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Tytuł:
Comparative simulation study of production scheduling in the hybrid and the parallel flow
Autorzy:
Varela, M. L. R.
Trojanowska, J.
Carmo-Silva, S.
Costa, N. M. L.
Machado, J.
Powiązania:
https://bibliotekanauki.pl/articles/407017.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
approach for supporting manufacturing scheduling decision making
heuristics
hybrid flow shop
parallel flow shops
makespan
Opis:
Scheduling is one of the most important decisions in production control. An approach is proposed for supporting users to solve scheduling problems, by choosing the combination of physical manufacturing system configuration and the material handling system settings. The approach considers two alternative manufacturing scheduling configurations in a two stage product oriented manufacturing system, exploring the hybrid flow shop (HFS) and the parallel flow shop (PFS) environments. For illustrating the application of the proposed approach an industrial case from the automotive components industry is studied. The main aim of this research to compare results of study of production scheduling in the hybrid and the parallel flow, taking into account the makespan minimization criterion. Thus the HFS and the PFS performance is compared and analyzed, mainly in terms of the makespan, as the transportation times vary. The study shows that the performance HFS is clearly better when the work stations’ processing times are unbalanced, either in nature or as a consequence of the addition of transport times just to one of the work station processing time but loses advantage, becoming worse than the performance of the PFS configuration when the work stations’ processing times are balanced, either in nature or as a consequence of the addition of transport times added on the work stations’ processing times. This means that physical layout configurations along with the way transport time are including the work stations’ processing times should be carefully taken into consideration due to its influence on the performance reached by both HFS and PFS configurations.
Źródło:
Management and Production Engineering Review; 2017, 8, 2; 69-80
2080-8208
2082-1344
Pojawia się w:
Management and Production Engineering Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of an automation system for iodine-125 brachytherapy seed encapsulated by Nd:YAG laser welding
Autorzy:
Somessari, S. L.
Feher, A.
Sprenger, F. E.
Rostelato, M. E. C. M.
da Costa, F. E.
Calvo, W. A. P.
Powiązania:
https://bibliotekanauki.pl/articles/147664.pdf
Data publikacji:
2011
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
iodine-125 seeds
prostate cancer
brachytherapy
Nd:YAG laser welding
Opis:
The aim of this work is to develop an automation system for iodine-125 radioactive seed production by Nd:YAG laser welding, which has been used successfully in low dose rate (LDR) brachytherapy treatment. This small seed consists of a welded titanium capsule, with 0.8 mm in diameter and 4.5 mm in length, containing iodine-125 adsorbed onto a silver rod. The iodine-125 seeds are implanted into the human prostate to irradiate the tumor for cancer treatment. Nowadays, the Radiation Technology Center, at Institute for Nuclear and Energy Research, Săo Paulo, Brazil (IPEN-CNEN/SP) imports and distributes 36,000 iodine-125 seeds per year, for the clinics and hospitals in the country. However, the Brazilian market potential is now over 8,000 iodine-125 seeds per month. The local production of these iodine-125 radioactive sources became a priority for the Institute, in order to reduce the price and the problems of prostate cancer management. It will permit to spread their use to a larger number of patients in Brazil. On the other hand, the industrial automation plays an important role for iodine-125 seeds in order to increase the productivity, with high quality and assurance, avoiding human factors, implementing and operating with good manufacturing practices (GMP). The technology consists of appliance electronic and electro-mechanical parts and components to control machines and processes. The automation system technology for iodine-125 seed production developed in this work was mainly assembled employing a programmable logic controller (PLC), a stepper motor, an Nd:YAG laser welding machine and a supervisory. The statistical repeatability of correctly encapsulated sealed sources with this automation system is greater than 95 per cent.
Źródło:
Nukleonika; 2011, 56, 4; 369-374
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical hydrolysis of hemicellulose from sugarcane bagasse. A comparison between the classical sulfuric acid method with the acidic ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate
Autorzy:
Rodrigues, Marcoaurélio Almenara
da Costa Lopes, André M.
Lukasik, Rafal M.
