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1

The OGLE Collection of Variable Stars. Over 15 000 δ Scuti Stars in the Large Magellanic Cloud

Soszyński I., Pietrukowicz P., Udalski A., Skowron J., Szymański M. K., Poleski R., Skowron D. M., Kozłowski S., Mróz P., Iwanek P., Wrona M., Ulaczyk K., Rybicki K., Gromadzki M., Mróz M.

Acta Astronomica

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2023

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Vol. 73, No. 2

105--126

EN

We present the OGLE collection of δ Scuti stars in the Large Magellanic Cloud and in its foreground. Our dataset encompasses a total of 15 256 objects, constituting the largest sample of extragalactic δ Sct stars published so far. In the case of 12 δ Sct pulsators, we detected additional eclipsing or ellipsoidal variations in their light curves. These are the first known candidates for binary systems containing δ Sct components beyond the Milky Way. We provide observational parameters for all variables, including pulsation periods, mean magnitudes, amplitudes, and Fourier coefficients, as well as long-term light curves in the I- and V-bands collected during the fourth phase of the OGLE project. We construct the period-luminosity (PL) diagram, in which fundamental-mode and first-overtone δ Sct stars form two nearly parallel ridges. The latter ridge is an extension of the PL relation obeyed by first-overtone classical Cepheids. The slopes of the PL relations for δ Sct variables are steeper than those for classical Cepheids, indicating that the continuous PL relation for first-overtone δ Sct variables and Cepheids is non-linear, exhibiting a break at a period of approximately 0.5 d. We also report the enhancement of the OGLE collection of Cepheids and RR Lyr stars with newly identified and reclassified objects, including pulsators contained in the recently published Gaia DR3 catalog of variable stars. As a by-product, we estimate the contamination rate in the Gaia DR3 catalogs of Cepheids and RR Lyr variables.

2

Candidates for Transiting Planets in OGLE-IV Galactic Bulge Fields

Mróz M., Pietrukowicz P., Poleski R., Udalski A., Szymański M. K., Gromadzki M., Ulaczyk K., Kozłowski S., Skowron J., Skowron D. M., Soszyński I., Mróz P., Ratajczak M., Rybicki K. A., Iwanek P., Wrona M.

Acta Astronomica

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2023

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Vol. 73, No. 2

127--158

EN

We present results of a search for transiting exoplanets in 10-yr long photometry with thousands of epochs taken in the direction of the Galactic bulge. This photometry was collected in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV). Our search covered ≈222 000 stars brighter than I=15.5 mag. Selected transits were verified using a probabilistic method. The search resulted in 99 high-probability candidates for transiting exoplanets. The estimated distances to these targets are between 0.4 kpc and 5.5 kpc, which is a significantly wider range than for previous transit searches. The planets found are Jupiter-size, with the exception of one (named OGLE-TR-1003b) located in the hot Neptune desert. If the candidate is confirmed, it can be important for studies of highly irradiated intermediate-size planets. The existing long-term, high-cadence photometry of our candidates increases the chances of detecting transit timing variations at long timescales. Selected candidates will be observed by the future NASA flagship mission, the Nancy Grace Roman Space Telescope, in its search for Galactic bulge microlensing events, which will further enhance the photometric coverage of these stars.

3

The Effect of Sulphur Content on the Microstructure of Vermicular Graphite Cast Iron

Mróz M., Orłowicz A. W., Tupaj M., Lenik M., Kawiński M., Kawiński M.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 1

18--22

EN

The application of ferritic-matrix vermicular graphite cast iron in the production of fireplace fireboxes improves their thermal output, but the consumer market for these products prioritises their price. Given this consideration, this work concerns a comparison of the quality of vermicular graphite cast iron types produced from 0.025%S pig iron (a less expensive material) and 0.010%S pig iron (a more expensive material) in terms of the number and shape of vermicular graphite precipitates varying with the magnesium level in the alloy. It turned out that the vermicular graphite cast iron made with the 0.025%S pig iron demonstrated a slightly lower number of vermicular graphite precipitates. For both vermicular graphite cast iron melts, 0.028%Mg and 0.020%Mg in the alloys provided a vermicular graphite precipitate share of approx. 50% and 95%, respectively.

