Basic geotechnical properties,chemistry and mineralogy of some laterite soils from S.W. Nigeria

Laterite soils derived from four basement complex rocks and a sedimentary formation from Southwestern Nigeria are analysed for their basic geotechnical properties, chemistry and mineralogy. Results obtained show that the granite gneiss derived and the sedimentary laterite soils are good engineering materials. The amphibolite derived laterite soil has a linear shrinkage of 10% and contains SO ₄ ^2? ions. The quartz schist derived and the micaschist derived laterite soils contain rather high amounts of muscovite ?30% and 25% respectively. The usability of the laterite soils and the implications of the presence of SO ₄ ^2? ions and mica and the high linear shrinkage are discussed.     

Greenhouse gases mitigation by CO<Subscript>2</Subscript> reforming of methane to hydrogen-rich syngas using praseodymium oxide supported cobalt catalyst

This study focuses on the potential of hydrogen-rich syngas production by CO₂ reforming of methane over Co/Pr₂O₃ catalyst. The Co/Pr₂O₃ catalyst was synthesized via wet-impregnation method and characterized for physicochemical properties by TGA, XRD, BET, H₂-TPR, FESEM, EDX, and FTIR. The CO₂ reforming of methane over the as-synthesized catalyst was studied in a tubular stainless steel fixed-bed reactor at feed ratio ranged 0.1–1.0, temperature ranged 923–1023 K, and gas hourly space velocity (GHSV) of 30,000 h^?1 under atmospheric pressure condition. The catalyst activity studies showed that the increase in the reaction temperature from 923 to 1023 K and feed ratio from 0.1 to 1.0 resulted in a corresponding increase in the reactant’s conversion and the product’s yields. At 1023 K and feed ratio of 1.0, the activity of the Co/Pr₂O₃ catalyst climaxed with CH₄ and CO₂ conversions of 41.49 and 42.36 %. Moreover, the catalyst activity at 1023 K and feed ratio of 1.0 resulted in the production of H₂ and CO yields of 40.7 and 40.90 %, respectively. The syngas produced was estimated to have H₂:CO ratio of 0.995, making it suitable as chemical building blocks for the production of oxygenated fuel and other value-added chemicals. The used Co/Pr₂O₃ catalyst which was characterized by TPO, XRD, and SEM-EDX show some evidence of carbon formation and deposition on its surface.     

A multi-server perishable inventory system with negative customer

In this paper, we consider a continuous review perishable inventory system with multi-server service facility. In such systems the demanded item is delivered to the customer only after performing some service, such as assembly of parts or installation, etc. Compared to many inventory models in which the inventory is depleted at the demand rate, however in this model, it is depleted, at the rate at which the service is completed. We assume that the arrivals of customers are according to a Markovian arrival process (MAP) and that the service time has exponential distribution. The ordering policy is based on (s, S) policy. The lead time is assumed to have exponential distribution. The customer who finds either all servers are busy or no item (excluding those in service) is in the stock, enters into an orbit of infinite size. These orbiting customers send requests at random time points for possible selection of their demands for service. The interval time between two successive request-time points is assumed to have exponential distribution. In addition to the regular customers, a second flow of negative customers following an independent MAP is also considered so that a negative customer will remove one of the customers from the orbit. The joint probability distribution of the number of busy servers, the inventory level and the number of customers in the orbit is obtained in the steady state. Various measures of stationary system performance are computed and the total expected cost per unit time is calculated. The results are illustrated numerically.     

Weighted dynamic time warping for time series classification

Dynamic time warping (DTW), which finds the minimum path by providing non-linear alignments between two time series, has been widely used as a distance measure for time series classification and clustering. However, DTW does not account for the relative importance regarding the phase difference between a reference point and a testing point. This may lead to misclassification especially in applications where the shape similarity between two sequences is a major consideration for an accurate recognition. Therefore, we propose a novel distance measure, called a weighted DTW (WDTW), which is a penalty-based DTW. Our approach penalizes points with higher phase difference between a reference point and a testing point in order to prevent minimum distance distortion caused by outliers. The rationale underlying the proposed distance measure is demonstrated with some illustrative examples. A new weight function, called the modified logistic weight function (MLWF), is also proposed to systematically assign weights as a function of the phase difference between a reference point and a testing point. By applying different weights to adjacent points, the proposed algorithm can enhance the detection of similarity between two time series. We show that some popular distance measures such as DTW and Euclidean distance are special cases of our proposed WDTW measure. We extend the proposed idea to other variants of DTW such as derivative dynamic time warping (DDTW) and propose the weighted version of DDTW. We have compared the performances of our proposed procedures with other popular approaches using public data sets available through the UCR Time Series Data Mining Archive for both time series classification and clustering problems. The experimental results indicate that the proposed approaches can achieve improved accuracy for time series classification and clustering problems.     

