatoms proved to be proportional to the increased number of cells in the sample only at the lowest levels of concentration in per cm3. Further increase of the level of 14C in diatoms has not been found as number of cells in the sample kept growing. Calculation of brutto photosynthesis has indicated that low concentration of Aroclor 1254 (0,01 to 1 ppm) may stimulate the photosynthetic incorporation of carbon, yet the photosynthetic release of carbon from cells within the photorespiratory process is stimulated to a higher degree. High concentration of Aroclor (1 to 50 ppm) inhibit the brutto assimilation, yet the release of carbon during the photorespiratory process is inhibited to a higher degree. A hypothesis is being considered implying that the relation between the intensity of photosynthesis and intensity of photorespiration may vary according to the rate of concentration of Aroclor.
Przejdź do artykułu

Abstrakt

Podczas wydobycia i przeróbki mechanicznej węgla kamiennego oraz w procesach jego spalania powstają różne odpady. Zaliczyć do nich można m.in. odpady z procesu wzbogacania węgla oraz uboczne produkty spalania (popioły lotne i żużle). Aktualne przepisy prawne i branżowe zalecają określanie w nich m.in. zawartości rtęci oraz definiują graniczne jej wartości. Celem pracy było określenie poziomu rtęci w odpadach z procesu wzbogacania węgli kamiennych oraz stałych ubocznych produktach spalania węgli w energetyce w aspekcie ich wykorzystania i/lub utylizacji. Określono zawartość rtęci w reprezentatywnych próbkach odpadów z procesu wzbogacania na mokro i suchej separacji węgla kamiennego oraz w ubocznych produktach spalania z ośmiu kotłów opalanych węglem kamiennym: próbkach żużla i popiołu lotnego. Zawartość rtęci w badanych odpadach ze wzbogacania na mokro węgli kamiennych zmieniała się w granicach od 54 do 245 μg/kg (średnia 98 μg/kg), a z procesu suchej separacji od 76 do 310 μg/kg (średnia 148 μg/kg), w przeliczeniu na stan roboczy. Zawartość rtęci w popiołach lotnych wynosiła od 70 do 1420 μg/kg (średnia 567 μg/kg), a w żużlach od 8 do 58 μg/kg (średnia 21 μg/kg). Obecnie – w świetle obowiązujących przepisów prawnych z punktu widzenia zawartości rtęci w odpadach – nie ma istotnych barier w ich wykorzystaniu. Niemniej jednak mogą pojawić się w przyszłości przepisy limitujące maksymalną zawartość rtęci oraz dopuszczalną ilość wymywanej rtęci. Może to utrudnić ich wykorzystanie i/lub utylizację według dotychczasowych sposobów. Zasadne jest więc przygotowanie się na taką sytuację, poprzez opracowanie innych alternatywnych sposobów wykorzystania tych odpadów.
Przejdź do artykułu

Abstrakt

W artykule omówiono zagadnienia związane z rozwojem międzynarodowych rynków węgla. W 2016 r. zużycie węgla na świecie spadło drugi rok z rzędu – przede wszystkim w wyniku słabego popytu w Chinach i USA. U dział węgla w globalnym zużyciu pierwotnych nośników energii zmniejszył do 28%. Światowa produkcja węgla w 2016 r. wyniosła 3,66 mld ton i w porównaniu z rokiem poprzednim była mniejsza 6,2%. Ponad 60% tego spadku miało miejsce w Chinach. Spadek globalnej produkcji był ponad 4-krotnie większy niż spadek zużycia. Wystarczalność światowych zasobów węgla szacowana jest na 153 lata – jest to trzy razy więcej niż wystarczalność ropy i gazu. Po kilkuletnich spadkach, ceny węgla w 2016 wzrosły o 77%. Obecne ceny spot są na poziomie 80 U SD/tonę i są zbliżone do cen z 2014 r. Na rynku europejskim po pierwszym półroczu ceny węgla są już wyższe około 66% w stosunku do analogicznego okresu ubiegłego roku. Średnia cena w pierwszym półroczu wyniosła 12,6 zł/GJ i jest zbliżona do cen z 2012 roku. U dział transakcji spot w całkowitej puli zakupów wynosi około 20%. Ceny w kontraktach terminowych można szacować na podstawie cen z umów Japonia – Australia i cen w dostawach do elektrowni niemieckich. Średnio w latach 2010–2016 ceny do elektrowni niemieckich były wyższe o około 9%, a ceny w kontraktach Australia –Japonia 12% wyższe od cen CIF ARA. w 2017 r. Światowy handel węglem energetycznym osiągnął w 2016 r. około 1,012 mld ton. W perspektywie 2019 roku oczekuje się spadku o 4,8% – przede wszystkim z powodu spodziewanego mniejszego zapotrzebowania na głównych rynkach importowych w Azji.
Przejdź do artykułu

