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Wyświetlanie 1-15 z 19
Tytuł:
Influence of Deforestation in Borgu Local Government Area of Niger State, Nigeria
Autorzy:
Ojo, B. S.
Alaye, S. A.
Buochuama, A.
Martins, A.
Powiązania:
https://bibliotekanauki.pl/articles/1112443.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
deforestation
ecological crisis
forest
influence
Opis:
There are ample facts that the whole world is facing an ecological crisis by reason of heavy deforestation. Thus, this study assesses the influence of deforestation on some selected villages in Borgu Local Government Area, Niger State. Data were collected from members of the community using a set of structured questionnaire. This was then analyzed using descriptive statistics (percentages and frequency count). Findings reveal that the major occupation is trading (33.3%), followed by farming (30%). The causes of deforestation in the study area include: fuelwood removal (31.7%), urbanization (25.0), logging (20.0%), subsistence farming (15.8%), population growth and overpopulation (3.3%), commercial farming (2.5%) and inequitable distribution of wealth and power (1.7%). Global warming (31.7%) was the major effect generated by deforestation in the study area, followed by soil erosion (24.2%). Encouragement of better agroforestry practices (30.8%) was seen as the major strategy for reducing deforestation by the respondents. Other best practices include: afforestation (27.5%), public enlightenment (13.3%), enforcement of forest land and policy (12.5%), forest education (8.3%), forest conservation and preservation (7.5%).
Źródło:
World News of Natural Sciences; 2018, 18, 2; 62-71
2543-5426
Pojawia się w:
World News of Natural Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design of an adaptive fuzzy variable structure compensator for the nonholonomic mobile robot in trajectory tracking task
Autorzy:
Begnini, M.
Bertol, W.
Martins, N. A.
Powiązania:
https://bibliotekanauki.pl/articles/971054.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
nonholonomic mobile robot
trajectory tracking
variable structure control
uncertainties and disturbances
fuzzy compensator
Lyapunov theory
Opis:
A robust adaptive kinematic control strategy, based on the methodology of variable structure control is considered in this paper. Because the dynamics of mobile robots is subject to uncertainties and disturbances, a fuzzy compensator is adopted to estimate them. In order to minimize the tracking errors and to attenuate the chattering phenomenon, an adaptation law for the fuzzy compensator is obtained by Lyapunov stability theory so as to asymptotically stabilize the control system as well as guarantee the convergence of the tracking errors. In terms of comparison with the boundary layer variable structure controller, simulations and experiments verify the feasibility and effectiveness of the proposed kinematic control strategy for the nonholonomic mobile robots under the incidence of uncertainties and disturbances.
Źródło:
Control and Cybernetics; 2018, 47, 3; 239-275
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stiffness control of robot manipulators in the operational space using fuzzy mapping of dynamic functions
Autorzy:
Bertol, D. W.
Barasuol, V.
Martins, N. A.
De Pieri, E. R.
Powiązania:
https://bibliotekanauki.pl/articles/971046.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
stiffness control
fuzzy mapping
robot manipulators
operational space
trajectory tracking
Opis:
In this paper a stiffness control strategy based on the fuzzy mapped nonlinear terms of the robot manipulator dynamic model is proposed. The proposed stiffness controller is evaluated on a research robot manipulator performing a task in the operational space. Tests attempted to achieve fast motion with reasonable accuracy associated with lower computational load compared to the non-fuzzy approach. The stability analysis is presented to conclude about the mapping error influence and to obtain precondition criteria for the gains adjustment to face the trajectory tracking problem. Simulation results that supported the implementation are presented, followed by experiments and results obtained. These tests are conducted on a robot manipulator with SCARA configuration to illustrate the feasibility of this strategy.
Źródło:
Control and Cybernetics; 2013, 42, 3; 639-661
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time domain reflectometry as a tool for the estimation of quality in foods
Autorzy:
Kent, M.
Knochel, R.
Daschner, F.
Schimmer, O.
Oehlenschlager, J.
Mierke-Klemeyer, S.
Barr, U.K.
