On the Regular Surface of Genus Three and Linear Genus Four

1933 ◽  
Vol s1-8 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Patrick du Val
Keyword(s):  
Regular Surface

AVRAMI–KOLMOGOROV–JOHNSON–MEHL KINETICS FOR NANOPARTICLES

2008 ◽  
Vol 15 (05) ◽  
pp. 605-612 ◽  
Author(s):  
VLADIMIR P. ZHDANOV
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Infinite Medium ◽  
Local State ◽  
Elementary Reaction ◽  
Regular Surface

In the conventional Avrami–Kolmogorov–Johnson–Mehl model, the reaction or phase transition occurring in the 2D or 3D infinite medium is considered to start and proceed around randomly distributed and/or appearing nucleation centers. The radius of the regions transformed is assumed to linearly increase with time. The Monte Carlo simulations presented, illustrate what may happen if the transformation takes place in nanoparticles. The attention is focused on nucleation on the regular surface, edge and corner sites, and on the dependence of the activation energy for elementary reaction events on the local state of the sites.

Sapphire substrates with a regular surface relief

2014 ◽  
Vol 59 (5) ◽  
pp. 732-735 ◽  
Author(s):  
A. V. Butashin ◽  
V. M. Kanevsky ◽  
A. E. Muslimov ◽  
A. L. Vasilyev ◽  
Yu. N. Emirov ◽  
...  
Keyword(s):  
Surface Relief ◽  
Regular Surface ◽  
Sapphire Substrates

Heat flux enhancement by regular surface roughness in turbulent thermal convection

2014 ◽  
Vol 763 ◽  
pp. 109-135 ◽  
Author(s):  
Sebastian Wagner ◽  
Olga Shishkina
Keyword(s):  
Heat Flux ◽  
Surface Roughness ◽  
Thermal Convection ◽  
Large Scale ◽  
Secondary Flows ◽  
Scaling Exponent ◽  
Wall Roughness ◽  
Regular Surface ◽  
Large Scale Circulation ◽  
Flux Enhancement

AbstractDirect numerical simulations (DNS) of turbulent thermal convection in a box-shaped domain with regular surface roughness at the heated bottom and cooled top surfaces are conducted for Prandtl number $\mathit{Pr}=0.786$ and Rayleigh numbers $\mathit{Ra}$ between $10^{6}$ and $10^{8}$. The surface roughness is introduced by four parallelepiped equidistantly distributed obstacles attached to the bottom plate, and four obstacles located symmetrically at the top plate. By varying $\mathit{Ra}$ and the height and width of the obstacles, we investigate the influence of the regular wall roughness on the turbulent heat transport, measured by the Nusselt number $\mathit{Nu}$. For fixed $\mathit{Ra}$, the change in the value of $\mathit{Nu}$ is determined not only by the covering area of the surface, i.e. the obstacle height, but also by the distance between the obstacles. The heat flux enhancement is found to be largest for wide cavities between the obstacles which can be ‘washed out’ by the flow. This is also manifested in an empirical relation, which is based on the DNS data. We further discuss theoretical limiting cases for very wide and very narrow obstacles and combine them into a simple model for the heat flux enhancement due to the wall roughness, without introducing any free parameters. This model predicts well the general trends and the order of magnitude of the heat flux enhancement obtained in the DNS. In the $\mathit{Nu}$ versus $\mathit{Ra}$ scaling, the obstacles work in two ways: for smaller $\mathit{Ra}$ an increase of the scaling exponent compared to the smooth case is found, which is connected to the heat flux entering the cavities from below. For larger $\mathit{Ra}$ the scaling exponent saturates to the one for smooth plates, which can be understood as a full washing-out of the cavities. The latter is also investigated by considering the strength of the mean secondary flow in the cavities and its relation to the wind (i.e. the large-scale circulation), that develops in the core part of the domain. Generally, an increase in the roughness height leads to stronger flows both in the cavities and in the bulk region, while an increase in the width of the obstacles strengthens only the large-scale circulation of the fluid and weakens the secondary flows. An increase of the Rayleigh number always leads to stronger flows, both in the cavities and in the bulk.

