Dynamic diffusion model for tracing the real-time potential response of polymeric membrane ion-selective electrodes

A numerical solution for the prediction of the time-dependent potential response of a polymeric-based ion-selective electrode (ISE) is presented. The model addresses short- and middle-term potential drifts that are dependent on changes in concentration gradients in the aqueous sample and organic membrane phase. This work has important implications for the understanding of the real-time response behavior of potentiometric sensors with low detection limits and with nonclassical super-Nernstian response slopes. As a model system, the initial exposure of membranes containing the well-examined silver ionophore O,O' '-bis[2-(methylthio)ethyl]-tert-butylcalix[4]arene was monitored, and the large observed potential drifts were compared to theoretical predictions. The model is based on an approximate solution of the diffusion equation for both aqueous and organic diffusion layers using a numerical scheme (finite difference in time and finite elements in space). The model may be evaluated on the basis of experimentally available parameters and gives time-dependent information previously inaccessible with a simpler steady-state diffusion model. For the cases studied, the model gave a very good correlation with experimental data, albeit with lower than expected diffusion coefficients for the organic phase. This model may address numerous open questions regarding the response time and memory effects of low-detection-limit ion-selective electrodes and for other membrane electrodes where ion fluxes are relevant.     

Adaptive equalization for high-speed indoor wireless data communication

The performance of a 4-QAM indoor wireless data communication system with adaptive equalizer is investigated. The effectiveness of using linear and decision-feedback equalizer for Rayleigh and Rician frequency-selective indoor channels is evaluated, and contrasted to the performance of a 4-QAM modem without equalizer. The effects of some important channel and system parameters (multipath spreads up to 200 ns, data rates up to 25 Mbit/s, signaling pulse rolloff factor between 0.5 and 1.0, and additive, white Gaussian noise) on the indoor communication system performance are examined and presented in the paper. The indoor propagation measurements, carried out in a research laboratory, provided data to be used for BER performance assessments of the system with and without equalizer. The performance results based on computer generated channels are then compared with those obtained for measured channel impulse responses.     

New access modes of parallel memory subsystem for sub-pixel motion estimation

Accessing pixels in memory is a well-known bottleneck of SIMD (single instruction multiple data) processors in video/imaging. To tackle it, we propose new block and row access modes of parallel on-chip memory subsystem, which enable a higher processing throughput and lower energy consumption than the access modes of the state-of-the-art subsystems. The new access modes significantly reduce the number of on-chip memory accesses, and thereby accelerate one of key video/imaging kernels: sub-pixel block-matching motion estimation. The main idea is to exploit spatial overlaps of blocks/rows accessed for pixel interpolation, which are known at the subsystem design-time, and merge multiple accesses into a single one by accessing somewhat more pixels at a time than with other parallel memories. To avoid the need for a wider, and, therefore, more costly SIMD datapath, we propose new memory read operations that split all pixels accessed at a time into multiple SIMD-wide blocks/rows, in a convenient way for further processing. As a proof of concept, we describe a parametric, scalable, and cost-efficient architecture that supports the new access modes. The architecture is based on a previously proposed set of memory banks with multiple pixels per bank word, and a previously proposed shifted scheme for arranging pixels in the banks. We analytically and experimentally demonstrate advantages of this work on a case study of sub-pixel motion estimation for video frame-rate conversion. The implemented motion estimator processes 2160p video at 60 fps in real time, while clocked at 600 MHz. Compared to the implementations based on the state-of-the-art subsystems, this work enables 40–70 % higher throughput, consumes 17–44 % less energy and has similar silicon area and off-chip memory bandwidth costs. That is 1.8–2.9 times more efficient than the prior art, considering the throughput and all costs, i.e., consumption, area, and off-chip bandwidth. Such a higher efficiency is the result of the new access modes, which reduced the number of on-chip memory accesses by 1.6–2.1 times, and the cost-efficient architecture.     

Assessment and Feedback

Assessment and learning must not be considered as two separate processes. In fact, assessment is an integral part of the learning process; it can be learning experience in itself. Active assessment strategies help students better understand the content they learn and develop skills that will be useful to them throughout their lives. Some of those skills are the ability to prepare effective oral and written reports and the ability to cooperate successfully with peers. Action research represents the process of systematic inquiry and it helps teachers to assess learning from the perspective of what they do in the classroom. The purpose is to find out ＂why＂ or ＂how＂ something happened the way it did. Therefore, a situation or problem should be carefully examined by a teacher. Teachers should analyze their own beliefs, values, and assumptions about teaching and learning, knowledge and curriculum, and how these impact the way they interact with students. Feedback should be used as part of assessment activities. Learning experience of students facilitated by teachers can be assessed through feedback.     

The dependence of the photocatalytic activity of TiO2/carbon nanotubes nanocomposites on the modification of the carbon nanotubes

Nanostructural TiO₂/modified multi-wall carbon nanotubes photocatalysts were prepared by hydrolysis of Ti(iso-OC₃H₇)₄ providing chemical bonding of anatase TiO₂ nanoparticles onto oxidized- or amino-functionalized multi-wall carbon nanotubes (MWCNT). The processes of functionalization of the MWCNT and the deposition of TiO₂ influence the photocatalytic activity of the synthesized nanocomposites. The phase composition, crystallite size, and the structural and surface properties of the obtained TiO₂/modified-MWCNT nanocomposite were analyzed from XRD, FEG-SEM, TEM/HRTEM and FTIR data, as well low temperature N₂ adsorption. In the photocatalytic study, the TiO₂/oxidized-MWCNT catalyst showed the highest and the TiO₂/amino functionalized-MWCNT catalysts somewhat lower degradation rates, indicating that the enhancement of photocatalysis was supported by the more effective electron transfer properties of the oxygen- than amino-containing functional groups, which support the efficient charge transportation and separation of the photogenerated electron-hole pairs.