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Number of results: 57
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Abstract

The time period of a jet engines full acceleration (from idle run rotating speed to full thrust) is a very important operational parameter. Minimization of this period is an important problem to be solved during the design of the fuel supply and control system. There are many methods of acceleration process control, especially in the case of engines with complicated design configurations. This work presents the problem of acceleration of a simple, single spool turbine jet engine with a so-called stable geometry, in which only one input (control) signal exists - fuel flow rate. Two methods of acceleration control consisting of limitation of the maximum allowable temperature of working medium in front of and behind the turbine in transient states were analyzed. In order to avoid difficulties associated with the direct measurement of actual temperatures, the so-called nonlinear engine observer was applied. With the use of the computer simulation method it was proven that the control algorithm with the limited maximum temperature in front of the turbine makes it possible the shortening of the acceleration time period significantly in comparison with a similar algorithm, that realizes the limitation of temperature behind the turbine.
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Authors and Affiliations

Wojciech I. Pawlak
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Abstract

The present-day methods of supervising the operational use of jet engines are based, among other things, on computerised procedures of monitoring and recording various failure modes, including the surge. This dangerous mode of operation of a turbojet engine occurs quite commonly while operating it. In some cases, it could result even in the engine destruction. What has been presented in this study is the way of applying a non-linear observer of a one-spool single-flow turbojet to generate a computer algorithm to detect the surging. An exemplary application of such an algorithm to monitor the surging that occurs in the K-15 engine has also been shown.
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Authors and Affiliations

Wojciech I. Pawlak
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Abstract

The effect of processes of accumulating mass and enthalpy of the working medium on the dynamics of transient processes thereof is often discussed in scientific publications on the mathematical modelling of turbine engines (treated as systems that undergo control and automatic adjustment). The paper is intended to make a comparison between findings gained from simulation carried out with two alternative models of an aircraft turbine engine (of the S0-3 type). The first model takes account of the dynamics of the processes of accumulating mass and energy of the working medium within the combustion-chamber volume and that of the convergent nozzle. The second, simplified model, neglects the dynamics of the processes of accumulating mass and energy of the working medium, since it has been assumed that it is the dynamics of the kinetic-energy accumulation in the rotor mass that predominates in various representations of transient processes. To conduct simulation-based experiments, each of the alternative models of an engine was connected to a special simulation unit, which simulated operation of fuel supply and control systems. Two rounds of experiments were carried out. The first one was intended to facilitate observations of transient processes effected with quick shifting of a control lever from the idle position to that of full thrust, and back. In the second round observed were processes resulting from changes in the critical jet area. The second, alternative model was used to investigate the effect of ever-greater hypothetical volumes of the nozzle on how the transient processes proceeded. It has been found that in the case of the S0-3 engine, low nozzle capacity remains of only slight effect on how the transient processes proceed. Hence, simplified modelling methodology is fully justified.
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Authors and Affiliations

Wojciech I. Pawlak
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Abstract

The UN Convention on the Law of the sea (10 December 1982) contains provisions that create the International Tribunal for the Law of the Sea. In the twentieth century the conviction has grown in the international community that conflicts should not only be solved by diplomacy, but also by arbitration and international adjudication, which would both issue judgments and offer expert opinion. The majority of EU states chose the International tribunal for the Law of the sea as the first international organ foreseen in Article 287 of the UN Convention on the Law of the Sea. Up to now, the Tribunal has considered 15 cases, 12 of which were connected with fisheries. The Tribunal has demonstrated that its procedures are speedy, transparent, and effective. The author of the article mentions all cases pending before the Tribunal in Hamburg from 1997 to 2008. All court costs are covered from the Tribunal's budget. The UN General Assembly in its annual resolutions referring to assessment of the Tribunal’s work underlines “the important role and the authority of the Tribunal in interpreting and implementing the Convention. ” As legal matters now stand, the International Tribunal for the law of the sea can consider any case brought by any state, including, therefore, piracy. It can do this not only on the basis of the UN Convention of 10 December 1982, but also on that o f all other international treaties that give it relevant jurisdiction.

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Authors and Affiliations

Stanisław Pawlak
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Abstract

The article presents the analysis of the rules of punctuation concentrated on the use of a comma in Spanish language. Nevertheless, in the introduction the author cite several exemples to show the differences and similarities between the use of a comma in Spanish, Polish, Russian, Czech, French, English and German languages in order to emphasize the conventional nature of the comma. The main part of the work presents the use of a comma in Spanish in five syntactic contexts. The article ends with conclusions that reveal the obligatory, distinctive and optional nature of the comma in the Spanish orthography.

