UHF Band Short Range Propagation Model

The purpose of this study is to characterize the indoor and indoor–outdoor propagation in different scenarios, using monopole antennas working at 410 and 890 MHz. Propagation of narrow band and wide bands have been studied. In scenarios with a continuous variation of the distance between the transmitter and receiver antenna (1 D scenarios), we use a log-distance path loss model to determine the equations that describe the mean value of the path loss. In scenarios where the position of the receiver is not a uniform function of the distance between the transmitter and the receiver, we represent the basic propagation gain as a function of the measurement point index. Results show that the indoor propagation gain can be described using two slopes propagation model. For the multiwall attenuation loss it is shown that each wall has an attenuation of almost 2.5 dB at 410 MHz increasing to almost 4 dB at 890 MHz. The obstruction gain (loss) due to human beings shows that this can be within a 40 dB interval.     

TCP CERL+: revisiting TCP congestion control in wireless networks with random loss

Wireless Networks - In this paper, we analyze the performance of wireless networks subject to random loss. In this regard, we revisit our TCP Congestion Control Enhancement for Random Loss (CERL)...     

Effects of pointing errors and channel fading on the performance of free‐space optically‐preamplified PPM systems

In this paper, we study the impact of pointing errors and channel fading on the performance of free‐space, optically preamplified, M ‐ary PPM systems. We consider two types of free‐space optical links: (i) inter‐satellite links and (ii) inter‐building links. For inter‐satellite links, only pointing error is considered. Starting with a Rayleigh model for the pointing error angle, we derive analytically the PDF for the pointing error parameter and for the signal‐to‐noise ratio (SNR) per bit. For inter‐building links, we derive the density function for the SNR per bit that includes the combined effects of pointing errors and channel fading, assuming Rayleigh‐distributed pointing errors. The channel fading models considered in this study for inter‐buildings links are the log‐normal and gamma–gamma models. We provide the error probability as a function of the average SNR per bit for both types of links. To cover systems with and without forward error correction, we compute the average SNR per bit required to achieve a bit error rate of 10^?4 and 10^?9. The corresponding power penalties are computed for different symbol sizes, scintillation indexes, and pointing jitters. Copyright © 2016 John Wiley & Sons, Ltd.     

Infostations for highway cigar-shaped cells

An infostation is an isolated pocket area, with small coverage of high bandwidth connectivity, which collects information requests of mobile users and delivers data while users are going through the coverage area. In this paper, the performance of infostations networks with single, double and triple frequencies is studied. The two-slope propagation loss model is used to calculate the signal-to-interference plus noise ratio. The effect of the propagation parameters on the infostation performance is studied.     

The concept of conversion distribution in reactive processing

A new concept of conversion distribution applied to the continuous chemical modification and polymerization of polymers in a twin screw extruder was discussed. The kinetics and the residence time distribution function (RTD) are two undissociable parameters in reactive extrusion because their combination reflects the degree of homogeneity of the modified polymer at the die die exit of the extruder. A function G defining the distribution of the modification rate allowed us to evaluate the distribution of the extent of the conversion around the mean conversion. This study has underlined the predominant role of the kinetics on the structural homogeneity of the modified product. This new concept was developed, within a framework of reactive processing, from previous works on chemical modification of polymers and polycondensation in corotating twin screw extruder. © 1996 John Wiley & Sons, Inc.     

Antibacterial activity of chitosan against Aeromonas hydrophila

The effect of chitosan on growth and production of haemolysin by Aeromonas hydrophila was investigated as well as the effects of temperature, pH, salts and irradiation on the antibacterial activity of chitosan. It was found that chitosan affected growth and haemolysin production of A. hydrophila in varying degrees compared to the control. Growth and haemolysin production were clearly suppressed at 0.04% of chitosan. Suppression was more effective at pH 6.0 than at pH 7.0. The bactericidal effects of chitosan increased with increasing temperature and decreasing pH. Divalent cations at concentrations of 10 and 25 mM reduced the antibacterial activity of chitosan, in the order of Ba2+ > Ca2+ > Mg2+. Sodium ions at concentrations of 10 and 25 mM also reduced chitosan's activity. Irradiation of chitosan at 150 kGy under dry condition was effective in slightly increasing its activity.     

