Perspectives of Porous Silicon Multilayer Technology

1998 ◽  
Vol 536 ◽  
Author(s):  
M. Thönissen
Keyword(s):  
Porous Silicon ◽  
Multilayer Systems ◽  
Interference Filters ◽  
Electrical Control ◽  
The Stability ◽  
And Diffusion ◽  
Multiple Interference ◽  
Multilayer Technology

AbstractThe exact control and adjustment of the etch parameters is important for the fabrication of well defined and reproducible devices based on porous silicon (PS) multilayers. In this paper the etch parameters “electrolyte volume” and “diffusion in the electrolyte” will be discussed as specific problems during a commercial fabrication of multilayer applications. Additionally the stability of the filter characteristics of multilayer systems will be analyzed by changing the climatic environments. New perspectives of multilayer applications will be given, e. g. the electrical control of filters, spatially graded interference filters and multiple interference filters on one sample.

The Photoluminescence Enhancement and Stability of Porous Silicon by Cathodic Reduction and Acid Treatment

2014 ◽  
Vol 887-888 ◽  
pp. 458-461
Author(s):  
Chang Qing Li ◽  
Kun Wang ◽  
Pei Jia Liu ◽  
Qi Ming
Keyword(s):  
Electron Microscope ◽  
Porous Silicon ◽  
Acid Treatment ◽  
Cathodic Reduction ◽  
Luminescence Properties ◽  
Sem Images ◽  
Photoluminescence Enhancement ◽  
The Stability ◽  
Scanning Electron ◽  
Cathode Reduction

Porous silicon (PSi) was fabricated by using electrochemical anodic etching method. Then acid treatment and cathode reduction treatment were employed to improve the luminescence properties and stability of PSi material. Photoluminescence (PL) measurements and scanning electron microscope (SEM) were used to observe the luminescence properties and microstructure of samples, respectively. The results of PL measurements showed that the PL intensity and the stability of luminescence of samples after cathodic reduction and acid treatment were significantly improved. The SEM images showed that the porosity of PSi may be increased through the cathodic reduction treated.

Global Hopf Bifurcation in a Phytoplankton–Zooplankton System with Delay and Diffusion

2021 ◽  
Vol 31 (08) ◽  
pp. 2150114
Author(s):  
Ming Liu ◽  
Jun Cao ◽  
Xiaofeng Xu
Keyword(s):  
Hopf Bifurcation ◽  
Global Existence ◽  
Upper And Lower Solutions ◽  
Positive Periodic Solutions ◽  
Global Hopf Bifurcation ◽  
System With Delay ◽  
Local Hopf Bifurcation ◽  
Distribution Of Eigenvalues ◽  
The Stability ◽  
And Diffusion

In this paper, the dynamics of a phytoplankton–zooplankton system with delay and diffusion are investigated. The positivity and persistence are studied by using the comparison theorem and upper and lower solutions method. The stability of steady states and the existence of local Hopf bifurcation are obtained by analyzing the distribution of eigenvalues. And the global existence of positive periodic solutions is established by using the global Hopf bifurcation result given by Wu [1996]. Finally, some numerical simulations are carried out to illustrate the analytical results.

Effects of Delay and Diffusion on the Dynamics of a Leslie–Gower Type Predator–Prey Model

2014 ◽  
Vol 24 (04) ◽  
pp. 1450043
Author(s):  
Jia-Fang Zhang ◽  
Xiang-Ping Yan
Keyword(s):  
Periodic Solutions ◽  
Positive Constant ◽  
Neumann Boundary ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Constant Equilibrium ◽  
Homogeneous Neumann Boundary Condition ◽  
Delayed System ◽  
The Stability ◽  
And Diffusion

In this paper, we consider the effects of time delay and space diffusion on the dynamics of a Leslie–Gower type predator–prey system. It is shown that under homogeneous Neumann boundary condition the occurrence of space diffusion does not affect the stability of the positive constant equilibrium of the system. However, we find that the incorporation of a discrete delay representing the gestation of prey species can not only destabilize the positive constant equilibrium of the system but can also cause a Hopf bifurcation at the positive constant equilibrium as it crosses some critical values. In particular, we prove that these Hopf bifurcations' periodic solutions are all spatially homogeneous if the diffusive rates are suitably large, which has the same properties as periodic solutions of the corresponding delayed system without diffusion. However, if the diffusive rates are suitably small, then the system will generate spatially nonhomogeneous periodic solutions. The results in this work demonstrate that diffusion plays an important role in deriving complex spatiotemporal dynamics.

