Correlation between fibre length characteristics and mechanical properties of Tectona grandis wood

This study considered the relationship between fibre length characteristics and mechanical properties of Tectona grandis wood aged 15, 20 and 25-year. Six trees of even aged and similar class diameter were used for the study. Wood samples used for the study were systematically collected from three portions at 10, 50 and 90% of the tree height. The test samples were prepared along the radial positions from the pith to the bark. The relationship between fibre length and mechanical properties were examined using linear regression models and correlation coefficient. The results obtained from the correlation analysis carried out to examine the linear relationship between fibre length and mechanical properties of T. grandis wood were 0.924, 0.929 and 0.940 for MOR, MOE and CS parallel to grain. The relationship was highly significant (p < 0.05). Also the correlation coefficient (r) between fibre length and mechanical properties of T. grandis wood were highly significant (p < 0.001). Therefore, fibre length characteristics can be used as an index in predicting the mechanical properties of T. grandis wood

Dynamics of vertical profile of Radio Refractivity in Akure South-Western Nigeria.

This research investigated fractal and chaotic dynamics in the vertical profile radio refractivity in the atmosphere using Tsallis Entropy, Hurst Exponent and Largest Lyapunov Exponent (LLE). Daily temperature, relative humidity and radio refractivity data obtained from the European Centre for Medium Range Weather Forecasts (ECMWF) Re-Analysis Project at thirty seven (37) different atmospheric pressure level from 1979-2014 were used in this study. The Hurst Exponent parameter obtained, using the method of Detrended Fluctuation Analysis, in the radio refractivity profile studied showed that there is persistence across all levels. Tsallis entropy did not reveal any structure or significant variations from the tropopause to the surface. To determine if any of the radio refractivity is chaotic at any of the studied level, the Largest Lyapunov Exponent (LLE) was computed. Positive values were obtained at all levels for radio refractivity, indicating deterministic chaos in the profile of radio refractivity

The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days

The deterministic chaotic behavior and dynamical complexity of the space plasma dynamical system over Nigeria are analyzed in this study and characterized. The study was carried out using GPS (Global Positioning System) TEC (Total Electron Content) time series, measured in the year 2011 at three GPS receiver stations within Nigeria, which lies within the equatorial ionization anomaly region. The TEC time series for the five quietest and five most disturbed days of each month of the year were selected for the study. The nonlinear aspect of the TEC time series was obtained by detrending the data. The detrended TEC time series were subjected to various analyses for phase space reconstruction and to obtain the values of chaotic quantifiers like Lyapunov exponents, correlation dimension and also Tsallis entropy for the measurement of dynamical complexity. The observations made show positive Lyapunov exponents (LE) for both quiet and disturbed days, which indicates chaoticity, and for different days the chaoticity of the ionosphere exhibits no definite pattern for either quiet or disturbed days. However, values of LE were lower for the storm period compared with its nearest relative quiet periods for all the stations. The monthly averages of LE and entropy also show no definite pattern for the month of the year. The values of the correlation dimension computed range from 2.8 to 3.5, with the lowest values recorded at the storm period of October 2011. The surrogate data test shows a significance of difference greater than 2 for all the quantifiers. The entropy values remain relatively close, with slight changes in these values during storm periods. The values of Tsallis entropy show similar variation patterns to those of Lyapunov exponents, with a lot of agreement in their comparison, with all computed values of Lyapunov exponents correlating with values of Tsallis entropy within the range of 0.79 to 0.81. These results show that both quantifiers can be used together as indices in the study of the variation of the dynamical complexity of the ionosphere. The results also show a strong play between determinism and stochasticity. The behavior of the ionosphere during these storm and quiet periods for the seasons of the year are discussed based on the results obtained from the chaotic quantifiers

The transient variation in the complexes of the low-latitude ionosphere within the equatorial ionization anomaly region of Nigeria

The quest to find an index for proper characterization and description of the dynamical response of the ionosphere to external influences and its various internal irregularities has led to the study of the day-to-day variations of the chaoticity and dynamical complexity of the ionosphere. This study was conducted using Global Positioning System (GPS) total electron content (TEC) time series, measured in the year 2011, from five GPS receiver stations in Nigeria, which lies within the equatorial ionization anomaly region. The non-linear aspects of the TEC time series were obtained by detrending the data. The detrended TEC time series were subjected to various analyses to obtain the phase space reconstruction and to compute the chaotic quantifiers, which are Lyapunov exponents LE, correlation dimension, and Tsallis entropy, for the study of dynamical complexity. Considering all the days of the year, the daily/transient variations show no definite pattern for each month, but day-to-day values of Lyapunov exponents for the entire year show a wavelike semiannual variation pattern with lower values around March, April, September and October. This can be seen from the correlation dimension with values between 2.7 and 3.2, with lower values occurring mostly during storm periods, demonstrating a phase transition from higher dimension during the quiet periods to lower dimension during storms for most of the stations. The values of Tsallis entropy show a similar variation pattern to that of the Lyapunov exponent, with both quantifiers correlating within the range of 0.79 to 0.82. These results show that both quantifiers can be further used together as indices in the study of the variations of the dynamical complexity of the ionosphere. The presence of chaos and high variations in the dynamical complexity, even in quiet periods in the ionosphere, may be due to the internal dynamics and inherent irregularities of the ionosphere which exhibit non-linear properties. However, this inherent dynamics may be complicated by external factors like geomagnetic storms. This may be the main reason for the drop in the values of the Lyapunov exponent and Tsallis entropy during storms. The dynamical behaviour of the ionosphere throughout the year, as described by these quantifiers, was discussed in this work

EFFECT OF NATURAL WEATHERING ON THE PHYSICAL PROPERTIES OF Nauclea diderrichii WOOD

Effect of natural weathering on the physical properties of Nauclea diderrichii wood was investigated in this study. Twenty four wood samples were obtained from four mature trees of Nauclea diderrichii. Physical properties investigated include specific density, texture and weight. Main changes in wood samples of N. diderrichii after six months of exposure to weathering factors include discoloration, surface checking, raised grain and the eventual loss of fibres. 4.89% and 3.86% of wood materials from sapwood and heartwood respectively were lost after exposure as some wood materials were eroded away during exposure. The study also showed that average values of moisture content were reduced from the initial value of 16.81% before exposure to 12.40% after six month of exposure. Wood degradation and loss of aesthetic value resulting from discoloration and loss of fibres from wood samples were attributed to prolonged exposure to weathering factors such as rainfall, humidity, temperature wind and sunlight. The adverse effects of weathering on the wood therefore indicated that wood materials should not be left for too long in the open before use, and that wood exposed to rainfall, humidity, et.c before application of preservatives or coatings stand the risk of degradation before protection. The study therefore recommended that wood protection against natural weathering be commenced immediately after the lumber is brought to the log yard as this step might reduce waste in the regions of wood degraded