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Tytuł:
A study of challenges in entrepreneurship development and potential role of public sector in mitigating them – evidence from Kurdistan region of Iraq
Autorzy:
Alavi, Hamed
Ghafour, Shano Ibrahim
Powiązania:
https://bibliotekanauki.pl/articles/2064722.pdf
Data publikacji:
2019
Wydawca:
STE GROUP
Tematy:
entrepreneurship
economy
entrepreneurship ecosystem
market
finance
Opis:
The purpose of this paper is to identify the main challenges faced by entrepreneurs in the Kurdistan region of Iraq and possible ways that regional public sector can take for the purpose of improving entrepreneurship development. Given the importance of entrepreneurs in the economic development and job creation, it’s critical to understand what drives entrepreneurs to become less effective and to investigate how the implementation of “entrepreneurship ecosystem” practiced by public policy makers mitigates these challenges. As a result, authors strive to answers two main questions in this paper: “What are the factors that hold back entrepreneurs in the Kurdistan Region to start their own businesses? “And “What measures the local government can take to mitigate such challenges?” The methodology used in this study is quantitative approach, involving a survey questionnaire. This paper consists of four parts: After the introduction, second part will provide empirical data on challenges facing entrepreneurs in Kurdistan Region of Iraq. Discussion and analysis of the findings are done in the third part. Finally, in the last part, paper will offer conclusions by summarizing the key findings.
Źródło:
Multidisciplinary Aspects of Production Engineering; 2019, 2, 1; 589--599
2545-2827
Pojawia się w:
Multidisciplinary Aspects of Production Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Risk Analysis in Construction Phase of Oil and Gas Projects: A Critical Literature Review
Autorzy:
Alavi, Hamed
Nadir, Soma Latif
Powiązania:
https://bibliotekanauki.pl/articles/2064865.pdf
Data publikacji:
2020
Wydawca:
STE GROUP
Tematy:
project management
construction projects
risk management
oil and gas industry
Opis:
The construction phase of oil and gas projects (OGPs) is a risky process and project managers face numerous challenges during this particular period. A proper risk analysis and management during the construction phase of the OGPs not only will affect the timely and successful operation of the project as a whole, it can also affect occurrence of risks in subsequent phases and overall economic viability of the project. As a result, via using extensive literature review, this study tries to answer the question of what are main risks involved in construction phase of OGPs and which methods are used for identifying them? The outcome of this research would likely be a valuable source for construction professionals to improve project performance while managing existing risks. It is also useful to avoid common problems that befall many project managers and will assist them to have a better understanding of risk management as part of a project plan.
Źródło:
Multidisciplinary Aspects of Production Engineering; 2020, 3, 1; 668--680
2545-2827
Pojawia się w:
Multidisciplinary Aspects of Production Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some features of salt-architecture in the medieval Sudanic cities: Taghaza in Mali as a model
Autorzy:
Ali, Ismail Hamed Ismail
Powiązania:
https://bibliotekanauki.pl/articles/18866582.pdf
Data publikacji:
2023-06-30
Wydawca:
Wydawnictwo Adam Marszałek
Tematy:
Salt-Architecture
West Africa
Taghaza
salinas
Sahara
Opis:
The Salt played a vital role in the life of west African societies, including the land of Sudan, from the dawn of their early history. In some cases, it was even more valuable than gold because of the lack of salt in most Sudanic kingdoms, such as Ghana, Mali & Songhai. The most famous of these Salinas was known as Taghaza, in addition to Ulil & Tatantatal, etc. They were related to what is called salt-architecture. We took Taghaza as an example of this rare architecture. West Africans used salt to preserve food, for healing and even for building houses, mosques and city walls. As the city of Taghaza, currently located in Mali, is in the most famous salt region, it is considered to be the best model of a salty city in west Africa. Salt contributed to the Sahara trade, known as the trade of salt and gold. Salt was indispensable for most inhabitants of West Africa. They lived near e salt quarries and used it mainly to build their houses and any other constructions they need.
Źródło:
African Journal of Economics, Politics and Social Studies; 2023, 2(1); 69-77
2956-2686
Pojawia się w:
African Journal of Economics, Politics and Social Studies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybrid binary whale optimization algorithm based on taper shaped transfer function for software defect prediction
Hybrydowy, binarny algorytm WOA oparty na transmitancji stożkowej do prognozowania defektów oprogramowania
Autorzy:
Alnaish, Zakaria A. Hamed
Hasoon, Safwan O.
Powiązania:
https://bibliotekanauki.pl/articles/27315468.pdf
Data publikacji:
2023
Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Tematy:
feature selection
binary whale optimization algorithm
taper-shaped transfer function
software defect prediction
wybór cech
algorytm optymalizacji binarnej
transmitancja stożkowa
przewidywanie defektów oprogramowania
Opis:
Reliability is one of the key factors used to gauge software quality. Software defect prediction (SDP) is one of the most important factors which affectsmeasuring software's reliability. Additionally, the high dimensionality of the features has a direct effect on the accuracy of SDP models.The objective of this paper is to propose a hybrid binary whale optimization algorithm (BWOA) based on taper-shape transfer functions for solving feature selection problems and dimension reduction with a KNN classifier as a new software defect prediction method. In this paper, the values of a real vector that representsthe individual encoding have been converted to binary vector by using the four types of Taper-shaped transfer functionsto enhance the performance of BWOA to reduce the dimension of the search space. The performance of the suggestedmethod (T-BWOA-KNN)was evaluatedusing eleven standard software defect prediction datasets from the PROMISE and NASA repositories depending on the K-Nearest Neighbor (KNN) classifier. Seven evaluation metrics have been used to assess the effectiveness of the suggested method. The experimental results have shownthat the performanceof T-BWOA-KNNproduced promising results compared to other methods including ten methods from the literature, four typesof T-BWOAwith the KNN classifier. In addition, the obtained results are compared and analyzed with other methods from the literature in termsof the average numberof selected features (SF) and accuracy rate (ACC) using the Kendall W test. In this paper, a new hybrid software defect prediction methodcalledT-BWOA-KNNhas been proposed which is concerned with the feature selection problem. The experimental results have provedthatT-BWOA-KNN produced promising performance compared with other methods for most datasets.
Niezawodność jest jednym z kluczowych czynników stosowanych do oceny jakości oprogramowania.Przewidywanie defektów oprogramowania SDP (ang. Software Defect Prediction) jest jednym z najważniejszych czynników wpływających na pomiar niezawodności oprogramowania. Dodatkowo, wysoka wymiarowość cech ma bezpośredni wpływ na dokładność modeli SDP.Celemartykułu jest zaproponowanie hybrydowego algorytmu optymalizacji BWOA (ang. Binary Whale Optimization Algorithm) w oparciu o transmitancję stożkową do rozwiązywania problemów selekcji cech i redukcji wymiarów za pomocą klasyfikatora KNN jako nowej metody przewidywania defektów oprogramowania.W artykule, wartości wektora rzeczywistego, reprezentującego indywidualne kodowanie zostały przekonwertowane na wektor binarny przy użyciu czterech typów funkcji transferu w kształcie stożka w celu zwiększenia wydajności BWOA i zmniejszenia wymiaru przestrzeni poszukiwań.Wydajność sugerowanej metody (T-BWOA-KNN) oceniano przy użyciu jedenastu standardowych zestawów danych do przewidywania defektów oprogramowania z repozytoriów PROMISE i NASA w zależności od klasyfikatora KNN. Do oceny skuteczności sugerowanej metody wykorzystano siedemwskaźników ewaluacyjnych. Wyniki eksperymentów wykazały, że działanie rozwiązania T-BWOA-KNN pozwoliło uzyskaćobiecujące wyniki w porównaniu z innymi metodami, w tym dziesięcioma metodami na podstawie literatury, czterema typami T-BWOA z klasyfikatorem KNN. Dodatkowo, otrzymane wyniki zostały porównanei przeanalizowane innymi metodami z literatury pod kątem średniej liczby wybranych cech (SF) i współczynnika dokładności (ACC), z wykorzystaniem testu W.Kendalla. W pracy, zaproponowano nową hybrydową metodę przewidywania defektów oprogramowania, nazwaną T-BWOA-KNN, która dotyczy problemu wyboru cech. Wyniki eksperymentów wykazały, że w przypadku większości zbiorów danych T-BWOA-KNN uzyskała obiecującą wydajnośćw porównaniu z innymi metodami.
Źródło:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2023, 13, 4; 85--92
2083-0157
2391-6761
Pojawia się w:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neuro-fuzzy modelling of blending process in cement plant
Autorzy:
Araromi, D O
Odewale, S A
Hamed, J O
Powiązania:
https://bibliotekanauki.pl/articles/102547.pdf
Data publikacji:
2015
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
neuro-fuzzy
blending
carbonate content
raw mix
Opis:
The profitability of a cement plant depends largely on the efficient operation of the blending stage, therefore, there is a need to control the process at the blending stage in order to maintain the chemical composition of the raw mix near or at the desired value with minimum variance despite variation in the raw material composition. In this work, neuro-fuzzy model is developed for a dynamic behaviour of the system to predict the total carbonate content in the raw mix at different clay feed rates. The data used for parameter estimation and model validation was obtained from one of the cement plants in Nigeria. The data was pre-processed to remove outliers and filtered using smoothening technique in order to reveal its dynamic nature. Autoregressive exogenous (ARX) model was developed for comparison purpose. ARX model gave high root mean square error (RMSE) of 5.408 and 4.0199 for training and validation respectively. Poor fit resulting from ARX model is an indication of nonlinear nature of the process. However, both visual and statistical analyses on neuro-fuzzy (ANFIS) model gave a far better result. RMSE of training and validation are 0.28167 and 0.7436 respectively, and the sum of square error (SSE) and R-square are 39.6692 and 0.9969 respectively. All these are an indication of good performance of ANFIS model. This model can be used for control design of the process.
Źródło:
Advances in Science and Technology. Research Journal; 2015, 9, 28; 27-33
2299-8624
Pojawia się w:
Advances in Science and Technology. Research Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Detection of partial rotor bar rupture of a cage induction motor using least square support vector machine approach
Autorzy:
Birame, M’hamed
Bessedik, Sid Ahmed
Benkhoris, Mohamed Fouad
Powiązania:
https://bibliotekanauki.pl/articles/1840890.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
fault diagnosis
partial rupture rotor bar
spectral analysis
least square support vector machine
LS-SVM
diagnostyka uszkodzeń
silnik indukcyjny
wirnik
analiza widmowa
maszyna wektorów nośnych
Opis:
Squirrel cage induction motors suffer from numerous faults, for example cracks in the rotor bars. This paper aims to present a novel algorithm based on Least Squares Support Vector Machine (LS-SVM) for detection partial rupture rotor bar of the squirrel cage asynchronous machine. The stator current spectral analysis based on FFT method is applied in order to extract the fault frequencies related to rotor bar partial rupture. Afterward the LS-SVM approach is established as monitoring system to detect the degree of rupture rotor bar. The training and testing data sets used are derived from the spectral analysis of one stator phase current, containing information about characteristic harmonics related to the partial rupture rotor bar. Satisfactory and more accurate results are obtained by applying LS-SVM to fault diagnosis of rotor bar.
Źródło:
Diagnostyka; 2021, 22, 1; 57-63
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A comparative assessment of meteorological drought in the Tafna basin, Northwestern Algeria
Autorzy:
Bougara, Hanane
Baba-Hamed, Kamila
Borgemeister, Christian
Tischbein, Bernhard
Kumar, Navneet
Powiązania:
https://bibliotekanauki.pl/articles/2048629.pdf
Data publikacji:
2021
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
drought
meteorological drought indices
Tafna basin
trend analysis
Opis:
The drought ranked first in terms the natural hazard characteristics and impacts followed by tropical cyclones, regional floods, earthquakes, and volcanoes. Drought monitoring is an important aspect of drought risk management and the assessment of drought is usually done through using various drought indices. The western region in Algeria is the most affected by the drought since the middle of the 70s.The current research focuses on the analysis and comparison of four meteorological drought indices (standardized precipitation index – SPI, percent of normal index – PN, decile index – DI, and rainfall anomaly index – RAI) in the Tafna basin for different time scales (annual, seasonal, and monthly) during 1979–2011. The results showed that the SPI and DI have similar frequencies for dry and wet categories. The RAI and PN were able to detect more drought categories. Meanwhile, all indices have strong positive correlations between each other, especially with Spearman correlation tests (0.99; 1.0), the meteorological drought indices almost showed consistent and similar results in the study area. It was determined in 1982 as the driest year and 2008 as the wettest year in the period of the study. The analysis of the trend was based on the test of Mann–Kendall (MK), a positive trend of the indices were detected on a monthly scale, this increasing of indices trend represent the increasing of the wet categories which explains the increasing trend of the rainfall in the last 2000s. These results overview of the understanding of drought trends in the region is crucial for making strategies and assist in decision making for water resources management and reducing vulnerability to drought.
Źródło:
Journal of Water and Land Development; 2021, 51; 78-93
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Taxonomic Descriptions of Two Marine Ciliates, Euplotes dammamensis n. sp. and Euplotes balteatus (Dujardin, 1841) Kahl, 1932 (Ciliophora, Spirotrichea, Euplotida), Collected from the Arabian Gulf, Saudi Arabia
Autorzy:
Chen, Xumiao
Zhao, Yan
Al-Farraj, Saleh A.
AL-QURAISHY, Saleh
El-Serehy, Hamed A.
Shao, Chen
Al-Rasheid, Khaled A. S.
Powiązania:
https://bibliotekanauki.pl/articles/763475.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Jagielloński. Wydawnictwo Uniwersytetu Jagiellońskiego
Tematy:
Marine ciliate, morphogenesis, morphology, new species, SSU-rRNA, taxonomy
Opis:
The morphology, morphogenesis and infraciliature of two marine euplotid ciliates, Euplotes dammamensis n. sp. and Euplotes balteatus (Dujardin, 1841) Kahl, 1932, isolated from a sandy beach of the Arabian Gulf, Saudi Arabia, were investigated using observations in vivo and protargol-impregnation methods. Euplotes dammamensis n. sp. is characterized by a combination of features including its huge body size (100–170 × 80–120 μm), 10 conspicuous dorsal ridges, 10 normal-sized frontoventral and two marginal cirri, and 11 dorsal kineties. Euplotes balteatus is mainly characterized by 10 frontoventral, two caudal, and two left marginal cirri, 7–10 dorsal kineties and 5–7 prominent dorsal ridges as well as double-eurystomus silverline system. The small subunit rRNA (SSU-rRNA) gene sequences were determined for both species and phylogenetic analyses based on these data indicated that E. dammamensis is most closely related to E. parabalteatus Jiang et al., 2010, and E. balteatus clusters with E. plicatum Valbonesi et al., 1997, E. orientalis Jiang et al., 2010, and E. bisulcatus Kahl, 1932.
Źródło:
Acta Protozoologica; 2013, 52, 2
1689-0027
Pojawia się w:
Acta Protozoologica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A combined field and automatic approach for lithological discrimination in semi-arid regions, the case of geological maps of bir later region and its vicinity, Nementcha mounts, Algeria
Autorzy:
Chibani, Abdelmouhcene
Hadji, Riheb
Younes, Hamed
Powiązania:
https://bibliotekanauki.pl/articles/2201670.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie
Tematy:
Nememcha Mountains
PCA
MNF
directional filter
unsupervised classification
Góry Nememcha
filtr kierunkowy
klasyfikacja nienadzorowana
Opis:
The Sahara’s Nememcha mountains chain suffers from a significant lack of large-scale geological information. In the Bir Later region with complex morpho-structural settings and arid climate conditions; geological maps have not been yet completed by competent authorities. However, this region harbours Algeria’s largest phosphate mine; with its reserves estimated at more than one billion tons of ore grading 20% phosphorus pentoxide. Geomatic-based techniques of Multisource Remote Sensing data allow the classification and identification of the lithologic features. The adopted method quarries the spectral signal, the alteration processes, and the thickness of the rocky banks. For this task, we apply Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), directional filters, and unsupervised classification (K-Means data) techniques to calibrate and correct Landsat 8 OLI and Sentinel-2A multispectral images. A petrographic study with field and laboratory work was carried out in order to confirm the machine description of the different facies. The results showed that the proposed lithology classification scheme can achieve accurate classification of all lithologic types, in the Cenozoic, Mesozoic, and Holocene deposits of the study area. The lithological map obtained from the GIS-RS-Processing is highly correlated with our field survey. Therefore, multispectral image data (Landsat 8 OLI and Sentinel-2A) coupled with an advanced image enhancement technique and field surveys are recommended as a rapid and cost-effective tool for lithologic discrimination and mapping. The experimental results fully demonstrated the advantages of the reliance on laboratory tests in the sensed lithology validation in an arid area.
Źródło:
Geomatics, Landmanagement and Landscape; 2022, 4; 7--26
2300-1496
Pojawia się w:
Geomatics, Landmanagement and Landscape
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficiency of some meteorological drought indices in different time scales, case study: wadi Louza basin (NW-Algeria)
Efektywność niektórych wskaźników suszy meteorologicznej w różnej skali czasu na przykładzie zlewni uedu Louza w północno-zachodniej Algierii
Autorzy:
Djellouli, F.
Bouanani, A.
Baba-Hamed, K.
Powiązania:
https://bibliotekanauki.pl/articles/293111.pdf
Data publikacji:
2016
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
drought
effective drought index
standardised precipitation index
wadi Louza
efektywny wskaźnik suszy
susza
ued Louza
wskaźnik standaryzowanego opadu
Opis:
Drought is an insidious hazard of nature in many parts of the world. It originates from persistent shortage of precipitation over a specific region for a specific period of time and has a conceptual and operational definition. Drought impact on some activity, group, or environmental sector depends on the extent of water shortage and ground conditions. Algeria and especially the western region has experienced several periods of drought over the last century, since 1975 to the present day. The most recent drought in 1981, 1989, 1990, 1992, 1994 and 1999 was characterized by its intensity and spatial extent. Drought is identified using various drought indices (meteorological, hydrological and agricultural). In this research, we focus on the meteorological drought, to assess the reliability of these indices under changing climatic conditions. Data was recorded for the period of 1980–2009 at wadi Louza catchment (NW-Algeria). For describing and monitoring drought severity periods, we calculated the correlation between both meteorological drought indices: Standardised Precipitation Index (SPI) and Effective Drought Index (EDI). The results show that the watershed of wadi Louza has experienced a severe meteorological drought. The correlation between meteorological drought indices was good for all time steps and the best was found for 9-month time step. The obtained results may provide some scientific support for fighting against droughts.
Susza jest naturalnym zagrożeniem w wielu częściach świata. Powstaje wskutek trwałego ograniczenia ilości opadów w danym regionie i okresie czasu. Jest zdefiniowana w sensie konceptualnym i operacyjnym. Wpływ suszy na różne rodzaje działalności człowieka i na środowisko zależy od rozmiaru deficytu wody i od warunków glebowych. Algieria, szczególnie jej zachodnia część doświadczyła okresów intensywnej suszy już w ubiegłym wieku, począwszy od roku 1975 r., i doświadcza ich po dzień dzisiejszy. Ostatnia susza charakteryzowała się dużą intensywnością i przestrzennym zasięgiem. Suszę identyfikuje się, używając różnych wskaźników meteorologicznych, hydrologicznych lub rolniczych. W badaniach prezentowanych w niniejszej pracy skupiono się na suszy meteorologicznej, aby ocenić wiarygodność tych wskaźników w zmieniających się warunkach klimatycznych. Dane notowano w okresie 1980–2009 w zlewni uedu Louza w północno-zachodniej Algierii. Na potrzeby charakterystyki i monitoringu okresów suszy obliczono korelację między dwoma wskaźnikami – wskaźnikiem standaryzowanego opadu (SPI) i efektywnym wskaźnikiem suszy (EDI). Wyniki dowodzą, że w zlewni uedu Louza wystąpiła głęboka susza meteorologiczna. Korelacja między wskaźnikami suszy meteorologicznej była dobra w odniesieniu do wszystkich kroków czasowych, ale najlepsza w odniesieniu do okresów 9-miesięcznych. Uzyskane wyniki mogą stanowić naukowe wsparcie w walce z suszą.
Źródło:
Journal of Water and Land Development; 2016, 31; 33-41
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A proposed preamble channel estimation scheme for flip FBMC-based indoor VLC systems
Autorzy:
El-Ganiny, Mohamed Y.
Khalaf, Ashraf A. M.
Hussein, Aziza I.
Hamed, Hesham F. A.
Powiązania:
https://bibliotekanauki.pl/articles/2063904.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
channel estimation
filter bank multicarrier
IEEE 802.15.7 standard
interference approximation method
visible light communication
Opis:
Filter bank multicarrier waveform is investigated as a potential waveform for visible light communication broadcasting systems. Imaginary inter-carrier and/or inter-symbol interference are causing substantial performance degradation in the filter bank multicarrier system. Direct current-biased optical filter bank multicarrier modulation overcomes all the problems of direct current-biased optical-orthogonal frequency division multiplexing modulation approaches in terms of speed and bandwidth. However, it also wastes a lot of energy while transforming a true bipolar signal into a positive unipolar signal by adding direct current-bias. In this paper, a flip-filter bank multicarrier-based visible light communication system was introduced to overcome this problem. In this system, a bipolar signal is converted to a unipolar signal by isolating the positive and negative parts, turning them to positive and then delivering the signal. Also, a new channel estimation scheme for a flip-filter bank multicarrier system is proposed which improves the channel estimation performance compared to that of each of the conventional schemes. The proposed system performance is measured in terms of bit error rate, normalized mean squared error, and constellation diagram. The superiority of the proposed scheme over other conventional structures has been successfully verified by MATLAB 2020b simulation experiments results. These results are evaluated under indoor visible light communication standard.
Źródło:
Opto-Electronics Review; 2022, 30, 1; art. no. e140859
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybrid PAPR reduction schemes for different OFDM-based VLC systems
Autorzy:
El-Ganiny, Mohamed Y.
Khalaf, Ashraf A. M.
Hussein, Aziza I.
Hamed, Hesham F. A.
Powiązania:
https://bibliotekanauki.pl/articles/2174839.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
peak-to-average power ratio
bit error rate
Opis:
Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peak-to-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLABTM software has been successfully used to show the validity of the proposed schemes.
Źródło:
Opto-Electronics Review; 2022, 30, 3; art. no. e141951
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybrid PAPR reduction schemes for different OFDM-based VLC systems
Autorzy:
El-Ganiny, Mohamed Y.
Khalaf, Ashraf A. M.
Hussein, Aziza I.
Hamed, Hesham F. A.
Powiązania:
https://bibliotekanauki.pl/articles/2174840.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
visible light communication
peak-to-average power ratio
bit error rate
Opis:
Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peak-to-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLABTM software has been successfully used to show the validity of the proposed schemes.
Źródło:
Opto-Electronics Review; 2022, 30, 3; art. no. e141951
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exact solution for heat conduction inside a sphere with heat absorption using the regularized Hilfer-Prabhakar derivative
Autorzy:
Elhadedy, Hager
Latif, Mohamed S. Abdel
Nour, Hamed M.
Kader, Abbas H. Abdel
Powiązania:
https://bibliotekanauki.pl/articles/2175524.pdf
Data publikacji:
2022
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
fractional derivatives
Laplace transform
finite sine-Fourier transform
heat transfer
pochodne ułamkowe
transformata Laplace'a
skończona transformata sinusoidalna-Fouriera
wymiana ciepła
Opis:
In this article, we utilize the finite Sine-Fourier transform and the Laplace transform for solving fractional partial differential equations with regularized Hilfer-Prabhakar derivative. These transforms are used to get analytical solutions for the time fractional heat conduction equation (TFHCE) with the regularized Hilfer-Prabhakar derivative associated with heat absorption in spherical coordinates. Two cases of Dirichlet boundary conditions are considered by obtaining an analytical solution in each case. The effect of the parameters of the regularized Hilfer-Prabhakar derivative on the heat transfer inside the sphere is discussed using some figures.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2022, 21, 2; 27--37
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of microwave system location on floatability of chalcopyrite and pyrite in a copper ore processing circuit
Autorzy:
Gholami, Hamed
Rezai, Bahram
Mehdilo, Akbar
Hassanzadeh, Ahmad
Yarahmadi, Mohammadreza
Powiązania:
https://bibliotekanauki.pl/articles/109728.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
microwave technology
chalcopyrite
pyrite
comminution circuits
separation efficiency
Opis:
The present work aims at investigating the effect of microwave local positions (i.e. before crushing (BC), after crushing (AC) and after milling (AM)) on microwave-assisted flotation of chalcopyrite and pyrite in a porphyry copper complex deposit. Individual given samples for each state were pre-treated with a variable power microwave at a power level of 90 to 900W for 15, 30, and 60s. Furthermore, froth floatation experiments were carried out using a laboratory mechanical Denver flotation cell on both microwave-treated and untreated samples. Particle surface properties were characterized by a scanning electron microscopy (SEM) and an energy-dispersive X-ray spectroscopy (EDX) analysis. The results showed that the chalcopyrite and pyrite floatabilities increased monotonically by rising the exposure time and power level for the uncrushed preconditioned samples (BC) due to the enhancement of mineral liberation degrees together with the formation of sulphide species and polysulphides on the mineral surfaces. However, flotation results of treated samples for the crushed one (AC) revealed an optimum range. Formation of intensive oxide layers on the mineral surfaces of milled samples (AM) led to a substantial reduction in their recoveries by increasing the microwave’s power level and the sample’s exposure time. The results obtained from mineral’s floatabilities in recleaner stage showed that the microwave-assisted sample at 900W for 30s at BC state favourably provided 5% higher S.E.’s than that of the untreated sample. Finally, it was concluded that the microwave pretreatment of samples induced the best floatability responses if it located before the crusher.
Źródło:
Physicochemical Problems of Mineral Processing; 2020, 56, 3; 432-448
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
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