Energy management strategy in cloud computing: a perspective study

Optimizing energy consumption in cloud computing is yet a challenge despite the diversity of the proposed energy management strategies. Indeed, and during our related work study we have observed that the different elements or components which should be considered in order to be able to properly manage energy consumption in a cloud computing context are not well defined and/or discussed in terms of importance. This makes the proper classification and/or comparison of the different proposed strategies or techniques very difficult. Consequently, this paper aims, on the one hand, at defining and discussing properly such components in order to create a guideline and, on the other hand, to ease both the classification and the comparison of these proposed strategies and techniques. Second and after discussing some common weaknesses related to the current energy consumption optimization techniques and methods, this paper proposes energy-saving technique which uses a novel load detecting policy. This policy is based on the median absolute deviation method which uses the median and the standard deviation to calculate upper and lower thresholds which aim to classify hosts into either overloaded or under-loaded state. Simulation results have shown better results of the proposed technique compared to the existing ones especially in reducing energy consumption and the number of virtual machine migrations in addition to better active host time. Indeed, we found that the average of saved energy is around 40% compared to the built in techniques in cloudSim.     

Performance Analysis of Novel Multi-band Monopole Antenna for Various Broadband Wireless Applications

Wireless Personal Communications - This study investigates a novel concept of using slot and Coplanar Waveguide fed antenna to obtain multiband operation. The compact antenna includes a star...     

Molecular-biological approaches to studying gene expression during regeneration

This paper constitutes a review of the methodical approaches allowing analysis of the mechanisms underlying development and differentiation. Progress in investigation of the mechanisms underlying embryogenesis is related to the discovery of genic families in the Drosophila genome, which are responsible for different periods of embryogenesis. The true revolution in studies of developmental mechanisms began with the application of molecular-genetic methods for analysis of Drosophila mutant lines. The clarification and analysis of the genes controlling regeneration is one of the most effective paths toward an understanding of the mechanisms underlying regeneration. No mutations affecting regeneration are, and the development of alternative (i.e., not based on mutation analysis) methods of discovery of the genes controlling regeneration is necessary for investigation of the genetic mechanisms of regeneration. The advantages and drawbacks of the two main approaches for discovery of the genes controlling regeneration are considered. The first approach is based on the production of a bank of sequences expressed in the regenerating structures and subsequent screening of the bank by the known probes. This approach also involves analysis of the structure, function, and expression pattern of the obtained homologs. The second approach is based on subtractive hybridization, which allows identification of the genes specifically expressed in the regenerating structures. This approach was made it possible to identify, for the first time, new genes specifically expressed during lens and retina regeneration in amphibians.     

D1 and D2 dopamine receptor mediation of amphetamine-induced acetylcholine release in nucleus accumbens

To assess the interaction of dopamine and acetylcholine systems in the rat nucleus accumbens in response to direct D-amphetamine administration, in vivo microdialysis measures of acetylcholine were used during reverse dialysis of amphetamine alone and in combination with D1 and D2 receptor antagonists SCH 23390 and sulpiride, respectively. During a 15-min exposure to amphetamine (50 microM) in the nucleus accumbens, acetylcholine increased to 33% above pre-infusion levels, became maximal at 15 min post-infusion (+41%) and gradually returned to baseline levels by 60 min post-amphetamine. Conversely, amphetamine (1 mM) administration caused a biphasic change in acetylcholine release with a trend toward a decrease (-14%) during exposure followed by a significant increase (+36%) at 30 min post-amphetamine that returned to baseline levels by 60 min after infusion. The increases observed during amphetamine (50 microM) exposure and during recovery from amphetamine (1 mM) were both blocked by co-administration with the D1 antagonist, SCH 23390 (10 microM), but not with the D2 antagonist, sulpiride (10 microM). Co-infusion of sulpiride eliminated the trend toward reduced acetylcholine release observed during 1 mM amphetamine whereas co-administration of SCH 23390 potentiated this decrease. A possible tonic D1 facilitation of nucleus accumbens acetylcholine release was indicated by the consistent reductions in acetylcholine release observed during infusion of SCH 23390. These results suggest that amphetamine administration in the nucleus accumbens induces a bidirectional change in acetylcholine release that is dependent on dose and opposing effects of nucleus accumbens D1 and D2 activation. In general, relatively low doses of amphetamine administered into the nucleus accumbens caused an increase in acetylcholine release that was dependent on dopamine D1 receptors whereas higher doses of amphetamine resulted in a D2-mediated decrease.