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Tytuł:
AC power regulation techniques for renewable energy sources
Techniki regulacji mocy odbiorników AC dla odnawialnych źródeł energii
Autorzy:
Ostrowski, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/28875039.pdf
Data publikacji:
2023
Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Tematy:
ac power regulators
pulse width modulation converters
renewable energy systems
regulatory mocy prądu przemiennego
przetwornice modulacji szerokości impulsu
systemy energii odnawialnej
Opis:
This article explores different AC power regulation techniques that can be employed to optimize the output of renewable energy sources, suchas solar and wind power systems. The article provides an overview of the challenges associated with regulating AC power output from renewable sources and examines various techniques that can be used to improve the performance of power regulation systems. These techniques include voltage control, phase control, reactive power compensation, and power factor correction. The article also discusses the benefits and limitations of each technique, as well as their potential applications in renewable energy systems. Overall, this article provides valuable insights for engineers and researchers workingto optimize power auto consumption in renewable energy systems.
W tym artykule omówiono różne techniki regulacji mocy prądu zmiennego, które można wykorzystać do optymalizacji produkcji energiize źródeł odnawialnych, takich jak systemy energii słonecznej i wiatrowej. Artykuł zawiera przegląd wyzwań związanych z regulacją mocy wyjściowej prądu przemiennego ze źródeł odnawialnych i analizuje różne techniki, które można wykorzystać do poprawy wydajności systemów odnawialnych źródeł energii. Techniki te obejmują sterowanie napięciem, sterowanie fazą, kompensację mocy biernej i korekcję współczynnika mocy. W artykule omówiono również zalety i ograniczenia poszczególnych technik, a także ich potencjalne zastosowania w systemach energii odnawialnej. Artykuł zawiera cenne informacje dla inżynierów i badaczy pracujących nad optymalizacją auto konsumpcji energii elektrycznej w systemach energii odnawialnej.
Źródło:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2023, 13, 4; 103--108
2083-0157
2391-6761
Pojawia się w:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation of effective hydraulic parameters of concrete irrigation canals
Autorzy:
Fatxulloyev, Alisher
Rakhimov, Qudratjon
Allayorov, Davronjon
Samiev, Luqmon
Otakhonov, Makhsud
Powiązania:
https://bibliotekanauki.pl/articles/2203516.pdf
Data publikacji:
2023
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
canal bottom relative width
concrete canal
irrigation canal
sediment transport capacity
sedimentation tank
best hydraulic section
trapezoidal shape
Opis:
When taking water from pre-mountain rivers, for transferring of large amounts of river sediments, rich in mineral fertilizers, along with water to crop fields through irrigation networks requires high sediment transport capacity and deformation resistance from irrigation networks. The projecting and construction of irrigation canals with these features in the foothills requires concreting the canal. The high content of river sediments in the Sokh River (5 kg∙m-3) and the low efficiency of the Right Bank Irrigation Reservoir (10-15%) require high hydraulic efficiency of water intake canals from this system. The main challenge is to reduce costs in concreted canals and ultimately ensure technical superiority. In the research were used generally accepted research methods in hydraulics, in particular field research and consequently, mathematical analysis. Kokandsay, Kartan and Bachkir irrigation canals were accepted as the object of research, the canals were designed on the basis of the best hydraulic section, the canal side slope was taken as a variable parameter and the technical and economic efficiency was checked using computer software. As a result, it was found that the consumption of concrete raw material for 1 running meter can save 0.2-0.3 m3, depending on the adoption of the canal side slope, the acceptance of the slope of the canal wall at values 1-1.5 will increase up to sedimentation 10%.
