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Oil shales have unstable mechanical and chemical properties, which makes their extraction for characterization and conventional mechanical testing uneasy and complex. Most often, mechanical property measurements are usually taken from core samples that are costly to extract and test using conventional testing methods. This paper presents a focused study carried out on oil shale cuttings obtained from the sidewalls of two different wellbore depths in the Niger Delta area of Nigeria. Using the X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) characterization techniques, the morphology of these shales was studied. The results obtained clearly showed the composition, bonding and variations in the morphology of the studied shale samples. Furthermore, the heterogeneity associated with these shales across varied depths were revealed. An efficient and less expensive technique compared to conventional testing methods, instrumented indentation testing (IIT) was carried out to obtain essential mechanical parameters of the shale specimen. These properties are important parameters in determining the hydrocarbon storage space of shale formations, wellbore stability, and optimization of hydraulic fracturing which is necessary for efficient drilling operations.

This paper examines volatility persistence in leverage loan market price series for Australia, Canada, Europe, Japan, Singapore, UK and USA in the presence of structural breaks. To the best of our knowledge, this is the first empirical study to examine volatility persistence in the leveraged loan markets. To this end, using fractional integration methods, the results indicate that both absolute and squared returns display long memory features, with orders of integration confirming the long memory hypothesis. However, after accounting for structural breaks, we find a reduction in the degree of persistence in the leveraged loan market. The evidence of persistence in volatility implies that market participants who want to make gains across trading scales need to factor the persistence properties of leveraged loan price series in their valuation and forecasting models since that will help improve long-term volatility market forecasts and optimal hedging decisions. post-print 759 KB

Polyethylene (PE) and cement are serious industrial wastes that promote environmental pollution, with these pollutants having tremendous effects on the lives of humanity and other living creatures, including animals. Therefore, this research presents the results of experimental and theoretical modeling of green composites (without the inclusion of cement) reinforced with recycled polyethylene waste for applications in the Mechanical and Civil Engineering industry. The composites are produced using different weight percentages of laterite and molten PE mixed homogeneously to produce unique green composites with excellent mechanical properties. The green composite with 40 wt.% laterite and 60 wt.% PE exhibited the highest compressive strength, flexural strength and fracture toughness of 25 MPa, 7.3 MPa and 0.6 MPa√m, respectively. Additionally, the green composite recorded maximum yield stress of ∼2 MP. The maximum yield stress of the green composites falls under the minimum range of yield stress for traditional concrete structures. The SEM images reveal evidence of bonding and ligament bridging in the green composites reinforced with 40 wt.% laterite and 60 wt.% PE. The probability distribution plots show that the polyethylene in the green composites follows the Weibull distribution with low Anderson Darling Statics and p-values greater than the significance level of 5%.

This current research work combines both experimental and theoretical study of the impact of cement mortar reinforced with recycled polyethylene waste for applications in the construction industry. The work explores incorporating low density polyethylene (LDPE) waste into cement mortar to improve its fracture toughness and flexural strength with balanced compressive strength. Different volume fractions (0, 5, 10, 15, 20, 30, and 40%) of the powdered LDPE were mixed with cement and the density, compressive strength, flexural strength, and the fracture toughness were observed under different testing conditions. All specimens were tested after curing of 7, 14, and 28 days. The results show that there was [Formula: see text]6% increase in the fracture toughness at 5 vol. %, [Formula: see text]7% increase at 10 vol. %, and 24% increases at 20 vol. % of LDPE. Also, it was observed that the weight and compressive strength decreased with increasing volume fraction up to 40 vol. % of LDPE waste. The results for the survival/failure probability show that the PE-mortar composites with PE volume percentages up to 20 vol. % had the highest survival probability. The composite with this volume percentage can withstand crack up to 6 mm, with a survival probability of 0.6.

