Explore the vast range of titles available.

Land use/land cover (LULC) changes have been observed in the Gaborone dam catchment since the 1980s. A comprehensive analysis of future LULC changes is therefore necessary for the purposes of future land use and water resource planning and management. Recent advances in geospatial modelling techniques and the availability of remotely sensed data have become central to the monitoring and assessment of both past and future environmental changes. This study employed the cellular automata and Markov chain (CA-Markov) model combinations to simulate future LULC changes in the Gaborone dam catchment. Classified Landsat images from 1984, 1995, 2005 and 2015 were used to simulate the likely LULCs in 2015 and 2035. Model validation compared the simulated and observed LULCs of 2015 and showed a high level of agreement with Kappa variation estimates of Kno (0.82), Kloc (0.82) and Kstandard (0.76). Simulation results indicated a projected increase of 26.09%, 65.65% and 55.78% in cropland, built-up and bare land categories between 2015 and 2035, respectively. Reductions of 16.03%, 28.76% and 21.89% in areal coverage are expected for shrubland, tree savanna and water body categories, respectively. An increase in built-up and cropland areas is anticipated in order to meet the population’s demand for residential, industry and food production, which should be taken into consideration in future plans for the sustainability of the catchment. In addition, this may lead to water quality and quantity (both surface and groundwater) deterioration in the catchment. Moreover, water body reductions may contribute to water shortages and exacerbate droughts in an already water-stressed catchment. The loss of vegetal cover and an increase in built-up areas may result in increased runoff incidents, leading to flash floods. The output of the study provides useful information for land use planners and water resource managers to make better decisions in improving future land use policies and formulating catchment management strategies within the framework of sustainable land use planning and water resource management.

The high-temperature superconducting material Bi 2 Sr 2 CaCuO 8 , (Bi-2212) holds major potential for advanced electronic and superconducting technological applications. The present study investigates the complete set of structural, electronic, and magnetic characteristics in Bi-2212 while focusing on interface and heterostructure features with Oxygen doping. The dominance of Cu orbital in the undoped system has been observed over the other orbitals. However, the oxygen contribution variation has been observed in the doped system with a tetragonal structure. Higher magnetic moments in the doped system resulted in the spin density modulation. The stripe order phases of Bi-2212 exhibit different local magnetic moments for Cu sites with a magnitude of ±0.58 μ B alternating in the upper and lower layers. The decrease in Cu occupancy is due to the hole buildup. The band structure shows a maximum near k ≈ 0.2 and a minimum around k ≈ 0.8, indicating the electronic states’ energy variations. The local Cu–O bond length changed due to planar oxygen position alterations along the α\\alpha-axis. The role of different kinds of defects in the doped system is well analyzed. The presence of oxygen interstitials enhances the critical temperature and improves conductivity by adding more carriers to the material. The Bi-2212/Bi 3 Se 3 exhibits the highest T c , showing exceptionally strong effects through their critical temperature (96 K), resulting in a high electrical conductivity (5900 S/cm). The optical conductivity maintains a gradual upward trend, as it implies that improved carrier response occurs at elevated frequencies. Interactions between heterojunction materials lead to advancements that allow better superconducting electronics, quantum devices, and energy-efficient technologies.

Uncertainties in rainfall have increased in the recent past exacerbating climate risks which are projected to be higher in semiarid environments. This study investigates the associated features of rainfall such as rain onset, cessation, length of the rain season (LRS), and dry spell frequency (DSF) as part of climate risk management in Botswana. Their trends were analysed using Mann-Kendall test statistic and Sen’s Slope estimator. The rainfall-evapotranspiration relationships were used in formulating the rain onset and cessation criteria. To understand some of the complexities arising from such uncertainties, artificial neural network (ANN) is used to predict onset and cessation of rain. Results reveal higher coefficients of variation in onset dates as compared to cessation of rain. Pandamatenga experiences the earliest onset on 28th of November while Tsabong the latest on 14th of January. Likewise, earliest cessation is observed at Tshane on 22nd of February and the latest on 30th of March at Shakawe. The shortest LRS of 45 days is registered at Tsabong whereas the northern locations show LRS greater than 100 days. Stations across the country experience strong negative correlation between onset and LRS of − 0.9. DSF shows increasing trends in 50% of the stations but only significant at Mahalapye, Pandamatenga, and Shakawe. Combining the LRS criteria and DSF, Kasane, Pandamatenga, and Shakawe were identified to be suitable for rainfed agriculture in Botswana especially for short to medium maturing cereal varieties. Predictions of onset and cessation indicate the possibility of delayed onset by 2–5 weeks in the next 5 years. Information generated from this study could help Botswana in climate risk management in the context of rainfed farming.

Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann–Kendall and Sen’s Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana.

This paper deals with channel modelling in free space optics (FSO) network using MATLAB 2017a. A detailed mathematical methodology to design an optical network is proposed under various small scales fading effects such as Rayleigh, and Rician fading which degrades the execution of a wireless channels. In the proposed work, the system is implemented at different sample rates, Various Doppler shifts through a flat fading channel. To modulate the data, Quadrature phase-shift keying (QPSK) modulation is used. The simulated effect of the fading channel of Rayleigh and Rician is contrasted in this paper.

