Land types and sustainable cocoa production: Lessons from GIS Application

Sustainable cocoa production demands a range of biophysical conditions of land. The paper reports on the levels of sustainability of cocoa production on different soil types under different tree cover intensities. Geographic Information System (GIS) analytical functionalities were extensively applied in the study. The spatial distribution of cocoa was modeled from geo-located samples, and related to tree cover generated from Landsat ETM+ image for 2000 and soils types. There was a strong spatial association between cocoa density-distribution surface, soil types and tree cover. It was observed that soils that are naturally suitable for cocoa were still supporting extensive cocoa farms, whereas unsuitable lands that were initially cultivated with cocoa had only remnant or no cocoa farms. The outcome of this study indicates that decisions for cocoa cultivation should be informed by accurate information on the suitability of lands for sustainable production

An experimental set up to probe the quantum transport through single atomic/molecular junction at room temperature

Understanding the transport characteristics at the atomic limit is the prerequisite for futuristic nano-electronic applications. Among various experimental procedures, mechanically controllable break junction (MCBJ) is one of the well adopted experimental technique to study and control the atomic or molecular scale devices. Here, we present the details of the development of a piezo controlled table top MCBJ set up, working at ambient condition, along with necessary data acquisition technique and analysis of the data. We performed conductance experiment on a macroscopic gold wire, which exhibits quantized conductance plateau upon pulling the wire with the piezo. Conductance peak up to $\sim 20 G_0$ ($G_0 = 2e^2/h$, $e$ being the electronic charge and $h$ being the plank's constant) could be resolved at room temperature. A well-known test bed molecule,$4, 4^\prime$ bipyridine, was introduced between the gold electrodes and conductance histogram exhibits two distinctive conductance peaks, confirming the formation of single molecular junction, in line with the previous reports. This demonstrate that our custom-designed MCBJ set up is capable of measuring quantum transport of a single molecular junction at ambient condition.Comment: 15 pages, 8 figure

Mathematical modelling of peritectic transformation in binary systems

A simple diffusional analysis of peritectic transformat-ion based on the linearized concentration gradient approximation and a rigorous numerical model of the peri-tectic transformation as well as the solid state homo-genization process following liquid depletion has been presented.The overall and interface mass balance equations are utilized to calculate the rate of movement of the interfaces in the finite geometry. The predictions of the present models, show a better agreement with the experi-mentally determined kinetic data from the Cd-Ag and Pd-Bi systems as compared to those by the earlier proposed 'models based on quasi-static interface or time-invariant or Laplacian concentration profiles. However, the computed kinetics differ from the observed rates of transformation at a later stage (-50% transformation), perhaps, due to the deviation from the idealized cell configuration consi-dered in the calculations

Initiation sites for discontinuous precipitation in some Cu-base alloys

A systematic effort has been made to investigate the suitability of various interfaces, natural as well as artificial, to initiate discontinuous precipitation. The interfaces studied in the present investigation include sample surface (external), and grain and interphase boundaries. It has been demonstrated that in addition to grain boundaries, non-conventional initiation sites like coherent faces of a twin or eutectic/eutectoid boundaries under favourable conditions may also nucleate discontinuous precipitation. In general, the ability of an interface to undergo thermally activated migration appears to be the most important criterion for the initiation of discontinuous precipitation

Linking Optical SPOT and Unmanned Aerial Vehicle data for a rapid biomass estimation in a Forest-savanna Transitional Zone of Ghana

The direct estimation of biomass using remote sensing technologies, such as LiDAR, RaDAR and Stereo Data is limited in utility, since it does not allow for historical analysis of biomass dynamics far back in time due to their recency in development. This study links Unmanned Aerial Vehicle (UAV)-measured tree height and optical SPOT image reflectance in a mathematical model for a quick and less expensive indirect biomass estimation, and the possibility of historical analysis using the earliest captured optical data. SPOT 6/7 images were used to map land-use/cover patterns. A Phantom 4 drone images were used for height and crown width estimation. A stepwise regression analysis was conducted to establish a relationship between SPOT 6/7 channels and the UAV-generated tree heights. The linear model was used to convert the reflectance values of SPOT images into tree heights, and in turn used for crown width estimation. The estimated tree height and crown width images were used to estimate biomass using an allometric equation. There was no statistically significant difference between UAV and manual tree height measurements. UAV-estimated tree height predicted 88.0% of crown width. Regressing the tree height on the SPOT bands yielded an R2 of 66.0%. It is recommended that further studies be conducted to improve on the accuracy of estimation. It is hoped this would facilitate a quick biomass estimation and long term historical dynamics