Floberg, P.
Tejada, M.
Huidobro, A.
Nunes, L.
Batista, I.
Martins, A.
Powiązania:
https://bibliotekanauki.pl/articles/24653.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
fish product
fish
microwave
food
fish fillet
time domain reflectometry
quality
storage condition
Źródło:
International Agrophysics; 2004, 18, 3
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trajectory tracking of a wheeled mobile robot with uncertainties and disturbances: proposed adaptive neural control
Autorzy:
Martins, N. A.
Alencar, M.
Lombardi, W. C.
Bertol, D. W.
Pieri, E. R.
Filho, H. F.
Powiązania:
https://bibliotekanauki.pl/articles/971045.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
wheeled mobile robot
trajectory tracking
kinematic control
variable structure control
dynamic control
sliding mode theory
neural networks
Lyapunov theory
Opis:
This paper analyses a trajectory tracking control problem for a wheeled mobile robot, Rusing integration of a kinematic neural controller (KNC) and a torque neural controller (TNC), in which both the kinematic and dynamic models contain uncertainties and disturbances. The proposed adaptive neural controller (PANC) is composed of the KNC and the TNC and is designed with use of a modeling technique of Gaussian radial basis function neural networks (RBFNNs). The KNC is a variable structure controller, based on the sliding mode theory and is applied to compensate for the disturbances of the wheeled mobile robot kinematics. The TNC is an inertia-based controller composed of a dynamic neural controller (DNC) and a robust neural compensator (RNC) applied to compensate for the wheeled mobile robot dynamics, bounded unknown disturbances, and neural network modeling errors. To minimize the problems found in practical implementations of the classical variable structure controllers (VSC) and sliding mode controllers (SMC), and to eliminate the chattering phenomenon, the nonlinear and continuous KNC and RNC of the TNC are applied in lieu of the discontinuous components of the control signals that are present in classical forms. Additionally, the PANC neither requires the knowledge of the wheeled mobile robot kinematics and dynamics nor the timeconsuming training process. Stability analysis, convergence of the tracking errors to zero, and the learning algorithms for the weights are guaranteed based on the Lyapunov method. Simulation results are provided to demonstrate the effectiveness of the proposed approach.
Źródło:
Control and Cybernetics; 2015, 44, 1; 47-98
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Corrosion Behavior of FeAl and Fe3Al Based Fe-Al-C Alloys in Sulfuric Acid
Autorzy:
Silva, A. P.
Brito, P. P.
Martins, N.
Powiązania:
https://bibliotekanauki.pl/articles/2134209.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
iron aluminides
microstructure
mechanical properties
corrosion resistance
Opis:
Iron aluminides are iron-aluminum alloys that have excellent resistance to oxidation at high temperatures with low density, high resistance/weight ratio and a low manufacturing cost. Due to its characteristics, these alloys are presented as an option to replace stainless steels in certain applications. This works intends report the casting process and subsequent analyses involving microstructure, mechanical properties, and corrosion resistance of two Fe-Al-C alloys (Fe-11wt%Al and Fe-25wt%Al, containing 0.31-0.37%C), which were prepared in an induction furnace and poured in a permanent mold. Samples of these alloys were characterized and presented elevated hardness values of 37 HRC (alloy Fe-11wt%Al) and 49.6HRC (alloy Fe-25wt%Al) and microstructure with aluminides type Fe3Al and FeAl and also carbides type K. The Fe-11wt%Al alloy exhibited superior resistance to uniform corrosion, although both Fe-Al-C alloys exhibited significantly higher corrosion rates compared to a binary iron aluminide in 0.5M H2SO4 containing naturally dissolved oxygen.
Źródło:
Archives of Foundry Engineering; 2022, 22, 2; 77--82
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preparation and characterization of drug delivery carriers for local administration of sodium alendronate
Autorzy:
Posadowska, U.
Moreira, A.
Martins, R.
Pamuła, E.