4

Influence of Microstructure and Heat Transfer Surface on the Thermal Power of Cast Iron Heat Exchangers

Mróz M., Orłowicz A. W., Tupaj M., Lenik M., Kawiński M. J., Kawiński M.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 4

93--96

EN

The paper presents the results of calorimetric tests of segment elements of fireplace inserts. The aim of the work was to optimize their thermal power by replacing the previously used gray cast iron with flake graphite with gray iron with vermicular graphite and replacing the existing geometry of the heat transfer surface with a more developed one. It turned out that the thermal power of the test segments made of cast iron with vermicular graphite was higher compared to the segments of the same shape made of gray cast iron with flake graphite. It was found that the use of segments made of vermicular cast iron with a ferritic matrix allowed for an increase in the thermal power value by dozen percent, compared to segments of the same shape made of vermicular cast iron with a pearlitic matrix. The test results showed that the thermal power of the test segments depends on the variant of the development of both the heat receiving surface and the heat giving off surface. The highest value of the thermal power was obtained when ribbing in the form of a lattice was used on both of these surfaces, and the lowest when using flat surfaces.

5

Ultrasonic Testing of Vermicular Cast Iron Microstructure

Tupaj M., Orłowicz A. W., Mróz M., Kupiec B., Pająk D., Kawiński M.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 4

36--40

EN

The paper presents results of a study on the effect of passage of time on magnesium content in iron alloys and the effect of magnesium content on the number of vermicular graphite precipitations per unit surface area and value of the longitudinal ultrasonic wave velocity for two different vermicularization methods. The study was carried out with the use of inspection bar castings. For specific production conditions, it has been found that in case of application of both the cored wire injection method and the method of pouring liquid metal over magnesium master alloy on ladle bottom, the satisfactory level of magnesium content in the bottom-pour ladle, for which it was still possible to obtain castings with vermicular graphite, was 0.018% Mg. In case of the cored wire injection method, the “time window” available to a pouring station at which castings of vermicular cast iron are expected to be obtained, was about 5 minutes. This corresponds to the longitudinal ultrasonic wave velocity values exceeding 5500 m/s and the number of graphite precipitations per unit surface area above 320 mm-2. In case of the master alloy method, the respective “time window” allowing to obtain castings of vermicular cast iron was only about 3 minutes long. This corresponds to the longitudinal ultrasonic wave velocity value above 5400 m/s and the number of graphite precipitations per unit surface area above 380 mm-2.

6

The Effect of Structure on Thermal Power of Cast-iron Heat Exchangers

Mróz M., Orłowicz A. W., Tupaj M., Jacek-Burek M., Radoń M., Kawiński M.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 1

27--30

EN

The objective of the study reported in this paper was to determine the effect of structure on thermal power of cast-iron heat exchangers which in this case were furnace chambers constituting the main component of household fireplace-based heating systems and known commonly as fireplace inserts. For the purpose of relevant tests, plate-shaped castings were prepared of gray iron with flake graphite in pearlitic matrix (the material used to date typically for fireplace inserts) as well as similar castings of gray cast iron with vermicular graphite in pearlitic, ferritic-pearlitic, and ferritic matrix. For all the cast iron variants of different structures (graphite precipitate shapes and matrix type), calorimetric measurements were carried out consisting in determining the heat power which is quantity representing the rate of heat transfer to the ambient environment. It has been found that the value of the observed heat power was affected by both the shape of graphite precipitates and the type of alloy matrix. Higher thermal power values characterize plate castings of gray iron with vermicular graphite compared to plates cast of the flake graphite gray iron. In case of plates made of gray cast iron with vermicular graphite, the highest values of thermal power were observed for castings made of iron with ferritic matrix.