Źródło:
Journal of Water and Land Development; 2023, 56; 14--20
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of Technologies for Mining Ores with Instable Hanging Wall Rocks
Rozwój technologii wydobywania rudy z niestabilnymi wiszącymi skałami
Autorzy:
Pysmennyi, Serhii
Chukharev, Serhii
Kourouma, Ibrahima Kalil
Kalinichenko, Vsevolod
Matsui, Anatolii
Powiązania:
https://bibliotekanauki.pl/articles/2200996.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Przeróbki Kopalin
Tematy:
mining system
stress
methods
pillar width
rock strength
losses
dilution
system wydobywczy
naprężenia
metody
szerokość filaru
wytrzymałość skały
straty
rozcieńczenie
Opis:
Underground mines of Kryvyi Rih iron ore deposit apply room mining systems or systems with bulk caving of ore and overlying rocks in a ratio of 35% to 65%. Most mines prefer room mining systems with pillar caving due to high, technical and economic indicators. However, when mining certain areas, the problem arises of hanging wall rocks stability. Under the same mining and geological conditions of the deposit, stopes are stable in some areas, but in others waste rocks get in the stope from the side of the hanging wall when a slight exposure is created. Thus, in conditions of instable rocks of the hanging wall, development and improvement of the technology involving room mining is an urgent issue. Analysis of researchers reveals factors that significantly indluence stability of the hanging wall rocks and ore. The developed methods enable determining stability parameters and applying an improved option of room mining system in conditions of the instable hanging wall with the help of a protective ore pillar located at the instable hanging wall. Calculations performed demonstrate that application of the proposed mining system enables an increase in the iron content in the mined ore mass by 0.94%, the increased amount of the ore mass extracted and a profit of 18.73 thousand euros for the whole of a block.
Kopalnie podziemne złoża rudy żelaza w Krzywym Rogu stosują systemy urabiania komorowego lub systemy z zawałem rudy i nadległych skał w stosunku 35% do 65%. Większość kopalń preferuje systemy eksploracji komorowej z zawałem filarowym ze względu na wysokie wskaźniki techniczne i ekonomiczne. Jednak podczas eksploatacji niektórych obszarów pojawia się problem ze stabilnością wiszących skał. W takich samych warunkach górniczo-geologicznych złoża stopnie na niektórych obszarach są stabilne, ale na innych skały płonne dostają się do stopu od strony wiszącej ściany, gdy powstaje niewielkie odsłonięcie. Dlatego też w warunkach niestabilnych skał wiszącej ściany pilnym zagadnieniem jest rozwój i doskonalenie technologii eksploatacji komorowej. Analiza badań ujawnia czynniki, które znacząco wpływają na stabilność wiszących skał i rudy. Opracowane metody umożliwiają wyznaczenie parametrów statecznościowych oraz zastosowanie udoskonalonego wariantu systemu eksploracji pomieszczenia w warunkach niestabilnej ściany wiszącej za pomocą filaru ochronnego rudy, znajdującego się przy niestabilnej ścianie wiszącej. Z przeprowadzonych obliczeń wynika, że zastosowanie proponowanego systemu urabiania umożliwia zwiększenie zawartości żelaza w wydobywanej masie rudy o 0,94%, zwiększenie ilości wydobywanej masy rudy oraz zysk w wysokości 18,73 tys. euro za cały blok.
Źródło:
Inżynieria Mineralna; 2023, 1; 103--112
1640-4920
Pojawia się w:
Inżynieria Mineralna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of spiral vanes width on the separation performance of a hydrocyclone
Autorzy:
Liu, Peikun
Wang, Xiaoguo
Jiang, Lanyue
Zhang, Yuekan
Yang, Xinghua
Li, Xiaoyu
Wang, Hui
Powiązania:
https://bibliotekanauki.pl/articles/27323656.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
hydrocyclone
vane width
numerical simulation
separation performance
Opis:
Aiming at the problem of “entrainment fine particles in underflow” of hydrocyclone in grinding and classification process, a hydrocyclone with spiral vanes (the SV hydrocyclone) was proposed. The CFD techniques were used to study the pressure field, velocity field, turbulence field, particle field and classification efficiency of hydrocyclones with spiral vanes of different widths. The results show that the pressure drop, axial velocity, tangential velocity, turbulence intensity of SV hydrocyclone are reduced in different degrees compared with conventional hydrocyclone, and the reduction becomes more obvious with the increase of vane width. In the case of a vane width of 0.04D, the underflow recovery rate of 5μm and 10μm fine particles was reduced by 16.2% and 15.7%. The selection of spiral vanes with small widths is beneficial to improve the separation accuracy of fine particles and reduce the cut particle size.