Abstrakt

The paper presents a Car Sequencing Problem, widely considered in the literature. The issue considered by the researchers is only a reduced problem in comparison with the problem in real automotive production. Consequently, a newconcept, called Paint Shop 4.0., is considered from the viewpoint of a sequencing problem. The paper is a part of the previously conducted research, identified as Car Sequencing Problem with Buffers (CSPwB), which extended the original problem to a problem in a production line equipped with buffers. The new innovative approach is based on the ideas of Industry 4.0 and the buffer management system. In the paper, sequencing algorithms that have been developed so far are discussed. The original Follow-up Sequencing Algorithm is presented, which is still developed by the authors. The main goal of the research is to find the most effective algorithm in terms of minimization of painting gun changeovers and synchronization necessary color changes with periodic gun cleanings. Carried out research shows that the most advanced algorithm proposed by the authors outperforms other tested methods, so it is promising to be used in the automotive industry.
Przejdź do artykułu

Abstrakt

The essence of advertising lies very often in unusual and surprising juxtapositions of apparently incongruous elements, which nevertheless successfully combine in producing a coherent and understandable message. A vital role is performed by a skillfully engineered context, which allows for simultaneous activation of certain otherwise inconspicuous senses and the construction of novel and attractive connections. Such theoretical proposals as Lemke’s traversals (2001; 2005), Fauconnier and Turner’s Conceptual Blending Theory (1998; 2002) and Kecskes’s Dynamic Model of Meaning (2008) seem to describe many vital aspects of the phenomenon in question. It is in advertising that we often come across the linking of elements by transgressing naturally existing borders between domains which are unrelated, and we are invited to map onto one another different mental spaces on the basis of their salient analogy or identity, and indulge in creative riddle-like exploration of contextual elements in order to reconstruct the intended message. These techniques’ true power lies in their ability to blur the distinction between ‘the real’ and ‘the imagined’ to such an extent that certain irrational but attractive connections, implanted in the minds of the audience, contribute to subsequent decisions in the real world. The present study attempts to uncover the ways in which certain unrelated elements are skillfully brought together in a context which allows for such a juxtaposition in selected Polish TV advertisements for various medicine and health-related products. The method employed is an in-depth content analysis of the material, followed by an attempt to integrate the identified mechanisms with the models of meaning-making mentioned above. The results will hopefully help in better understanding of the ways in which particular components of the context may interact with the message expressed verbally or pictorially in the construction of multilevel meanings in advertising communication.
Przejdź do artykułu