Powiązania:
https://bibliotekanauki.pl/articles/2201973.pdf
Data publikacji:
2023
Wydawca:
Centrum Badań i Innowacji Pro-Akademia
Tematy:
sugarcane bagasse
acidic ionic liquids
biomass pretreatment
dilute sulfuric acid
pentose
furfural
wytłoki trzciny cukrowej
kwaśne ciecze jonowe
wstępna obróbka biomasy
rozcieńczony kwas siarkowy
pentoza
Opis:
Dilute sulfuric acid and acidic ionic liquids are pretreatment methods used to selectively hydrolyze hemicellulose from lignocellulosic biomasses. In this work, a comparison between these techniques is carried out by treating sugarcane bagasse both with 1-ethyl-3-methylimidazolium hydrogen sulfate at different ionic-liquid and water contents and with H 2 SO 4 at the same conditions and equivalent ionic liquid molar contents. Results from the use of ionic liquid showed that it was possible to tune the biomass treatment either to achieve high hemicellulose hydrolysis yields of 72.5 mol% to very low furan and glucose co-production, or to obtain furfural at moderate yields of 18.7 mol% under conditions of low water concentration. In comparison to the use of ionic liquid, sulfuric acid pretreatment increased hemicellulose hydrolysis yields by 17%, but the 8.6 mol% furfural yield was also higher, and these yields were obtained at high water concentration conditions. Besides, no such tuning ability of the biomass treatment conditions can be made.
Źródło:
Acta Innovations; 2023, 46; 35--53
2300-5599
Pojawia się w:
Acta Innovations
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear elastic brittle damage: numerical solution by means of operator split methods
Autorzy:
Pires-Domingues, S.M.
Costa-Mattos, H.
Rochinha, F.A.
Powiązania:
https://bibliotekanauki.pl/articles/279553.pdf
Data publikacji:
1999
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
damage mechanics
finite elements
splitting technique
Opis:
The avoid the loss of well-posedness in the post localization range, some continuum damage theories for elastic materials introduce higher order gradients of the damage variable into constitutive model. Although such theories allow for mathematically correct modelling of the strain localization phenomena, they are usually considered to be very complex to handle from the numerical point of view. The present work deals with the numerical implementation of a gradient-enhanced damage theory for elastic materials. A simple numerical technique, based on the finite element method, is proposed to approximate the solution to the resulting nonlinear mathematical problems. The coupling between damage and strain variables is circumvented by means of a splitting technique.
Celem poprawności sformułowania problemu w pewnych teoriach zniszczenia do modelu konstytutywnego materiałów sprężystych wprowadza się wyższe gradienty zmiennych opisujących zniszczenie. Chociaż teorie takie umożliwiają matematycznie poprawne modelowanie zjawisk lokalizacji odkształceń, to z punktu widzenia numeryki stosowanie ich uważa się zwykle za bardzo skomplikowane. W niniejszej wersji przedstawiono zastosowanie numeryczne teorii zniszczenia z wyższymi gradientami do materiałów sprężystych. Do przybliżonego rozwiązania otrzymanych nieliniowych zadań matematycznych zaproponowano prostą metodę numeryczną opartą na metodzie elementów skończonych. Użycie metody operatorowej pozwoliło uniknąć sprężenia między zmiennymi opisującymi zniszczenie i odkształcenie.
Źródło:
Journal of Theoretical and Applied Mechanics; 1999, 4; 847-861
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tracking young talented swimmers : follow-up of performance and its biomechanical determinant factors
Autorzy:
Morais, J. E.
Saavedra, J. M.
Costa, M. J.
Silva, A. J.
Marinho, D. A.
Barbosa, T. M.