Źródło:
Physicochemical Problems of Mineral Processing; 2023, 59, 6; art. no. 173563
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimizing the Width and Compressive Strength of Artificial Protective Pillar in the Mining of Medium-Thick Coal Seams in Quang Ninh Using the Numerical Model
Autorzy:
Bui, Manh Tung
Dinh, Van Cuong
Powiązania:
https://bibliotekanauki.pl/articles/27323230.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Przeróbki Kopalin
Tematy:
medium thick coal seam
entry gate road
artificial support pillar
pillar width
compressive strength
górnictwo
filary
koszty
Opis:
Currently, in many countries with the coal mining industry, the technology of using artificial pillars has been successfully applied to replace coal pillars to protect the entry gate road, thereby reducing the rate of resource loss, as well as the cost of entry gate road, and mining costs. However, in order to optimize the required width and compressive strength of artificial pillars with thickness, slope angle and mining depth, more detailed studies are required for each specific geological condition. This research uses Phase 2 numerical simulation software to analyze the stability of artificial protective pillar of the roadway prepared in the mining of medium-thick coal seams in the Quang Ninh coal region (Vietnam). The research results show that the relationship between the width of the artificial pillar and the slope angle follows the rule of a linear function. The size of the artificial protection pillar increases according to the mining depth. When the mining depth is 350m, the size of the pillar changes from 1.0 ÷ 2.4m, and to 1.4 ÷ 2, 8m at a depth of 500m. When the slope angle increases, the required pillar width also increases. That is due to the fact that at a large slope angle, the pressure acting on the pillar is not at the center, but deflects to the side adjacent to the entry gate road that needs to be protected, the compression force is not distributed evenly. The required compressive strength of the artificial pillar varies according to the condition of the slope angle, when the seam slopes 10°, the required compressive strength is from 8 to 12 MPa, when the slope angle increases to 20°, the required compressive strength of the pier increases to 18 ÷ 28 Mpa, but when the slope angle increases to 35°, the required compressive strength of the pillar tends to decrease to 16 ÷ 17 MPa. Thus, when operating in the corresponding conditions, it is necessary to choose the size and required compressive strength of the artificial pillar to ensure the working capacity of the pillar.
Źródło:
Inżynieria Mineralna; 2023, 2; 143--154
1640-4920
Pojawia się w:
Inżynieria Mineralna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the effecting parameters on laser cutting process by using response surface methodology (RSM) method
Autorzy:
Hasan, H. K.
Powiązania:
https://bibliotekanauki.pl/articles/2055753.pdf
Data publikacji:
2022
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
laser cutting process
non-linear inclined cutting
kerf width
laser parameters
cięcie laserowe
szerokość szczeliny
parametry lasera
Opis:
Purpose: The main aim of this research is to analyse the effects of the laser cutting parameters on the kerf width of stainless steel (2505), and develop a model of laser cutting that can predict the relation between the characteristics of the resultant kerf width and the process input parameters. Design/methodology/approach: To achieve the minimum kerf width; the optimal setting of the effecting parameters like; power supply, cutting speed, and gas pressure for the response surface methodology, and factorial design-based optimal parametric analysis has been carried out for this purpose. A mathematical model for analysis of the kerf width was developed using the (Minitab 16) on the basis of experimental results. Findings: It’s found that the interaction between power value, cutting speed, and pressure has a significant effect on the response value. Also, it’s found that, when the power and cutting speed are set at optimal values i.e. 1250 watt and 5 mm/min, the minimum kerf width will be 0.389 mm. The mathematical model has been established based on regression analysis by factorial design and response surface model. Research limitations/implications: The cutting quality in this process widely depend on the technical specifications of a laser machine. Consequently, machine operation parameters are considered the main limitations factor in this process. Practical implications: In this current work, the 4 mm thickness stainless steel (2505) has been used in the experimental investigation to measure the Influence of laser cutting machine parameters. In addition, optimal laser cutting parameter values that minimize the width of kerf width were identified. The optimization problem was formulated and solved by the second-order model method. The laser cutting experiment was planned and conducted according to the (RSM) central composite design approach (uncode). Originality/value: The validation with experimental results shows that the factorial analysis gives an average error 5%, and the (R-sq) is equal to 69.02%. It’s concluded that the model that has the (R-sq) value greater than 41% is considered as a fit model and can be used for the next machining process.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2022, 110, 2; 59--66
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Applying optimization techniques on cold-formed C-channel section under bending
Autorzy:
El-Lafy, Heba F.