Emission of pollutants from wood waste incineration at sawmills in Abeokuta metropolis,Nigeria

This paper reports an assessment of the effects of wood waste burning on air quality and the perceived human health in an urban setting. The concentrations of particulates and selected gases were monitored within the vicinity of sawmills in Abeokuta metropolis. The levels of CO, CO₂, SO₂, NO_x, NO₂, H₂S, CH₄ and particulates at distances from sawmill dumps were measured using portable samplers. Additionally, information on sawmill operations and health problems encountered by the exposed population were collected from a community survey. From the data analyses, between 60 and 100% of wood waste generated by sawmills were burned openly, leading to pollutants emission. The mean concentrations of PM_0.3–0.5 (32 523–40 284 μg/m³), NO₂ (1.0 ppm), SO₂ (3.3 ppm), CO (759 ppm) and CO₂ (4.9%) were higher than the permissible limits at 0–15 m from the dump sites. Almost all sampled parameters showed positive association (R = 0.90–0.98; p < 0.05) at sample sites. Moreover, distance of sites to the dumps explained 51–93% of the variation in parameters levels. Both respiratory and dermal diseases were frequently experienced by the exposed population. Strict land-use zoning, pollution abatement measures, environmental quality monitoring and waste-to-energy interventions are urgently required in the study area.     

Catalysis of semihydrogenation of acetylene to ethylene: current trends,challenges, and outlook

Ethylene is an important feedstock for various industrial processes, particularly in the polymer industry. Unfortunately, during naphtha cracking to produce ethylene, there are instances of acetylene presence in the product stream, which poisons the Ziegler–Natta polymerization catalysts. Thus, appropriate process modification, optimization, and in particular, catalyst design are essential to ensure the production of highly pure ethylene that is suitable as a feedstock in polymerization reactions. Accordingly, carefully selected process parameters and the application of various catalyst systems have been optimized for this purpose. This review provides a holistic view of the recent reports on the selective hydrogenation of acetylene. Previously published reviews were limited to Pd catalysts. However, effective new metal and non-metal catalysts have been explored for selective acetylene hydrogenation. Updates on this recent progress and more comprehensive computational studies that are now available for the reaction are described herein. In addition to the favored Pd catalysts, other catalyst systems including mono, bimetallic, trimetallic, and ionic catalysts are presented. The specific role(s) that each process parameter plays to achieve high acetylene conversion and ethylene selectivity is discussed. Attempts have been made to elucidate the possible catalyst deactivation mechanisms involved in the reaction. Extensive reports suggest that acetylene adsorption occurs through an active single-site mechanism rather than via dual active sites. An increase in the reaction temperature affords high acetylene conversion and ethylene selectivity to obtain reactant streams free of ethylene. Conflicting findings to this trend have reported the presence of ethylene in the feed stream. This review will serve as a useful resource of condensed information for researchers in the field of acetylene-selective hydrogenation.     

Magnetic resonance diffusion imaging of ovarian masses: a first experience with 12 cases

Objective: The objective of the study was to determine the feasibility of using apparent diffusion coefficient (ADC) measurement for the differential diagnosis of malignancy in ovarian masses. Materials and methods: Twelve cases involving ovarian masses were imaged using spin echo diffusion magnetic resonance imaging (MRI). Five cases involved malignant ovarian masses, on the basis of postoperative histologic examination, and the rest involved benign masses. The ovarian masses were imaged in vivo (10 cases) before surgery and ex vivo (8 cases) after surgical resection. Diffusion-weighted data were corrected for motion using the phase data from unweighted data in nine cases. Multifactorial analysis of variance was used to evaluate the effects of malignancy, location (in vivo versus ex vivo), and motion correction on the measurement of ADC intensity and texture. Results: Motion correction caused an undesirable spatial smoothing of the ADC maps and a significant interaction ( ) was found between location and motion correction. ADC value ( ) and texture ( ) differences were found between malignant and nonmalignant ovarian masses. Conclusion: Measurement of ADC intensity and texture has the potential to differentially diagnose malignancy in individual ovarian masses if the problem of image motion artifact can be eliminated through the use of faster imaging sequences.Acknowledgements. The cooperation of Dr. Vance Chow in the acquisition of the in vivo diffusion MRI data is gratefully acknowledged. Thanks to Ron Borowsky for discussions on the statistical data analysis. Data management, final data analysis, and figure preparation was completed by Jennifer Hadley. This work was supported by the Canadian Institutes for Health Research (CIHR) and the Saskatchewan Health Services Utilization and Research Commission (HSURC).     

Degree of stability of geodesic domes with independent loading parameters

Solution techniques and guidelines for convergence and error controls are presented for static and dynamic stability investigations of imperfection-sensitive reticulated space structures. The structure may be subjected to independent loading parameters and finite disturbances. The state of stability investigations of reticulated space structures is briefly described and reflected by the references cited. The determination of the static stability parameters including the degree of stability of equilibrium, which forms the basis of a sufficient condition of dynamic stability, is illustrated for a geodesic dome model.     

A comprehensive view of agent-oriented patterns

This paper presents a comprehensive framework for classifying, analyzing and describing agent-oriented software patterns. We present a two dimensional scheme for classifying agent-oriented patterns. We define agent-oriented pattern attributes and use these attributes in a process for analyzing and placing agent-oriented patterns within the classification scheme. Using the proposed classification scheme, we classify 28 patterns written by a variety of agent researchers, chosen from almost 100 patterns which we have studied.