Range Extension in IEEE 802.11ah Systems Through Relaying

A great number of Internet of Things (IoT) and machine-to-machine (M2M) based applications, which are telecommunication areas with the highest foreseen growth in the future years, require energy efficient, long range and low data rate wireless communication links. In order to offer a competitive solution in these areas, IEEE 802.11 standardization group has defined the “ah” amendment, the first sub-1 GHz WLAN standard, with flexible channel bandwidths, starting from 1 MHz, up to 16 MHz, and many other physical and link layer improvements, enabling long-range and energy efficient communications. However, for some regions, like Europe, the maximum transmitted power in dedicated frequency band is limited to only 10 mW, thus disabling the achievement of ranges which would be close to targeted of up to 1 km. In this paper we examine possibilities for range extension through implementation of half-duplex decode-and forward (DF) relay station (RS) in communication between an access point (AP) and an end-station (ST). Assuming a Rician fading channel between AP and RS, and a Rayleigh fading channel on RS–ST link, we analytically derive results on achievable ranges for the most robust modulation and coding schemes (MCSs), both on downlink (DL) and uplink (UL). Analyses are performed for two different standard adopted deployment scenarios on RS–ST link, and variable end-to-end link outage probabilities. Moreover, we have analyzed whether the considered most robust MCSs, known for supporting the longest range, but the lowest data rates, can meet the defined requirement of at least 100 kb/s for the greatest attainable AP–RS–ST distances. We examine data rate enhancements, brought by coding and using of short packets, for both DL and UL. Finally, we present bit error rate results, obtained through simulations, of a dual-hop DF IEEE 802.11ah relay system for the considered MCs. All presented results confirm that IEEE 802.11ah systems through deployment of relay stations, become an interesting solution for M2M and IoT based applications, due to flexibility they offer in many aspects, meeting requirements for wide transmission ranges in such applications.     

Marginal adaptation of composite resins under two adhesive techniques

In the present research, different adhesive techniques were used to set up fillings with composite resins. After the application of etch and rinse or self etch adhesive technique, marginal adaptation of composite fillings was estimated by the length of margins without gaps, and by the microretention of resin in enamel and dentin. The study material consisted of 40 extracted teeth. Twenty Class V cavities were treated with 35% phosphorous acid and restored after rinsing by Adper Single Bond 2 and Filtek Ultimate‐ASB/FU 3M ESPE composite system. The remaining 20 cavities were restored by Adper Easy One‐AEO/FU 3M ESPE composite system. Marginal adaptation of composite fillings was examined using a scanning electron microscope (SEM). The etch and rinse adhesive technique showed a significantly higher percentage of margin length without gaps (in enamel: 92.5%, in dentin: 57.3%), compared with the self‐etch technique with lower percentage of margin length without gaps, in enamel 70.4% (p < .001), and in dentin‐22.6% (p < .05). In the first technique, microretention was composed of adhesive and hybrid layers as well as resin tugs in interprismatic spaces of enamel, while the dentin microretention was composed of adhesive and hybrid layers with resin tugs in dentin canals. In the second technique, resin tugs were rarely seen and a microgap was dominant along the border of restoration margins. The SEM analysis showed a better marginal adaptation of composite resin to enamel and dentin with better microretention when the etch and rinse adhesive procedure was applied.     

RF channelizer architectures using 3-way iterative down conversion for concurrent or fast-switching spectrum analysis

A wide-band RF channelizer architecture using the concept of 3-way iterative down-conversion is introduced. An example RF channelizer implementation splits the input spectrum of 0.6–9 GHz into 7 channels each with a 1.2 GHz bandwidth. This RF channelizer implementation has the ability of concurrently down-converting 3 channels enabling multi-Gbps aggregate data reception. It further demonstrates the ability to rapidly switch from receiving one channel to another which is crucial for rapid spectrum analysis. A prototype of the RF channelizer has been fabricated in a 65 nm standard CMOS process. A 400 Mbps (BPSK) data reception has been demonstrated by down-converting two channels concurrently. Channel switching can be as fast as 8 ns and is always faster than \(1\,\upmu s\). The chip occupies an area of 2 mm \(\times\) 1 mm and consumes an average power of 435 mW while offering a dynamic range between 58 and 63 dB.     

Run-to-run control of blood glucose concentrations for people with Type 1 diabetes mellitus

Run-to-run control has been applied to several traditional batch processes in the chemical industry. The 24-h cycle of eating meals, measuring blood glucose concentrations, and delivering the correct insulin bolus, with the goal of achieving the optimal blood glucose profile, can be viewed in the same spirit as traditional batch processes such as emulsion polymerization. In this paper, we aim to exploit the "repetitive" nature of the insulin therapy of people with Type 1 diabetes. A run-to-run algorithm is used on a virtual diabetic patient model to control blood glucose concentrations. The insulin input is parameterized into the timing and amount of the dose while the glucose output is parameterized into the maximum and minimum glucose concentrations. Robustness of the algorithm to variations in the meal amount, meal timing, and insulin sensitivity parameter is addressed. In general, the algorithm is able to converge when the meal timing is varied within +/- 40 min. If the meal size is underestimated by approximately 10 grams (g), the algorithm is able to converge within a reasonable time frame for breakfast, lunch, and dinner. If the meal size is overestimated by 20-25 g, the algorithm is able to converge. When random variations in the meal timing and the meal amount are introduced, the variation on the output variables, Gmax and Gmin, scales according to the amount of variation allowed. Along with this, the insulin sensitivity of the virtual patient model is varied. The algorithm is robust for differences in insulin sensitivity less than +/- 50% of the nominal value.     

