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Tytuł:
A general class of McKean-Vlasov stochastic evolution equations driven by Brownian motion and Lèvy process and controlled by Lèvy measure
Autorzy:
Ahmed, N.
Powiązania:
https://bibliotekanauki.pl/articles/729570.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
McKean-Vlasov stochastic differential equation
Hilbert spaces
existence of optimal controls
Opis:
In this paper we consider McKean-Vlasov stochastic evolution equations on Hilbert spaces driven by Brownian motion and L`evy process and controlled by L`evy measures. We prove existence and uniqueness of solutions and regularity properties thereof. We consider weak topology on the space of bounded Le´vy measures on infinite dimensional Hilbert space and prove continuous dependence of solutions with respect to the Le´vy measure. Then considering a certain class of Le´vy measures on infinite as well as finite dimensional Hilbert spaces, as relaxed controls, we prove existence of optimal controls for Bolza problem and some simple mass transport problems
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2016, 36, 2; 181-206
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A relaxation theorem for partially observed stochastic control on Hilbert space
Autorzy:
Ahmed, N.
Powiązania:
https://bibliotekanauki.pl/articles/729417.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
partially observed control
infinite dimensional Hilbert space
relaxed controls
Zakai equation
Opis:
In this paper, we present a result on relaxability of partially observed control problems for infinite dimensional stochastic systems in a Hilbert space. This is motivated by the fact that measure valued controls, also known as relaxed controls, are difficult to construct practically and so one must inquire if it is possible to approximate the solutions corresponding to measure valued controls by those corresponding to ordinary controls. Our main result is the relaxation theorem which states that the set of solutions corresponding to ordinary controls is weakly dense in the set of solutions corresponding to relaxed controls. This is presented in Theorem 5.3 after giving some existence results on optimal controls for the infinite dimensional Zakai equation used for its proof.
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2007, 27, 2; 295-314
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An assessment of unstimulated salivary flow rate, IgA and clinical oral dryness among active and passive smokers
Autorzy:
Nigar, Seeme
Hassan, Sobia
Maqsood, Afsheen
Ahmed, Naseer
Al-Askar, Mansour
Mokeem, Sameer A.
Alqutub, Montaser N.
Aldahian, Nada
AlSagob, Eman I.
AlMubarak, Abdulrahman A.
Vohra, Fahim
Abduljabbar, Tariq
Powiązania:
https://bibliotekanauki.pl/articles/2085673.pdf
Data publikacji:
2022-02-15
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
IgA
xerostomia
passive smokers
active smokers
salivary flow rate
oral dryness
Opis:
ObjectivesThe aim of this study was to assess the impact of smoking on the whole salivary flow rate (SFR), IgA levels and clinical oral dryness (COD) among active and passive smokers.Material and MethodsThe participants were categorized as active smokers (N = 54) or passive smokers (N = 163). Saliva was collected in tubes and placed in ice storage at –70°C. Salivary IgA levels were assessed in duplication using the enzyme linked immunosorbent assay (ELISA) method. Following the saliva sample collection, the subjects were assessed for COD using the COD score, SFR and caries. Chi-square test, the t-test and ANOVA were employed to compare the clinical impact of the smoking status associated with specific variables (smoking status, number of cigarettes, active caries, gender, age, COD score, IgA level and SFR). A p-value of <0.05 was considered significant.ResultsTwo hundred and seventeen subjects with the mean age of 32.86±6.30 years, with 145 males (66.8%) and 72 females (33.2%), were included in the study. Among the active smokers, 88.8% were males compared to 11.2% females. The active smokers had the mean age of 32.52 years, a COD score of 1.43, an IgA level of 1.39 g/l, and a SFR of 0.37 ml/min. Among the passive smokers, 59.5% were males and 40.5% were females, with the mean age of 32.97 years, a COD score of 0.87 g/l, an IgA level of 1.47, and a SFR of 0.42 ml/min. Active caries showed a positive correlation with the number of cigarettes, with significance in the >35 years age group (p < 0.05).ConclusionsThe study demonstrated significant differences in SFR, IgA and COD scores among the active and passive smokers. The number of cigarettes had a negative impact on saliva production, IgA levels, the oral health status, and the progression of caries with respect to age and gender. Smoking potentially leads to xerostomia associated with active caries.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2022, 35, 1; 39-51
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biological synthesis of Titanium Dioxide nanoparticles by Curcuma longa plant extract and study its biological properties
Autorzy:
Abdul Jalill, Raghad DH.
