This paper reports the large eddy simulations of the effects of a saw-tooth plasma actuator and the laidback fan-shaped hole on the film cooling flow characteristics, and the numerical results are compared with a corr...This paper reports the large eddy simulations of the effects of a saw-tooth plasma actuator and the laidback fan-shaped hole on the film cooling flow characteristics, and the numerical results are compared with a corresponding standard configuration（cylindrical hole without the sawtooth plasma actuator）. For this numerical research, the saw-tooth plasma actuator is installed just downstream of the cooling hole and a phenomenological plasma model is employed to provide the 3D plasma force vectors. The results show that thanks to the downward force and the momentum injection effect of the saw-tooth plasma actuator, the cold jet comes closer to the wall surface and extends further downstream. The saw-tooth plasma actuator also induces a new pair of vortex which weakens the strength of the counter-rotating vortex pair（CRVP） and entrains the coolant towards the wall, and thus the diffusion of the cold jet in the crossflow is suppressed.Furthermore, the laidback fan-shaped hole reduces the vertical jet velocity causing the disappearance of downstream spiral separation node vortices, this compensates for the deficiency of the saw-tooth plasma actuator. Both effects of the laidback fan-shaped hole and the saw-tooth plasma actuator effectively control the development of the CRVP whose size and strength are smaller than those of the anti-counter rotating vortex pair in the far field, thus the centerline and the spanwise-averaged film cooling efficiency are enhanced. The average film cooling efficiency is the biggest in the Fan-Dc=1 case, which is 80% bigger than that in the Fan-Dc=0 case and 288% bigger than that in the Cyl-Dc=0 case.展开更多
Background: Gingival biotype is one of the most important factors that impede success in dental treatments;it affects the outcomes of periodontal surgery, and restorative treatments. Researchers classified gingival bi...Background: Gingival biotype is one of the most important factors that impede success in dental treatments;it affects the outcomes of periodontal surgery, and restorative treatments. Researchers classified gingival biotypes into thin biotype and thick biotype. It is crucial to identify tissue biotype before treatment. Aim of Study: To determine the prevalence of gingival biotypes in a Syrian population, in addition, to study the distribution of gingival biotypes according to gender and tooth shape. Material and Methods: This cross sectional study included 500 volunteers (300 males and 200 females) from the patients who had visited the department of periodontology-dental faculty at Damascus University. Gingival thickness was assessed to determine the gingival biotype for the maxillary central incisors using the direct measurement technique (Trans-gingival probing). Shapes of the maxillary incisors were recorded. A written informed consent was taken from each patient. Statistical analysis was done using test k2 p < 0.05. Results: The mean age was 26.8 ± 4.4 years. Thick gingival biotype was detected in 58.4% of the sample and most of patients are men while the prevalence of thin gingival biotype was 41.6% of the sample. It was also observed that patients with thin gingival biotype had triangular tooth shape in 99.5% (p < 0.05). Conclusion: Thick gingival biotype was observed to be more prevalent in a Syrian population than thin biotype. Most Syrian males had thick gingival biotype with square tooth shape while females had thinner biotype and triangular tooth shape.展开更多
基金supported by National Natural Science Foundation of China(Grant No.51306042)the Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2013092)
文摘This paper reports the large eddy simulations of the effects of a saw-tooth plasma actuator and the laidback fan-shaped hole on the film cooling flow characteristics, and the numerical results are compared with a corresponding standard configuration（cylindrical hole without the sawtooth plasma actuator）. For this numerical research, the saw-tooth plasma actuator is installed just downstream of the cooling hole and a phenomenological plasma model is employed to provide the 3D plasma force vectors. The results show that thanks to the downward force and the momentum injection effect of the saw-tooth plasma actuator, the cold jet comes closer to the wall surface and extends further downstream. The saw-tooth plasma actuator also induces a new pair of vortex which weakens the strength of the counter-rotating vortex pair（CRVP） and entrains the coolant towards the wall, and thus the diffusion of the cold jet in the crossflow is suppressed.Furthermore, the laidback fan-shaped hole reduces the vertical jet velocity causing the disappearance of downstream spiral separation node vortices, this compensates for the deficiency of the saw-tooth plasma actuator. Both effects of the laidback fan-shaped hole and the saw-tooth plasma actuator effectively control the development of the CRVP whose size and strength are smaller than those of the anti-counter rotating vortex pair in the far field, thus the centerline and the spanwise-averaged film cooling efficiency are enhanced. The average film cooling efficiency is the biggest in the Fan-Dc=1 case, which is 80% bigger than that in the Fan-Dc=0 case and 288% bigger than that in the Cyl-Dc=0 case.
文摘Background: Gingival biotype is one of the most important factors that impede success in dental treatments;it affects the outcomes of periodontal surgery, and restorative treatments. Researchers classified gingival biotypes into thin biotype and thick biotype. It is crucial to identify tissue biotype before treatment. Aim of Study: To determine the prevalence of gingival biotypes in a Syrian population, in addition, to study the distribution of gingival biotypes according to gender and tooth shape. Material and Methods: This cross sectional study included 500 volunteers (300 males and 200 females) from the patients who had visited the department of periodontology-dental faculty at Damascus University. Gingival thickness was assessed to determine the gingival biotype for the maxillary central incisors using the direct measurement technique (Trans-gingival probing). Shapes of the maxillary incisors were recorded. A written informed consent was taken from each patient. Statistical analysis was done using test k2 p < 0.05. Results: The mean age was 26.8 ± 4.4 years. Thick gingival biotype was detected in 58.4% of the sample and most of patients are men while the prevalence of thin gingival biotype was 41.6% of the sample. It was also observed that patients with thin gingival biotype had triangular tooth shape in 99.5% (p < 0.05). Conclusion: Thick gingival biotype was observed to be more prevalent in a Syrian population than thin biotype. Most Syrian males had thick gingival biotype with square tooth shape while females had thinner biotype and triangular tooth shape.