THE STABILITY OF LOW INDEX METAL SURFACES TO TOPOLOGICAL DEFECTS

1991 ◽  
Vol 05 (03) ◽  
pp. 427-459 ◽  
Author(s):  
EDWARD H. CONRAD
Keyword(s):  
Metal Surfaces ◽  
Surface Defects ◽  
Defect Formation ◽  
Fundamental Problem ◽  
Topological Defects ◽  
Surface Roughening ◽  
Thermal Generation ◽  
Diffusion Mechanisms ◽  
The Stability ◽  
And Diffusion

The study of defect formation at metal surfaces is a fundamental problem in surface physics. An understanding of defect formation is pertinent to growth and diffusion mechanisms. In addition, surface roughening, faceting, and surface melting are all defect mediated phase transitions involving the formation of different topological defects. While the importance of defects at surfaces is well recognized, the study of surface defects has been hampered by the lack of sufficiently accurate experimental techniques. In fact, it is only in the past 6 years that experiments on the thermal generation of defects on metal surfaces have been performed. This review attempts to outline both the theoretical and experimental work on surface defect formation on metal systems.

scholarly journals Chitosan–Azide Nanoparticle Coating as a Degradation Barrier in Multilayered Polyelectrolyte Drug Delivery Systems

Biomolecules ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 573 ◽  
Author(s):  
Steffen Sydow ◽  
Armin Aniol ◽  
Christoph Hadler ◽  
Henning Menzel
Keyword(s):  
Drug Delivery Systems ◽  
Uv Light ◽  
Film Structure ◽  
Layer By Layer ◽  
Multilayer Systems ◽  
Ionotropic Gelation ◽  
Physiological Conditions ◽  
Degree Of Acetylation ◽  
Implant Coating ◽  
The Stability

Therapeutics, proteins or drugs, can be encapsulated into multilayer systems prepared from chitosan (CS)/tripolyphosphat (TPP) nanogels and polyanions. Such multilayers can be built-up by Layer-by-Layer (LbL) deposition. For use as drug-releasing implant coating, these multilayers must meet high requirements in terms of stability. Therefore, photochemically crosslinkable chitosan arylazide (CS–Az) was synthesized and nanoparticles were generated by ionotropic gelation with TPP. The particles were characterized with regard to particle size and stability and were used to form the top-layer in multilayer films consisting of CS–TPP and three different polysaccharides as polyanions, namely alginate, chondroitin sulfate or hyaluronic acid, respectively. Subsequently, photo-crosslinking was performed by irradiation with UV light. The stability of these films was investigated under physiological conditions and the influence of the blocking layer on layer thickness was investigated by ellipsometry. Furthermore, the polyanion and the degree of acetylation (DA) of chitosan were identified as additional parameters that influence the film structure and stability. Multilayer systems blocked with the photo-crosslinked chitosan arylazide showed enhanced stability against degradation.

On the correctness of a model for phase transitions in binary alloys

1990 ◽  
Vol 1 (4) ◽  
pp. 327-338 ◽  
Author(s):  
I. G. Götz
Keyword(s):  
Phase Transitions ◽  
Heat Conduction ◽  
Stability Criterion ◽  
Binary Alloys ◽  
The Self ◽  
Self Similar Solution ◽  
Self Similar ◽  
The Stability ◽  
Similar Solutions ◽  
And Diffusion

The main result of this paper is a non-uniqueness theorem for the self-similar solutions of a model for phase transitions in binary alloys. The reason for this non-uniqueness is the discontinuity in the coefficients of heat conduction and diffusion at the inter-phase. Also the existence of a self-similar solution and the stability criterion are discussed.

Interference filters from porous silicon with laterally varying wavelength of reflection

1998 ◽  
Vol 80 (1-4) ◽  
pp. 133-136 ◽  
Author(s):  
D. Hunkel ◽  
R. Butz ◽  
R. Ares-Fisher ◽  
M. Marso ◽  
H. Lüth
Keyword(s):  
Porous Silicon ◽  
Interference Filters
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