Light mediated emergence of surface patterns in azopolymers at low temperatures

Polymer thin films doped with azobenzene molecules do have the ability to organize themselves in spontaneous surface relief gratings (SRG) under irradiation with a single polarized beam. To shed some light in this still unexplained phenomenon, we use a new method that permits us to access experimentally the very first steps of the pattern formation process. Decreasing the temperature, we slow down the formation and organization of patterns, due to the large increase of the viscosity and relaxation time of the azopolymer. As a result decreasing the temperature allows us to access and study much shorter time scales,in the physical mechanisms underlying the pattern formation, than previously reported. We find that the patterns organize themselves in sub-structures which size increase with the temperature, following the diffusion coefficient evolution of the material. That result suggests that the pattern formation and organization is mainly governed by diffusive processes, in agreement with some theories of the SRG formation. Decreasing further the temperature we observe the emergence of small voids located at the junction of the sub-structures.Comment: 6 figures, 13 pages

Electric surface properties of Delrin used for high voltage insulation.

In this study surface properties of Delrin have been investigated. Delrin is a homopolymer of acetal resin. To study the degradation and the effect of the environment on the surface of this material, samples of Delrin were immersed in saline water with salinities of 0.005-100 mS/cm at 0, 23, 60 and 98 °C. Specimens were also placed in air at these four temperatures. The contact angle of a 4 mu1 sessile droplet of distilled water on the surface of Delrin as a measure of the surface wetability or the hydrophobicity has been measured in this study. Increasing the parameters of temperature, salinity (up to certain level), and the length of time of immersion decreased the contact angle until it reached saturation. The dc and ac breakdown, water absorption and surface roughness of Delrin were also measured and were found to have correlations with the hydrophobicity of Delrin. After the reduction of hydrophobicity had reached saturation, the specimens were removed from the saline solutions. The effects of volume of the droplet of distilled water and the time to measure the contact angle after placing the droplet on the surface were also studied. (Abstract shortened by UMI.)Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .T35. Source: Masters Abstracts International, Volume: 44-03, page: 1466. Thesis (M.A.Sc.)--University of Windsor (Canada), 2005

Policy-Based Immunization Framework for MANET

Mobility is one of the most important driving forces of hyper-interconnected world that we are living in. Mobile computing devices are becoming smaller, more ubiquitous and simultaneously providing more computing power. Various mobile devices in diff rent sizes with high computing power cause the emergence of new type of networks\u27 applications. Researchers in conferences, soldiers in battlefields, medics in rescue missions, and drivers in busy high- ways can perform more efficiently if they can be connected to each other and aware of the environment they are interacting with. In all mentioned scenarios, the major barrier to have an interconnected collaborative environment is the lack of infrastructure. Mobile Ad hoc Networks (MANETs) are very promising to be able to handle this challenge. In recent years, extensive research has been done on MANETs in order to deliver secure and reliable network services in an infrastructure-less environment. MANETs usually deal with dynamic network topologies and utilize wireless technologies, they are very susceptible to different security attacks targeting different network layers. Combining policy-based management concepts and trust evaluation techniques in more granular level than current trust management frameworks can lead to interesting results toward more secure and reliable MANETs

Power and area efficient MOSFET-C filter for very low frequency applications

New circuit design techniques for implementing very high-valued resistors are presented, significantly improving power and area efficiency of analog front-end signal processing in ultra-low power biomedical systems. Ranging in value from few hundreds of \hbox{M}\Upomega to few hundreds of \hbox{G}\Upomega , the proposed floating resistors occupy a very small area, and produce accurately tunable characteristics. Using this approach, a low-pass MOSFET-C filter with tunable cutoff frequency (f C =20Hz-184kHz) has been implemented in a conventional 0.18μm CMOS technology. Occupying 0.045mm2/pole, the power consumption of this filter is 540 pW/Hz/pole with a measured IMFDR of 70 d

An Analysis of Impact of Merger and Acquisition of Financial Performance of Banks: A case of Pakistan

This study is testing the impact of merger and acquisition of banks and provides insights about their role after merger on banks profitability. In this paper six financial ratios are used for analysis these ratios are profit after tax, return on asset, return on equity, debt to equity ratio, deposit to equity ratio and EPS. Ten banks are selected as sample for analysis which gets into merger from 2007-10. 3 year pre-merger and 3 year post-merger data points are taken for all the 10 cases and their averages are compared. In SPSS paired sample T-test is applied for analysis and findings shows that only at 5% level of significance only ROE is affected by the merger and acquisition and other ratios have no impact from this strategy. Keywords: merger, impact, financial performance, Pakistan, acquisitio

Letter to Editor: Tokophobia in Iranian women during the COVID-19 pandemic

This is a Letter to the Editor and does not have an abstract. Please download the PDF or view the article HTML

Birefringence properties and surface relief grating formation on methlacrylate polymers with photochromic side chains

International audienc

An area and power optimization technique for CMOS bandgap voltage references

This article explores the main tradeoffs in design of power and area efficient bandgap voltage reference (BGR) circuits. A structural design methodology for optimizing the silicon area and power dissipation of CMOS BGRs will be introduced. For this purpose, basic equations of the bandgap circuit have been adapted such that can simply be applied in the optimization process. To improve the reliability of the designed circuit, the effect of amplifier offset has been also included in the optimization process. It is also shown that the minimum achievable power consumption and area are highly depending on the fabrication process parameters especially sheet resistivity of the available resistors in the technology and also the area of bipolar transistors. The proposed technique does not depend on a special process and can be applied for designing bandgap reference circuits with different topologie