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Authors and Affiliations

Aneta Pawlak
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Abstract

Results of mathematical modelling and computer simulation of transient processes in the turbine jet engine SO-3 have been presented. The transient processes result from two different fault conditions. In the first case, the transient process has been induced with a rapid fuel shut-off. In the second case, the transient process follows some failure to the shaft that connects the turbine rotor to that of the compressor. The failure occurred in the area of the middle engine bearing support.

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Authors and Affiliations

Wojciech Pawlak
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Abstract

The paper presents the results of diachronic analysis of independent grammatical morphemes which function in the grammatical systems of Chadic languages. The following markers are being considered: genitive-linking morpheme, subject and object markers, copula, focus marker. Etymologically, the markers are traced back to Chadic (and Afroasiatic) system of determiners identified by the three phonological elements, namely *n, *t, and *k which have their vestiges in contemporary systems. It is claimed that what is a retention on phonological ground, contributes to innovation processes on the grammatical level.

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Authors and Affiliations

Nina Pawlak
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Abstract

The aspects of surface stability and groundwater exchange recognized by many researchers due to the intensification of agriculture and industry (manifested in, e.g., regulation and dredging of riverbed sediments of rivers) are now widely discussed on the international forum of water policy and management. It is essential to assess the spatial variability of water exchange through the river length and cross sections for the preparation of data and calculation of the groundwater flow model. This article presents research which describes the spatial distribution of the surface water-groundwater interaction within the river cross-section. Two measurement series were carried out to describe its variability. Additionally, a groundwater flow model was developed to simulate and represent the variable nature of water exchange in the hyporheic zone in the river’s cross-section. The model was successfully verified by means of measurements of water flux in the hyporheic zone. The precise spatial description of this variability is the first step to determine the possibility of introducing this variable in an accurate manner, within the limits of measurement uncertainties or simulation assumptions, in the construction of mathematical models of groundwater flow.
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Bibliography