In the current dynamic world, those with no or little access to key financial products and services suffer a great deal of disservice. This study examines the effect of remittance channels (commercial banks and alternative sources) have on financial inclusion and then check the moderating effect of money remittance regulation on the relationship between the remittance channels and financial inclusion in Kenya. It uses the World Bank and Central Bank of Kenya’s dataset on remittances and financial inclusion covering the period from 2009 to 2018. We estimate our model using the Ordinary Least Square assumptions to find the association. We find that remittances from alternative channels other than commercial banks influence financial inclusion in Kenya. We further notice that the money remittance regulations have no moderating effect on the relationship between remittance channels and financial inclusion in Kenya. Our results suggest that commercial banks are not able to appropriately sell their products and services to remittance-receiving households while fintech and other internet remitting service providers seem to roll on products and services that enhance the use of savings and credit facilities. We suggest that more avenues and policies should be enacted to foster the use of alternative sources while improving structures within commercial banks to empower financial inclusion in Kenya

International audience; This paper presents the results of the experimental and analytical studies of the mechanical and thermal properties of laterite composites mixed with reprocessed low-density polyethylene waste (LDPE), calcium phosphate (CaP) and phosphogypsum wastes, and biochar to form brick composites. Bricks with mixtures of 20% by volume LDPE, 15% by volume CaP, and 15% by volume gypsum were shown to have excellent compressive strength, flexural strength, and fracture toughness. The composites with 1% by volume LDPE and 15% by volume biochar had the best blend of mechanical properties, such as flexural strength and fracture toughness, after sintering for ∼24h. There was a linear association between the strength and the weight loss of the bricks. Scanning electron microscopy and optical microscopy images revealed evidence of crack bridging by LDPE particles. The laterite–LDPE composite mixed with 5%, 10%, and 15% by volume biochar had sintering temperatures of ∼850°C, ∼720°C, and ∼710°C, respectively, after undergoing softening, cold crystallization, and cooling.

The levels of heavy metals pollution in water and soil around landfill sites are increasing due to the indiscriminate dumping of domestic and industrial wastes at these sites. This research was conducted to study the characterisation and stabilisation of heavy metals in soils and leachate at the Dompoase landfill site, Kumasi-Ghana. Nine surface composite soil samples (< 40 cm deep) were collected at Dompoase landfill site from the middle (hotspot) of the landfill site through a 15 m radius away from the landfill cell where there were no dumping activities. Untreated leachate sample was also collected from a dugout around the landfill cell at a 4 m distance. This untreated leachate sample is estimated to be over 10 years and has a pH of 7.5. Physicochemical properties (i.e., electrical conductivity, pH, temperature, moisture and clay contents) and heavy metals (i.e., Cu, Cd, Fe, Ni and Zn) analyses were conducted on the collected samples. The results showed that the mean concentrations of all the heavy metals in soil studied were all above the Ghana Environmental Protection Agency (EPA) and WHO guidelines with the exception of Ni. All the psychochemical parameters were also within the EPA guidelines. Concentrations of Ni and Cd in the leachate sample were low and could not be detected. Cu and Zn recorded concentrations below the EPA and WHO guidelines while Fe recorded concentrations above the EPA and WHO limits. The contamination factor revealed that Cu (CF = 0.00) can be classified as exhibiting low contamination with Fe (CF = 1.50), Cd (CF = 1.80) and Zn (CF = 2.35) showing moderate contaminations. Low-grade CaO in varying quantities was utilised as stabilising agent to stabilise the heavy metals within various samples for a 21-day period. The physicochemical properties were monitored within the 21-day period during the heavy metal stabilisation. The results showed a percentage reduction in concentrations of metals within the period. The work shows that low-grade CaO can effectively be used in the remediation of contaminated sites as a result of anthropogenic activities.

