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    Wyświetlanie 1-15 z 15
    Tytuł:
    Experimental and numerical parametric study of resistance spot welding process of AISI 1008 steel sheets
    Autorzy:
    Khabaz-Aghdam, Ata
    Rahmani, Azhdar
    Fadaei, Abbas
    Powiązania:
    https://bibliotekanauki.pl/articles/279896.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    resistance spot welding
    nugget geometry
    residual stresses
    simulation
    experimentation
    Opis:
    In the present research, a parametric study in Resistance Spot Welding (RSW) of thin AISI 1008 steel sheets is investigated via FEM. All the time steps through the RSW process, including squeeze time, welding time, holding time and cooling time are taken into account. First, the effects of various parameters such as electrical current, welding time and electrode tip diameter are investigated in the nugget geometry. Then, a time history stress diagram and residual stresses are obtained in RSW weldment. FEM results are validated very well by some experiments which were performed in two parts of nugget geometry and residual stresses.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2019, 57, 4; 807-820
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mechanical guidelines on the properties of human healthy arteries in the design and fabrication of vascular grafts: experimental tests and quasi-linear viscoelastic model
    Autorzy:
    Faturechi, Rahim
    Hashemi, Ata
    Abolfathi, Nabiollah
    Solouk, Atefeh
    Powiązania:
    https://bibliotekanauki.pl/articles/307007.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    elastyczność
    model konstytutywny
    tętnica
    elasticity
    constitutive model
    human artery
    artificial artery
    quasi-linear viscoelasticity
    Opis:
    Knowledge of mechanical behavior of healthy human arteries as the guidelines to target properties of vascular grafts deserves special attention. There is a lack of mathematical model to characterize mechanical behavior of biomaterial while many mathematical models to reflect mechanics of human arteries have been proposed. The objective of this paper was set to measure mechanical properties of healthy human arteries including Common Carotid Artery (CCA), Abdominal Aorta Artery (AAA), Subclavian Artery (SA), Common Iliac Artery (CIA) and Right and Left Iliac Artery (RIA and LIA) and compare them to those of commercial ePTFE and Dacron®. Methods: Series of stress relaxation and strain to failure tests vere performed on all samples. The experimental data was utilized to develop quasi-linear viscoelastic (QLV) model of both natural and artificial arteries. Results: ePTFE is the stiffest sample, while the CCA is the most compliant one among all. RIA and CIA are more viscous than the other natural arteries, while AA and CCA are less viscous. The proposed model demonstrated an accurate fit to the experimental results, a proof of its ability to model both nonlinear elasticity and viscoelasticity of the human arteries and commercial ones. Conclusions: ePTFE and Dacron® are much stiffer than human arteries that may lead to the disruption of blood hemodynamic and may not be biomechanically feasible as a replacement.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2019, 21, 3; 13-21
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Air Quality Assessment and Forecasting Using Neural Network Model
    Autorzy:
    Hamdan, Mohammad A.
    Ata, Mohammad F. Bani
    Sakhrieh, Ahmad H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1838288.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    air pollutant
    ANN
    MATLAB
    forecasting
    Opis:
    Air pollution is a major obstacle faced by all countries which impacts the environment, public health, socioeconomics, and agriculture. In this study, the air pollutants in the city of Amman were presented and analyzed. Nonlinear Autoregressive Exogenous (NARX) model was used to forecast the daily average levels of pollutants in Amman, Jordan. The model was built using the MATLAB software. The model utilized a Marquardt-Levenberg learning algorithm. Its performance was presented using different indices, R2 (Coefficient of Determination), R (Coefficient of Correlation), NMSE (Normalized Mean Square Error), and Plots representing network predictions vs original data. Historical measurements of air pollutants were obtained from 4 of the Ministry of Environment (MoEnv) air quality monitoring stations in Amman. The meteorological data representing three years (2015, 2016, and 2017) were used as predictors to train the Artificial Neural Network (ANN) while the data of the year 2018 were used to test it. The results showed good performance when forecasting SO2, O3, CO, and NO2, and acceptable performance when forecasting Particulate Matter (PM10) at the given 4 locations.
