Estimating forage quantity and quality under different stress and senescent biomass conditions via spectral reflectance

Assessing forage quantity and quality through remote sensing can facilitate grassland and pasture management. However, the high spatial and temporal variability of canopy conditions may limit the predictive accuracy of models based on reflectance measurements. The objective of this work was to develop this type of models, and to challenge their capacity to predict plant properties under a wide range of environmental conditions. We manipulated Paspalum dilatatum canopies through different stress treatments (flooding, drought, nutrient availability, and control) and by artificially varying the amount of senescent biomass. We measured canopy reflectance and constructed simple models, based on either normalized vegetation indices or a few selected wavebands, to estimate biomass and two variables related to forage quality: proportion of photosynthetic vegetation and biomass C:N ratio. General models satisfactorily predicted plant properties for the whole set of environmental conditions, but failed under specific conditions such as drought (for estimates of plant biomass), fertilization (for estimates of C:N ratio), and different levels of senescent tillers (for estimates of the proportion of photosynthetic vegetation). Where general models failed, specific models, based on different bands, achieved satisfactory accuracy. The general models performed better when based on a few selected bands than when based on two-band vegetation indices, having better accuracy (higher R²) and parsimony (lower BIC). However specific models performed similarly for both approaches (similar R² and BIC). These results indicate that these plant properties can be predicted from reflectance information under a broad range of conditions, but not for some particular conditions, where ancillary data or more complex models are probably needed to increase predictive accuracy.     

Experimental Study of an Adding Interferometer at Millimeter Waves

In order to study an original detection architecture for future cosmology experiments based on wide band adding interferometry, we have tested a single baseline bench instrument based on commercial components. The instrument has been characterized in the laboratory with a wide band power detection setup. A method which allows us to reconstruct the complete transfer function of the interferometer has been developed and validated with measurements. This scheme is useful to propagate the spurious effects of each component till the output of the detector.     

Rural electrification systems based on renewable energy: The social dimensions of an innovative technology

Many areas in rural non-Western regions are installing electrification systems based on renewable energy. Although these projects are usually welcome, they sometimes fail. Explanations for failures often cite technical reasons. In this research, partly based on the results of the SOPRA_RE project, we focus on the users, studying the relationships between technology and society. By analysing potential sources of failures, we identify the root of the problem as how a new technology is received by the local society. In this paper we introduce dimensions that we consider to be especially important in the process of technology integration. We defend the importance of combining the technical outlook with the sociological one, based on the idea that the latter is often indispensable as a complementary element of technical explanations of system failures, which in turn provides a better basis for solving them. We use specific examples to bolster our insistence on the need to achieve convergence between the technical and the sociological outlooks.     

An improved formula for the determination of the polysilicon doping

This letter describes an improved formula for the extraction of the polysilicon doping from the C-V characteristic of MOS transistors. Analytical approximations are presented for the inversion layer contribution, which was neglected in previous work. The new approach returns an estimate error smaller than 10% when the full substrate and poly quantization are accounted for. Practical application to experimental data is also addressed     

Optimization of a process for the synthesis of a sperm whale oil analogue

The development and optimization of the synthesis of an analogue of sperm whale oil have been carried out. The product is an ester with characteristics similar to those of natural sperm whale oil. A central composite design was applied in the synthesis of this fine chemical. The variables selected for the present study are reaction temperature, initial concentration of catalyst and working pressure. Temperature is the most significant factor in the esterification process, and its influence is positive. Pressure influence can be neglected, and the catalyst concentration has a positive influence on the process. Depending on the temperature value, the influence of the interactions can be more important than that of the other two main effects, pressure and catalyst concentration. Response surface models have been found adequate to represent the yield of ester. The commercial quality of the synthesized product is very similar to that of natural spermaceti. Because of its low cost, this synthesis process is considered, from an economical point of view, very attractive.     

Structural changes in sardine (Sardina pilchardus) muscle during iced storage: Investigation by DRIFT spectroscopy

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used for the first time to evaluate the postmortem changes in structure of components from sardine muscle in relation to quality loss. Sardines (Sardina pilchardus) were stored in ice for up to thirteen days. The spectroscopic study was focussed on the structural changes produced on the lipids and proteins.     

Fast,clean, low-cost screening of cadmium and lead in the mussel Mytilus galloprovincialis Lmk. by visible spectroscopy and partial least squares regression

The potential of visible (VIS) spectroscopy for screening cadmium and lead contents in the mussel Mytilus galloprovincialis Lmk. was assessed. The spectra of the samples were recorded (400–700 nm). The Cd and Pb contents were determined by graphite furnace atomic absorption spectroscopy, and were regressed against different spectral transformations by modified partial least square (PLSm) regression. Coefficients of determination in the cross-validation (Cd = 0.95; Pb = 0.77) were indicative of equations with excellent and good quantitative information, respectively. The standard deviation to standard error of cross-validation ratio (Cd = 4.43; Pb = 2.10) showed sufficient predictive accuracy for the equations to be used for screening purposes. PLSm loading plots corresponding to the first terms of the equations showed that chromophores influenced them significantly. This pioneering use of the VIS spectrum to predict Cd and Pb in mussels represents an important saving in time and cost of analysis in comparison to other methods.     

Equilibrated strategy for population variance estimation

Summary Under the hypothesis that a statistical population can be represented by a density function in a similar way to that of the optimum stratification problem dealt with in Dalenius (1957) and Dalenius and Hodges (1959) the estimation of the population variance is analysed by means of the technique of equilibrated stratification. An unbiased estimator is suggested and it is shown that, with optimum allocation, the precision of the estimator for sufficiently large sample size is always at least that of the classical minimum variance unbiased estimator for a distribution-free setting. A numerical study complete the article.     

Microstructural evolution during upward and downward transient directional solidification of hypomonotectic and monotectic Al–Bi alloys

Upward directional unsteady-state solidification experiments were performed with both a hypomonotectic Al–2.0 wt% Bi alloy and a monotectic Al–3.2 wt% Bi alloy. Besides, the monotectic composition (3.2 wt% Bi) was directionally solidified under downward transient heat flow conditions, which enables the effects of melt convection on the final microstructure to be evaluated since the collective downward movement of Bi-rich particles is favored in such case. This is due to the density differences between the two coexisting liquid phases. The thermal parameters such as cooling rate, growth rate and thermal gradient were experimentally determined by data collected from cooling curves recorded along the casting length. The monotectic features observed in the Al–3.2 wt% Bi alloy castings, i.e. the interphase spacing and Bi-rich particles diameter were correlated with the growth rate and thermal gradient. The cell spacing was experimentally determined for the Al–2.0 wt% Bi alloy as a function of both the cooling rate and tip growth rate. These experimental data were compared with the main predictive cellular growth models from the literature. A comparison between upward and downward unsteady-state solidification results for the interphase spacing and Bi-rich particles diameter has also been conducted.     

Dual-mode design of fully differential circuits using fully balanced operational amplifiers

Fully differential (F-D) analogue circuits are usually designed focusing only on their differential-mode (DM) behaviour, without considering common-mode (CM) responses. A technique is presented for the design of both DM and CM circuit responses, using fully balanced operational amplifiers (FBOAs) as analogue building blocks. FBOAs work with CM and DM voltages as a whole, having an ideally infinite gain for both modes. This allows independent design of CM and DM dynamics. Inverting and non-inverting F-D topologies can be implemented in a simple way, similar to the implementation of their single-ended counterparts. Some typical application circuits are analysed and discussed and, as a design example, a 'double-mode oscillator' (a circuit that has independent CM and DM oscillations) was built and experimentally evaluated.