The Experts below are selected from a list of 21678 Experts worldwide ranked by ideXlab platform
Gianpaolo Papaccio - One of the best experts on this subject based on the ideXlab platform.
-
scaffold s Surface geometry significantly affects human stem cell bone tissue engineering
Journal of Cellular Physiology, 2008Co-Authors: Antonio Graziano, A. Giordano, Riccardo Daquino, Maria Gabriella Cusella De Angelis, Francesco De Francesco, Gregorio Laino, Adriano Piattelli, Tonino Traini, Alfredo De Rosa, Gianpaolo PapaccioAbstract:In this study, we have observed dental pulp stem cells (SBP-DPSCs) performances on different scaffolds, such as PLGA 85:15, hydroxyapatite chips (HA) and titanium. Stem cells were challenged with each engineered Surface, either in plane cultures or in a rotating apparatus, for a month. Gingival fibroblasts were used as controls. Results showed that stem cells exerted a different response, depending on the different type of Textured Surface: in fact, microconcavities significantly affected SBP-DPSC differentiation into osteoblasts, both temporally and quantitatively, with respect to the other Textured Surfaces. Actually, stem cells challenged with concave Surfaces differentiated quicker and showed nuclear polarity, an index of secretion, cellular activity and matrix formation. Moreover, bone-specific proteins were significantly expressed and the obtained bone tissue was of significant thickness. Thus, cells cultured on the concave Textured Surface had better cell-scaffold interactions and were induced to secrete factors that, due to their autocrine effects, quickly lead to osteodifferentiation, bone tissue formation, and vascularization. The worst cell performance was obtained using convex Surfaces, due to the scarce cell proliferation on to the scaffold and the poor matrix secretion. In conclusion, this study stresses that for a suitable and successful bone tissue reconstruction the Surface texture is of paramount importance. J. Cell. Physiol. 214:166–172, 2008. © 2007 Wiley-Liss, Inc.
Weili Liu - One of the best experts on this subject based on the ideXlab platform.
-
investigation on the tribological performance of micro dimples Textured Surface combined with longitudinal or transverse vibration under hydrodynamic lubrication
International Journal of Mechanical Sciences, 2020Co-Authors: Peng Wang, Weili Liu, Hailong ChenAbstract:Abstract A method of combining Surface texturing with longitudinal or transverse micro-vibration was proposed to further enhance the tribological performance of mechanical components. The influences of vibration parameters and micro-dimple geometrical parameter on the tribological performance were studied to verify the feasibility of tribology enhancement by numerical and experimental methods. Results show that the friction coefficients can be significantly reduced by superimposing longitudinal or transverse vibration on the Textured Surfaces under different lubrication conditions. The friction coefficient slightly increases with the increase of vibration frequency and significantly diminishes with the increase of vibration velocity amplitude. The improvement of lubrication condition is the main mechanism of friction reduction. Since the vibrations can enhance the average load capacity of the Textured Surface and drag out the lubricant reserved in the micro-dimples, in turn, enlarge the thickness of lubricant film. These results provide a novel perspective to reduce friction and save energy in mechanical systems and metal processing.
-
numerical simulation and experimental investigation on tribological performance of micro dimples Textured Surface under hydrodynamic lubrication
International Journal of Mechanical Sciences, 2019Co-Authors: Hailong Chen, Weili Liu, Peng WangAbstract:Abstract Aiming at establishing an effective and efficient optimization method of texture parameters to further enhance the tribological performance of mechanical equipment, numerical simulation and experimental studies were undertaken to assess the tribological performance of Textured Surface. Pressure distributions and velocity distributions of the lubricant flow were analyzed by three-dimensional computational fluid dynamic simulation to comprehensively understand the effects of geometric parameters and operating conditions. It is found that the tribological performance of the Textured Surface is significantly affected by the micro-dimple geometric parameters, and the optimum texturing geometric parameters are highly dependent on the operating conditions. The comparative tribological experiments of unTextured and Textured specimens were conducted, and the specimen with area density of 28.26% achieves a maximum friction reduction rate of 26.61% under the tested conditions. The numerical simulation and experimental results were cross-checked and consistent with each other to verify that the Textured Surface can achieve a remarkable friction reduction effect. The friction reduction mechanism is mainly attributed to the improvement of carrying capacity, lubricant reservation, contact area reduction and secondary lubrication. Results can provide theoretical guidance for the optimization of texture geometric parameters under different application conditions.
Seock Sam Kim - One of the best experts on this subject based on the ideXlab platform.