    Źródło:
    Journal of Ecological Engineering; 2021, 22, 6; 1-11
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Air Quality Assessment and Forecasting Using Neural Network Model
    Autorzy:
    Hamdan, Mohammad A.
    Ata, Mohammad F. Bani
    Sakhrieh, Ahmad H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1838392.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    air pollutant
    ANN
    MATLAB
    forecasting
    Opis:
    Air pollution is a major obstacle faced by all countries which impacts the environment, public health, socioeconomics, and agriculture. In this study, the air pollutants in the city of Amman were presented and analyzed. Nonlinear Autoregressive Exogenous (NARX) model was used to forecast the daily average levels of pollutants in Amman, Jordan. The model was built using the MATLAB software. The model utilized a Marquardt-Levenberg learning algorithm. Its performance was presented using different indices, R2 (Coefficient of Determination), R (Coefficient of Correlation), NMSE (Normalized Mean Square Error), and Plots representing network predictions vs original data. Historical measurements of air pollutants were obtained from 4 of the Ministry of Environment (MoEnv) air quality monitoring stations in Amman. The meteorological data representing three years (2015, 2016, and 2017) were used as predictors to train the Artificial Neural Network (ANN) while the data of the year 2018 were used to test it. The results showed good performance when forecasting SO2, O3, CO, and NO2, and acceptable performance when forecasting Particulate Matter (PM10) at the given 4 locations.
    Źródło:
    Journal of Ecological Engineering; 2021, 22, 6; 1-11
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of the effects of flat cushioning insole on gait parameters in individuals with chronic neck pain
    Autorzy:
    Kirmizi, Muge
    Simsek, Ibrahim Engin
    Elvan, Ata
    Akcali, Omer
    Angin, Salih
    Powiązania:
    https://bibliotekanauki.pl/articles/306371.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    ból szyi
    parametry chodu
    siła reakcji podłoża
    obciążenie dynamiczne
    amortyzacja
    chronic neck pain
    flat cushioning insole
    gait parameters
    ground reaction force
    dynamic loading
    shock absorption
    Opis:
    Individuals with chronic neck pain (CNP) walk with a stiffer spine known to cause an increase in dynamic loading on the spine. They also exhibit altered spatiotemporal gait variables, however, it is still unclear whether flat cushioning insole, which reduces dynamic loading on the musculoskeletal system by absorbing the ground reaction force, affects gait parameters in individuals with CNP. The aim of this work was to investigate the effects of flat cushioning insole on neck pain during walking and gait parameters in individuals with CNP. Methods: Twenty-one individuals with CNP and 21 asymptomatic controls were included. Assessments of gait parameters and pain were conducted in two sessions, standard shoe only and standard shoe with flat cushioning. In both sessions, all participants performed the 10-meter walk test in two walking conditions: preferred walking, walking at maximum speed. The force sensitive insoles and the video analysis method were used to assess plantar pressure variables and spatiotemporal gait variables, respectively. Pain was assessed using the Visual Analogue Scale. Results: Our results indicated that flat cushioning reduced the maximum force and force-time integral in both groups ( p < 0.05). Flat cushioning increased walking speed and step length in both walking conditions and reduced neck pain during walking at maximum speed in individuals with CNP ( p < 0.05). In asymptomatic individuals, no difference was found in spatiotemporal gait variables between two sessions ( p > 0.05). Conclusions: These results have suggested that the use of flat cushioning insole may improve neck pain during walking and spatiotemporal gait variables in individuals with CNP.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2019, 21, 2; 135-141
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural Analysis of Ce Doped $La_{1-x}Sr_xCo_{1-y}Fe_yO_{3-δ}$ Nanopowders Synthesized by Glycine-Nitrate Gel Combustion
    Autorzy:
    Yildiz, Ö.