7

Ductile Cast Iron Microstructure Adjustment by Means of Heat Treatment

Mróz M., Orłowicz A. W., Tupaj M., Kupiec B., Kawiński M.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 3

37--40

EN

The study presented in this paper concerned the possibility to apply a heat treatment process to ductile cast-iron thin-walled castings in order to remove excessive quantities of pearlite and eutectic cementite precipitates and thus meet the customer’s requirements. After determining the rates of heating a casting up to and cooling down from 900°C feasible in the used production heat treatment furnace (v_h = 300°C/h and v_c = 200°C/h, respectively), dilatometric tests were carried out to evaluate temperatures T_gr, TAc₁ ^start, TAc₁ ^{, TAr₁ ^start, and TAr₁ ^end. The newly acquired knowledge was the base on which conditions for a single-step ferritizing heat treatment securing disintegration of pearlite were developed as well as those of a two-step ferritization process guaranteeing complete disintegration of cementite and arriving at the required ferrite and pearlite content. A purely ferritic matrix and hardness of 119 HB was secured by the treatment scheme: 920°C for 2 hours / v_c = 60°C/h / 720°C for 4 hours. A matrix containing 20–45% of pearlite and hardness of 180–182 HB was obtained by applying: 920°C for 2 hours or 4 hours / v_c = 200°C/h to 650°C / ambient air.}

8

Improvement of Operating Performance of a Cast-Iron Heat Exchanger by Application of a Copper Alloy Coating

Mróz M., Orłowicz A. W., Tupaj M., Jacek-Burek M., Radoń M., Kawiński M.

Archives of Foundry Engineering

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2019

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iss. 3

84--87

EN

The paper deals with possibility to improve operating performance of cast-iron heat exchangers by providing them with a copper alloy (CuTi2Cr) with the use of the flame spraying method. A test exchanger was cast of a gray cast iron with vermicular graphite in ferritic-pearlitic matrix obtained in production conditions at KAW-MET Iron Foundry with the wire method used to vermicularize the material. The test samples were two plates cast in sand molds, of which one was given a flame-sprayed CuTi2Cr coat on one side. The operating performance of such model cast-iron heat exchangers, with and without CuTi2Cr coating, was tested on a set-up for determining the heat flow rate (thermal power) transferred by the heat exchanger to environment. The obtained results indicate that the value of the heat flow rate characterizing the CuTi2Cr-coated cast-iron heat exchanger was by 10% higher compared to the flow rate of heat conveyed to environment by the heat exchanger without coating.

9

Improvement of Al-Si Alloy Fatigue Strength by Means of Refining and Modification

Tupaj M., Orłowicz A. W., Trytek A., Mróz M.

Archives of Foundry Engineering

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2019

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iss. 4

61--66

EN

The paper presents results of a study concerning an AlSi7Mg alloy and the effect of subjecting the liquid metal to four different processes: conventional refining with hexachloroethane; the same refining followed by modification with titanium, boron, and sodium; refining by purging with argon carried out in parallel with modification with titanium and boron salts and strontium; and parallel refining with argon and modification with titanium, boron, and sodium salts. The effect of these four processes on compactness of the material, parameters of microstructure, and fatigue strength of AlSi7Mg alloy after heat treatment. It has been found that the highest compactness (the lowest porosity ratio value) and the most favorable values of the examined parameters of microstructure were demonstrated by the alloy obtained with the use of the process including parallel purging with argon and modification with salts of titanium, boron, and sodium. It has been found that in the fatigue cracking process observed in all the four variants of the liquid metal treatment, the crucial role in initiation of fatigue cracks was played by porosity. Application of the process consisting in refining by purging with argon parallel to modification with Ti, B, and Na salts allowed to refine the microstructure and reduce significantly porosity of the alloy extending thus the time of initiation and propagation of fatigue cracks. The ultimate effect consisted in a distinct increase of the fatigue limit value.

10

Odporność na korozję powłoki NiCrFeSi obciążonej cieplnie w atmosferze powietrza i w środowisku siarki

Orłowicz A. W., Mróz M., Tupaj M., Trytek A., Kupiec B., Radoń M., Jacek M.

