Group delay modulation for pulse position coding based on periodically coupled C-sections

Chipless radio frequency identification (RFID) is an emerging research area nowadays. The recent development in this area proves its efficiency to compete with low cost identification systems like barcodes in the upcoming years. Chipless RFID encodes data using different kinds of spectral signature produced from some planar images as in the case of barcodes, the difference here is those images are made with conductive materials. Among the different ways of information encoding, a powerful way of encoding is time domain approach. This paper incorporates a tag using group delay encoding. The proposed chipless tag is composed of commensurate cascaded transmission line sections coupled at alternative ends (also known as C-sections). It consists of single group of C-sections. However, in order to increase the coding capacity, the proposed tag can allow multi-frequencies also. In addition to this, the tag is also compatible with commercial ultra wide band radar. The proposed tag is validated experimentally. It exhibits a good reading range of 1.2 m.     

A scoping study characterizing prevalence, risk factor and intervention research, published between 1990 and 2010, for microbial hazards in leafy green vegetables

A scoping study was conducted to identify all published prevalence, risk factor, and intervention research investigating 16 microbial hazards in leafy green vegetables and to evaluate the volume, main characteristics, basic aspects of methodological soundness and/or reporting, and the main knowledge gaps and research needs. Our study included a comprehensive literature search, a replicable two-level relevance screening (abstract and article levels), and a two-phase quality assessment and data extraction (article level). All steps were conducted by two independent reviewers following general principles of systematic review methodology. From the initial 7961 citations, 657 articles were relevant, reporting one or more research themes: prevalence (314 studies), risk factor (472) and intervention research (269). These articles were published in 190 different scientific journals, 15% between 1990 and 2000, and the remaining 85% after year 2000. Sixty-five percent of studies was conducted in the USA, Canada, or Europe. Over 70% of all studies investigated lettuce. Collectively, four leafy greens (lettuce, cabbage, spinach, and fresh leafy herbs) and microorganism (Escherichia coli, Salmonella, Listeria and coliforms) combinations accounted for almost 80% of relevant studies. Forty-one percent of the research was conducted at the processing stage of production. Lack of reporting sufficient data and/or replicable laboratory protocols (first phase assessment) resulted in exclusion of 60% of relevant articles. In total, 231 papers were retained following second phase quality evaluation, and only 152 (20% of all relevant articles) met all ranking criteria. A lack of well designed, executed, and reported prevalence studies with sampled populations representative of the target populations and of experimental studies investigating the efficacy of intervention(s) under real-life conditions was observed. A limited number of articles investigating commonly accepted important risk factors, for example worker hygiene and health, equipment sanitation, and wildlife, was identified. We highlight research areas with the data potentially feasible for full systematic review-meta-analysis methodology and areas warranting additional investigation. The resulting information is necessary for the establishment of evidence-informed guidelines for food safety enhancement.     

Decision-making between a grid extension and a rural renewable off-grid system with hydrogen generation

Most populations in rural Africa have no access to electricity, in this study, a comparative analysis between grid extension and the implementation of renewable off-grid hybrid power system is carried out. The objective of the study is to determine the best feasible option. Napier, a farming village in the Western Cape province of South Africa was selected as the site for the comparative analysis and HOMER PRO software was used to develop an optimal system using the wind and solar resources of the selected site. The load profile considered in the analysis includes lighting, cooking and hot water demands. The best feasible option is determined based on the Net Present Cost of each feasible scenario. Sensitivity analysis on the current cost and the projected cost of hydrogen storage w conducted to observe the impact of the cost of hydrogen storage on the renewable off-grid system cost of energy.     

Assessment of carcass contamination with E. coli O157 before and after washing with water at abattoirs in Nigeria

The study was carried out to assess the level of beef carcass contamination with Escherichia coli including O157 strains before and after washing with water. Samples of water used for washing carcasses were collected and thirty beef carcasses were swabbed within a period of one month in each of three abattoirs located in North-Western states of Nigeria. E. coli were enumerated as indicator organisms. Using conventional biochemical tests, the isolation rate of E. coli in the 120 swab samples collected in each abattoir from external and internal surfaces of the carcasses was 58.3% at Kano abattoir, 70.8% at Sokoto abattoir, while 76.7% was recorded at Zango abattoir. E. coli counts from external and internal surfaces of the carcasses were enumerated as mean log and ranged between 4.3 Log(10) and 4.6 Log(10) cfu/cm(2) before washing, while the values were 4.6 Log(10) and 4.9 Log(10) cfu/cm(2) after washing. Data analysis revealed that the increase in E. coli counts after washing carcasses with water was statistically significant (P<0.05) in all the abattoirs. However, there was no statistically significant difference (P>0.05) between the 3 abattoirs in mean log of E. coli counts from external surfaces of carcass after washing. E. coli O157 was identified from both the water and surfaces of carcasses using Latex agglutination kit. A prevalence of 2.8% of E. coli O157 was detected in 360 swab samples from 90 beef carcasses examined. E. coli counts from water used in washing carcasses were between 22 and 120 cfu/100 ml. Of the 72 water samples, 3(4.2%) were positive for E. coli O157. In conclusion, there was increased contamination of carcasses during processing and water used in washing carcasses might have contributed to carcass contamination in all the abattoirs studied due to use of non-potable water.     