    Soydan, A.
    Ata, A.
    İpçızade, E.
    Akin, D.
    Uçak, Ö.
    Powiązania:
    https://bibliotekanauki.pl/articles/1312023.pdf
    Data publikacji:
    2014-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.07.Wx
    81.07.-b
    81.20.Ka
    88.30.pn
    Opis:
    Ce doped $La_{1-x}Sr_xCo_{1-y}Fe_yO_3$ (LCSCF) is a widely used cathode material due to its high catalytic activity for oxygen reduction and high oxygen exchange coefficient. LCSCF is also known with its high ionic and electronic conductivities and low electrode polarization losses which are highly critical properties for low temperature solid oxide fuel cell applications. In this study, structural properties of the LCSCF cathode nanopowder materials synthesized by glycine-nitrate gel combustion have been investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and nanosizer. Synthesized nanopowders represent volcanic ash like structures and morphologies. Ce, Sr, Co, and Fe are found to have significant effects on the structural properties of powders in terms of powders morphology, agglomerate structure, crystallite size and also lattice parameter of perovskite crystal. All synthesized ash powders have particle sizes around 50-600 nm, varying crystalline structures of perovskite and fluorite depending on molar ratio of Ce in the composition. Increasing molar Ce ratio over 0.4 is found to lead to the formation of a separate nano ceria phase in fluorite crystal structure on the surface of the synthesized powder.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 2; 669-672
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Properties of Ceria Based Novel Anode Nanopowders Synthesized by Glycine-Nitrate Process
    Autorzy:
    Yıldız, Ö.
    Soydan, A.
    Ata, A.
    Tunaboylu, B.
    Akın, D.
    İpcizade, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399974.pdf
    Data publikacji:
    2013-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    82.47.Ed
    81.07.Wx
    81.20.Ka
    81.20.Ev
    81.05.Mh
    61.46.Df
    Opis:
    Novel anode nanopowder materials consisting of ceria-based components synthesized by glycine-nitrate process were investigated for solid oxide fuel cells. Glycine-nitrate process involves a self-combustion reaction at 220C of water-based nitrate and glycine solutions which subsequently can reach up to 1200°C. The resulting morphology, the size of particles and the formation of crystalline phases were characterized by differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, the Brunauer-Emmett-Teller method and Nanosizer. It was determined that dopants in ceria such as Co, Ni, Cu, V and Fe had significant effect on the morphology and size. The size distribution measured by Nanosizer was 50-600 nm, transmission electron microscopy, 5-200 nm and the Brunauer-Emmett-Teller method 100-120 nm and specific surface area of powders in the range 67.45-72.05 $m^2 g^{-1}$ as measured by the Brunauer-Emmett-Teller method. Particles were observed to have spherical structures for Cu and Fe doped powders and rod-shaped in a porous tuff microstructure for those doped with Co and Ni. Vanadium doping helped to decrease the porosity and initiated the process of spheroidization of particles.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 2; 432-435
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reducing central catheter-associated infections in pediatric surgery clinic: Implementation of a care bundle
    Autorzy:
    Dolgun, Eda
    Aliye, Okgün Alcan
    Islamoğlu, Ayşe
    Eroğlu, Birsen
    Polat, Meltem
    Yavuz van Gıersbergen, Meryem
    Erdener, Ata
    Powiązania:
    https://bibliotekanauki.pl/articles/1918955.pdf
    Data publikacji:
    2021-06-14
    Wydawca:
    Uniwersytet Medyczny w Białymstoku
    Tematy:
    Central venous catheter
    care bundle
    infection
    Opis:
    Purpose: Central line care bundle comprises a few evidence-based interventions for improving patients' outcomes and recovery process. This semi-experimental study aimed to determine the effect of pediatric central line care bundle implementation on central line-associated bloodstream infections (CLABSI) rates. Materials and methods: A central line care bundle was implemented for pediatric surgery patients (n=70). Baseline observations were made to determine the central line care bundle compliance of healthcare professionals for 435 catheter days. Subsequently, physicians and nurses were educated about the central line care bundle. After the implementation period, 722 catheter days were observed to determine post-implementation compliance. Baseline CLABSI rates were compared with post-implementation CLABSI rates. Results: It was found that the entire central line care bundle compliance was 32.4% pre-implementation and 86.3% post-implementation. After education, the physicians' and nurses' central line care bundle compliance showed statistically significant improvement (p= 0.0001). There were five CLABSI events in the pre-implementation period and three CLABSI events in the post-implementation period. It was determined that the number of CLABSI decreased in the post-implementation period compared to the pre-implementation period, but this difference was not statistically significant (p= 0.207). Conclusions: Central line care bundle implementation decreased the CLABSI rates. It is recommended the Implementation of a central line care bundle on the care of pediatric surgery patients with the central venous catheter.