Novel alginate based nanocomposite hydrogels with incorporated silver nanoparticles

Alginate colloid solution containing electrochemically synthesized silver nanoparticles (AgNPs) was investigated regarding the nanoparticle stabilization and possibilities for production of alginate based nanocomposite hydrogels in different forms. AgNPs were shown to continue to grow in alginate solutions for additional 3 days after the synthesis by aggregative mechanism and Ostwald ripening. Thereafter, the colloid solution remains stable for 30 days and could be used alone or in mixtures with aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) while preserving AgNPs as verified by UV–Vis spectroscopy studies. We have optimized techniques for production of Ag/alginate microbeads and Ag/alginate/PVA beads, which were shown to efficiently release AgNPs decreasing the Escherichia coli concentration in suspensions for 99.9% over 24 h. Furthermore, Ag/hydrogel discs based on alginate, PVA and PVP were produced by freezing-thawing technique allowing adjustments of hydrogel composition and mechanical properties as demonstrated in compression studies performed in a biomimetic bioreactor.     

Frequency Estimation of Three-Phase Power System Using Weighted-Least-Square Algorithm and Adaptive FIR Filtering

A new technique for estimation of the instantaneous frequency based on simultaneous sampling of three-phase voltage signals is presented. The structure consists of two decoupled modules: the first is for adaptive filtering of input signals, and the second is for frequency estimation. A suitable and robust algorithm for frequency estimation is obtained. This technique provides better performance, compared with the technique based on a single-phase signal in relation to waveforms with noise. The technique is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, it allows the measurement of the instantaneous frequency value of real signals for single- or three-phase systems. To demonstrate the performance of the developed algorithm, computer-simulated data records and calibrator-generated signals are processed. The proposed algorithm has been put to test with distorted three-phase voltage signals.      

Rheological and Breadmaking Properties of Wheat Flours Supplemented with Octenyl Succinic Anhydride-Modified Waxy Maize Starches

The feasibility of emulsifying starches as bread improvers was investigated by incorporating starch sodium octenyl succinate (OSA-st), pre-gelatinized OSA-st and hydrolysed spray-dried OSA-st at 2.5, 5 and 10 % into wheat flour. Dough rheological properties (creep and recovery measurements; Mixolab, Alveograph) and bread quality parameters (specific loaf volume, crust and crumb colour, crumb moisture, crumb grain features, texture) were evaluated. The substituted flours, except hydrolysed OSA-st, significantly increased water absorption measured by Mixolab. The study on the rheological behaviour of doughs containing emulsifying starches, performed using a rheometer and an Alveograph, showed that OSA-st incorporation yielded strengthened dough, whereas pre-gelatinized and hydrolysed OSA-st addition led to more extensible dough. With regard to the thermal behaviour, investigated in water-limited systems by Mixolab, doughs prepared from pre-gelatinized OSA-st and hydrolysed OSA-st exhibited lower maximum peak torque, whilst all three examined starches increased cooking stability and decreased the setback value. Specific volumes of loaves baked from the substituted flours increased, and the highest effect was observed with pre-gelatinized OSA-st, which consequently produced bread crumbs with the largest mean gas cell area. The bread crumbs baked with octenyl succinate starches were whiter and softer. Although upon 1 day of storage no significant moisture retention capacity of emulsifying starches was noticed, the firmness values of OSA-st and pre-gelatinized OSA-st-supplemented bread crumbs, after 24 h of storage, were similar to or significantly lower than those of the control determined 2 h after baking. The obtained results indicate a requirement for further optimization of the octenyl succinate starch-supplemented doughs in terms of the combination of different types and levels of modified starches in order to obtain maximum bread quality.     

The effect of selenium on antioxidant system in erythrocytes and liver of the carp (Cyprinus carpio L.)

The effect of selenium‐supplemented diet (sodium selenate and selenium yeast) on antioxidant in erthrocytes and liver of the carp (Cyprinus carpio L.) fingerlings was studied. With this goal, the activities of glutathione peroxidase (GSH‐Px), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione‐S‐transferase (GST), as well as glutathione (GSH + GSSG) level, were determined. In the group supplemented with sodium selenate, no significant changes in the activity of the above enzymes were recorded in both the erythrocytes and in the liver, with the exception of GST activity that was significantly reduced in the plasma compared with the controls. Glutathione content was at the control level. In the group supplemented with selenium‐yeast, the activities of GSH‐Px, CAT, and SOD were significantly increased in erythrocytes, whereas GST activity and plasma content of GSH + GSSG were reduced compared with the controls. At the same time, the activities of hepatic SOD and GST were increased compared with the controls. These results demonstrate that organically bound selenium (selenium‐yeast) acts more efficiently on antioxidant system of the carp fingerlings than inorganic selenium salts.