Elgendi, Elbadr O.
Morsy, Alaa M.
Powiązania:
https://bibliotekanauki.pl/articles/27312402.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
kształtownik zimnogięty
optymalizacja
algorytm genetyczny
cold-formed sections
single optimization
multi-objective optimization
genetic algorithms
effective width method
C-channel beams
Opis:
There are no standard dimensions or shapes for cold-formed sections (CFS), making it difficult for a designer to choose the optimal section dimensions in order to obtain the most cost-effective section. A great number of researchers have utilized various optimization strategies in order to obtain the optimal section dimensions. Multi-objective optimization of CFS C-channel beams using a non-dominated sorting genetic algorithm II was performed using a Microsoft Excel macro to determine the optimal cross-section dimensions. The beam was optimized according to its flexural capacity and cross-sectional area. The flexural capacity was computed utilizing the effective width method (EWM) in accordance with the Egyptian code. The constraints were selected so that the optimal dimensions derived from optimization would be production and construction-friendly. A Pareto optimal solution was obtained for 91 sections. The Pareto curve demonstrates that the solution possesses both diversity and convergence in the objective space. The solution demonstrates that there is no optimal solution between 1 and 1.5 millimeters in thickness. The solutions were validated by conducting a comprehensive parametric analysis of the change in section dimensions and the corresponding local buckling capacity. In addition, performing a single-objective optimization based on section flexural capacity at various thicknesses The parametric analysis and single optimization indicate that increasing the dimensions of the elements, excluding the lip depth, will increase the section’s carrying capacity. However, this increase will depend on the coil’s wall thickness. The increase is more rapid in thicker coils than in thinner ones.
Źródło:
International Journal of Applied Mechanics and Engineering; 2022, 27, 4; 52--65
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of fibre laser welding parameters on the microstructure and weld geometry of commercially pure titanium
Autorzy:
Abdulridha, M.M.
Jilabi, A.S.J.A.Z.
Powiązania:
https://bibliotekanauki.pl/articles/24200584.pdf
Data publikacji:
2022
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
fibre laser welding
laser power
welding speed
CP titanium
depth penetration weld
weld width
spawanie laserem światłowodowym
moc lasera
prędkość spawania
CP tytan
głębokość wtopienia spoiny
szerokość spoiny
Opis:
Purpose: The primary purpose of the study was the metallurgical characterization of laser welds. The weldability of commercial production of pure titanium and titanium alloy (CP-Ti) has also been examined. Design/methodology/approach: In this research, the laser fibre method was used to weld sheets of pure titanium, and then microscopy and scanning electron microscopy were used to study the changes in the microstructure, the depth of weld penetration and the width of the weld area with changing welding parameters. Findings: The results proved that increasing the laser power significantly increases the depth of weld penetration and weld width. When the heat input is increased, the shape of the weld pool changes from a V shape to an hourglass shape. It was also observed that the depth of the crater formed increases with the increase in the laser power due to the increase in the melting and evaporation of the weld metal. Increasing the welding speed also has a negative impact on the weld geometry because it reduces the heat input and absorption of laser energy by the weld metal and thus reduces the melting of the metal. The microstructure of the fusion zone consists of acicular α. Fine grains formed in the weld centre at low heat input; the granules became columnar-like. Since commercially pure titanium contains a small amount of beta-phase stabilizers, the cooling rate is extremely high for martensite to occur. Research limitations/implications: In the future, it is recommended to study the effect of changing welding parameters on the mechanical properties of pure titanium because of its great importance in industrial and medical applications. Originality/value: Studying the effect of changing laser power and welding speed on the metallurgical properties of pure titanium, and consequently its effect on the mechanical properties of welds.