Abstrakt

The insecticidal efficiency of Ag-loaded 4A-zeolite (ZAg) and its formulations with Rosmarinus officinalis essential oil (RO) was evaluated against Sitophilus oryzae (L.) and Rhyzopertha dominica (F.). For comparison, different rates of ZAg (0.25, 0.5, 0.75, and 1 g ⋅ kg–1 wheat) were used solely and in a combination with LC50 concentrations of RO. Mortality was assessed after 7, 14, and 21 days of insect exposure to treated wheat. The progeny production was also evaluated. The use of ZAg accomplished a complete mortality (100%) on S. oryzae and 96.67% on R. dominica as well as 100% mortality of progeny against the two insect species after the longest exposing duration (21 days), at the highest rate (1 g ⋅ kg–1). On the other hand, the complete mortalities of ZAg formulations on S. oryzae were obtained after 14 d of treatment with F1 formulation (0.605 g ⋅ kg–1 RO + 0.25 g ⋅ kg–1 ZAg) and after 7 days with the other tested formulations. In addition, the complete mortality on R. dominica was obtained only by F8 (0.059 g ⋅ kg–1 RO + 1 g ⋅ kg–1 ZAg) formulation after 14 days of treatment. Concerning the efficiency of the examined formulations on the progeny of S. oryzae, F1 (0.605 g ⋅ kg–1 RO + 0.25 g ⋅ kg–1 ZAg) and F2 (0.605 g ⋅ kg–1 RO + 0.5 g ⋅ kg–1 ZAg) formulations recorded 100% mortality. In addition, F3 (0.605 g ⋅ kg–1 RO + 0.75 g ⋅ kg–1 ZAg) and F4 (0.605 g ⋅ kg–1 RO + 1 g ⋅ kg–1 ZAg) formulations suppressed the progeny production. Furthermore, the complete mortality of R. dominica progeny was obtained with F7 (0.059 g ⋅ kg–1 RO + 0.75 g ⋅ kg–1 ZAg) and F8 (0.059 g ⋅ kg–1 RO + 1 g ⋅ kg–1 ZAg) formulations. ZAg, especially its formulations with R. officinalis oil, had potential effects against two stored-product insects. F1 and F8 formulations could be treated efficiently on S. oryzae and R. dominica, respectively.
Przejdź do artykułu

Abstrakt

Produkcja węgla w 2018 r. wzrosła o 3,3% i wyniosła 7,81 mln ton. W porównaniu do 2010 r. wzrosła 620 mln ton. Struktura produkcji węgla na świecie jest bardzo stabilna w analizowanym okresie lat 2010–2018. W produkcji dominuje węgiel energetyczny z udziałem 77%. Od 1990 r. udział węgla w zużyciu pierwotnych nośników energii spadł w światowej gospodarce o 3%. W U E udział węgla w zużyciu pierwotnych nośników energii jest ponad dwukrotnie mniejszy niż na świecie. W 2018 r. wyniósł 13%. BP szacuje wystarczalność zasobów węgla na podstawie danych za 2018 r. na okres następnych 132 lat. W przypadku ropy i gazu szacowane są one na 51 lat. Spadek produkcji węgla kamiennego w U nii Europejskiej można datować prawie nieprzerwanie od 1990 r., gdyż produkcja zmniejszyła się o 74%. W 2018 roku w U nii wyprodukowano 74 mln ton węgla. W ubiegłym roku zużycie węgla kamiennego w krajach członkowskich spadło do 226 mln ton, czyli o 20,6%. W 2018 roku globalny handlem w węglem energetycznym wyniósł 1,14 mld ton. Dla międzynarodowego rynku węglem kluczowa jest sytuacja w Chinach. Niewielka zmiana w polityce importowej tego kraju wpływa istotnie na sytuację w międzynarodowym handlu węglem energetycznym. W 2019 r. ceny węgla energetycznego (w portach Newcastle, Richards Bay, ARA) spadły średnio o 23 U SD/tonę. Średnie spadki dla tych trzech indeksów wyniosły 33%. Ceny węgla energetycznego w przedstawionych w artykule prognozach znajdują się pod presją spadającego popytu.
Przejdź do artykułu