Adaptive strategies of smallholder farming systems to changing climate conditions in the vicinity of Kogyae Strict Nature Reserve within the Forest-Savanna Transitional Zone of Ghana

The strong climate linkages to farming systems render them and dependent communities vulnerable to climate change and variability. Knowledge of existing responses to climate change is important for the formulation of policies and adaptive strategies for resilience. The paper examines a fifty-year climatic record from 1961-2011, community perceptions, experiences and knowledge for evidence of climate change and impacts. Climate change-driven farmer adaptive responses were critically examined relative to farming practices; and crop climatic requirements for growth, development, maturity and harvesting. A mixed methodological approach was adopted to address issues of climate change, exposures, sensitivities and adaptive responses. The results showed that the area has experienced a steady rise in temperature, reduced rainfall amounts of 3.0mm per annum, reducing events of rainfall excesses and increasing deficits, narrowing of rainfall period and a shift of the double to a single rainfall maxima regime. Farmers have observed these patterns of changes and experienced the impacts. Consequently, evidence-driven adaptive responses in the transformation of farming practices, timing of cultivation and choice of crops have been developed by farmers. It is recommended that further adaptive strategies be planned to improve farmers’ adaptive capacities and reduce sensitivity of crops to climate perturbations

Mechanism and kinetics of type II discontinuous coarsening in a Zn-4 at% Ag alloy

Discontinuous coarsening (DC) may succeed discontinuous precipitation (DP) either at the same (DCI) or another temperature (DCII). The present study concerns mechanism and kinetics of DCII in a Zn-4 at% Ag alloy in the range 353-513 K following DP at 393 K for 60 h. DCII colonies prefer to initiate either from one or both sides of the interfaces between the former DP colonies. A suitable comparison of the kinetic data reveals that interlamellar spacing (λ) and steady-state growth velocity (v) values in DCII are significantly different than those in DP. On the other hand, the kinetics of DCIvis-a-vis DCII in terms of λ and v are comparable to each other, though the calculated values of the driving forces between them differ marginally. A detailed kinetic analysis of DCII through the Livingston-Cahn model leads to an underestimation of the activation energy (Q b) of grain boundary chemical diffusion of Ag in Zn-Ag (=30.7 kJ mol-1), whereas the same obtained from the modified Petermann-Hornbogen model (=61.0 kJ mol-1) compares well with that for DP/DCI (reported elsewhere by us), and grain boundary self diffusion of Zn. Considering thatQ b in DCII is nearly 50% of the activation energy for volume/matrix diffusion of Ag in Zn, it appears that DCII in the present alloy is a boundary diffusion controlled process

Structure of nanocomposites of Al-Fe alloys prepared by mechanical alloying and rapid solidification processing

Structures of Al-based nanocomposites of Al-Fe alloys prepared by mechanical alloying (MA) and subsequent annealing are compared with those obtained by rapid solidification processing (RSP). MA produced only supersaturated solid solution of Fe in Al up to 10 at.% Fe, while for higher Fe content up to 20 at.% the nonequilibrium intermetallic Al5Fe2 appeared. Subsequent annealing at 673 K resulted in more Al5Fe2 formation with very little coarsening. The equilibrium intermetallics, Al3Fe (Al13Fe4), was not observed even at this temperature. In contrast, ribbons of similar composition produced by RSP formed fine cellular or dendritic structure with nanosized dispersoids of possibly a nano-quasicrystalline phase and amorphous phase along with α-Al depending on the Fe content in the alloys. This difference in the product structure can be attributed to the difference in alloying mechanisms in MA and RSP

Codeposition of nanocrystalline aluminides on a copper substrate

The present study concerns codeposition of nanocrystalline aluminide particles (NbAl3 and Cu9Al4) along with electrodeposition of Cu on a Cu substrate. It is shown that the success of codeposition primarily depends on the selection of an appropriate electrolyte. Following codeposition under an optimum deposition condition, the microstructure, phase identity and composition of the deposit layer have been studied. In addition, microhardness and electrical resistivity of the deposit have been determined. A suitable correlation of the microstructure and composition of the deposit with its properties suggests that codeposition of NbAl3 is more effective in enhancing the hardness. However, codeposition beyond a limit adversely affects the electrical conductivity. The optimum conditions for codeposition to enhance hardness without adversely affecting conductivity have been determined. Finally, it is predicted codeposition could be a suitable technique for developing a surface composite microstructure with uniform distribution of nanocrystalline aluminide particles

Prediction of Solubility of Carbonitrides in High Strength Low Alloy Steel

High Strength Low Alloy Steels are of particular interest for large submarines, offshore structures, line-pipe and other structural applications that require a combination of strength and toughness