Źródło:
Archives of Materials Science and Engineering; 2022, 117, 1; 34--41
1897-2764
Pojawia się w:
Archives of Materials Science and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Single-source three-phase switched-capacitor-based MLI
Autorzy:
Jena, Kasinath
Gupta, Krishna Kumar
Bhatnagar, Pallavee
Jain, Sanjay K.
Stala, Robert
Waradzyn, Zbigniew
Piróg, Stanisław
Penczek, Adam
Mondzik, Andrzej
Skała, Aleksander
Powiązania:
https://bibliotekanauki.pl/articles/2175942.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
multilevel inverter
switched capacitor
multicarrier pulse width modulation
cost function
ANPC inverter
Opis:
This article proposes a novel three-phase inverter based on the concept of switched capacitors (SCs), which uses a single DC source. A three-phase, seven-level line-to-line output voltage waveform is synthesised by the proposed topology, which includes eight switches, two capacitors, and one diode per phase leg. The proposed topology offers advantages in terms of inherent voltage gain, lower voltage stresses on power switches, and a reduced number of switching components. Additionally, the switched capacitors are self-balanced, thereby eliminating the need for a separate balancing circuit. The proposed structure and its operating principle, the self-balancing mechanism of the capacitors, and the control strategy are all thoroughly explained in the article. The proposed topology has also been compared with some recent SC topologies. Lastly, the proposed topology has been shown to be feasible through simulation and experimentation.
Źródło:
Power Electronics and Drives; 2022, 7, 42; 197--209
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The results of the introduction of twisted pine (Pinus contorta) in Bolshoy Solovetsky Island
Autorzy:
Sobolev, A.
Feklistov, P.
Bolotov, I.
Barzut, O.
Powiązania:
https://bibliotekanauki.pl/articles/2106672.pdf
Data publikacji:
2022
Wydawca:
Instytut Badawczy Leśnictwa
Tematy:
forestry
Bolshoy Solovetsky Island
twisted pine
Pinus contorta
height
diameter
tree ring width
late wood
assimilation apparatus
pathology
Opis:
In the central part of the Bolshoy Solovetsky Island, in the same type of growing conditions, two plots were created in 1988: the first consisted of twisted pine (Pinus contorta Loud. var. latifolia S. Wats) crops and the second one was of Scots pine (Pinus sylvestris L.). The aim of the study was to establish the morphological parameters of the twisted pine and its growth in the conditions of the Bolshoy Solovetsky Island in comparison with the native species P. sylvestris L. Also, we aimed to identify the features of P. contorta var. latifolia and determine the possibility and necessity of further introduction of the species. The preservation of the twisted pine and scots pine cultures was determined. Accounting trees were selected (62 and 31 trees, respectively), in which morphometric indicators were measured. Wood samples (cores) were taken from them with an age drill to measure radial growth. The radial increment was measured using the MBS-9 microscope and the Lintab device. To measure the increase in height, six medium-sized model trees were cut down. According to the taxation indicators, the two types differed slightly and the differences were most often unreliable. The average height of the twisted pine trees was significantly higher compared to that of Scots pine. The thickness of the bark varied; on average, at the age of 18, it was 1.35 ± 0.038 mm for twisted pine and 1.86 ± 0.095 for Scots pine, that is, the native pine bark was 38% thicker. Typical for twisted pine were a significant number of pathologies noted in 22% of the studied trees. Twisted pine was distinguished by a stronger development of the assimilation apparatus: the number of branches of the first order, the number of branches in the whorl, the life span of needles. An increase in radius (the width of the annual ring) was observed at 14–15 years, and then with age, the value decreased in twisted pine and remained at a consistently high level in Scots pine. The width of the late zone of the annual ring was 12% in Scots pine and 14% in twisted pine; but at a young age, the late wood in twisted pine was very small. The increase in height of the twisted pine was on average less than that of Scots pine. The dependence of the trunk volume on the diameter was almost identical in both species.