Abstrakt

W artykule przedstawiony został stan aktualny w zakresie struktury produkcji zakładów wzbogacania węgla kamiennego w Polsce z uwzględnieniem wydajności, zakresu ziarnowego wzbogacanego urobku oraz typu zastosowanych urządzeń. Zebrane dane zostały przedstawione w układzie tabelarycznym dla każdej funkcjonującej na rynku polskim spółki węglowej. Zaprezentowany został również uproszczony blokowy schemat technologiczny zakładów wzbogacania węgla energetycznego i koksowego. W oparciu o przedstawione dane opisane zostały planowane potrzeby i trendy w zakresie zwiększenia efektywności produkcji, minimalizacji zużycia wody oraz bezpieczeństwa pracy. Przedstawiona została również lista niezbędnych do podjęcia prac badawczo-rozwojowych w tym zakresie oraz wykaz głównych czynników determinujących rozwój technologiczny zakładów wzbogacania węgla kamiennego.
Przejdź do artykułu

Abstrakt

The engine simulations have become an integral part of engine design and development. They are based on approximations and assumptions. The precision of the results depends on the accuracy of these hypotheses. The simplified models of frozen composition, chemical equilibrium and chemical kinetics provide the compositions of combustion products for engine cycle simulations. This paper evaluates the effects of different operating conditions and hypotheses on the exergetic analysis of a spark-ignition engine. The Brazilian automotive market has the highest number of flex-fuel vehicles. Therefore, a flex-fuel engine is considered for simulations in order to demonstrate the effects of these different hypotheses. The stroke length and bore diameter have the same value of 80 mm. The in-cylinder irreversibility is calculated for each case at the closed part of the engine cycle. A comparative analysis of these hypotheses provides a comprehensive evaluation of their effects on exergetic analysis. Higher values of accumulated irreversibility are observed for the oversimplified hypothesis.
Przejdź do artykułu

Abstrakt

The high pressure die casting technology allows the production of complex casts with good mechanical properties, with high production repeatability within narrow tolerance limits. However, the casts are somewhat porous, which may reduce their mechanical properties. There are several recommendations for reducing the porosity of casts, which are aimed at setting the technological parameters of the casting cycle. One of the primary and important ways to reduce the porosity and air entrapment in the melt is a suitable gating system design. Submitted contribution is devoted to assessing the influence of the runner branching geometry on the air entrapment within the cast volume during the filling phase of the casting cycle. Four variants of the gating system for a particular cast are compared with different design of main runner branching. The initial design is based on a real gating system where the secondary runner is connected to the main runner at an angle of 90 °. The modified designs are provided with a continuous transition of the main runner into the secondary ones, with the change in the branching runner radius r1 = 15 mm, r2 = 25 mm and r3 = 35 mm. The air entrapment in the melt is assessed within the cast volume behind the cores, which have been evaluated as a critical points with respect to further mechanical treatment. When designing the structural modification of geometry it was assumed that by branch changing using the radius value r3 = 35 mm, the melt flows fluently, and thus the value of the entrapped air in the volume of the cast will be the lowest. This assumption was disproved. The lowest values of entrapped air in the melt were found in the casts with runner transition designed with radius r1 = 15 mm. The conclusion of the contribution explains the causes of this phenomenon and from a designing point of view it presents proposal for measures to reduce the entrapment of the air in casts.
Przejdź do artykułu

Abstrakt

Final quality of casts produced in a die casting process represents a correlation of setting of technological parameters of die casting cycle, properties of alloy, construction of a die and structure of gating and of bleeding systems. Suitable structure of a gating system with an appertaining bleeding system of the die can significantly influence mechanical and structural properties of a cast. The submitted paper focuses on influence of position of outfall of an gate into the cast on its selected quality properties. Layout of the test casts in the die was designed to provide filling of a shaping cavity by the melt with diverse character of flowing. Setting of input technological parameters during experiment remained on a constant level. The only variable was the position of the gate. Homogeneity represented by porosity f and ultimate strength Rm were selected to be the assessed representative quality properties of the cast. The tests of the influence upon monitored parameters were realized in two stages. The test gating system was primarily subjected to numerical tests with the utilization of a simulation program NovaFlow&Solid. Consequently, the results were verified by the experimental tests carried out with the physical casts produced during operation. It was proved that diverse placement of the gate in relation to the cast influences the mode of the melt flowing through the shaping cavity which is reflected in the porosity of the casts. The experimental test proved correlation of porosity f of the cast with its ultimate strength Rm. At the end of the paper, the interaction dependencies between the gate position, the mode of filling the die cavity, porosity f and ultimate strength Rm.
Przejdź do artykułu