Self-organized regular surface patterning by pulsed laser ablation

2009 ◽  
Vol 6 (3) ◽  
pp. 681-686 ◽  
Author(s):  
Juergen Reif ◽  
Florenta Costache ◽  
Olga Varlamova ◽  
Guobin Jia ◽  
Markus Ratzke
Keyword(s):  
Laser Ablation ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Surface Patterning ◽  
Regular Surface ◽  
Self Organized

Influences of Ultrasonic Assistance in High Speed Lapping of Nano ZTA Engineering Ceramic on the Surface Machining Quality

2007 ◽  
Vol 359-360 ◽  
pp. 355-359 ◽  
Author(s):  
Feng Jiao ◽  
Bo Zhao ◽  
Chuan Shao Liu ◽  
Xun Sheng Zhu
Keyword(s):  
High Speed ◽  
Chip Thickness ◽  
Surface Profile ◽  
Abrasive Material ◽  
Regular Surface ◽  
Surface Machining ◽  
Machining Quality ◽  
Engineering Ceramic ◽  
Precision Finishing

Ultrasonic aided high speed lapping with solid abrasive material was put forward aimed at the precision finishing of nano ZTA engineering ceramic. Through theoretical analysis and contrast lapping experiments, the influences of ultrasonic assistance on the surface machining quality were clarified. Research results show that the maximum undeformed chip thickness in ultrasonic aided lapping is smaller than that in conventional lapping under the same conditions; ultrasonic assistance is beneficial to enlarging the range of ductile lapping regime and improving the surface quality of nano ZTA ceramic; with the application of ultrasonic vibration, smaller surface roughness and more regular surface profile can be obtained.

scholarly journals How Can Different Polishing Timing Influence Methacrylate and Dimethacrylate Bulk Fill Composites? Evaluation of Chemical and Physical Properties

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Riccardo Monterubbianesi ◽  
Vincenzo Tosco ◽  
Simona Sabbatini ◽  
Giulia Orilisi ◽  
Carla Conti ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Vickers Microhardness ◽  
Scanning Electron Micrographs ◽  
Regular Surface ◽  
Significance Level ◽  
Group I ◽  
Before And After ◽  
The Right ◽  
Group D ◽  
Composite Samples

The polishing procedure is commonly performed after direct composite restorations, and little information exists regarding the right timing during which it should be performed on bulk fill composites. This study investigated the effect of polishing timing on the degree of conversion (DC), Vickers microhardness (VMH), and surface morphology of a methacrylate- (MET-) and dimethacrylate- (DMET-) based bulk fill composite, by using FT-NIR, microhardness tester, and SEM. Composite samples were divided as follows: in Group I (immediate), samples were polished immediately after curing (t0); in Group D (delayed), samples were polished after 24 h from curing (t24), whereas the unpolished samples were considered as controls (Group C). The DC and VMH values were evaluated before and after polishing, at t0 and t24. Statistical analysis was performed with a significance level set at p<0.05. At t0, DC increased after polishing in both tested composites (p<0.05), while at t24, Group I and Group D were not different. By considering VMH, in the case of MET, all groups were not different both at t0 and t24. On the other hand, at t0, VMH values of DMET increased after polishing. At t24, DMET Group I and DMET Group D were not different. Qualitative evaluations of scanning electron micrographs showed that the surface morphology of MET presented a more irregular aspect than the DMET one. In summary, since the immediate polishing of MET can improve the DC, without negatively affecting VMH, but showing an irregular surface, it is suggested to wait 24 hours before proceeding with polishing. Otherwise, for DMET, the immediate polishing could definitively be recommended, since it improves both DC and VMH, also producing a regular surface. Therefore, clinicians may always safely polish a restoration performed using DMET-based bulk fill composites in one-chair appointment, avoiding a second appointment.

Structure of the regular surface layer of Bacillus polymyxa

1983 ◽  
Vol 29 (7) ◽  
pp. 775-780 ◽  
Author(s):  
S. K. Burley ◽  
R. G. E. Murray
Keyword(s):  
Surface Layer ◽  
Image Enhancement ◽  
Digital Image ◽  
General Scheme ◽  
Bacillus Polymyxa ◽  
Surface Layers ◽  
Regular Surface ◽  
Protein Subunits ◽  
Digital Image Enhancement ◽  
Spore Forming Bacteria

The structure of the regular surface layer of Bacillus polymyxa has been examined to a resolution of 2.5–3.0 nm in electron micrographs of negatively stained preparations supplemented by optical-digital image enhancement. The layer is composed of morphological units, each consisting of four identical protein subunits, and has p4 symmetry with a = 10.0 nm. Within each unit cell are areas of high stain density of a limiting diameter of 2–3 nm, which are interpreted as holes penetrating the layer. A comparison is made with other tetragonal regular surface layers of spore-forming bacteria, B. sphaericus and Sporosarcina ureae, solved to 2.5-nm resolution. These layers are similar in the conformation of their protein units and in the distribution of the holes in the layer. A general scheme for the architecture of the tetragonal regular surface layers is derived.

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