Źródło:
Folia Forestalia Polonica. Series A . Forestry; 2022, 64, 1; 1-6
0071-6677
Pojawia się w:
Folia Forestalia Polonica. Series A . Forestry
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Bidirectional Buck-Boost Converter-Based Switching Ripple Communication Strategy for Intelligent Street Lighting Systems
Autorzy:
Zhang, Yixuan
Hu, Yihua
Tse, Zion
Liu, Yuwei
Deng, Jiamei
Xu, Hui
Wang, Yangang
Li, Wei
Powiązania:
https://bibliotekanauki.pl/articles/1955998.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
bidirectional switching ripple communication
buck-boost converter
intelligent street lighting system
pulse width modulation
smart city
Opis:
The light-emitting diode (LED) is an essential component of intelligent street lighting (ISL) systems. An efficient ISL system can not only reduce power consumption by planning LED illuminating time but also reduce maintenance costs through a high degree of automation. In this paper, a buck-boost converter is used to realise composite transmission of power and signals for an ISL system. The power is modulated by the pulse width modulation (PWM) approach, and the switching ripple generated in the PWM process is utilised as the carrier of the signals transmitted between the remote-control centre and the slave nodes. Moreover, the proposed model involves a ‘request to send (RTS)/confirm to send (CTS)’ mechanism to avoid signal conflicts. Compared with the conventional power line communication (PLC) approach, the proposed transmission scheme has the advantages of simple circuit structure and simple system wiring. Additionally, a simulation model built in MATLAB/Simulink proves the designed transmission method has strong anti-noise ability.
Źródło:
Power Electronics and Drives; 2021, 6, 41; 260-275
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Algorithmic Aspects of Secure Connected Domination in Graphs
Autorzy:
Kumar, Jakkepalli Pavan
Reddy, P. Venkata Subba
Powiązania:
https://bibliotekanauki.pl/articles/32327157.pdf
Data publikacji:
2021-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
secure domination
complexity classes
tree-width
chordal graphs
Opis:
Let G = (V, E) be a simple, undirected and connected graph. A connected dominating set S ⊆ V is a secure connected dominating set of G, if for each u ∈ V \ S, there exists v ∈ S such that (u, v) ∈ E and the set (S \ {v}) ∪ {u} is a connected dominating set of G. The minimum size of a secure connected dominating set of G denoted by γsc(G), is called the secure connected domination number of G. Given a graph G and a positive integer k, the Secure Connected Domination (SCDM) problem is to check whether G has a secure connected dominating set of size at most k. In this paper, we prove that the SCDM problem is NP-complete for doubly chordal graphs, a subclass of chordal graphs. We investigate the complexity of this problem for some subclasses of bipartite graphs namely, star convex bipartite, comb convex bipartite, chordal bipartite and chain graphs. The Minimum Secure Connected Dominating Set (MSCDS) problem is to find a secure connected dominating set of minimum size in the input graph. We propose a (∆(G)+1)-approximation algorithm for MSCDS, where (G) is the maximum degree of the input graph G and prove that MSCDS cannot be approximated within (1 − ɛ) ln(|V|) for any ɛ > 0 unless NP ⊆ DTIME |V|O(log log |V|)) even for bipartite graphs. Finally, we show that the MSCDS is APX-complete for graphs with Δ(G) = 4.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 4; 1179-1197
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An active power filter based on a hybrid converter topology – Part 1
Autorzy:
Gwóźdź, Michał
Ciepliński, Łukasz
Powiązania:
https://bibliotekanauki.pl/articles/2173586.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
shunt active power filter
pulse width modulation
PWM
sigma-delta modulator
silicon carbide
bocznikowy filtr mocy czynnej
modulacja szerokości impulsu
modulator sigma-delta
węglik krzemu
Opis:
This paper presents a concept of a shunt active power filter, which is able to provide more precise mapping of its input current drawn from a power line in a reference signal, as compared to a typical filter solution. It can be achieved by means of an interconnection of two separate power electronics converters making, as a whole, a controlled current source, which mainly determines the quality of the shunt active filter operation. One of these power devices, the “auxiliary converter”, corrects the total output current, being a sum of output currents of both converters, toward the reference signal. The rated output power of the auxiliary converter is much lower than the output power of the main one, while its frequency response is extended. Thanks to both these properties and the operation of the auxiliary converter in a continuous mode, pulse modulation components in