Frequency-Domain Stochastic Error Concealment for Wireless Audio Applications

Real time digital audio delivery over Wireless Local Area Networks (WLANs) represents an attractive, flexible and cost effective framework for realizing high-quality, multichannel home audio applications. However, the unreliable nature of WLANs IP link frequently imposes significant playback quality degradation, due to delay or permanent loss of a number of transmitted digital audio packets. In this paper, a novel packet error concealment technique is presented, based on the spectral reconstruction of the statistical equivalent of a previously successfully received audio data packet. It is shown that the proposed data reconstruction scheme outperforms previously published error concealment strategies, in both terms of objective and perceptual criteria.     

Multiple hypothesis tracking for data association in vehicular networks

The introduction of Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications in Intelligent Transportation Systems of the future brings new opportunities and new challenges into the automotive scene. Vehicular communications broaden the information spectrum that is available to each vehicle, allowing the enhancement of existing applications and the introduction of new ones. Undoubtedly, the impact of this new technology in transportation safety, efficiency and infotainment is expected to be very important.A significant part of research in vehicular networks (VANETs) is dedicated to networking issues like routing and safety. However, perception systems which until now were based on onboard sensors only, need to incorporate the wirelessly received information in order to extend the situation awareness of the vehicle and the driver. This paper presents an algorithm for associating targets tracked from an onboard radar sensor with the position and motion data received from the VANET. The core of the algorithm is a track oriented multiple hypothesis tracker that is modified for incorporating information included in VANET messages. The algorithm is tested in real scenarios using two experimental vehicles and then compared with two other algorithmic approaches. One is using a simpler single hypothesis algorithm for association of VANET messages and the second is using only the onboard sensors for environment perception. As a result, the advantages of the Multiple Hypothesis Algorithm regarding association performance and the added value of wireless information in the perception system are highlighted.     

Efficiency of urease and nitrification inhibitors in reducing ammonia volatilization from diverse nitrogen fertilizers applied to different soil types and wheat straw mulching

BACKGROUND: Some authors suggest that the absence of tillage in agricultural soils might have an influence on the efficiency of nitrogen applied in the soil surface. In this study we investigate the influence of no‐tillage and soil characteristics on the efficiency of a urease inhibitor (N‐(n‐butyl)thiophosphoric triamide, NBPT) and a nitrification inhibitor (diciandiamide, DCD) in decreasing ammonia volatilization from urea and ammonium nitrate (AN), respectively. RESULTS: The results indicate that ammonia volatilization in soils amended with urea was significantly higher than in those fertilized with AN. Likewise, the main soil factors affecting ammonia volatilization from urea are clay and sand soil contents. While clay impedes ammonia volatilization, sand favours it. The presence of organic residues on soil surface (no‐tillage) tends to increase ammonia volatilization from urea, although this fact depended on soil type. The presence of NBPT in urea fertilizer significantly reduced soil ammonia volatilization. This action of NBPT was negatively affected by acid soil pH and favoured by soil clay content. CONCLUSION: The presence of organic residues on soil surface amended with urea increased ammonia volatilization, and was particularly high in sandy compared with clay soils. Application of NBPT reduced ammonia volatilization although its efficiency is reduced in acid soils. Concerning AN fertilization, there were no differences in ammonia volatilization with or without DCD in no‐tillage soils. Copyright © 2011 Society of Chemical Industry     

A cross‐layer information centric‐relay transmission strategy for MIMO–OFDMA multicellular networks

Power control has been a standard issue in modern wireless communications. As a result, several cooperative schemes have been developed towards reducing the downlink transmission power. One possible approach is the use of relays that forward information from the base station (BS) to the mobile stations (MSs). However, up to now, the proposed relaying schemes are focusing solely on channel characteristics. In this work, a novel, content‐aware relaying scheme is introduced, where the MSs can act as active relays based on their requested content and channel quality. Content awareness is achieved with a cross‐layer algorithm, which considers an information‐centric networking layer. The performance of the proposed approach has been evaluated considering a multiple input multiple output (MIMO) cellular configuration with one tier of cells around the central cell, where the downlink transmission power (in terms of mean values) has been compared to the typical non‐content‐aware case. For this reason, a hybrid system—link level simulator has been developed that executes independent Monte Carlo (MC) simulations in parallel. Moreover, the orthogonal frequency division multiple access (OFDMA) physical layer protocol has been employed as well, in order to comply with fourth generation standards. The derived results indicate that, compared to the non‐content‐aware case, the proposed relay transmission algorithm can provide up to 7/17% transmission power gain in medium or highly loaded networks (i.e., 10% and 40% blocking probabilities, respectively) in a symmetric 2 × 2 MIMO configuration (i.e., equal number of transmit and receive antennas). Moreover, compared to the case where no relay transmission is supported, then the aforementioned gain can reach up to 20%. Finally, the proposed algorithm can provide up to 25% reduction on the overall transmission delay from the relay node to the destination compared to the non‐content‐aware case. Copyright © 2014 John Wiley & Sons, Ltd.     