Przegląd Spawalnictwa

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2018

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R. 90, nr 4

73--75

PL

Praca dotyczy natryskiwanej plazmowo powłoki NiCrFeSi na podłoże ze stali kotłowej (P 250GH). Powłokę obciążano cieplnie w atmosferze powietrza i w środowisku siarki. Obciążenie cieplne wynosiło 2000 cykli. Jeden cykl obejmował: nagrzewanie do temperatury 560 °C i wygrzewanie w tej temperaturze w czasie 3 minut, chłodzenie do temperatury 300 °C, nagrzewanie do 560 °C i wygrzewanie w tej temperaturze w czasie 1,5 minuty oraz chłodzenie do temperatury 150 °C. Efektem obciążeń cieplnych było zmniejszenie grubości powłoki o 39 μm. Stwierdzono, że siarka dyfundowała w warstwę przypowierzchniową. Tworzące się produkty jej reakcji z niklem i chromem sprzyjały wykruszaniu się składników tej warstwy, które następnie ulegały utlenianiu.

EN

The paper deals with a NiCrFeSi coating plasma-sprayed on a boiler steel (P 250GH) substrate. The coating was heat-loaded in atmosphere of air and in sulfur environment. The heat load comprised 2000 cycles, whereas each of the cycles included: heating up to 560 °C and soaking at the temperature for 3 minutes; cooling down to 300 °C and soaking at the temperature for 1.5 minutes; and cooling down to 150 °C. As a result of such thermal cycling, thickness of the coating was reduced by 39 μm. It has been found that sulfur had diffused into the superficial layer. The occurring products of sulfur reacting with chromium and nickel contributed to spalling of components of the layer which subsequently were subject to oxidation.

11

Możliwości poprawy odporności na erozję kawitacyjną staliwnych zaworów hydraulicznych

Orłowicz A.W., Mróz M., Radoń M., Kupiec B., Jacek M., Sobolewska P.

Przegląd Spawalnictwa

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2018

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R. 90, nr 4

56--58

PL

Powierzchnie wewnętrzne gniazd uszczelniająco-odwadniających zaworów hydraulicznych są zwykle odwzorowane przez wkładki wykonane ze stopu miedzi, które są mechanicznie połączone z korpusem zaworu. Wskutek gwałtownych zmian ciśnienia wody, wkładki te mogą ulec poluzowaniu, co powoduje nieszczelność zaworów. W pracy zaproponowano nowe rozwiązanie poprzez zastosowanie powłoki natryskiwanej plazmowo. Przedstawiono wyniki badań odporności na erozję kawitacyjną dotychczas stosowanego materiału wkładki ze stopu CuZn39Pb2Al oraz materiału powłoki wykonanej z proszku WCCoCr 86104. Oceniono strukturę geometryczną powierzchni kraterów kawitacyjnych (parametr Rt). Stwierdzono, że powłoka naniesiona plazmowo charakteryzuje się zdecydowanie wyższą odpornością na erozję kawitacyjną, w porównaniu do dotychczas stosowanego materiału wkładki ze stopu CuZn39Pb2Al.

EN

Inner surfaces of sealing-draining seats in hydraulic valves are usually reproduced by inserts made of a copper alloy joined mechanically with valve housing. As a result of sudden variations in water pressure, they can be subject to loosening which leads to deterioration of valve tightness. In the paper, a new solution is proposed for finishing surfaces of valve seats by application of a plasma-sprayed coating. The solution is validated by results of cavitation erosion resistance test performed for both the CuZn39Pb2Al alloy used earlier for the inserts and the material of coating made of WCCoCr 86104 powder. The resistance assessment was based on geometrical structure of cavitation craters (parameter Rt). It has been found that the plasma-sprayed coating demonstrated a definitely higher resistance to cavitation erosion compared to CuZn39Pb2Al alloy used earlier for valve seat inserts.

12

Prognozowanie procesów logistycznych metodą wag harmonicznych

Mróz M.