Nuaman, Rasha S.
Abd, Ahmed N.
Powiązania:
https://bibliotekanauki.pl/articles/1182934.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
biosynthesis
curcuma longa
damping-off
nanoparticles
plant
tio2
Opis:
The objective of this study was biosynthesis of titanium dioxide nanoparticles (TiO2 NPs) using Curcuma longa aqueous extract and characterize them. Study their effect on the growth, sporulation, pathogenicity of Fusarium graminearum and some wheat plants parameters compared with standards industrials nanoparticles. C. longa aquatic extract was used to biosynthesis TiO2 NPs by two methods. At first method, TiO2 was found in both colloidal solutions (CS) and nanopawder while it found in jest nanopawder in second method. All biosynthetic nanoparticles were in nano size. It was: 91.37 nm, 76.36 nm of (CS) and nanopawder for first methods respectively while it was 92.6 nm of nanopawder in second method. All nanoparticles have good optical properties. Crystal’s shape of nanopawder were in three form: anatase, rutilr and brookite and it was anatase in colloidal solutionat first method while it was pure anatase innanopawder when at second method. The average crystallite size of was calculate by Scherer's equation, it was 43.088 nm and 22.881 nm for nanopawder and colloidal solution respectively at first method. It was 45.808 nm for nanopawder at second method. All concentrations of nanoparticles were reduced fungal and spores. These decreasing were more effective using biosynthetic compare with industrial synthetic nanoparticles. There were reductions in damping-off caused by F. graminearum by biosynthetic NBs in both varieties of plant (Al-Rasheed and Tamuze-2). These was better than the effect of industrial synthetic nanoparticles. The resistance to damping off and the growth of plant in Al-Rasheed variety was more sensitive compared with Tamuze-2 variety especially at higher concentrations. There were decrease in all plant's parameters at most concentrations of TiO2 biological synthetic compare with industrial synthetic nanoparticles in Al-Rasheed variety, while there were inductions in some plant's parameters by biosynthetic nanoparticles compared with industrial synthetic in Tamuze-2 variety. Finally, C. longa can be used to biosynthesis TiO2 NPs with good biological properties.
Źródło:
World Scientific News; 2016, 49, 2; 204-222
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Collection of hospital wastewater data using deduplication approaches
Autorzy:
Khan, N. A.
Sinha, G. R.
Ahmed, S.
Feshchenko, A.
Changani, F.
Qureshi, A.
Mazhar, M. A.
Neklonskyi, I.
Powiązania:
https://bibliotekanauki.pl/articles/1818511.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
statistics
hospital wastewater
medical waste
deduplication
approaches
servers
statystyka
ścieki szpitalne
odpady medyczne
deduplikacja
podejścia
serwery
Opis:
Purpose: This investigation aims to study the various approaches currently used to reduce the load on computer servers in order to better manage data on hospital wastewater treatment and solid waste generation. Design/methodology/approach: This manuscript investigates the taxonomies of deduplication procedures based on literature and other data sources, thereby presenting its classification and its challenges in detection. Findings: Based on the literature survey of deduplication techniques, the method of deduplication dispensed on cloud gadget devices has been found to be a promising research challenge. The gaps discussed include a reduction in storage space, bandwidth, type of disks used, and expenditure on energy usage and heat emissions when implementing these strategies. The art work on a scalable, robust, green and allocated approach to deduplication for a cloud gadget will remain of interest in destiny. Research limitations/implications: Considerable attention is focused on the deduplication due to efficient, extensive storage system. Practical implications: This research paper will be useful to identify deduplication techniques which are nowadays used in different hospital wastewater data collection systems and put significant proposals for further improvements in deduplication. Originality/value: This manuscript portrays a broader assessment of the available literature for data duplication along with the classification of different methods for the data storage used in the different level of storage of hospital wastewater data collection.
Źródło:
Archives of Materials Science and Engineering; 2020, 104, 1; 5--18
1897-2764
Pojawia się w:
Archives of Materials Science and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Controllability of evolution equations and inclusions driven by vector measures
Autorzy:
Ahmed, N.U.