Powiązania:
https://bibliotekanauki.pl/articles/951824.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
prepubescent swimmers
longitudinal assessment
kinematics
drag force
anthropometrics
efficiency
kinematyka
efektywność
pływak
biomechanika
Opis:
The aim of the study was to follow-up the stability of young talented swimmers’ performance and its biomechanical determinant factors (i.e., anthropometrics, kinematics, hydrodynamics and efficiency) during a competitive season. Thirty three (15 boys and 18 girls) young swimmers (overall: 11.81 ± 0.75 years old and Tanner stages 1–2 by self-evaluation) were evaluated. Performance, anthropometrics, hydrodynamics, kinematics and efficiency variables were assessed at three moments during a competitive season. Performance had a significant improvement (with minimum effect size) and a moderate-very high stability throughout the season. In the anthropometrics domain all variables increased significantly (ranging from without to minimum effect size) between moments and had a moderate-very high stability. Hydrodynamics presented no variations between all moments and had a low-very high stability throughout the season. In the kinematics domain, there were no variations between moment one and three, except for an increase in stroke frequency (without size effect). Speed fluctuation remained constant, with no significant variations. All kinematic variables had a low-very high stability. Efficiency variables did not present variations between moment one and three and had a low-moderate stability. Overall, young swimmers showed a minimum improvement in performance and in anthropometric factors; and a moderate stability of performance and its determinant factors (i.e., anthropometrics, hydrodynamics, kinematics and efficiency) during the competitive season.
Źródło:
Acta of Bioengineering and Biomechanics; 2013, 15, 3; 129-138
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
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
Tytuł:
A 3D trabecular bone homogenization technique
Autorzy:
Marques, Marco Costa
Belinha, J.
Oliveira, A. F.
Manzanares Cespedes, M.C.
Natal Jorge, R.M.
Powiązania:
https://bibliotekanauki.pl/articles/27324130.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
fabric tensor
homogenization technique
multiscale
bone
tensor tkaniny
technika homogenizacji
wieloskalowe
kość
Opis:
Purpose: Bone is a hierarchical material that can be characterized from the microscale to macroscale. Multiscale models make it possible to study bone remodeling, inducing bone adaptation by using information of bone multiple scales. This work proposes a computationally efficient homogenization methodology useful for multiscale analysis. This technique is capable to define the homogenized microscale mechanical properties of the trabecular bone highly heterogeneous medium. Methods: In this work, a morphology-based fabric tensor and a set of anisotropic phenomenological laws for bone tissue was used, in order to define the bone micro-scale mechanical properties. To validate the developed methodology, several examples were performed in order to analyze its numerical behavior. Thus, trabecular bone and fabricated benchmarks patches (representing special cases of trabecular bone morphologies) were analyzed under compression. Results: The results show that the developed technique is robust and capable to provide a consistent material homogenization, indicating that the homogeneous models were capable to accurately reproduce the micro-scale patch mechanical behavior. Conclusions: The developed method has shown to be robust, computationally less demanding and enabling the authors to obtain close results when comparing the heterogeneous models with equivalent homogenized models. Therefore, it is capable to accurately predict the micro-scale patch mechanical behavior in a fraction of the time required by classic homogenization techniques.
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 3; 139--152
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulated nuclear contamination scenario, solid cancer risk assessment, and support to decision
Autorzy:
Lima, Sergio X.
Costa, Karolina P. S.
Lima, Zelmo R.
Rother, Fagner C.
Araujo, Olga M. O.
Vital, Helio C.
Brum, Tercio
Junior, Wilson F. R. S.
Amorim, Jose Carlos C.
Healy, Matthew J. F.
Andrade, Edson R.
Powiązania:
https://bibliotekanauki.pl/articles/146554.pdf
Data publikacji:
2019
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
improvised nuclear device
IND
induced cancer
risk assessment
decision
ocena ryzyka
decyzja
Opis:
The detonation of an (hypothetical) improvised nuclear device (IND) can generate atmospheric release of radioactive material in the form of particles and dust that ultimately contaminate the soil. In this study, the detonation of an IND in an urban area was simulated, and its effects on humans were determined. The risk of solid cancer development due to radiation was calculated by taking into account prompt radiation and whole-body exposure of individuals near the detonation site up to 10 km. The excess relative risk (ERR) of developing solid cancer was evaluated by using the mathematical relationships from the Radiation Effects Research Foundation (RERF) studies and those from the HotSpot code. The methodology consists of using output data obtained from simulations performed with the HotSpot health physics code plugging in such numbers into a specific given equation used by RERF to evaluate the resulting impact. Such a preliminary procedure is expected to facilitate the decision-making process significantly.