Gospodarka Materiałowa i Logistyka

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2018

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nr 11

311--329, CD

PL

Tematem artykułu jest prognozowanie procesów logistycznych metodą wag harmonicznych. Głównym celem jest pokazanie w ujęciu teoretycznym otrzymywania najlepszej prognozy procesów logistycznych wykorzystując metodę wag harmonicznych. Natomiast problem badawczy dotyczył właściwego wykorzystania do prognozowania procesów logistycznych metody wag harmonicznych, aby otrzymać w konsekwencji dokładniejszą prognozę. Oczywistym działaniem opisanego algorytmu prognozowania metodą wag harmonicznych jest wygładzanie szeregu czasowego metodą trendu pełzającego przy właściwym doborze stałej wygładzenia za pomocą weryfikacji błędem średniokwadratowym. W metodzie trendu pełzającego, w wygładzeniu szeregu czasowego, zastosowano pięć sposobów szacowania parametrów strukturalnych modelu z jedną zmienną. Takie alternatywne podejście, powinno pomóc każdemu badaczowi dobrać właściwy sposób do swoich potrzeb. Ujęcie teoretyczne problemu pozwoliło na podjęcie próby uporządkowania obszaru wiedzy związanej z prognozowaniem metodą wag harmonicznych, a w tym głównie z wygładzaniem szeregu czasowego metodą trendu pełzającego.

EN

The subject of the article is predicting logistic processes using the harmonic weight method. The main goal is to show in the theoretical approach how to obtain the best prediction of logistics processes using the harmonics method. However, the research problem concerned the proper use of harmonic weight methods for predicting logistic processes to obtain a more accurate prediction as a consequence. The obvious operation of the described algorithm of prediction using the harmonic weights method is smoothing the time series with the creeping trend method with the proper selection of the constant smoothing by means of the mean square error verification. In the creeping trend method, in smoothing the time series, five methods of estimating the structural parameters of the model with one variable were applied. Such an alternative approach should help every researcher to choose the right way to suit their preferences. Theoretical approach to the problem allowed to organize the area of knowledge related to prediction using the harmonic weight method, and mainly with smoothing the time series with the creeping trend method.

13

The Effect of the Heat Flux Density on Microstructure of Surface Remeltings on C355 Alloy Castings

Orłowicz A. W., Mróz M., Tupaj M., Trytek A., Jacek M., Radoń M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

35--38

EN

The paper presents results of a study on the effect of the flux density of heat carried away for the remelting area to substrate in the course of surface remelting with concentrated heat stream on values of structural parameters λ1D and λ2D of α(Al) phase dendrites in C355 alloy. The remeltings were made with the use of GTAW method, at arc current intensity I = 200 A and concentrated heat stream scanning speed vs = 200, 400, 600, and 800 mm/min. The used protective gas was argon supplied at rate of 20 l/min. It has been found that the increase of the rate of scanning with concentrated heat stream results in a change of the remelting-substrate separation surface shape consisting in reduction of the remelting width and depth. This increases the value of the flux density of heat transmitted from the remelting area to substrate which in turn acts in favor of reduction of structural parameters λ1D and λ2D characterizing α(Al) phase dendrites in C355 alloy.

14

Morphology and Material Properties of Carbides in High (24%) Chromium Cast Iron

Orłowicz A. W., Mróz M., Tupaj M., Trytek A., Jacek M., Radoń M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 1

77--80

EN

The present paper is a presentation of results of a study on morphology, chemical composition, material properties (HVIT, HIT, EIT), and nanoindentation elastic and plastic work for carbide precipitates in chromium cast iron containing 24% Cr. It has been found that the carbides differ in chemical composition, as well as in morphology and values characterizing their material properties. The carbides containing the most chromium which had the shape of thick and long needles were characterized with highest values of the analyzed material properties.

15

Improvement of Resistance of Cast-iron Heat Exchangers to High-temperature Corrosion

Orłowicz A. W., Tupaj M., Trytek A., Mróz M., Radoń M., Jacek M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 3

49--52

EN

The paper discusses the possibility of improving resistance of heat exchangers made of gray cast iron with flake graphite to high-temperature corrosion by providing them with metallic coatings. A metallic coating containing 76.9% Ni, 19.8% Cr, 1.7% Si, 0.9% Fe, and 0.9% Mn was applied by means of the plasma spraying method and subjected to cyclically variable thermal loads in the atmosphere of solid fuels combustion products (oxygen, sulfur, chlorine, and sodium). In a 30-day thermal load test held at temperature 500°C it has been found that thickness of the metallic coating decreased from the initial (240 ± 6) μm to (231 ± 6) μm. The depth to which sulfur, chlorine, and sodium penetrated the coating was about 30 μm. Increased oxygen content occurred along the whole coating depth. In the coating area adjacent to the substrate surface, the content was twice as high compared to this observed in the initial coating material. Although presence of oxygen was found within the whole depth of the coating, i.e. (231 ± 6) μm, no signs of susceptibility of the sprayed metallic layer to separation from substrate of gray cast iron with flake graphite were found.

