The point interaction approximation for diffusion in regions with many small holes

Author(s):  
R. Figari ◽  
G. Papanicolaou ◽  
J. Rubinstein
2019 ◽  
Vol 267 (4) ◽  
pp. 2104-2191 ◽  
Author(s):  
Habib Ammari ◽  
Durga Prasad Challa ◽  
Anupam Pal Choudhury ◽  
Mourad Sini

Author(s):  
Persi Diaconis ◽  
David Elworthy ◽  
Hans Föllmer ◽  
Edward Nelson ◽  
George Papanicolaou ◽  
...  

Author(s):  
L. Andrew Staehelin

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.


Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 828
Author(s):  
Zhaolong Li ◽  
Ye Dai

This paper presents a simulation and experimental study of the structure of small holes in GH4169 alloy electrolytic ally processed by tube electrodes with different characteristic power sources. It analyzes the multi-physical field coupling relationship of flow, temperature, and electric fields within the interstitial space. The results indicate that the tube electrode electrolytic processing of the GH4169 alloy small hole structure with a pulsed power supply has more uniform temperature and current density distribution within the gap, which is beneficial to the processing accuracy and smoothness of the small hole structure. Meanwhile, SEM was used to analyze the microscopic morphology of the electrode end surface during short-circuiting, and it was concluded that as the processing continued, the electrode end surface gradually produced a non-metallic oxide layer, which destroyed the electric field of the gap and affected the processing stability. The use of high-frequency positive and negative pulse power can effectively avoid the generation of a non-metallic oxide layer. Through the combination of simulation analysis and experimental verification, it is concluded that increasing electrolyte pressure in stages can effectively improve machining accuracy and stability. The interstitial current increases as the feed rate of the tool electrode increases, and the diameter of the machined small hole decreases as it increases.


1996 ◽  
Vol 29 (18) ◽  
pp. 6073-6085 ◽  
Author(s):  
José María Román ◽  
Rolf Tarrach

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