1. Anibas, C., Verbeiren, B., Buis, K., Chormański, J., De Doncker, L., Okruszko, T., Meire, P. & Batelaan, O. (2012). A hierarchical approach on groundwater-surface water interac-tion in wetlands along the upper Biebrza River, Poland. Hydrol. Earth Syst. Sci. , 16, pp. 2329–2346. https://doi.org/10.5194/hess-16-2329-2012
2. Baraniecka, M. D., (1976). Description of the detailed geological map of Poland 1:50 000 Sheet Otwock, (in Polish).
3. Boano, F., Camporeale, C., Revelli, R. & Ridolfi, L. (2006). Sinuosity-driven hyporheic exchange in meandering rivers. Geophys. Res. Lett. , 33. https://doi.org/10.1029/2006GL027630
4. Boano, F., Harvey, J. W., Marion, A., Packman, A. I., Revelli, R., Ridolfi, L. & Wörman, A. (2014). Hypohreic flow and transport processes: Mechanisms models, and biogeo-chemical implications. Rev. Geophys. , 52, pp. 603–679. https://doi.org/10.1002/2012RG000417
5. Brunetti, E., Jones, J. P., Petitta, M. & Rudolph, D. L. (2013). Assessing the impact of large-scale dewatering on fault-controlled aquifer systems: a case study in the Acque Albule basin (Tivoli, central Italy). Hydrogeol. J. , 21, pp. 401–423. https://doi.org/10.1007/s10040-012-0918-3
6. Brunke, M. & Gonser, T. (1997). The ecological significance of exchange processes be-tween rivers and groundwater. Freshw. Biol. , 37, pp. 1–33. https://doi.org/10.1046/j.1365-2427.1997.00143.x
7. Duda, R., Witczak, S. & Żurek, A. (2011). Map of Polish groundwater sensitivity to pol-lution 1: 500,000 - Methodology and textual explanations. Akademia Górniczo–Hutnicza im. Stanisława Staszica w Krakowie Wydział Geologii, Geofizyki i Ochrony Środowiska, ISBN: 13 978-83-88927-24-9 (in Polish).
8. Elango, L., Brindha, K., Kalpana, L. & Sunny, F. (2012) Groundwater flow and radionu-clide decay-chain transport modelling around a proposed uranium tailings pond in In-dia. Hydrogeol. J. , 20, pp. 797–812. https://doi.org/10.1007/s10040-012-0834-6
9. Grodzka-Łukaszewska, M., Nawalany, M. & Zijl, W. (2017). A Velocity-Oriented Ap-proach for Modflow. Transp. Porous Media, 119, pp. 373–390. https://doi.org/10.1007/s11242-017-0886-0
10. Grygoruk, M. & Acreman, M. (2015). Restoration and management of riparian and river-ine ecosystems: Ecohydrological experiences, tools and perspectives. Ecohydrol. Hydrobiol. , 15, pp. 109-110. https://doi.org/10.1016/j.ecohyd.2015.07.002
11. Harvey, J. & Gooseff, M. (2015). River corridor science: Hydrologic exchange and eco-logical consequences from bedforms to basins. Water Resour. Res., 51, pp. 6893–6922. https://doi.org/10.1002/2015WR017617
12. Hendriks, D. M. D., Okruszko, T., Acreman, M., Grygoruk, M., Duel, H., Buijse, T., Schutten, J., Mirosław-Świątek, D., Henriksen, H.J., Sanches-Navarro, R., Broers, H.P., Lewandowski, J., Old, G., Whiteman, M., Johns, T., Kaandorp, V., Baglioni, M., Holgersson, B. & Kowalczyk, A. (2015). Bringing groundwater to the surface; Groundwater-river interactions as driver for river ecology. D77 Policy Discuss. Pap. no 2
13. Hidayat, H. N. & Permana, M. G. (2018). Geothermal reservoir simulation of hot sedi-mentary aquifer system using FEFLOW®. IOP Conference Series: Earth and Envi-ronmental Science, 103, 12002, DOI: https://doi.org/10.1088/1755-1315/103/1/012002
14. IMGW-PIB 2016 Report on the implementation of flood hazard maps and flood risk maps, appendix 1, (in Polish)
15. Iqbal, Z., MacLean, R. T., Taylor, B. D., Hecker, F. J. & Bennett, D. R. (2002). Seepage losses from irrigation canals in southern Alberta. Can. Biosyst. Eng. / Le Genie des Biosyst. au Canada, 44, pp. 21–27
16. Israelsen, O. W. & Reeve, R. C. (1944). Bulletin No . 313 - Canal Lining Experiments in the Delta Area, Utah Canal Lining Experiments - the Delta Area, Utah. UAES Bull 52
17. Janik, B., Kowalik, A. & Marciniak, M. (1989). Infiltrometric measurements as an estima-tion base of the quota of river water in the feeding of the drainage intake Reda-Pieleszewo. Przegląd Geologiczny, 37, pp. 511–516 (in Polish).
18. Jekatierynczuk-Rudczyk, E. (2007). The hyporheic zone, its functioning and meaning. Kosmos. 56, pp. 181-196 (in Polish)
19. Kasperek, R., Mokwa1, M. & Wiatkowski, M. (2012). Modelling of pollution transport with sediment on the example of the Widawa river. Archives of Environmental Protection, 39, 2, pp.29-43, DOI: 10.2478/aep-2013-0017
20. Lee, D. R. (1977). A device for measuring seepage flux in lakes and estuaries1. Limnol. Oceanogr. , 22, pp. 140–147. https://doi.org/10.4319/lo.1977.22.1.0140
21. Magliozzi, C., Grabowski, R. C., Packman, A. I. & Krause, S. (2018) Toward a concep-tual framework of hyporheic exchange across spatial scales. Hydrol. Earth Syst. Sci., 22, pp. 6163–6185 https://doi.org/10.5194/hess-22-6163-2018