Powiązania:
https://bibliotekanauki.pl/articles/284303.pdf
Data publikacji:
2013
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
Tematy:
nanocarriers
microcarriers
poly(lactide-co-glycolide) (PLGA)
osteoporosis
controlled drug delivery
sodium alendronate
Opis:
Osteoporosis is often treated with the use of sodium alendronate - a drug that inhibits osteoclast-mediated bone resorption and regulates rate of bone turnover. However the disadvantage of oral administration of sodium alendronate is poor drug absorption from the gastrointestinal track and severe adverse effects. Therefore we propose local sustained drug delivery systems based on poly(lactide-co-glycolide) (PLGA) micro- and nanocarriers, which can be administered directly by simple injections to the required place in the body. In this study we encapsulated sodium alendronate into PLGA micro- and nanospheres via a double-emulsification technique. Emulsion formation in different shear rate conditions was used to optimize the size of the carriers. The prepared microspheres were observed under an inverted optical microscope which confirmed their micrometric size. The nanospheres were analyzed by atomic force microscopy, which allowed visualization of their shape and measurement of their size. Moreover the hydrodynamic diameter of the nanospheres, polydispersity index as well as zeta potential were examined by dynamic light scattering. The experiments show that drug release does not depend on the size of the carriers. Analyzed carriers do not cause cytotoxicity upon contact with osteoblast like-cells.
Źródło:
Engineering of Biomaterials; 2013, 16, 119; 8-12
1429-7248
Pojawia się w:
Engineering of Biomaterials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Integrating coagulation and Fenton’s oxidation for pharmaceutical effluents treatment
Koagulacja połączona z utlenianiem Fentona w oczyszczaniu ścieków farmaceutycznych
Autorzy:
Martins, R. C.
Oliveira, A. C.
Quinta-Ferreira, R. M.
Powiązania:
https://bibliotekanauki.pl/articles/2073214.pdf
Data publikacji:
2015
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
pharmaceutical wastewater
heterogeneous Fenton's process
photo-Fenton process
low cost catalysts
biodegradability
ścieki farmaceutyczne
heterogeniczny proces Fentona
reakcja foto-Fentona
kataliza nisko-kosztowa
biodegradowalność
Opis:
Pharmaceutical industry produces complex and bio-refractory wastewater whose discharge throughout water courses constitutes an environmental danger. Although several works can be found handling with simulated pharmaceutical effluents, data reporting results gathered using actual wastewater is still scarce. This work reveals that Fe-Ce-O and red volcanic rock are interesting catalysts for dark and photo-Fenton. Furthermore, the light/H2O2 system showed interesting results and it is now being explored at the pilot scale by the pharmaceutical industry that provided the effluent.
Przemysł farmaceutyczny wytwarza złożone i bioodporne ścieki, których zrzut zwykła drogą stwarza zagrożenie dla środowiska. Pomimo tego, że kilka prac zajmuje się transportem symulowanych ciekłych odpadów farmaceutycznych, dane dotyczące rzeczywistych ścieków są wciąż skąpe. W prezentowanej pracy stwierdzono, że Fe-Ce-O i czerwona skała wulkaniczna są ciekawymi katalizatorami w reakcji foto-Fentona. Ponadto układ światło/H2O2 wykazał się interesującymi właściwościami i obecnie jest badany w skali pilotowej przy obróbce ścieków w przemyśle farmaceutycznym.
Źródło:
Inżynieria i Aparatura Chemiczna; 2015, 4; 174--177
0368-0827
Pojawia się w:
Inżynieria i Aparatura Chemiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Internal Friction and Microstructure of Ti and Ti-Mo Alloys Containing Oxygen
Autorzy:
Martins Jr, J. R. S.
Araújo, R. O.
Nogueira, R. A.
Grandini, C. R.