-
improvement of tribological characteristics of multi scale laser Textured Surface in terms of lubrication regime
Journal of the Korean Society of Tribologists and Lubrication Engineers, 2014Co-Authors: Jonghyoung Kim, Si Geun Choi, Dawit Zenebe Segu, Yongsub Jung, Seock Sam KimAbstract:Laser Surface Texturing(LST) is a Surface engineering process used to improve tribological characteristicsof materials by creating patterned microstructures on the mechanical contact Surface. In LST technology, a pulsatedlaser beam is used to create arranged dimples on a Surface by a material ablation process, which can improve such asload capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect ofmulti-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI52100) to create arranged dimples. To optimize the Surface texturing effect on friction, multi-scale texture dimples withsome specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tri-bological testing of multi-scale Textured Surface was performed by a flat-on-flat unidirectional tribometer under lubri-cation and the results compared with that of the non-Textured Surface. Through an increase in sliding speed, thebeneficial effect of multi-scale LST performance was achieved. The multi-scale Textured Surface had lower frictioncoefficient performances than the non-Textured Surface due to the hydrodynamic lubrication effect.Keywords: laser Surface texture (레이저 표면 텍스처), lubrication regime (윤활영역), friction (마찰), Surfacemodification (표면개질)
-
The effect of multi-scale laser Textured Surface on lubrication regime
Applied Surface Science, 2013Co-Authors: Dawit Zenebe Segu, Si Geun Choi, Jae Hyouk Choi, Seock Sam KimAbstract:Abstract Laser Surface texturing (LST) is a Surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact Surface. In LST technology, a pulsated laser beam is used to create arranged dimples on Surface by a material ablation process, which can improve load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on steel (AISI 52100) to create arranged dimples. To optimize the Surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by laser ablation process by combining circles and ellipses. The tribological testing of multi-scale Textured Surface was performed by a flat-on-flat unidirectional tribometer under lubrication, and the results compared with that of unTextured Surface. Through an increase in sliding speed and dimple depth the beneficial effect of multi-scale LST performance was achieved. The multi-scale Textured Surface had lower friction coefficient performance than the unTextured Surface due to hydrodynamic lubrication effect.
Antonio Graziano - One of the best experts on this subject based on the ideXlab platform.
-
scaffold s Surface geometry significantly affects human stem cell bone tissue engineering
Journal of Cellular Physiology, 2008Co-Authors: Antonio Graziano, A. Giordano, Riccardo Daquino, Maria Gabriella Cusella De Angelis, Francesco De Francesco, Gregorio Laino, Adriano Piattelli, Tonino Traini, Alfredo De Rosa, Gianpaolo PapaccioAbstract:In this study, we have observed dental pulp stem cells (SBP-DPSCs) performances on different scaffolds, such as PLGA 85:15, hydroxyapatite chips (HA) and titanium. Stem cells were challenged with each engineered Surface, either in plane cultures or in a rotating apparatus, for a month. Gingival fibroblasts were used as controls. Results showed that stem cells exerted a different response, depending on the different type of Textured Surface: in fact, microconcavities significantly affected SBP-DPSC differentiation into osteoblasts, both temporally and quantitatively, with respect to the other Textured Surfaces. Actually, stem cells challenged with concave Surfaces differentiated quicker and showed nuclear polarity, an index of secretion, cellular activity and matrix formation. Moreover, bone-specific proteins were significantly expressed and the obtained bone tissue was of significant thickness. Thus, cells cultured on the concave Textured Surface had better cell-scaffold interactions and were induced to secrete factors that, due to their autocrine effects, quickly lead to osteodifferentiation, bone tissue formation, and vascularization. The worst cell performance was obtained using convex Surfaces, due to the scarce cell proliferation on to the scaffold and the poor matrix secretion. In conclusion, this study stresses that for a suitable and successful bone tissue reconstruction the Surface texture is of paramount importance. J. Cell. Physiol. 214:166–172, 2008. © 2007 Wiley-Liss, Inc.
Satish C Sharma - One of the best experts on this subject based on the ideXlab platform.
-
Performance of two-lobe hole-entry hybrid journal bearing system under the combined influence of Textured Surface and couple stress lubricant
'EDP Sciences', 2018Co-Authors: Chandra B Khatri, Satish C SharmaAbstract:Textured Surface in journal bearings is becoming an important area of investigation during the last few years. Surface textures have the shapes of micro-dimple with a small diameter and depth having order of magnitude of bearing clearance. This paper presents the influence of couple stress lubricant on the circular and non-circular hole-entry hybrid journal bearing system and reports the comparative study between the Textured and non-Textured circular/non-circular hybrid journal bearing system. The governing Reynolds equation has been modified for the couple stress lubricant flow in the clearance of bearing and journal. The FEM technique has been applied to solve the modified Reynolds equation together with restrictor flow equation. The numerically simulated results indicate that the influence of couple stress lubricant is significantly more in Textured journal bearing than that of non-Textured journal bearing. Further, it has been observed that the Textured two-lobe (δ = 1.1) hybrid journal bearing lubricated with couple stress lubricant provides larger values of fluid film stiffness coefficients and stability threshold speed against other bearings studied in the present paper
-
influence of Textured Surface on the performance of non recessed hybrid journal bearing operating with non newtonian lubricant
Tribology International, 2016Co-Authors: Chandra B Khatri, Satish C SharmaAbstract:Abstract In the present work, a comparative study between Textured Surface and non-Textured Surface non-recessed hybrid journal bearing configurations is presented. To obtain the performance characteristics parameters of non-recessed hybrid journal bearing, the Reynolds equation, which governs the flow of lubricant in the clearance space, is solved using FEM and the performance parameters are computed. The shear stress–strain relation of lubricant is modeled with the help of a power-law fluid model. The numerically simulated results show that the Textured non-recessed hybrid journal bearing provides improved stability parameter than that of journal bearing with non-texturing.