22. Marciniak, M. & Chudziak, Ł. (2015). A new method of measuring the hydraulic con-ductivity of the bottom sediment. Przegląd Geologiczny, 63, pp. 919-925 (in Polish)
23. Marciniak, M., Szczucińska, A. & Kaczmarek, M. (2017). Variability of the hydraulic conductivity in the hyporheic zone in the light of laboratory research). Przegląd Geologiczny, 65, pp. 1115-1120 (in Polish)
24. McDonald, M. G. & Harbaugh, A. W. (1984). A modular three-dimensional finite-difference ground-water flow model. U.S. Geological Surv.
25. Nawalany, M. (1993). Mathematical Modeling of River-Aquifer Interactions, Report SR 349. HR Wallingford.
26. Pandian, R. S., Nair, I. S. & Lakshmanan, E. (2016). Finite element modelling of a heavi-ly exploited coastal aquifer for assessing the response of groundwater level to the changes in pumping and rainfall variation due to climate change. Hydrol Res., 47, pp. 42–60. https://doi.org/10.2166/nh.2015.211
27. Peralta-Maraver, I., Reiss, J. & Robertson, A. L. (2018). Interplay of hydrology, commu-nity ecology and pollutant attenuation in the hyporheic zone. Sci. Total Environ., 610–611, pp. 267–275. https://doi.org/10.1016/j.scitotenv.2017.08.036
28. Pietrzak, K., Przybylski, B., & Repliński, M. (2018). Environmental impact assessment of the Environmental Protection Program for the Latowicz municipality until 2021 (in Polish).
29. Revelli, R., Boano, F., Camporeale, C. & Ridolfi, L. (2008). Intra-meander hyporheic flow in alluvial rivers. Water Resour. Res., 44. https://doi.org/10.1029/2008WR007081
30. Robinson, A. R., & Rohwer, C. (1959). Measuring seepage from irrigation channels. USDA Tech. Bull. 1203.
31. Rozporządzenie Ministra Gospodarki Morskiej i Żeglugi Śródlądowej z dnia 11 października 2019 r. w sprawie klasyfikacji stanu ekologicznego, potencjału ekologicznego i stanu chemicznego oraz sposobu klasyfikacji stanu jednolitych części wód powierzchniowych, a także środowiskowych norm jakości dla substancji priorytetowych (Regulation of the Minister of Maritime Economy and Inland Navigation of 11 October 2019 on the classification of ecological status, ecological potential and chemi-cal status and on the classification of surface water bodies and environmental quality standards for priority substances) (in Polish)
32. Schmadel, N. M., Ward, A. S. & Wondzell, S. M. (2017). Hydrologic controls on hyporheic exchange in a headwatermountain stream. Water Resour. Res. , 53, pp. 6260-6278. https://doi.org/10.1002/2017WR020576
33. Siergieiev, D., Lundberg, A. & Widerlund, A. (2014). Hyporheic water exchange in a large hydropower-regulated boreal river – directions and rates. Hydrol. Res. , 45, pp. 334–348. https://doi.org/10.2166/nh.2013.011
34. Ward, A. S. (2016). The evolution and state of interdisciplinary hyporheic research. WIREs Water, 3, pp. 83–103. https://doi.org/10.1002/wat2.1120
35. Worstell, R. V. & Carpenter, C. D. (1969). Improved Seepage Meter Operation for Lo-cating Areas of High Water Loss in Canals and Ponds. 58th Annu. Oregon Reclam. Congr.
36. Zieliński, P. & Jekatierynczuk-Rudczyk, E. (2010). Dissolved organic matter transfor-mation in the hyporheic zone of a small lowland river. Oceanol. Hydrobiol. Stud. , 39, pp. 97–103. https://doi.org/10.2478/v10009-010-0021-9
38. Zijl, W. & Nawalany, M. (1993) Natural groundwater flow. Lewis Publishers
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Authors and Affiliations

Maria Grodzka-Łukaszewska
1
Zofia Pawlak
1
Grzegorz Sinicyn
1

  1. Faculty of Building Services, Hydro and Environmental Engineering, Warsaw University of Technology, Poland
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Abstract

This paper presents the concept and methodology for the designing of a “tree-shaped” production line. The concept is a result of the search for production unit organization that meets the Lean Production assumptions, i.e. focusing on lead time (throughput time) shortening with simultaneous ability of use in conditions of varied product range. The varied product range characterized by lower technological-organizational similarity when compared to “Ushaped” units typical for Lean Production. The paper presents an algorithm for the designing of a “tree-shaped” production line and examples of its application. The designed unit underwent evaluation according to the criteria preferred by Lean Manufacturing experts. The designed production unit achieved results confirming the effectiveness of the proposed concept for the analysed sets of input data on the product range and production capacities.
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Authors and Affiliations

Natalia Pawlak
1
Lukasz Hadas
1
Marek Fertsch
1

  1. Poznan University of Technology

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