Źródło:
Nukleonika; 2019, 64, 2; 41-48
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extraction of Ziziphus lotus fruit syrups: effect of enzymatic extraction and temperature on their rheological and chemical properties
Autorzy:
Letaief, T.
Mejri, J.
Ressureicao, S.
Abderrabba, M.
Costa, R.
Powiązania:
https://bibliotekanauki.pl/articles/2083051.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
Ziziphus lotus L.
syrup
shear-thinning
rheology
enzymatic extraction
Opis:
Fruit syrups are attracting increasing interest in the food industry. Ziziphus lotus fruit syrups were elaborated through the traditional and enzymatic methods with 30, 50 and 70° Brix. A chemical analysis revealed that Ziziphus lotus fruit powder and syrups present a potential source of energy through their relatively higher content of carbohydrates. Rheological oscillatory tests showed that syrups of 30°Brix demonstrate a viscous type of behaviour, the 70°Brix syrups possess an elastic behaviour, while the 50°Brix syrups present a mixed behaviour over the temperature range of 20 to 80°C. These syrups did not demonstrate any thixotropy or time dependence of viscosity. The complex viscosity was described successfully with a mathematical model that incorporates both independent variables, with an Arrhenius-type dependence on temperature, with an activation energy of 21.94 kJ mol-1 for the whole Brix range. The flow behaviour evaluation of the 30 and 50°Brix showed that these are shear-thinning fluids, tending to Newtonian fluids at higher temperatures. The dynamic viscosity was well described by the power law and the dependence of its parameters on temperature was adequately described by a Turian approach. The syrups of Ziziphus lotus fruit demonstrated a potential for further beneficial research with a view to obtaining a commercial food product.
Źródło:
International Agrophysics; 2021, 35, 1; 31-40
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Air-assistance in spray booms which have different spray volumes and nozzle types for chemically controlling Spodoptera frugiperda on corn
Autorzy:
Gimenes, M.J
Raetano, C.G.
Ferreira, M.H
Pereira-Prado, E.
Souza-Christovam, R.
Tourino-Rezende, D.
Almeida-Costa, S.I.
Powiązania:
https://bibliotekanauki.pl/articles/66410.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
The study aimed to evaluate the performance of air assistance in spray booms using different types of nozzles and spray volumes. We took into account spray deposits, fall armyworm control and crop corn performance in a narrow row cropping system. The experiment was carried out at the experimental area of Sao Paulo State University, Botucatu/SP, Brazil, during the 2008/2009 agricultural season, in randomized blocks with a factorial scheme (2×2+1) and four replications. Two spray nozzles (flat fan nozzle and hollow cone nozzle) were tested, combined with two air assistance levels in the spray boom (with and without air assistance) and a treatment control. In the experimental spraying, Spinosad insecticide was sprayed in amounts of 48 g active substance (a.s.)/ha. The air assistance in the spray boom increased the spray deposits in the V4 growth stage of the corn plants. Moreover, the application of this technology showed higher efficiency on fall armyworm control, reaching a 100% level 15 days after spraying, in the V10 growth stage of the plants. The hollow cone nozzle increased the spray deposit level on the corn plants compared with the flat fan nozzle, at growth stage V4. However, the flat fan nozzle, combined with air assistance technology, was more effective for controlling fall armyworm in the same growth stage (V4), although the hollow cone nozzle increased the deposit levels on the plants. All the technologies tested in the study promoted a reduction of plant damage from fall armyworm attack. Corn productivity is directly related to the control efficiency of fall armyworm.
Źródło:
Journal of Plant Protection Research; 2012, 52, 2
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water-based poly(urethane-urea) dispersions —meeting the European Union legislation
Dyspersje wodne poli(uretanowo-mocznikowe) w świetle wymagań prawodawstwa Unii Europejskiej
Autorzy:
Fernandes, I. P.
Costa, M. R.
Ferreira, M. J.
Barreiro, M. F.