Powiązania:
https://bibliotekanauki.pl/articles/351840.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
mechanical spectroscopy
anelasticity
internal friction
Ti-Mo alloys
interstitials
biomaterials
Opis:
Ti-Mo alloys are promising materials for use as biomaterials, because these alloys have excellent corrosion resistance and a good combination of mechanical properties such as fatigue, low elastic modulus, hardness, and wear resistance. The objective of this paper was to study the effect of heavy interstitial atoms on anelastic properties of Ti-Mo alloys using mechanical spectroscopy. The internal friction and Young’s modulus were measured as a function of temperature using dynamic mechanical analyser. The internal friction spectra were brought about by relaxation processes attributed to shortrange stress induced reorientation of interstitial and substitutional complexes in solid solution. It is suggested that the nature of the relaxing entities can be worked out in further research on Ti-Mo single crystals.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 1; 25-30
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Substrate Temperature Influenced Structural and Electrical Behaviour of~RF Magnetron Sputtered $Ag_2Cu_2O_3$ Films
Autorzy:
Sreedhar, A.
Hari Prasad Reddy, M.
Uthanna, S.
Martins, R.
Elangovan, E.
Pierson, J.
Powiązania:
https://bibliotekanauki.pl/articles/1492600.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.15.Mb
78.20.Ci
74.25.Gz
Opis:
$Ag_2Cu_2O_3$ films were deposited on glass and silicon substrates by RF magnetron sputtering of metallic equimolar $(Ag_{50}Cu_{50})$ alloy target in $Ar-O_{2}$ mixture at different substrate temperature $(T_{s})$ ranging between 303 and 523 K. The effect of $T_{s}$ on the core level binding energies, structural and electrical properties of the films was systematically studied. The films deposited at room temperature were amorphous. The films deposited at 373 K were polycrystalline and the crystallinity was increased when the $T_{s}$ was increased to 423 K. The films deposited at 423 K and subsequently annealed at 498 K exhibits single phase $Ag_2Cu_2O_3$. In the case of films deposited at higher $T_{s}$ of 523 K, $Ag_2O$ was decomposed into Ag. The electrical resistivity of the films deposited at 303 K was $1.2 \times 10^{-5}$ Ω cm, whereas the films formed at 423 K and subsequently annealed at 498 K showed electrical resistivity of $2.2 \times 10^{-3}$ Ω cm due to improvement in the crystallinity of single phase $Ag_2Cu_2O_3$.
Źródło:
Acta Physica Polonica A; 2011, 120, 6A; A-037-A-039
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural and Optical Behaviour οf~Ni Doped CdS Nanoparticles Synthesized by Chemical Co-Precipitation Method
Autorzy:
Siva Kumar, K.
Divya, A.
Sreedhara Reddy, P.
Uthanna, S.
Martins, R.
Elangovan, E.
Powiązania:
https://bibliotekanauki.pl/articles/1492639.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.Cp
61.72.-y
78.55.Et
78.67.Bf
Opis:
Pure and Ni (2 at.%) doped cadmium sulfide (CdS) nanoparticles have been synthesized by chemical co-precipitation method at room temperature. Effect of Ni doping on CdS compound semiconductors has been analyzed using X-ray diffractometer, transmission electron microscope, energy dispersive spectroscopy, Raman and optical absorption studies. X-ray diffraction study confirmed the structure of the obtained nanoparticles to be single-phase zinc blende with the diffractions from (111), (220) and (311) planes. Energy dispersive spectroscopy study confirmed the presence of Ni in the CdS lattice. The average particle size obtained from the transmission electron microscopy studies are in agreement with the crystallite size calculated from X-ray diffraction data. The optical studies exhibited a clear red shift of absorption edge as a function of Ni doping.
Źródło:
Acta Physica Polonica A; 2011, 120, 6A; A-052-A-054
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study of Hough technique in surgery of otosclerosis, using the finite element method
Autorzy:
Gentil, F.
Parente, M.
Martins, P.
Santos, C.
Almeida, E.
Ferreira, A.
Natali, R.