Abstrakt

The article presents the results of research on the finishing of M63 Z4 brass by vibratory machining. Brass alloy was used for the research due to the common use of ammunition elements, cartridge case and good cold forming properties on the construction. Until now, the authors have not met with the results of research to determine the impact of abrasive pastes in container processing. It was found that the additive for container abrasive treatment of abrasive paste causes larger mass losses and faster surface smoothing effects. The treatment was carried out in two stages: in the first stage, the workpieces were deburred and then polished. Considerations were given to the impact of mass of workpieces, machining time and its type on mass loss and changes in the geometric structure of the surface. The surface roughness of machining samples was measured with the Talysurf CCI Lite optical profiler. The suggestions for future research may be to carry out tests using abrasive pastes with a larger granulation of abrasive grains, and to carry out tests for longer processing times and to determine the time after which the parameters of SGP change is unnoticeable.
Przejdź do artykułu

Abstrakt

In this paper a 600 MW oxy-type coal unit with a pulverized bed boiler and a membrane-cryogenic oxygen separator and carbon capture installation was analyzed. A membrane-cryogenic oxygen separation installation consists of a membrane module and two cryogenic distillation columns. In this system oxygen is produced with the purity equal to 95%. Installation of carbon capture was based on the physical separation method and allows to reduce the CO2emission by 90%. In this work the influence of the main parameter of the membrane process – the selectivity coefficient, on the efficiency of the coal unit was presented. The economic analysis with the use of the break-even point method was carried out. The economic calculations were realized in view of the break-even price of electricity depending on a coal unit availability.
Przejdź do artykułu

Abstrakt

The purpose of the paper is to present the author’s reflections on the origin and popularity of various approaches to maintenance and improvement of production processes, their terminological consistency, understanding, and practical application of their principles. The author’s reflections are based on his observations made over his many years of activity as a lecturer and consultant in the area of production engineering and management. It was shown that there is a need to make scientists and practitioners aware of the relatively large degree of freedom in defining the scope and way of application of strategies of continuous improvement. The author’s proposal is to refer to all approaches to maintenance and improvement of production processes with the title “Strategies of Efficient Action” and all supporting methods as “Practices of Efficient Action”. Considerations presented in the paper can be useful in more and more efficiently applying the power of TQM, Six Sigma, Lean Manufacturing and other strategies of processes maintenance and improvement in the daily activities of companies.
Przejdź do artykułu

Abstrakt

Hornsund and Kongsfjorden are two similar-sized Arctic fjords on the West coast of Spitsbergen. They are influenced by cold coastal Arctic water (Hornsund) and warmer Atlantic water (Kongsfjorden). Environmental conditions affect the timing, quantity, spatial distribution (horizontal and vertical) of spring and summer blooms of protists as well as the taxonomic composition of those assemblages. Here, we compile published data and unpublished own measurement from the past two decades to compare the environmental factors and primary production in two fjord systems. Kongsfjorden is characterized by a deeper euphotic zone, higher biomass and greater proportion of autotrophic species. Hornsund seems to obtain more nutrients due to the extensive seabird colonies and exhibits higher turbidity compared to Kongsfjorden. The annual primary production in the analysed fjords ranges from 48 g C m-2 y-1 in Kongsfjorden to 216 g C m-2 y-1 in Hornsund, with a dominant component of microplankton (90%) followed by macrophytes and microphytobenthos.
Przejdź do artykułu

Ta strona wykorzystuje pliki 'cookies'. Więcej informacji