Powiązania:
https://bibliotekanauki.pl/articles/947121.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
Tematy:
poly(urethane-urea)
water-based dispersion
European Union legislation
N-methyl-pyrrolidone free products
poli(uretano-mocznik)
dyspersja wodna
prawodawstwo Unii Europejskiej
produkty wolne od N-metylo-pirolidonu
Opis:
This article discusses the synthesis methods of water-based poly(urethane-urea) dispersions (PUD), which over the past few decades have developed a solid reputation for high performance applications, particularly in the field of adhesives and coatings. PUDs are mostly environmentally compatible products since they do not contain or contain only low amounts of volatile organic compounds (VOC). This is an important feature in view of the present environmental policies, where governments and internal agencies are placing emphasis on developing sustainable processes, improving work conditions and reducing emissions of toxic and polluting substances into the atmosphere. In this context, this paper will discuss the main approaches applied to PUD synthesis in order to meet severe environmental restrictions resulting from the EU legislation.
Omówiono metody syntezy dyspersji wodnych poli(uretanowo-mocznikowych) (PUD), które znajdują coraz szersze zastosowanie, szczególnie w produkcji klejów i powłok. PUD są na ogół produktami bezpiecznymi dla środowiska, ze względu na brak lub małą zawartość lotnych związków organicznych (VOC), co jest ważne w świetle obecnej polityki ochrony środowiska. Przedstawione w pracy metody syntezy PUD uwzględniają wymagania wynikające z prawodawstwa Unii Europejskiej w zakresie spełniania surowych ograniczeń środowiskowych.
Źródło:
Polimery; 2015, 60, 9; 536-540
0032-2725
Pojawia się w:
Polimery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation modelling of Vitória-Minas closed-loop rail network
Modelagem de simulação do circuito fechado da ferrovia Vitória Á Minas
Autorzy:
Faria, C. H. F. de
Cruz, M. M. da Costa
Powiązania:
https://bibliotekanauki.pl/articles/375477.pdf
Data publikacji:
2015
Wydawca:
Politechnika Śląska. Wydawnictwo Politechniki Śląskiej
Tematy:
railway
simulation
closed loop
heavy haul
transportation of iron ore
rolling stock
kolej żelazna
symulacja
pętla zamknięta
transport rud żelaza
tabor kolejowy
Opis:
This paper presents a closed loop simulation model that represents the mining logistics chain of the Vitória Minas Railway (VMR), Brazil. The simulator includes the loading process, circulation of loaded trains, unloading of ores for external and internal markets and the distribution of empty trains for new loads. General cargo and passengers trains are also included in the model, which, along with the queues formed in the circulation and the preventive and corrective maintenance of rolling stock, tracks and equipment, interfere with the transportation of iron ore. The primary objective of the iron ore transport is to meet the daily loading and unloading schedules and minimize queues by maximizing the operations at the loading and unloading points. The VMR simulator developed uses macro-mesoscopic approach with Monte Carlo simulation. To validate the simulator, we used actual data of the railway and compared with reality. We obtained a very good adhesion to the value of 2.9% for the validation scenario (Scenario 1) and 3.4% for the scenario with reducing the number of lots of wagons (Scenario 2). We concluded with this simulation that it is possible to reduce the number of GDE wagons without reducing the current level of productivity of the rail system.
Este artigo apresenta o modelo de simulação do circuito fechado da rede logística de minério de ferro da ferrovia Vitória Á Minas (VMR), Brasil. O simulador inclui o processo de carregamento, circulação dos trens carregados, descarregamento para os mercados externos e internos e a distribuição dos trens vazios para novos carregamentos. Os trens de carga geral e de passageiros também foram incluídos no modelo, bem como suas filas de formação e as manutenções preventivas e corretivas do material rodante, que interferem no transporte do minério de ferro. O principal objetivo do transporte de minério de ferro é atender as programações de carregamento e descarregamento e minimizar as filas maximizando as operações nos pontos de carregamento e descarregamento. O simulador VMR desenvolvido utiliza uma abordagem macro-mesoscópica de simulação de Monte Carlo. Para validar o simulador, foi utilizado dados da ferrovia e comparado com a realidade. Obtivemos uma aderência muito de 2,9% para o cenário de validação (cenário 1) e 3,4% para o cenário com a redução do número de lotes de vagão (cenário 2). Concluímos que com esta simulação é possível reduz o número de lotes de vagões GDE sem reduzir a produtividade da ferrovia.
Źródło:
Transport Problems; 2015, T. 10, z. spec.; 125-139
1896-0596
2300-861X
Pojawia się w:
Transport Problems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relationship between performance, dry-land power and kinematics in master swimmers
Autorzy:
Espada, M. C.
Costa, M. J.
Costa, A. M.
Silva, A. J.
Barbosa, T. M.
Pereira, A. F.
Powiązania:
https://bibliotekanauki.pl/articles/307228.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
pływanie
kinematyka
energia
master swimmers
kinematic
dry-land power
performance
Opis:
The purpose of the study was to analyze the relationships between sprint swimming performance, dry-land power, and kinematics in master swimmers. Twenty-two male master swimmers were separated in two groups based on their chronological age: (i) 30–39 years and; (ii) 40–49 years. Maximum dry-land power was determined through counter movement jump and 3 kg medicine ball throwing (Hmax and Tmax, respectively). Kinematic determinants of performance were measured during a maximal bout of 15, 25 and 50 m front crawl (T15, T25, T50). Stroke frequency (SF), stroke length (SL) and stroke index (SI) were calculated as kinematical aspects of the stroke. In the 30-39 group, SI25 was correlated to T25 (r = –0.76, p < 0.01, η2 = 0.96), the same was observed between SI50 and T50 (r = –0.83, p < 0.01, η2 = 0.96). Only SI50 was significantly correlated to T50 (r = –0.86, p < 0.01, η2 = 0.97) in the 40–49 years age cohort. In dryland power variables, Hmax and Tmax were only correlated in the younger master swimmers group (r = –0.87, p < 0.01, η2 = 0.97). There were no significant differences (p < 0.05) between younger (30–39 years) and older (40–49 years) swimmers groups in dry-land tests (Hmax 28.5 ± 5.9 vs. 26.5 ± 3.9 cm and Tmax 4.2 ± 1.0 vs. 4.2 ± 1.1 m). Our results suggest that swimming performance in younger master swimmers (30–39 years) seem more dependent on kinematic swimming variables than on strength parameters, which were most related to swimming performance in the older master swimmers (40–49 years).
Źródło:
Acta of Bioengineering and Biomechanics; 2016, 18, 2; 145-151
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Shot Peening With Glass Microspheres on the Fatigue Behavior of a Low Carbon Steel
Autorzy:
de Lacerda, J. C.
Pereira, I. R.
Costa, J. M. G.
Pinto, J. S.
Souza, H. F. M.
Fonseca, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/352156.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
fatigue
shot peening
Wöhler curve
low carbon steel
glass microspheres
Opis:
The present work has the objective of studying the effect of shot peening with glass microspheres on SAE 1020 steel in its resistance to fatigue. Fatigue tests were carried out by rotary bending with load control and loading on balance in specimens with and without shot peening. A rotation speed of approximately 750 rpm (12.5 Hz) was employed in the fatigue tests. Vickers microhardness tests were performed in order to verify the surface hardening produced by shot peening with glass microspheres. Analysis of the steel surface and fatigue fractures was performed using scanning electron microscopy (SEM). Fatigue tests were performed in order to obtain S-N curves (Wöhler curves). It was observed that shot peening with glass microspheres improved the fatigue strength of the steel at high cycle.
Źródło:
Archives of Metallurgy and Materials; 2019, 64, 4; 1513-1518
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Formation and Annealing of Micropores in Hematite
Autorzy:
Dauwe, C.
Da Costa, G. M.
Van Hoecke, T.
Segers, D.
Powiązania:
https://bibliotekanauki.pl/articles/1933484.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
In iron oxide powders positrons are trapped in the surface layers and the value of the S-parameter is an indicator of the total specific surface, including external surface and internal surfaces of micropores. The evolution of micropores is followed when α-FeOOH is thermally decomposed into α-Fe$\text{}_{2}$O$\text{}_{3}$. It is shown that the micropore formation is not linked to the decomposition process, but that they also form in hematite synthesized from a ferrihydrite precursor in aqueous solution.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 119-123
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 32

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