Trace metals contamination has recently been a major issue due to its damaging effects on public health and environmental receptors. This study focussed on the health risk assessment of trace metals (As, Pb, Cr, and Ni) associated with the direct intake of some selected food crops (namely cocoyam and plantain) at Abuakwa South Municipal, Ghana. The food crops and soil samples were selected randomly from three reclaimed mined sites and one non-mining site in the study area. Results from the trace metal concentration analyses in the soil samples showed that As, Cr, and Ni were above the control. The daily intake of metals (DIM), target hazard quotient (THQ), and carcinogenic risk (CR) assessments of health risks accompanied by the continuous ingestion of the selected food crops polluted through these trace metals were evaluated. 0.23 mg/kg and 0.05 mg/kg, 0.11 mg/kg and 0.02 mg/kg, 0.78 mg/kg and 0.65 mg/kg, and 0.23 mg/kg and 0.09 mg/kg were recorded for As, Cr, Ni, and Pb in that order in the cocoyam and plantain, respectively. The As and Pb concentrations in the food crops were above the WHO recommended limits. This implies that individuals within the vicinity are exposed to high levels of As and Pb through food intake which could result in varying health implications. The DIM and THQ for the studied trace metals were below their permissible limits suggesting that there is a tolerable non-carcinogenic adverse health risk level for adults and children within the studied area. In addition, the lifetime probability of contracting cancer by ingesting Ni, Pb, and Cr in plantain grown in the study area is high. It is recommended that regular monitoring of these trace metals in food crops be carried out in preventing their excessive accumulation.

Study region : Lower Pra River (LPR) Basin, Ghana Study focus : This study examines the potential for Small Hydropower Development in a semi-arid environment albeit the lack of data. Geographic and site specific information acquired through geographic and remote sensing techniques are applied in a physically based semi-distributed hydrologic model to simulate discharges for ungauge areas for consideration of hydropower. Flow Duration Curves (FDC) and Power Duration Curves (PDC) have been constructed for suitable sites from which design flow and firm energy is established. New hydrological insights for the region : The final assessment resulted in the identification of ten sites (HP1 – HP10) along the LPR with potential for hydropower generation. The maximum and minimum mean annual flows were 172.9 m3/s and 5.3 m3/s at hydropower sites HP1 and HP2 respectively. HP1 demonstrated the highest hydropower potential with firm power and annual firm energy at 90 % dependability estimated as 12.22 MW and 77.10 GW h with a total annual energy production (AEP) of 183.77 GW h. Hydropower sites HP3 and HP7 also had relatively high hydropower potential with firm power and annual firm energy of 10.0 MW, 47.01 GW h and 9.0 MW, 40.77 GW h respectively with AEP expected to be in the order of 157.67 GW h and 141.91 GW h respectively. A cascade system is proposed for hydropower sites HP1, HP3 and HP7 with estimated combined AEP of 483.4 GW h.

Most locally-manufactured corn-mill plates in tropical countries are made of grey cast iron due to its relatively low cost, good wear resistance, good hardness and other mechanical properties in general. However, these corn-mill plates are prone to corrosion and abrasive wear resulting to contamination of milled corn which is consumed by humans. This work focuses on the use of computer-aided selection and weighted property methods to identify alternative materials for grey cast iron corn-mill plates. Requirements such as non-toxicity, good corrosion resistance, good wear resistance, low friction coefficient, high thermal conductivity, low specific gravity, high compressive strength and low cost were used in the initial material selection stages. The derivation of material performance index in addition to Ashby’s materials selection chart are used to find suitable materials to replace grey cast iron. The decision method showed that white cast iron with high-chromium alloy had the highest weighted performance index (93.75%), while nodular graphite cast iron had the least weighted performance index (65.55%). High-chromium alloyed white cast iron was therefore considered as substitute for the grey cast iron corn-mill plates.