Process variation-aware performance analysis of asynchronous circuits

Current technology trends have led to the growing impact of process variations on performance of asynchronous circuits. As it is imperative to model process parameter variations for sub-100nm technologies to produce a more real performance metric, it is equally important to consider the correlation of these variations to increase the accuracy of the performance computation. In this paper, we present an efficient method for performance evaluation of asynchronous circuits considering inter- and intra-die process variation. The proposed method includes both statistical static timing analysis (SSTA) and statistical Timed Petri-Net based simulation. Template-based asynchronous circuit has been modeled using Variant-Timed Petri-Net. Based on this model, the proposed SSTA calculates the probability density function of the delay of global critical cycle. The efficiency for the proposed SSTA is obtained from a technique that is derived from the principal component analysis (PCA) method. This technique simplifies the computation of mean, variance and covariance values of a set of correlated random variables. In order to consider spatial correlation in the Petri-Net based simulation, we also include a correlation coefficient to the proposed Variant-Timed Petri-Net which is obtained from partitioning the circuit. We also present a simulation tool of Variant-Timed Petri-Net and the results of the experiments are compared with Monte Carlo simulation-based method.     

A robust multivariate Shewhart chart for contaminated normal environments

Lately, the multivariate setup of control charts, especially the memory-less chart has received less attention of researchers as compared to the univariate setup. However, the multivariate setup is of paramount importance in this big-data era. In this research work, we study the multivariate Shewhart chart for monitoring location parameter by examining the robustness of this scheme with the mean estimator. We also explored the scheme with some other robust parametric estimators in different process environments. The multivariate estimators such as median, midrange, tri-mean (TM), and Hodges–Lehmann (HL) estimators were examined under uncontaminated, location contaminated, variance contaminated, and both location–variance contaminated normal environments. Through a synthetic Monte Carlo simulation and application of the schemes on a real-life dataset, the findings suggest that the proposed estimators outperform the default estimator of the multivariate scheme (mean). The performance measures of comparing these estimators through the charts are the average run length, standard deviation run length, extra-quadratic loss, and relative average run length. The charts resulting from applying the schemes on real-life dataset recorded from glass manufacturing process also buttresses the simulation findings.     

A preliminary chlorine survey of the savanna soils of Nigeria

Chlorine contents of 32 surface soils representing the four savanna zones in Nigeria, the major soil parent materials and the main agricultural fields were examined. Total chlorine contents varied from 47.2 to 296.5 mg kg^-1 while the water-soluble chloride varied from 0.1 to 7.7 mg kg^-1 in all the soils. Total Cl and water-soluble Cl^- did not vary by either ecological zones or by soil parent material. However, according to the order of magnitude, the contents in the ecological zones may be arranged as follows: Southern Guinea > Sudan > Northern Guinea > Sahel while, with respect to parent material, the contents could be arranged as follows: Basement Complex > Basalt > Sedimentary > Aeolian. Preliminary results tend to indicate that over eighty percent of the Nigerian savanna soils may be deficient in Cl, though detailed study may be necessary. Lack of significant correlation between Cl and selected soil properties tends to indicate that neither texture, organic matter nor soil reaction has a controlling influence on Cl occurrence in the study area.     

Thermophysical characterization of a laminated solid-wood pine wall

The experimental results obtained by the thermophysical characterization of a wall made of stacked laminated solid-wood planks are reported in this article. The interface between two logs is filled with a felt packing that is compressed under the weight of the upper plank. The characteristics which affect heat, air and water vapour transfers through the wall have been determined, i.e. the sorption isotherm, density, thermal conductivity and diffusivity, water vapour diffusion coefficient, and air permeability of the wall. The results achieved demonstrate the influence of the presence of the laminating adhesive on water vapour and air diffusion, and the influence of the presence of the felt packing on air permeability. The result is that the hygrothermal behaviour of the wall studied cannot be described properly by simply taking into account the properties of the solid wood, and it is thus necessary to determine the global properties of the composite wall.