Powiązania:
https://bibliotekanauki.pl/articles/307201.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
metoda elementów skończonych
otoskleroza
wycięcie strzemiączka
strzemiączko
finite element method
otosclerosis
stapedectomy
stapedotomy
stapes
Opis:
Purpose: Otosclerosis is a metabolic bone disease of the otic capsule that can cause the stapes fixation, resulting in conductive hearing loss or, in a profound sensorineural deafness threshold. Surgery is one of the possible treatments for the otosclerosis. To repair small focus of otosclerosis in the anterior crus of the stapes, in 1960, Hough suggested the implementation of a technique in which part of the anterior crus is fractured and the stapes turned. As a result, the posterior crus of the stapes is the only connection with the inner ear. In this work, the outcome of Hough’s surgical technique was simulated. Methods: Based on computerized images, a finite element model of middle ear ossicles and tympanic membrane was created, as well as a model where the stapes has changed. The discretization of the tridimensional solid model was made using the ABAQUS software. The mechanical properties used were taken from the literature and adequate boundary conditions were applied. Results: The results obtained with the Hough technique simulation were compared with a representative model of the normal ear, taking into account the displacements obtained on the central part of the stapes footplate and the maximum principal stress in the stapes crus. Conclusions: The results obtained are closer to the normal ear model, therefore Hough technique stands out as a good option to correct small focus of otosclerosis.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 4; 149-153
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tailings reprocessing from Cabeco do Piao dam in Central Portugal: a kinetic approach of experimental data
Autorzy:
Figueiredo, J.
Vila, M. C.
Matos, K.
Martins, D.
Futuro, A.
de Lurdes Dinis, M.
Góis, J.
Leite, A.
Fiúza, A.
Powiązania:
https://bibliotekanauki.pl/articles/92190.pdf
Data publikacji:
2018
Wydawca:
Główny Instytut Górnictwa
Tematy:
tailings
multi-criteria optimization
reprocessing
zinc
tungsten
odpadki
optymalizacja wielokryterialna
utylizacja
cynk
wolfram
Opis:
The mining waste and tailing dam are object of discussion due to the accidents that occur due to a lack of control or due to interest in the remaining minerals present in these materials. Most of the old tailings dams have high contents of heavy metals which could represent potential risks to the environment or be an alternative source of some critical raw materials. The case study of the Cabeco do Piao dam in Central Portugal involved tailings from a processing plant that belonged to the Panasqueira Mine Complex, which has been in operation for over 120 years. Waste rock and mining tailings were deposited in the area until 1995, and they represent an environmental liability for the local population due to their high content of toxic metals. Tailings reprocessing can be considered as a solution that minimizes social and environmental impacts, recovers some essential minerals, such as Zn, W, and Cu which can help to offset investments made. The project design involves several stages of metal concentration, determined by experiments, as well as a model of the process. The overall model will take into account technological constraints, social-economic conditions and environmental impacts. A preliminary result of an optimization study of the kinetic approach is presented in this piece of work.
Źródło:
Journal of Sustainable Mining; 2018, 17, 3; 139-144
2300-1364
2300-3960
Pojawia się w:
Journal of Sustainable Mining
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A comparative study on the performance of radiation detectors from the HgI2 crystals grown by different techniques
Autorzy:
Martins, J. F. T.
Costa, F. E.
dos Santos, R. A.
de Mesquita, C. H.
Hamada, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/146916.pdf
Data publikacji:
2012
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
crystal growth
iodide mercury crystal
physical vapor transport (PVT)
radiation detector
semiconductor crystal
Opis:
In this work, the establishment of a technology for HgI2 purification and crystal growth is described, aiming at a future application of this crystal as a room temperature radiation semiconductor detector. Two methods of crystal growth were studied in the development of this work: (1) physical vapor transport (PVT) and (2) saturated solution from dimethylsulphoxide (DMSO) complexes. In order to evaluate the crystals obtained using each of these methods, systematic measurements were carried out for determining the stoichiometry, structure, orientation, surface morphology and impurity of the crystal. The influence of these physicochemical properties of the crystals developed was evaluated in terms of their performance as a radiation detector. The best response to radiation was found for the crystals grown by the PVT technique. Significant improvement in the performance of HgI2 radiation detector was found, purifying the crystal by means of two successive growths by the PVT technique.
Źródło:
Nukleonika; 2012, 57, 4; 555-562
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 19

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