This study examined the effect of diaspora remittances on financial inclusion in Kenya for a quarterly period from 2008 to 2018. The Kenyan government’s commitment to include the Kenyan diaspora into the national development process led to the launching of Kenyan Diaspora Policy in 2015 as part of the Kenya’s vision 2030 blue print of which financial inclusion is a pillar. This study sought to check if the policy interventions achieved its objective by testing the moderating effect of Diaspora Policy on the relationship between diaspora remittances and financial inclusion. The descriptive research design specifically longitudinal and explanatory non-experimental designs were employed in this study. The target population for this study comprised the three million Kenyans living at the diaspora. The census and stratified sampling design were utilised where census method was first used to include the formal diaspora remittance inflows for the forty four quarterly period and then stratified into corridors for the period under study. Data from the Central Bank of Kenya and Kenya National Bureau of Statistics were analysed using time series multiple regression model. The results of the study showed that formal diaspora remittances received had a positive and statistically significant effect on financial inclusion. Formal diaspora remittances from Rest of the World greatly influenced financial inclusion. Remittance inflows from North America also influenced financial inclusion to some extent while formal diaspora remittances from Europe had no effect on financial inclusion in Kenya. Further, the study established that the moderating effect between formal diaspora remittances and financial inclusion was positive and statistically significant implying that the diaspora policy implemented by government greatly influenced diaspora remittances and financial inclusion in the right direction in Kenya. The study recommended among others, that government of Kenya continues to strategically strengthen the diaspora policies in order to increase the flow of diaspora remittances into the country to boost financial inclusion.

This study evaluated the hyperaccumulation potential of four indigenous plant species: Chromolaena ordorata (CO), Paspalum viginatum (PV), Chrysopogon zizanioides (CZ) and Cynodon dactylon (CD) using soil polluted by the illegal gold mining activities. Nine treatments were used in this study: Control, CO, CZ, PV, CD, CO+PV, CO+CD, CZ+PV and CZ+CD samples. The soils’ physico-chemical properties and the concentration of some selected heavy metals and metalloid (As, Cd, Cu, Ni and Pb) were determined. Plant growth and dynamics of pH, electrical conductivity and heavy metals and metalloid in the gold ore mined soil were monitored for nine weeks. Accumulation, bioaccumulation and translocation potentials were determined. The mined soil was loamy textured and acidic with pH ranging between 5.71 and 6.24. Soil organic carbon, total nitrogen and phosphorous contents were relatively low (0.21 %, 0.09 % and 4.79 mg/kg soil, respectively). Concentrations of Pb, Cu, Ni, As and Cd (40.22, 30.54, 23.58, 6.18 and 0.27 mg/kg, respectively) in the area were below the WHO permissible limits. CO+PV combination resulted in higher reductions in As, Cd, Cu, Ni and Pb (40.1, 53.1, 36.8, 29.3 and 41.2%, respectively) from the mined soil. All the investigated plant species recorded BR > 1 for Cd and BR < 1 for As, Cu, Ni and Pb. Therefore, all studied plant species are good phytoextractors for Cd.

The growing need to preserve our natural resources and protect the environment has resulted in a continuous effort to develop clean, renewable, and sustainable materials for energy storage and conversion. Supercapacitors (SCs) are electrochemical storage devices that have attracted the attention of the scientific community owing to their high power density, high charge/discharge efficiency, and relatively infinite cycle-life. Recent efforts have been devoted to the development of hybrid materials for supercapacitor electrodes by combining the properties of electric double-layer (EDL) and pseudocapacitive materials to improve energy density, capacitance, rate capability, and cycle-life. In this work, the electrochemical properties of a hybrid electrode made of activated carbon (AC) and titanium dioxide nanotubes (TNT) were assessed and compared to a pristine AC electrode. The AC/TNT and the 100% AC electrodes were prepared by electrophoretic deposition (EPD) using a reticulated vitreous carbon (RVC) substrate. The electrochemical behavior of the as-prepared electrodes was analyzed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Generally, the TNTs facilitated the EPD and enhanced the electrochemical performance of the as-prepared AC/TNT electrodes. The specific capacitances of the hybrid and pristine electrodes were 128.4 Fg−1 and 41.73 Fg−1 at 0.5 Ag−1, respectively.