16

A Possibility to Improve Resistance of Cast-iron Wood Chip Fine Grinder Liners to Abrasive Wear

Orłowicz A. W., Mróz M., Tupaj M., Kupiec B., Jacek M., Radoń M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 4

35--38

EN

The paper deals with the issue of potential for improvement of resistance of wood chip fine grinders to abrasive wear by providing them with WCCoCr coating applied with the use of atmospheric plasma spraying (APS). The study focused on establishing parameters of the technological process of spraying a 250–270 μm thick coating onto surface of ductile cast iron castings used to date as grinder linings. The presented data include results of microstructure examination, chemical composition analysis, HV hardness measurements, and scratch tests for both previous and new variant of linings. The obtained scratch test results indicate that the material of the coating is characterized with definitely lower susceptibility to scratching. The scratch made on coating was 75–84 μm wide and 7.2–8.2 μm deep, while the scratch on cast iron was distinctly wider (200–220 μm) and deeper (8.5–12.8 μm). In case of cast iron, the range of variability in scratch width and depth was definitely larger. This can be explained with large difference in hardness of individual components of microstructure of cast iron and significantly larger plastic deformation of cast iron compared to the coating revealed in the course of indenter motion over surfaces of the two materials. It has been found that application of WCCoCr coating offered better resistance of lining surfaces to scratching which can be considered a rationale for undertaking in-service tests.

17

A Possibility to Improve Resistance of Cast-iron Hydraulic Valves to Cavitation Wear

Orłowicz A. W., Tupaj M., Mróz M., Kupiec B., Jacek M., Radoń M.

Archives of Foundry Engineering

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2018

|

Vol. 18, iss. 4

31--34

EN

A common problem encountered in hydraulic valves is a progressing deterioration of tightness of their water flow cutting-off seats. The seats are provided usually with a copper-alloy insert joined mechanically with cast-iron valve housing. The problem of unreliability of such joints can be solved by providing surface of the seat with a coating, deposited with the use of HVOF method and resistant to abrasive and cavitation wear. The tests were carried out for a sealing-draining seat insert made of CuZn39Pb2Al brass used to date and a specimen taken from the cast-iron valve housing which was the substrate for a plasma-sprayed coating of powder containing 86.1% Cr, 7.2% Ni, and 6.7% C. The coating, 345 ± 15 μm thick, was characterized with good quality of bonding with cast-iron substrate and high compactness of the material. The cavitation wear test on materials used in the study were carried out with the use of Vibra-Cell ultrasonic liquid processor (Sonics) equipped with a piezoelectric probe operating at the frequency of 20 kHz. Based on profilograms taken along a line crossing centers of cavitation craters, measurements of the height parameter Rt, and microscopic observations of surfaces it has been found that the coating plasma-sprayed onto substrate of nodular cast iron demonstrated higher resistance to cavitation compared to copper-alloy inserts used so far in cast-iron hydraulic valves. Cavitation craters on the material used typically for valve seats to date were more distinctly outlined and deeper compared to craters observed on the coating. Larger were also sizes of local tear-outs which resulted in larger difference between the peaks line and the valleys line.

18

Practical Ways to Improve SAIDI and SAIFI Power Supply Reliability Indicators in an MV Grid

Janiszewski P., Sawicki J., Kurpas J., Mróz M.