the filter input current are minimized. Benefits of the filter are paid for by a relatively small increase in the complexity and cost of the system. The proposed solution can be especially attractive for devices with higher output power, where, due to dynamic power loss in power switches, a pulse modulation carrier frequency must be lowered, leading to the limitation of the “frequency response” of the converter. The concept of such a system was called the “hybrid converter topology”. In the first part of the paper, the rules of operation of the active filter based on this topology are presented. Also, the results of comparative studies of filter simulation models based on both typical, i.e. single converter, and hybrid converter topologies, are discussed.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; art. no. e136218
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An active power filter based on a hybrid converter topology – Part 1
Autorzy:
Gwóźdź, Michał
Ciepliński, Łukasz
Powiązania:
https://bibliotekanauki.pl/articles/2090725.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
shunt active power filter
pulse width modulation
PWM
sigma-delta modulator
silicon carbide
bocznikowy filtr mocy czynnej
modulacja szerokości impulsu
modulator sigma-delta
węglik krzemu
Opis:
This paper presents a concept of a shunt active power filter, which is able to provide more precise mapping of its input current drawn from a power line in a reference signal, as compared to a typical filter solution. It can be achieved by means of an interconnection of two separate power electronics converters making, as a whole, a controlled current source, which mainly determines the quality of the shunt active filter operation. One of these power devices, the “auxiliary converter”, corrects the total output current, being a sum of output currents of both converters, toward the reference signal. The rated output power of the auxiliary converter is much lower than the output power of the main one, while its frequency response is extended. Thanks to both these properties and the operation of the auxiliary converter in a continuous mode, pulse modulation components in the filter input current are minimized. Benefits of the filter are paid for by a relatively small increase in the complexity and cost of the system. The proposed solution can be especially attractive for devices with higher output power, where, due to dynamic power loss in power switches, a pulse modulation carrier frequency must be lowered, leading to the limitation of the “frequency response” of the converter. The concept of such a system was called the “hybrid converter topology”. In the first part of the paper, the rules of operation of the active filter based on this topology are presented. Also, the results of comparative studies of filter simulation models based on both typical, i.e. single converter, and hybrid converter topologies, are discussed.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2021, 69, 1; e136218, 1--10
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An approach to suppress high-frequency resonance using model predictive and selective harmonic elimination combined strategy
Autorzy:
Chen, Sitong
Chen, Xiaoqiang
Wang, Ying
Xiong, Ye
Powiązania:
https://bibliotekanauki.pl/articles/1841300.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
CRH5 EMUs and traction power supply coupled system
high-frequency oscillation
high speed railway
model predictive control (MPC)
selective harmonic elimination pulse-width modulation (SHEPWM)
CRH5 EMU i system sprzężony z zasilaniem trakcyjnym
oscylacja wysokiej częstotliwości
kolej dużych prędkości
kontrola predykcyjna modelu (MPC)
selektywna eliminacja harmoniczna modulacja szerokości impulsu (SHEPWM)
Opis:
High-frequency resonance is a prominent phenomenon which affects the normal operation of the high-speed railway in China. Aiming at this problem, the resonance mechanism is analyzed first. Then, model predictive control and selective harmonic elimination pulse-width modulation (MPC-SHEPWM) combined control strategy is proposed, where the harmonics which cause the resonance can be eliminated at the harmonic source. Besides, the MPC is combined to make the current track the reference in transients. The proposed control has the ability to suppress the resonance while has a faster dynamic performance comparing with SHEPWM. Finally, the proposed MPC-SHEPWM is tested in a simulation model of CRH5 (Chinese Railway High-speed), EMUs (electric multiple units) and a traction power supply coupled system, which shows that the proposed MPC-SHEPWM approach can achieve the resonance suppression and shows a better dynamic performance.
Źródło:
Archives of Electrical Engineering; 2021, 70, 2; 415-430
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 128

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