Kaolin from Teleku Bokazo, a town in the Ellembele district of the Western Region in Ghana was used to synthesize zeolite by hydrothermal process and further modified with aluminium sulphate (alum). The kaolin and zeolite samples were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray fluorescence (XRF). The characterization processes were done to identify their composition, crystalline phases present, morphology, and to help determine if the synthesis and modification processes were successful. The as-synthesized zeolite and alum-modified zeolite were used for batch fluoride adsorption to compare their efficiency in removing fluoride ions from water. It was observed that the modified zeolite had the highest efficiency in removing fluoride ions from the contaminated water with a maximum of 98.87% removal. The Langmuir model best described the adsorption process with a maximum adsorption capacity of 2.43 mg/g.

This paper presents the results of an experimental study of the effects of biocyaniding with dried cassava leaves obtained from Manihot spp. with BaCO3 energizer. These are processed and used for the surface hardening of AISI 8620 steel. The case microstructures associated with carbo-nitriding are elucidated along with the effects of bio-cyaniding on the microstructure, microhardness and wear properties of the carbo-nitrided surfaces. The bio-processed waste (B-PW) was diffused (by heat treatment) into the surfaces of AISI 8620 steel using four different powder sizes (212, 300, 600 and 850 µm) and four different temperatures (750, 800, 850 and 900 °C). The resulting microstructures and micro-hardness profiles were then characterized along with the pin-on-disk wear behavior of the “case microstructures” that were formed. Superficial hardness and wear resistance were observed to increase with increasing particle size of B-PW and increasing pack cyaniding temperature. Finally, the wear mechanisms were also investigated by using scanning electron observations of the worn surfaces of the disks. The implications of the results are discussed for value addition to cassava waste.

Cassava-leaf-enhanced carbonitriding is a surface hardening procedure that utilizes the high cyanide content that is present in processed cassava leaves to thermochemically diffuse carbon and/or nitrogen into the interstitial sites of steel. This paper presents analytical models for the prediction of carbon and nitrogen concentration profiles, as well as the total case depths associated with the diffusion of carbon and nitrogen during the cassava-leaf-enhanced carbonitriding of low carbon steel. Using Fick's second law of diffusion and approximate initial and boundary conditions, two separate analytical models were presented for intermediate and high temperature cassava-leaf-enhanced carbonitriding processes. The trends in the total case depths are shown to be qualitatively similar to experimental measurements of case depths. The implications of the results are discussed for the surface hardening of steels by carbonitriding processes.

In this paper, ductile iron was produced using a rotary furnace. The microstructures of the ductile iron (with and without cyanided coatings) were then characterized using optical microscopy, scanning electron microscopy (SEM) and energy diffraction X-ray spectroscopy (EDS). The surfaces of the ductile iron were then subjected to high temperature carbonitriding using a pack cementation process in which carbon and nitrogen were diffused into the ductile iron from powder mixtures consisting of ground cassava leaves and barium carbonate (BaCO3) energizers. The wear behavior of the coated and uncoated ductile iron was studied using the pin-on-disk method. The wear mechanisms were also elucidated using a combination of SEM and EDS. The mechanisms of wear were also studied using nanoscratch experiments. The resulting wear rates are then compared with those from micron-scale wear tracks obtained from pin-on-disk experiments. The implications of the results are then discussed for the design of wear resistant ductile irons.

This paper presents a comprehensive review on surface hardening of ferrous materials using in- situ diffusion of nascent carbon and nitrogen from cyanide-based bio-processed cassava wastes with BaCO3and BaCl2energizers (bio-cyaniding). The review focuses on the research efforts on bio-cyaniding (also known as pack cyaniding) of iron and steel during the last decade. A brief description of the processes is elucidated along with the effects of bio-cyaniding on the microstructure, micro-/nano-hardness and wear properties of the bio-cyanided surfaces. Both intermediate-temperature bio-cyaniding (in-situ diffusion into ferrite) and high-temperature bio- cyaniding (in-situ diffusion into austenite) are also described. The bio-cyaniding hardening technique is compared with competing hardening techniques. It was concluded that the use of bio-cyaniding for the surface hardening of metals provides an alternative technique to the conventional surface hardening processes and offers potential advantages such as relatively low capital cost of the equipment, operating temperature and time.