Acta Energetica

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2018

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nr 1

45--50

EN

Based on a mathematical model of an existing MV network and analysis of its failures, remedies to improve SAIDI and SAIFI reliability indicators are proposed. Factors are identified and described that significantly affect electricity supply interruptions’ duration, frequency of their occurrence, and the number of not supplied recipients. A methodology is proposed for a relatively quick location of the failure site, isolation of the damaged grid element, and restoration of the supply of as many recipients as possible, considering the specificity of grids in mountainous areas. By simulation of potential failures based on the deterministic reliability model (DRM), the effectiveness of the adopted solutions is demonstrated in the perspective of a dozen years or so.

PL

Na podstawie modelu matematycznego rzeczywistej sieci SN oraz analizy awarii w niej występujących wskazano środki zaradcze mające na celu poprawę wskaźników niezawodności zasilania SAIDI i SAIFI. Zidentyfikowano i opisano czynniki istotnie wpływające na czas trwania przerw w dostawach energii elektrycznej, częstotliwość ich występowania oraz liczbę odbiorców pozostających wówczas bez napięcia. Zaproponowano metodykę pozwalającą na możliwie szybką lokalizację miejsca wystąpienia awarii, wyizolowanie uszkodzonego elementu sieci oraz przywrócenie napięcia maksymalnej liczbie odbiorców, uwzględniając specyfikę sieci w terenach górzystych. Symulując potencjalne awarie w oparciu o deterministyczny model niezawodnościowy (DMZ), wykazano poprawność przyjętych rozwiązań w kilkunastoletniej perspektywie.

19

Dobór zmiennych niezależnych w modelowaniu procesów logistycznych metodą analizy grafów

Mróz M.

Zeszyty Naukowe Akademii Sztuki Wojennej

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2017

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nr 3(108)

129--155

PL

Tematem artykułu jest dobór zmiennych niezależnych w modelowaniu procesów logistycznych metodą analizy grafów. Celem głównym jest teoretyczna i empiryczna analiza możliwości stosowania metody analizy grafów do doboru zmiennych niezależnych w modelach ekonometrycznych. Problem badawczy natomiast obejmował swym zasięgiem także poszukiwanie rozwiązań dotyczących uzyskania właściwych kryteriów wyboru zmiennych niezależnych spośród zmiennych kandydujących, przy wykorzystaniu właściwie stawianych i weryfikowanych hipotez zerowych. Niewątpliwym osiągnięciem zastosowania metody analizy grafów jest możliwość uzyskania macierzy współczynników korelacji liniowej Pearsona, które obrazują powiązania między poszczególnymi zmiennymi oraz pozwalają na ich podstawie wyeliminować te zmienne kandydujące, które nie są statystycznie istotne dla badanego procesu logistycznego.

EN

The theme of the article is the selection of independent variables in the modelling of logistic processes using the analysis graphs method. The main objective is theoretical and empirical analysis of the applicability of the analysis graphs method for the selection of independent variables in econometric models. The research included seeking solutions for obtaining the appropriate criteria for the selection of independent variables of the variables candidate, using properly posed and verified hypotheses. The unquestionable achievement of the analysis graphs method is rendering it possible to obtain a matrix of correlation Pearson coefficients which illustrate the relationships between the candidate variables and allow these variables to be eliminated, which is not statistically significant for the test of the logistics process.

20

Prace remontowe Mostu Cłowego w Szczecinie

Żółtowski K., Binczyk M., Kalitowski P., Żółtowski P., Rosiak M., Mróz M.

Mosty

|

2017

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nr 6

16--20

PL

W artykule przedstawiono historię budowy i eksploatacji Mostu Cłowego w Szczecinie. W ciągu 56 lat wykonywano kilka prac eksperckich i napraw. Most został zamknięty po poważnej awarii konstrukcji zewnętrznego kabla sprężającego. Przedstawiono główne przyczyny degradacji oraz koncepcję demontażu. Opisano także prace konstruktorskie dotyczące remontu mostu.

EN

The paper presents the history of the construction and lifecycle of the post-tensioned Most Cłowy (Customs Bridge) in Szczecin. Several expert works and repairs were performed during the 56 years of its service. Finally the bridge was closed after a serious structural failure of the external prestressing cable. The main causes of the degradation are explained and the concept of the design of the dismantling is presented. Moreover, the construction works concerning the rehabilitation of the bridge are described.