Powiązania:
https://bibliotekanauki.pl/articles/729615.pdf
Data publikacji:
2004
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
controlability
impulsive systems
differential inclusions
Hilbert spaces
vector valued measures
C₀ semigroups
Opis:
In this paper, we consider the question of controllability of a class of linear and semilinear evolution equations on Hilbert space with measures as controls. We present necessary and sufficient conditions for weak and exact (strong) controllability of a linear system. Using this result we prove that exact controllability of the linear system implies exact controllability of a perturbed semilinear system. Controllability problem for the semilinear system is formulated as a fixed point problem on the space of vector measures and is concluded controllability from the existence of a fixed point. Our results cover impulsive controls as well as regular controls.
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2004, 24, 1; 49-72
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cotton leaf blight disease caused by Alternaria alternata in Sudan
Autorzy:
Mohamed, O.E.
Beshir, M.M.
Ahmed, N.E.
Powiązania:
https://bibliotekanauki.pl/articles/2084617.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Alternaria alternata
conidia
Gossypium spp.
internal transcribed spacer
(ITS)
morphological variability
pathogenicity
Opis:
Genetically modified Bt cotton (Gossypium hirsutum) leaves with typical symptoms of Alternaria early blight disease resembling that of tomato and potato were observed in the main cotton growing schemes in Sudan. Symptoms on leaves appeared as either brown 2leaf spot with gray centers or leaf blight with concentric rings. Pathogenicity tests using isolates with both symptoms showed that the isolated fungi were highly pathogenic to both G. hirsutum and G. barbadense cotton varieties. Alternaria alternata isolated from infected tomato and potato leaves with early blight symptoms was included for comparison. Microscopic examination showed that the mean length of conidia from cotton, tomato and potato isolates ranged from 26.25 to 45.45 µm, while the width ranged from 9.56 to 13.64 µm. The mean number of transverse septa among all isolates was 3.4 to 5.7 and the peak length ranged from 3.75 to 7.8 µm. Based on morphological characteristics the two isolates from cotton were identified as A. alternata. Genomic DNA was extracted directly from fungal cultures grown on potato dextrose agar (PDA) plates using a Zymo Research Quick DNA kit. A species-specific primer using the internal transcribed spacer ribosomal DNA (ITS rDNA) PCR scoring indicated the presence of A. alternata using primer pair ITS4/ITS5. Amplifications of the internal transcribed spacer region of 600 bp revealed 100% identity of the isolated fungus from cotton with A. alternata from tomato and potato. These data oblige us to reconsider the presence of A. alternata in the four main cotton growing schemes in Sudan while these symptoms have always been described for tomato and potato early blight disease.
Źródło:
Journal of Plant Protection Research; 2019, 59, 3; 412-417
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design of water supply networks for water transfer to the urban area Case study: Balikpapan city
Autorzy:
Huy, Dinh T.N.
Dwijendra, Ngakan K.A.
Poltarykhin, Andrey
Suksatan, Wanich
Nahi, Nooraldeen S.
Mahmudiono, Trias
Hai, Nguyen T.
Kadhim, Mustafa M.
Singh, Krishanveer
Ahmed, Alim A.A.
Powiązania:
https://bibliotekanauki.pl/articles/2174373.pdf
Data publikacji:
2022
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
network design
water distribution
water shortage
water supply network
water transmission
Opis:
The growing population and the development of industries in all countries of the world have created a very important and complex issue for water supply to cities. Today, many parts of the world are facing the problem of water shortage and this problem cannot be easily solved. In addition to the proper use of water resources and preventing the loss of natural water, the establishment of regional water supply networks is effective in meeting the future needs of the people. A water distribution network (water supply network) is a set of interconnected pipelines used to transport and distribute water in a complex. In designing the water distribution network, factors such as the type of water distribution network, water pressure, water velocity, design flow, minimum pipe diameter, pipe material and many other factors should be considered. In this study, we have tried to design the water supply network of a part of Balikpapan city in Indonesia. The design method led to the determination of pressure values in the connection nodes, pipe diameters, flow rate and velocity in the pipes. All the existing criteria are considered in the design of the water supply network. Although this study has been implemented for a specific study area, it can be of great help to designers in designing the water supply network.
Źródło:
Journal of Water and Land Development; 2022, 54; 251--254
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamical complexity of human responses: a multivariate data-adaptive framework
Autorzy:
Ahmed, M.
Rehman, N.
Looney, D.
Rutkowski, T.
Mandic, D.
Powiązania:
https://bibliotekanauki.pl/articles/201559.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
multivariate sample entropy
multivariate empirical mode decomposition (MEMD)
multivariate multiscale entropy
complexity analysis
multivariate complexity
postural sway analysis
stride interval analysis
brain consciousness analysis
alpha-attenuated EEG data
Opis:
Established complexity measures typically operate at a single scale and thus fail to quantify inherent long-range correlations in real-world data, a key feature of complex systems. The recently introduced multiscale entropy (MSE) method has the ability to detect fractal correlations and has been used successfully to assess the complexity of univariate data. However, multivariate observations are common in many real-world scenarios and a simultaneous analysis of their structural complexity is a prerequisite for the understanding of the underlying signal-generating mechanism. For this purpose, based on the notion of multivariate sample entropy, the standard MSE method is extended to the multivariate case, whereby for rigor, the intrinsic multivariate scales of the input data are generated adaptively via the multivariate empirical mode decomposition (MEMD) algorithm. This allows us to gain better understanding of the complexity of the underlying multivariate real-world process, together with more degrees of freedom and physical interpretation in the analysis. Simulations on both synthetic and real-world biological multivariate data sets support the analysis.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 3; 433-445
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of molarity on the structural and optical properties of ZnO thin films deposit by CSP
Autorzy:
Habubi, Nadir F.
Abood, Ziad M.
Algamel, Ahmed N.
Powiązania:
https://bibliotekanauki.pl/articles/1193915.pdf
Data publikacji:
2015
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Urbach energy
ZnO
ZnO thin films
optical properties
structural properties
Opis:
ZnO thin films have been prepared by chemical spray pyrolysis technique CSP). XRD pattern reveals that the preferred orientation was varied with concentration, topography analysis was done by AFM micrograph which confirm the existence of nonstructural films. The optical properties was done by recorded the transmittane and absorbance which were affected by an increase in concentration. The values of optical energy gap obtained from Tauc relation were 3.17, 3.18 and 3.19 eV for 0.05, 0.1 and 0.5 M respectively. Urbach energy confirms the decrease in band tail as the concentration increase.
Źródło:
World Scientific News; 2015, 22; 55-69
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Triangular Core Rotation of a Hybrid Porous Core Terahertz Waveguide
Autorzy:
Ali, S.
Ahmed, N.
Alwee, S.
Islam, M.
Rana, S.
Bhuiyan, T.
Powiązania:
https://bibliotekanauki.pl/articles/227154.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
porous core waveguide
THz waveguide
flat EML
hybrid design
flat dispersion
triangular design
core rotation
Opis:
In this paper, we investigate the effects for rotating the triangular core air hole arrangements of a hybrid design porous core fiber. The triangular core has been rotated in anticlockwise direction to evaluate the impact on different waveguide properties. Effective Material Loss (EML), confinement loss, bending loss, dispersion characteristics and fraction of power flow are calculated to determine the impacts for rotating the triangular core. The porous fiber represented here has a hybrid design in the core area which includes circular rings with central triangular air hole arrangement. The cladding of the investigated fiber has a hexagonal array of air hole distribution. For optimum parameters the reported hybrid porous core fiber shows a flat EML of ±0.000416 cm⁻¹ from 1.5 to 5 terahertz (THz) range and a near zero dispersion of 0.4±0.042 ps/THz/cm from 1.25 to 5.0 THz. Negligible confinement and bending losses are reported for this new type of hybrid porous core design. With improved concept of air hole distribution and exceptional waveguide properties, the reported porous core fiber can be considered as a vital forwarding step in this field of research.
Źródło:
International Journal of Electronics and Telecommunications; 2017, 63, 1; 25-31
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of robotic cleaning technologies: preserving a british iconic building
Autorzy:
Haqqani, Ahmed A.H
Seenu, N
Janardhanan, Mukund
Kuppan, Chetty RM
Powiązania:
https://bibliotekanauki.pl/articles/118264.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Promocji Wiedzy
Tematy:
wall climbing robot
multicriteria decision analysis
cleaning robot
quality function deployment
robot wspinający się po ścianie
analiza decyzji według wielu kryteriów
robot czyszczący
wdrażanie funkcji jakości
Opis:
The engineering building of the University Leicester built-in 1963 has been a British icon for decades now. Applications of Robotic technologies are uprising nowadays, which provides a contingency to manipulate the benefits of robotics for executing challenging and precarious facade cleaning processes. This paper surveys the facade cleaning robotic technologies exist in the market. It exhibits the comparative analysis of four notorious robotic facade cleaning solutions namely Sky Pro, Gekko, BFMR (Building Façade Maintenance Robot) and Sirius_c. The comparison is executed using Multi Criteria Decision Analysis (MCDA) and Quality Function Deployment (QFD) techniques. This study analyses the performance of the robots based on the critical parameters such as water consumption, cleaning efficiency, cleaning dimensions and ease of implementation. Although none of these robotic solutions are implemented off the shelf, some adaptation on these solutions is necessary for the development of robotic techniques work successfully in real time. This paper proposes a hybrid robotic solution combining the vacuum pump adhesion and wheeled locomotion for the effective cleaning of the complex external building structure based on the MCDA and QFD analysis. It highlights the significant future research directions in this field.
Źródło:
Applied Computer Science; 2020, 16, 2; 95-111
1895-3735
Pojawia się w:
Applied Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of water treatment plants quality in Basrah Province, by factor and cluster analysis
Autorzy:
Al Saad, Zainb A.A.
Hamdan, Ahmed N.A.
Powiązania:
https://bibliotekanauki.pl/articles/293213.pdf
Data publikacji:
2020
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
cluster analysis (CA)
factor analysis (FA)
multivariate statistics
the Shatt Al Arab River
water quality
water treatment plant
Opis:
The Shatt Al Arab River (SAAR) is a major source of raw water for most water treatment plants (WTP’s) located along with it in Basrah province. This study aims to determine the effects of different variables on water quality of the SAAR, using multivariate statistical analysis. Seventeen variables were measured in nine WTP’s during 2017, these sites are Al Hussain (1), Awaissan (2), Al Abass (3), Al Garma (4), Mhaigran (5), Al Asmaee (6), Al Jubaila (7), Al Baradia (8), Al Lebani (9). The dataset is treated using principal component analysis (PCA) / factor analysis (FA), cluster analysis (CA) to the most important factors affecting water quality, sources of contamination and the suitability of water for drinking and irrigation. Three factors are responsible for the data structure representing 88.86% of the total variance in the dataset. CA shows three different groups of similarity between the sampling stations, in which station 5 (Mhaigran) is more contaminated than others, while station 3 (Al Abass) and 6 (Al Asmaee) are less contaminated. Electrical conductivity (EC) and sodium adsorption ratio (SAR) are plotted on Richard diagram. It is shown that the samples of water of Mhaigran are located in the class of C4-S3 of very high salinity and sodium, water samples of Al Abass station, are located in the class of C3-S1 of high salinity and low sodium, and others are located in the class of C4-S2 of high salinity and medium sodium. Generally, the results of most water quality parameters reveal that SAAR is not within the permissible levels of drinking and irrigation.
Źródło:
Journal of Water and Land Development; 2020, 46; 10-19
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of hydraulic sweeps in horizontal wells
Badanie możliwości oczyszczania hydraulicznego w otworach poziomych
Autorzy:
Nguyen, T. N.
Miska, S. Z.
Yu, M.
Takach, N. E.
Ahmed, R.
Powiązania:
https://bibliotekanauki.pl/articles/300465.pdf
Data publikacji:
2010
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
otwory poziome
oczyszczanie hydrauliczne
horizontal wells
hydraulic sweeps
Opis:
Drilling fluid sweeps are commonly run in the field to help clean the borehole of cuttings that have not been removed with normal drilling fluid circulation, especially in high angle or extended reach wells where efficient hole cleaning is more difficult to maintain. This study focuses on the use of "conventional" and "enhanced" sweeps in horizontal well bores. Not much information pertaining to the use of drilling fluid sweeps is available in the literature. Furthermore, there has been a lack of agreement as to which types of sweep fluids are most effective. Conventional sweeps most often include high viscosity fluids, high density fluids or a combination of both. In addition to conventional sweep fluids, an attempt was made to use enhanced sweep fluids, in which surfactants are used to attach cuttings to oil droplets that are intentionally introduced to the drilling fluid system. Because of their low density, oil droplets can have the ability to keep cuttings particles in suspension. The use of oil droplets is a new concept in cleaning horizontal and deviated wellbores. This work focuses on experimental analysis of sweep fluids with the goal of quantifying the sweep "efficiency". A small-scale sweep loop (SSL) was mainly used to conduct sweep experiments. Moreover, some experiments were carried out in a field-scale flow loop that operates at low-pressure ambient temperature (LPAT) conditions. Results show that pipe rotation plays a very important role in improving hole cleaning. Particularly, the improvement is substantial with high-viscosity fluids. The rotation of pipe has agitation effect that forces the cuttings particles into the main flow and facilitates the removal process. As anticipated, increasing the flow rate enhances the sweep efficiency or cuttings removal regardless of the drillpipe rotation. Furthermore, the study suggests that with a more rigorous evaluation of sweep efficiency, one can objectively determine the type and frequency of drilling sweep. The results of this study are useful for selection of the optimal sweep fluid.
Płuczki czyszczące są powszechnie stosowane do oczyszczania otworów z pozostałości zwiercin, których nie udało się wynieść na powierzchnię za pomocą tradycyjnych płynów płuczkowych, głównie w przypadku otworów kierunkowych i rozgałęzionych, gdzie możliwość oczyszczenia jest ograniczona. Badania skoncentrowały się na wykorzystaniu konwencjonalnych i ulepszonych systemów czyszczących w otworach kierunkowych. W literaturze niezbyt wiele można znaleźć informacji na ten temat. Co więcej, brak jest zgody co do tego, która płuczka czyszcząca jest najskuteczniejsza. Tradycyjne płuczki czyszczące często zawierają płyny o wysokiej lepkości i/lub gęstości. Ponadto podjęto próbę stworzenia ulepszonych płuczek czyszczących, w których zastosowane surfaktanty mają powodować przyklejanie się zwiercin do drobin oleju, który celowo wprowadzono do systemu płuczkowego. Ze względu na niską gęstość, krople oleju utrzymują zwierciny w zawieszeniu. Zastosowanie kropli oleju to nowa koncepcja oczyszczania otworów horyzontalnych. W artykule skoncentrowano się na przeanalizowaniu płuczek czyszczących mających na celu zwiększenie skuteczności oczyszczania. Do badań z reguły stosowano mały obieg czyszczący SSL (small-scale sweep loop). Niektóre eksperymenty prowadzono na złożu w warunkach niskiego ciśnienia i temperatury otoczenia. Wyniki pokazują, że ruch rur odgrywa istotną rolę w zwiększeniu skuteczności oczyszczania otworu. Służy temu również zastosowanie wysoko lepkich płuczek. Rotacja rur podrywa zwierciny doprowadzając je do głównego strumienia, wspomagając proces oczyszczania. Jak przewidywano, ruch w otworze wzmaga wydajność oczyszczania lub wynoszenia zwiercin, niezależnie od rotacji rur. Z badań wynika, że szacując bardziej rygorystycznie zdolności czyszczące, można obiektywnie określić rodzaj i częstotliwość oczyszczania. Wyniki badań pozwalają na stosowny wybór optymalnego środka czyszczącego.
Źródło:
Wiertnictwo, Nafta, Gaz; 2010, 27, 1--2; 307-331
1507-0042
Pojawia się w:
Wiertnictwo, Nafta, Gaz
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication and Characterization of Porous Silicon
Autorzy:
Duaa, Jabbar Hussein
Alzubaidy, Muneer H. Jaduaa
Abd, Ahmed N.
Powiązania:
https://bibliotekanauki.pl/articles/1157178.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Anodization
Nanocrystalline porous silicon
XRD
porous silicon
Opis:
In this work, nanocrystalline porous silicon layers were fabricated by photoelectrochemical etching of n type silicon (n-Si) wafer. Different etching time (15, 20, 25 and 30) min and 10 mA/cm2 current density were tested to study their effect on the formation nanosized pore array. Porous silicon is investigation by X-Ray diffractions (XRD) and atomic force microscopy properties (AFM). Crystallites size was estimated by X-Ray diffraction. Atomic Force microscopy confirmed the nonmetric size Chemical Anodization the electrochemical etching was noticed of PS. The atomic force microscopy investigation showed the rough silicon surface which increased with etching time porous structure nucleates which leads to an increase in the depth and width (diameter) of surface pits.
Źródło:
World Scientific News; 2018, 94, 2; 321-328
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
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