This work investigates the physical, thermal and mechanical properties of thermal insulating bricks produced from Ghanaian red anthill clay (RAC) reinforced with sawdust, rice husk and their combinations. Mineralogical and chemical compositions using X-ray diffractometer (XRD) and X-ray fluorescence (XRF) techniques, respectively, were performed on the samples. 5, 10, 15 and 20 wt. % of reinforcements were used and the fabricated bricks were fired at 1200°C. Apparent porosity, bulk density, linear shrinkage, thermal conductivity, resistance to thermal shock and compressive strength of the samples were investigated. Results showed that the RAC composed of 52.35% silica and 31.16% alumina with a mineralogical composition of mainly quartz, kaolinite and iron oxide. Apparent porosity, linear shrinkage and resistance to thermal shock increased with an increase in weight percent of the additives while bulk density, thermal conductivity and compressive strength decreased with an increase in weight percent of additives. Results obtained indicated that the materials studied satisfy the physical, thermal and mechanical properties requirement for use as refractory material with the potential of improving the efficiency of refractory materials. Hence, these waste materials can be used in a sustainable manner for more productive applications.

This paper presents the results of experimental studies of the mechanical and physical properties of reprocessed polyethylene (PE) waste as reinforcement in laterite bricks for sustainable ...

This paper presents the results of an experimental study of nano- and macro-scale wear in a carbo-nitrided AISI 8620 steel. Carbo-nitriding is carried out using a novel method that involves the use of dried, cyanide-containing cassava leaves, as sources of carbon and nitrogen. These are used in a pack cementation that is used to diffuse carbon and nitrogen into case layers at intermediate temperatures [673.15 K, 723.15 K, 773.15 K, and 823.15 K (400 °C, 450 °C, 500 °C, and 550 °C)]. Nano- and macro-scale wear properties are studied in the case-hardened surfaces, using a combination of nano-scratch and pin-on-disk experiments. The measured wear volumes (at both nano- and macro-length scales) are shown to increase with decreasing pack cyaniding temperature. The nano- and macro-wear resistances are also shown to be enhanced by the in situ diffusion of carbon and nitrogen from cyanide-containing bio-processed waste. The underlying wear mechanisms are also elucidated via atomic force microscopy and scanning electron microscopy observations of the wear tracks. The implications of the results are discussed for the design of hardened carbo-nitrided steel surfaces with improved wear resistance.

This paper explores the indentation size effect (ISE) in pack carbo-nitrided AISI 8620 steel surfaces. The surfaces of the AISI 8620 steel samples were pack carbo-nitrided at 900 °C using cyanide-containing dried cassava leaves (bio-processed waste). This was achieved by quenching in different pH levels of cyanide-based bio-processed solution (BPS). Nanoindentation was carried out (using a Berkovich tip) on the surface modified steels. This was used to measure the hardness and reduced elastic moduli of the quenched-carbonitrided and the as-received steel surfaces. The surface-modified steel was shown to have higher hardness than the as-received steel. The hardness was also found to depend strongly on the indentation size. The paper also considers the potential contributions from microstructure, geometrically necessary dislocations (GNDs) and C/N diffusion on the measured hardness values. However, the measured ISEs are attributed largely to the role of GNDs that are modeled using the Nix and Gao mechanism-based strain gradient plasticity model. The implications of the results are then discussed for the design of hard carbo-nitrided steel surfaces.

This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs). The effects of impurities (within the possible interfaces) are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces) on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding) is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures.