The distribution of pressure coefficient formed when the fluid contacts with the kayak oar blade is not been studied extensively. The CFD technique was employed to calculate pressure coefficient distribution on the front and rear faces of oar blade resulting from the numerical resolution equations of the flow around the oar blade in the steady flow conditions (4 m/s) for three angular orientations of the oar (45°, 90°, 135°) with main flow. A three-dimensional (3D) geometric model of oar blade was modeled and the k-ε turbulent model was applied to compute the flow around the oar. The main results reported that, under steady state flow conditions, the drag coefficient (Cd = 2.01 for 4 m/s) at 90° orientation has the similar evolution for the different oar blade orientation to the direction of the flow. This is valid when the orientation of the blade is perpendicular to the direction of the flow. Results indicated that the angle of oar strongly influenced the Cd with maximum values for 90° angle of the oar. Moreover, the distribution of the pressure is different for the internal and external edges depending upon oar angle. Finally, the difference of negative pressure coefficient Cp in the rear side and the positive Cp in the front side, contributes toward propulsive force. The results indicate that CFD can be considered an interesting new approach for pressure coefficient calculation on kayak oar blade. The CFD approach could be a useful tool to evaluate the effects of different blade designs on the oar forces and consequently on the boat propulsion contributing toward the design improvement in future oar models. The dependence of variation of pressure coefficient on the angular position of oar with respect to flow direction gives valuable dynamic information, which can be used during training for kayak competition.

The purpose of this study was to analyze the hydrodynamic characteristics of a realistic model of an elite swimmer hand/forearm using three-dimensional computational fluid dynamics techniques. A three-dimensional domain was designed to simulate the fluid flow around a swimmer hand and forearm model in different orientations (0°, 45°, and 90° for the three axes Ox, Oy and Oz). The hand/forearm model was obtained through computerized tomography scans. Steady-state analyses were performed using the commercial code Fluent. The drag coefficient presented higher values than the lift coefficient for all model orientations. The drag coefficient of the hand/forearm model increased with the angle of attack, with the maximum value of the force coefficient corresponding to an angle of attack of 90°. The drag coefficient obtained the highest value at an orientation of the hand plane in which the model was directly perpendicular to the direction of the flow. An important contribution of the lift coefficient was observed at an angle of attack of 45°, which could have an important role in the overall propulsive force production of the hand and forearm in swimming phases, when the angle of attack is near 45°.

O uso combinado de cimento de ionômero de vidro (CIV) e resina composta é largamente indicado nos procedimentos clínicos odontológicos. Ao associar os dois materiais objetiva-se que as características desejáveis de cada um sejam somadas, melhorando as propriedades e a taxa de sucesso da restauração final. Com base nisso, o objetivo do trabalho foi avaliar, através de ensaio de microcisalhamento, nos estágios imediato e após envelhecimento simulado, o melhor tratamento de superfície sobre o cimento de ionômero de vidro convencional a fim de garantir uma adesão eficaz e duradoura com resinas compostas. Para confecção dos corpos de prova, foram feitas cavidades padrão (0,2x1x1cm) em uma matriz circular de resina acrílica no qual o CIV (Ionofil Plus VOCO, Alemanha) foi inserido. Foram ao todo 80 amostras de CIV divididas em 8 grupos (n=10). Em cada amostra foram confeccionados 5 corpos de prova de resina composta, gerando 50 por grupo e um total de 400. Os grupos foram divididos de acordo com o tratamento de superfície (somente aplicação de adesivo, dessecamento com ar comprimido, condicionamento ácido e asperização com broca) e de acordo com o tipo de sistema adesivo utilizado (convencional de dois passos e autocondicionante de passo único). Após os tratamentos, as amostras foram armazenadas em meio úmido por 48h e, em seguida, metade dos corpos de prova de cada grupo foi submetido ao ensaio de microcisalhamento e a outra metade ao envelhecimento em uma termocicladora com 10.000 ciclos de 20s cada a temperaturas de 5 e 55ºC para posteriormente ser submetida ao mesmo ensaio. Os resultados de resistência ao microcisalhamento foram analisados por ANOVA (two-way) e pelo teste de Tukey HSD post hoc com nível de significância de 5% (p<0,05). Os valores de resistência adesiva no grupo envelhecido foram inferiores e apresentaram diferença estatisticamente significativa (p=0). A asperização da superfície seguida de condicionamento ácido apresentou os maiores valores de resistência adesiva nos dois estágios avaliados. Todos os corpos de prova foram analisados no microscópio óptico para avaliar o tipo de fratura ocorrida. Em seguida, amostras representativas foram preparadas para análise em microscopia eletrônica de varredura (MEV) e espectroscopia de raios-x por dispersão em energia (EDX/ EDS). Nas condições do estudo, foi possível concluir que a asperização da superfície do ionômero de vidro, seguida de condicionamento ácido e sistema adesivo convencional representou a melhor opção de estratégia adesiva.

This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic.&nbsp;Methodology: For SBS test, 32 blocks (7x7x2 mm) of lithium disilicate were obtained and randomly divided into eight groups (four blocks per group) according to each surface treatment (HF 20 s, 60 s, 120 s + silanization/S or Scotch Bond Universal/ SBU) and the Monobond Etch &amp; Prime - MEP application followed or not by SBU. On each treated surface ceramic block, up to four dual-curing resin cement cylinders were prepared and light-cured for 40s (N=120/n=15). The specimens were thermocycled (10,000 cycles, 5-55°C, 30 s) and the SBS test (50KgF, 0.5 mm/min) was performed. Furthermore, failure analysis, wettability, AFM, and SEM were carried out. SBS data (MPa) were analyzed using Student's t-test, two-way ANOVA, Tukey's test (5%) and Weibull's analysis.&nbsp;Results: For HF experimental groups, two-way ANOVA presented the factors “etching time” and “bonding agent” as significant (p&lt;0.05). After silane application, the HF groups presented similar bond strength. SBU application compromised the SBS, except for 120s etching time (HF120sS: 23.39ᵃ±6.48 MPa; HF120sSBU: 18.76ᵃ±8.81MPa). For MEP groups, SBU application did not significantly affect the results (p=0.41). The MEP group presented the highest Weibull modulus (4.08A) and they were statistically different exclusively from the HF20sSBU (0.58B).&nbsp;Conclusion: The HF 20s, 60s, 120 s followed by silane, promoted similar resin-bond strength to ceramic and the SBU application after HF or MEP did not increase the SBS.

A study was conducted to evaluate the performance of glued laminated timber (glulam) of maritime pine treated with a copper azole preservative product. Shear strength of glue lines met the requirements of EN 386 (2001) with no influence of clamping pressure and cure temperature. According to the same standard, delamination was satisfactory for higher cure temperatures applied with a clamping pressure of 0.6 N/mm2. Finger joints made with treated wood gave satisfactory bending strength. The preservative treatment did not influence the modulus of elasticity of the beams. According to a Monte Carlo simulation and following the requirements of EN 1194 (2002), glulam of class GL 28c can be manufactured if visually graded maritime pine of classes E and EE (NP 4305 1995) is used in the inner and outer lamellas, respectively, and class GL 24h when using both grades in equal proportions randomly distributed through the glulam element.

Com a presente dissertação pretende-se contribuir para a implementação industrial do processo Tool Assisted Friction Spot Welding (TAFSW) na soldadura por pontos de chapas de aço. Com este objetivo, foram produzidas e analisadas diversas soldaduras num aço de alta resistência e baixa liga (HC420LA), variando o número de chapas (2, 3 e 4 chapas) e o tempo de soldadura (5, 15 e 30 segundos). Durante a produção das soldaduras foram registadas as temperaturas, utilizando uma câmara termográfica, assim como, o binário e a força, através do equipamento onde foram produzidas as soldaduras. O pós-processamento destes dados, permitiu concluir que nenhum dos parâmetros avaliados condicionou de forma determinante os valores máximos da temperatura ou do binário, tendo sido registados, em todos os ensaios, uma temperatura máxima de aproximadamente 1200 °C e um binário máximo de aproximadamente 30 Nm. Os valores registados para a força máxima apresentaram uma dispersão aleatória, não tendo sido possível estabelecer qualquer relação entre a sua evolução e os parâmetros do processo em análise. A análise microestrutural das soldaduras produzidas permitiu observar uma zona afetada pelo processo em todas as amostras, mesmo nas soldaduras de 4 chapas produzidas em 5 segundos. Foi registado um gradiente decrescente do tamanho de grão ao longo da secção vertical das soldaduras, apresentando uma microestrutura ferrítica acicular com grãos de bainite dispersos na matriz. Foram ainda analisadas as regiões correspondentes à última interface das soldaduras produzidas, tendo-se observado uma concentração maior de descontinuidades na região da ligação para as chapas soldadas em apenas cinco segundos. Foi ainda efetuada a caracterização mecânica das soldaduras. Os ensaios de dureza revelaram um gradiente decrescente de dureza ao longo das secções verticais das soldaduras, o qual foi associado ao gradiente térmico imposto pela ferramenta de soldadura. Os ensaios de tração revelaram que as soldaduras com maior resistência foram as produzidas em 30 segundos. A força máxima registada, foi de aproximadamente 16 kN, independentemente da interface avaliada.

Introduction: Caries-detecting dyes are widely used as diagnostic adjuncts to identify carious dentin during restorative procedures. However, their application may raise concerns regarding potential interference with dentin adhesion, particularly whenfollowed by adhesive restoration with composite resin.Objective: This in vitro study aimed to evaluate the effect of the prior application of three commercially available caries-detecting dyes on the immediate shear bond strength of a composite resin bonded to sound permanent dentin.Methods: Forty sound human permanent molars were randomly assigned to four experimental groups (n=10): a control group (no dye application); Caries Detector (Kuraray Noritake Dental Inc., Japan) group; Sable™ Seek™ (Ultradent Products Inc., USA) group; and Caries Marker (VOCO, Germany) group. Occlusal surfaces were removed to expose flat, standardized mid-coronal sound dentin. In the experimental groups, the respective dyes were applied for 10 seconds and rinsed with water for 20 seconds. Subsequently, a two-step self-etch adhesive system (Clearfil™ SE Bond 2 [Kuraray Noritake Dental Inc., Japan]) was applied, followed by composite resin build-up (Grandio® SO [VOCO, Germany]). Shear bond strength testing was performed using a universal testing machine, and values were recorded in MPa. Statistical analysis was performed using one-way ANOVA, with a significance level of 5%.Results: The control group exhibited a mean shear bond strength of 14.50±2.65 MPa. The Sable™ Seek™, Caries Detector, and Caries Marker groups showed mean values of 14.25±2.05 MPa, 13.35±2.29 MPa, and 15.38±2.21 MPa, respectively. Although the Caries Marker group showed the highest numerical mean and Caries Detector the lowest, one-way ANOVA revealed no statistically significant differences in dentin bond strength among any of the groups (p=0.201).Discussion: The stable shear bond strength values and uniform fracture patterns suggest that the water-rinsing protocol effectively removed the caries-detecting agents, preventing any negative interference with the bonding performance of the adhesive system.Conclusion: The prior application of the evaluated caries-detecting agents did not significantly compromise the immediate shear bond strength of composite resin bonded to sound dentin when the Clearfil™ SE Bond 2 adhesive system was used. A 20-second water-rinsing protocol appears sufficient to eliminate surface residues and preserve interfacial bonding integrity.

Abstract This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic. Methodology: For SBS test, 32 blocks (7x7x2 mm) of lithium disilicate were obtained and randomly divided into eight groups (four blocks per group) according to each surface treatment (HF 20 s, 60 s, 120 s + silanization/S or Scotch Bond Universal/ SBU) and the Monobond Etch & Prime - MEP application followed or not by SBU. On each treated surface ceramic block, up to four dual-curing resin cement cylinders were prepared and light-cured for 40s (N=120/n=15). The specimens were thermocycled (10,000 cycles, 5-55°C, 30 s) and the SBS test (50KgF, 0.5 mm/min) was performed. Furthermore, failure analysis, wettability, AFM, and SEM were carried out. SBS data (MPa) were analyzed using Student's t-test, two-way ANOVA, Tukey's test (5%) and Weibull's analysis. Results: For HF experimental groups, two-way ANOVA presented the factors “etching time” and “bonding agent” as significant (p<0.05). After silane application, the HF groups presented similar bond strength. SBU application compromised the SBS, except for 120s etching time (HF120sS: 23.39ᵃ±6.48 MPa; HF120sSBU: 18.76ᵃ±8.81MPa). For MEP groups, SBU application did not significantly affect the results (p=0.41). The MEP group presented the highest Weibull modulus (4.08A) and they were statistically different exclusively from the HF20sSBU (0.58B). Conclusion: The HF 20s, 60s, 120 s followed by silane, promoted similar resin-bond strength to ceramic and the SBU application after HF or MEP did not increase the SBS.

Abstract Dual-cured buildup composites and simplified light-cured adhesive systems are mixed with a chemical activator to prevent the incompatibility between them. Objective: To evaluate microshear bond strength (μSBS) and nanoleakage (NL) of three universal adhesives used under buildup composites using different curing modes, at baseline and after 6-months (6m). Methodology: Dentin specimens of 55 molars were assigned to: Clearfil Universal Bond[CFU], Prime&Bond Elect[PBE] and One Coat 7 Universal[OCU]. All-Bond Universal[ABU] and Adper Scotchbond Multi-Purpose[SMP] were used as controls. CFU, PBE, and OCU were: light-cured [LC], dual-cured using a self-curing activator [DC], and self-cured, using a self-curing activator and waiting for 20 min [SC]. Upon the application of the adhesive, transparent matrices were filled with a dual-cured buildup composite and light cured, then tested in mSBS. For NL, the specimens were submersed in ammoniacal silver nitrate and sectioned to observe under the SEM. Three-way ANOVA and Tukey's test were applied (α=0.05). Results: OCU/LC-PBE/LC resulted in higher mean μSBS than ABU/LC. For SMP/DC higher mean μSBS were obtained than for both CFU/DC and OCU/DC (baseline). No universal adhesive was significantly affected by curing mode or storage time. CFU, PBE, and OCU did not undergo significant changes in any curing mode (p>0.05). NL (baseline) PBE/LC resulted in higher %NL compared to ABU/LC. SMP/DC resulted in higher %NL than CFU/DC-OCU/DC. CFU/LC/DC resulted in lower %NL than CFU/SC. PBE/SC resulted in lower %NL than PBE/DC. OCU/LC/SC showed lower %NL than OCU/DC. OCU showed significant lower %NL than CFU and PBE. All CFU groups, as well as OCU/SC, resulted in increased %NL at 6m when compared with baseline. Conclusion: For universal adhesives used in etch-and-rinse mode, self-cured activator and different curing modes did not influence μSBS. However, some interactions were observed for NL, but this influence was material-specific.