Gaborone city water distribution system (GCWDS) is rapidly expanding and has been faced with the major problems of high water losses due to leakage, water shortages due to drought and inadequate chlorine residuals at remote areas of the network. This study investigated the probable causes of chlorine decay, due to pipe wall conditions and distribution system water quality in the GCWDS. An experimental approach, which applied a pipe-loop network model to estimate biofilm growth and chlorine reaction rate constants, was used to analyse pipe wall chlorine decay. Also, effects of key water quality parameters on chlorine decay were analysed. The water quality parameters considered were: natural organic matter (measured by total organic carbon, TOC; dissolved organic carbon, DOC; and ultraviolet absorbance at wavelength 254, UVA-254, as surrogates), inorganic compounds (iron and manganese) and heterotrophic plate count (HPC). Samples were collected from selected locations in the GCWDS for analysis of water quality parameters. The results of biofilm growth and chlorine reaction rate constants revealed that chlorine decay was higher in pipe walls than in the bulk of water in the GCWDS. The analysis of key water quality parameters revealed the presence of TOC, DOC and significant levels of organics (measured by UVA-254), which suggests that organic compounds contributed to chlorine decay in the GCWDS. However, low amounts of iron and manganese (< 0.3 mg/L) indicated that inorganic compounds may have had insignificant contributions to chlorine decay. The knowledge gained on chlorine decay would be useful for improving water treatment and network operating conditions so that appropriate chlorine residuals are maintained to protect the network from the risks of poor water quality that may occur due to the aforementioned problems.

The main focus of this paper is to study a new type of Caputo fractional Chebyshev–Halley family method (CFCHFM) of order at least 3 μ to approximate zeros x ∗ of nonlinear equations. In the present manuscript, we have explained and illustrated the effect of the Caputo-type fractional derivative on the Chebyshev–Halley family of iterative methods in the search for zeros of nonlinear equations using the convergence plane. Here we have analyzed the 3 μ th order of convergence and efficiency index of the Chebyshev method, Halley method, and super-Halley method using fractional calculus and compared their methods’ performance with the fractional Newton method.

Forecast rise in global temperature is expected to have variable spatial and temporal impacts on rainfall patterns and crop productivity. In Aswa catchment, with a population of over two million, of which 70% are peasant farmers, there are concerns about increasing frequency of droughts, food shortage, and famine. However, hydro-climate data over the catchment are insufficient and often inconsistent to be used for spatial hydrological modeling and water resource management. This study explores the use of secondary data, such as the Tropical Rainfall Measuring Mission (TRMM) and the National Centers for Environmental Prediction (NCEP) reanalysis data, to generate future climatic information over Aswa catchment. This is achieved by interrogating the relationships between these secondary datasets and the available station data and using the secondary data to downscale two General Circulation Models (GCMs): Hadley Centre Coupled Model 3 and Canadian Earth System Model with Statistical Downscaling Model (SDSM). Correlation coefficients between secondary and station data lie between 0.75 and 0.85. Calibration and validation of the SDSM are satisfactory. For instance, Agago location gave correlation coefficient value of 0.64–0.96, standard error for temperature of 0.37–1.30 °C, and monthly rainfall of 23–45 mm. By 2099, minimum temperature is expected to rise by 3.25 °C and maximum temperature by 1.95 °C above the 2015 value. The annual rainfall coefficient of variability lies between 14 and 56%. These results suggest that the future temperature and rainfall patterns over Aswa catchment are likely to depart from the present and produce extreme events and challenges.

Integrity assessment of 10Cr ferritic steel/alloy 617M dissimilar metal weld joint (DMWJ) fabricated from hot-wire narrow-gap TIG (NG-TIG) welding process using alloy 617 filler wire (ERNiCrCoMo-1) was carried out under creep testing at 888 K. Microstructural constituents and hardness across the weld joint (10Cr steel-alloy 617 butter layer-alloy 617 weld metal-alloy 617 M) were found to vary significantly. Alloy 617 weld metal and butter layer have possessed higher hardness as compared to base metals of alloy 617M and 10Cr steel. However, lower hardness was observed in the alloy 617 butter layer, which is adjacent to 10Cr steel, and in the outer edge of HAZ in the 10Cr steel. The carbon migration was predominantly observed across the interface between 10Cr steel and alloy 617 butter layer. Creep tests performed on 10Cr steel and DMWJ at 888 K have revealed the lower creep strain accumulation in DMWJ than the 10Cr steel base metal. An early onset of tertiary creep deformation and consequent premature failure of DMWJ were noticed as compared to the 10Cr steel. Creep rupture strength of the DMWJ was about 31% lower than the 10Cr steel. Fracture in the weld joint has occurred at the interface between 10Cr steel and alloy 617 buttered layer with significant reduction in ductility. The formation of coarse M 23 C 6 precipitates and Laves phase (enriched by Mo and W), oxidation, heterogeneity in strength across the interface have facilitated the extensive cavitation at the interface, thereby leading to premature failure of the DMWJ. Weld strength reduction factor of about 0.69 at 888 K for 10 4  h has been obtained for the DMWJ.