A Delay Optimal Scheduling Policy for Real Time Services in WCDMA Systems

Enhanced Uplink operation of WCDMA-UMTS systems utilizes fast Node B scheduling and a short Transmission Time Interval (TTI) of 2 ms. The scheduling decisions are based on Scheduling Information (SI) sent from each User Equipment (UE) to the Node B. The weakness of the existing scheduling framework is that the SI does not include information regarding the delay sensitivity of each traffic flow, as well as the actual delay that the buffered data have experienced, especially for real-time services. In this paper, we propose the inclusion of such information in SI by introducing modifications into the respective 3GPP specifications. Thus, we propose a Delay Aware Channel Prioritization (DACP) criterion optimized for real-time services. Furthermore, we propose a DACP-based packet Scheduler (DACP-S) which is able to dynamically manage the Enhanced Dedicated Channel’s (E-DCH) transmissions and offer Quality of Service differentiation. The performance of the proposed scheme is evaluated by means of system level simulations.     

Low-frequency Raman scattering in alkali tellurite glasses

Raman scattering has been employed to study the alkali-cation size dependence and the polarization characteristics of the low-frequency modes for the glass-forming tellurite mixtures, 0·1M₂O–0·9TeO₂ (M = Na, K, Rb and Cs). The analysis has shown that the Raman coupling coefficient alters by varying the type of the alkali cation. The addition of alkali modifier in the tellurite network leads to the conversion of the TeO₄ units to TeO₃ units with a varying number of non-bridging oxygen atoms. Emphasis has also been given to the low-frequency modes and particular points related to the low-frequency Raman phenomenology are discussed in view of the experimental findings.     

Water-to-Air Mass Transfer of VOCs: Laboratory-Scale Air Sparging System

Nonequilibrium air-water mass transfer experiments for six volatile organic compounds (VOCs) were conducted using a bench-scale air sparging system. VOCs used were carbon tetrachloride, trichloroethylene, tetrachloroethylene, chloroform, dichloromethane, and toluene. The average particle size of the porous media used ranged from 0.278 to 1.71 mm. The air-water mass transfer coefficients were estimated by fitting the experimental data to a lumped parameter model. The model assumed that the saturated porous media under air sparging conditions consisted of two zones. In the “mass transfer” zone, VOCs were directly impacted by the flow of air in the air channels, while in the “bulk water” zone, VOCs were not directly affected by the air flow in the air channels. The estimated air-water mass transfer coefficients (KGa) were found to increase for higher injected air flow rates and for larger mean particle sizes of porous media but were inversely proportional to the Henry's law constant of the VOCs. An empirical correlation was developed by correlating the Sherwood number with the Péclet number, the Henry's law constant, and the mean particle size of porous media. The estimated fraction (F) of the total volume of the porous media directly affected by air channels was between 5 and 20% for fine sand, indicating that a small fraction of the porous media was affected by the advecting air stream.     

Headspace Solid Phase Micro Extraction Gas Chromatographic Determination of Fenthion in Human Serum

A simple and effective analytical procedure was developed for the determination of fenthion residues in human serum samples. The sample treatment was performed using the headspace solid-phase micro extraction with polyacrylate fiber, which has the advantage to require low amount of serum (1 mL) without tedious pre-treatment. The quantification of fenthion was carried out by gas chromatography-mass spectrometry and the recoveries ranged from 79 to 104% at two spiking levels for 6 replicates. Detection and quantification limits were calculated as 1.51 and 4.54 ng/mL of serum respectively. Two fenthion metabolites fenoxon and fenthion–sulfoxide were also identified.     

Enzymatic Methylation and Structure–Activity‐Relationship Studies on Polycarcin V,a Gilvocarcin‐Type Antitumor Agent

Polycarcin V, a polyketide natural product of Streptomyces polyformus, was chosen to study structure–activity relationships of the gilvocarcin group of antitumor antibiotics due to a similar chemical structure and comparable bioactivity with gilvocarcin V, the principle compound of this group, and the feasibility of enzymatic modifications of its sugar moiety by auxiliary O‐methyltransferases. Such enzymes were used to modify the interaction of the drug with histone H3, the biological target that interacts with the sugar moiety. Cytotoxicity assays revealed that a free 2′‐OH group of the sugar moiety is essential to maintain the bioactivity of polycarcin V, apparently an important hydrogen bond donor for the interaction with histone H3, and converting 3′‐OH into an OCH₃ group improved the bioactivity. Bis‐methylated polycarcin derivatives revealed weaker activity than the parent compound, indicating that at least two hydrogen bond donors in the sugar are necessary for optimal binding.