    Źródło:
    Progress in Health Sciences; 2021, 11(1); 57-65
    2083-1617
    Pojawia się w:
    Progress in Health Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Physical restrictions of the flotation of fine particles and ways to overcome them
    Autorzy:
    Karakashev, Stoyan I.
    Grozev, Nikolay A
    Ozdemir, Orhan
    Guven, Onur
    Ata, Seher
    Bournival, Ghislain
    Batjargal, Khandjamts
    Boylu, Feridun
    Hristova, Svetlana
    Çelik, Mehmet Sabri
    Powiązania:
    https://bibliotekanauki.pl/articles/2146879.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fine particle flotation
    frequency of collisions
    surface force manipulation
    thin wetting films
    Opis:
    This work analyses the basic problems of the fine particles flotation and suggests new ways to overcome them. It is well accepted that the poor recovery of fine particles is due to the small collision rate between them and the bubbles due to the significant difference between their sizes. This common opinion is based on a theory, assuming in its first version a laminar regime, but later has been advanced to intermediate turbulence. It accepts that the particles are driven by the streamlines near the bubbles. In reality, the high turbulence in the flotation cells causes myriads of eddies with different sizes and speeds of the rotation driving both bubbles and particles. Yet, a theory accounting for high turbulence exists and states that the collision rate could be much higher. Therefore, we assumed that the problem consists of the low attachment efficiency of the fine particles. Basically, two problems could exist (i) to form a three-phase contact line (TPCL) the fine particle should achieve a certain minimal penetration into the bubble, requiring sufficient push force; (ii) a thin wetting film between the bubble and the particle forms, thus increasing the hydrodynamic resistance between them and making the induction time larger than the collision time. We assumed particles with contact angle θ = 80°, and established a lower size flotation limit of the particles depending mostly on the size of the bubbles, with which they collide. It spans in the range of Rp = 0.16 um to Rp = 0.40 um corresponding to bubbles size range of Rb = 50 um to Rb = 1000 um. Hence, thermodynamically the particle size fraction in the range of Rp = 0.2 um to Rp = 2 um are permitted to float but with small flotation rate due to the small difference between the total push force and maximal resistance force for formation of TPCL. The larger particles approach slowly the bubbles, thus exceeding the collision time. Therefore, most possibly the cavitation of the dissolved gas is the reason for their attachment to the bubbles. To help fine particles float better, the electrostatic attraction between bubbles and particles occurred and achieved about 92% recovery of fine silica particles for about 100 sec. The procedure increased moderately their hydrophobicity from θ ≈ 27.4° to θ ≈ 54.5°. Electrostatic attraction between bubbles and particles with practically no increase of the hydrophobicity of the silica particles ended in 47% recovery. All this is an indication of the high collision rate of the fine particles with the bubbles. Consequently, both, an increase in the hydrophobicity and the electrostatic attraction between particles and bubbles are key for good fine particle flotation. In addition, it was shown experimentally that the capillary pressure during collision affected significantly the attachment efficiency of the particles to the bubbles.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 5; art. no. 153944
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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