Investigating the cause of excessive seepage in a dam foundation using seismic and electrical surveys—a case study of Asa Dam,West Africa

Bulletin of Engineering Geology and the Environment - A case study is reported in this paper, where a combination of seismic refraction and electrical resistivity surveys is used to investigate the...     

Novel fabrication of extremely high aspect ratio and straight nanogap and array nanogap electrodes

Microsystem Technologies - We reported a reproducible, simple and novel method for fabricating electrodes with high aspect ratio and highly straight nanometer size gap. The gap size could be...     

Design and manufacture of knitted tubular fabric with auxetic effect

Auxetic materials refer to materials that exhibit a negative Poisson’s ratio. They behave directly opposite to conventional materials by becoming wider when stretched and narrower when compressed. The unique property of this group of materials has led to them gaining a wider range of applications. This paper presents a study on the use of a flatbed knitting machine to fabricate and experiment on an arrow-headed auxetic tubular fabric. The study used three kinds of yarns: nylon (PA), PES, and cotton as the materials for knitting the tubular samples. Three variations of an arrow-head design (4 × 4, 6 × 6, and 8 × 8) were also used as the three main structural patterns. The results reveal that the ‘6 × 6’ structure gives the best auxetic effect among the three and the nylon (PA) yarn had the best auxeticity.     

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.     

Properties of α-amylase produced by different barley lines and their hybrids during germination

The amount of activity, the thermal stability and the calcium retaining ability of α-amylases produced by different barley varieties and their reciprocal hybrids have been investigated. α-Amylase was produced by seeds germinated normally and by de-embryonated seeds incubated with gibberellic acid. The activity of the enzyme has been compared between lines on various bases and the validity of these comparisons is discussed. The inactivation constants of the partly purified enzymes dialysed against EDTA in the presence of trypsin have been calculated and compared. Similarly the rate of thermal inactivation of the enzymes has been investigated. In general, little evidence was found to suggest that heterosis existed in terms of any of the characteristics studied.