Physical Layer Design Alternatives for High Speed Outdoor Packet Radio Local and Medium Area Networks

In the last few years, the development of wireless local area networks (WLANs) has become a major goal in the field of computer and wireless communications. The Network Technologies Research group at the Communications Research Center in Canada has been working on a project to develop a high speed outdoor WLAN. In contrast to many existing WLANs, the new WLAN supports multimedia traffic such as voice, data and video; and will be used mainly in an outdoor environment with a cell coverage range of approximately 20 km. In this paper the physical layer design alternatives for the outdoor WLAN with a speed of 10 to 20 Mbps are described. Simulation results for some of the techniques considered to be used for the WLAN system are presented. The study is concluded by proposing two possible systems that one may consider for the implementation of a high speed outdoor WLAN. Although this study was primarily focused on WLAN applications, the results presented in this paper are applicable to several high speed wireless networks.     

Diffusion analysis and modeling of kinetic behavior for treatment of brine water using electrodialysis process

In this study, the removal of monovalent and divalent cations, Na⁺, K⁺, Mg²⁺, and Ca²⁺, in a diluted solution from Chott-El Jerid Lake, Tunisia, was investigated with the electrodialysis technique. The process was tested using two cation-exchange membranes: sulfonated polyether sulfone cross-linked with 10% hexamethylenediamine (HEXCl) and sulfonated polyether sulfone grafted with octylamine (S-PESOS). The commercially available membrane Nafion® was used for comparison. The results showed that Nafion® and S-PESOS membranes had similar removal behaviors, and the investigated cations were ranked in the following descending order in terms of their demineralization rates: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. Divalent cations were more effectively removed by HEXCl than by monovalent cations. The plots based on the Weber–Morris model showed a strong linearity. This reveals that intra-particle diffusion was not the removal rate-determining step, and the removal process was controlled by two or more concurrent mechanisms. The Boyd plots did not pass through their origin, and the sole controlling step was determined by film-diffusion resistance, especially after a long period of electrodialysis. Additionally, a semi-empirical model was established to simulate the temporal variation of the treatment process, and the physical significance and values of model parameters were compared for the three membranes. The findings of this study indicate that HEXCl and S-PESOS membranes can be efficiently utilized for water softening, especially when effluents are highly loaded with calcium and magnesium ions.     

Phased arrays in communication system based on Taguchi‐neural networks

Phased antenna array design is one of the most important electromagnetic optimization problems. This research combined the Taguchi method and artificial intelligence methods, used them as the prediction tool in designing parameters for the communication system, and then constructed a set of the optimal parameter analysis flow and steps. In this paper, we present an application of artificial neural networks in the electromagnetic domain. We particularly look at the multilayer perceptron network, which has been the most used of artificial neural networks architectures both in the electromagnetic domain and in the Taguchi optimization technique and describes the Taguchi method to optimize the excitations elements of the linear array to produce a radiation pattern with minimum side lobe level and null placement control. This paper investigates how the implementation of the signal processing in hardware affects the performance of the adaptive array antenna. The investigation is confined to uplink or receive antenna array only. Results of a prototype of antenna array with feeding values designed using the proposed techniques are also presented. Copyright © 2013 John Wiley & Sons, Ltd.     

A New Approach to Volumes Irradiated by Unknown Sources

We suggest an approach to the characterization of electromagnetic (EM) environments irradiated by unknown sources. The approach is based on the numerical solution of Maxwell's equations subject to the constraints imposed by the measured values of the field at a small number of measurement points and by boundary conditions. A thorough examination of a method for the numerical solution is presented. The examples attempted demonstrate the approach but reveal deficiencies in the numerical method. Possible future directions are suggested.     

Inhibition of acid sialidase by inorganic sulfate

Sulfated glycosaminoglycans are known to inhibit mammalian acid-active sialidase. Although the inhibition depends clearly on the presence of sulfate groups on these macromolecules, there was no information on the intrinsic inhibitory potency of inorganic sulfate. In this study, we demonstrate that inorganic sulfates inhibit acid-active Mu-Neu5Ac sialidase of U937 cells. This inhibition was found to be reversible and it appeared to be of the mixed competitive type. Sulfate-induced inhibition was also observed in other cells as well as with other substrates such as sialyl lactose and bovine mixed brain gangliosides. We conclude that the intrinsic inhibitory potency of sulfate groups may be significantly involved in the inhibition of acid-active sialidase by sulfated glycosaminoglycans. In addition, inorganic sulfate by its apparent potency to selectively inhibit acid sialidases might constitute an interesting tool for the characterisation of the minor forms of sialidases occurring in mammalian cells.     

Correction factor for nonplanar incident field in monopolecalibrations

In calibrating monopole antennas, the length of the antenna can be comparable to the separation distance. In that case, there is a significant variation in both the magnitude and the phase of the incident field along the length of the antenna under test. An expression for a correction factor is presented to account for this effect. The correction factor is evaluated for some representative cases, and some guidelines are given for when this factor should be taken into account. The effect can exceed 1 dB in some practical cases     

Pattern-recognition analysis of sound radiation in metal cutting

Pattern-recognition analysis of sound radiation was developed as a basis for monitoring the metal-cutting process. The sound-pressure signals radiated during cutting under fixed conditions were recorded using a sharp tool, a worn tool and a broken tool. A round bar of heat-treated AISI 4340 steel was machined in cylindrical turning, using a titanium-carbide-coated cutting tool. The spectral components in the 0–10 kHz range were used as features. Using resubstitution, signals coming from sharp and worn tools were easily distinguished, resulting in a 100% classification with just two features, being the average of the low (0–5 kHz) and high (5–10 kHz) frequency ranges. With tool breakage, two acceptable classifications were obtained using independent testing, the first with a performance of 100%, 75% and 100% for sharp, worn and breakage signals respectively, using nine features, and the second with 80%, 88% and 80%, using eight features.     

Advanced image steganography based on exploiting modification direction and neutrosophic set

A new variant of image steganography based on exploiting modification directions (EMD) named advanced EMD (AEMD) is introduced. In this method the secret digits in mⁿ -ary notional systems are embedded into a group of n pixels of the cover image. To increase data hiding capacity, edge masking characteristics of human visual system is exploited to embed more bits at image edge pixels than non-edge pixels. To do this, a neutrosophic set edge detector, named as MNSED is also introduced to classify cover image into 2?×?2 non-overlapping edge and non-edge blocks without any overhead information. Hence the secret digits in two different bases are embedded into the edge and non-edge blocks. Experimental results show that the proposed method provides higher embedding capacity and better quality compared to the existing schemes, while its resistance to steganographic attack is still higher.

     

Auto-organization approach with adaptive frame periods for IEEE 802.15.4/zigbee forest fire detection system

Wireless Networks - Using efficiently the wireless sensor networks based on IEEE 802.15.4/zigbee remains a real challenge for the forest fire detection and monitoring applications. The most...