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•A device based on a NIR camera and a Xenon lamp was set up for kiwifruit assessments.•Image analysis was conducted according to the distribution of the gray pixel.•Kiwifruit firmness ...models were built by exploring univariate, PLS and ANN tools.•PLS model allowed firmness prediction of with R2 of 0.777 (RMSE = 13 N).•Sugar content appeared less correlated with optical parameters respect to firmness.
A prototype based on a NIR sensitive camera and a Xenon lamp was set up and used to capture 8 bit gray scale (from 0 = black to 255 = white) image of the radiation that passes through the fruit. The count of the pixels with different gray tone was used to build statistical-mathematical models to correlate and predict the kiwifruit flesh firmness. One hundred sixteen fruits conveniently stored to obtain firmness within a range of penetrometric force from 0.8 N to 87 N, were submitted to the optical measurements. Simple regression between the gray tone having the maximum number of pixels and the firmness showed an exponential correlation with R2 values of 0.717. On the contrary, the tone uniformity (maximum number of pixels with the same gray tone) resulted linearly correlated with hardness (R2 = 0.687). PLS algorithm allowed prediction of the flesh firmness with R2 of 0.777 (RMSE = 13 N). Artificial neural networks produced similar results. Although the current technique does not fully satisfies the need of an accurate selection, it could be considered for on-line applications by improving performances (e.g. acting on lamp spectral emissions and camera detection) and with easy mechanical modifications of the sorting lines.
Manipulation of populations of living cells on an individual basis is essential for the investigation of complex interactions among cells. We present a new approach to the integration on silicon of ...dielectrophoretic actuators and optical sensors that allow us to carry out this task. The device presented in this paper is an 8/spl times/8 mm/sup 2/ chip implemented in a two-poly three-metal 0.35-/spl mu/m CMOS technology, featuring 102,400 actuation electrodes, arranged in an array of 320/spl times/320, 20 /spl mu/m/spl times/20/spl mu/m microsites each comprising addressing logic, an embedded memory for electrode programming, and an optical sensor. The chip enables software-controlled displacement of more than 10,000 individual living cells, allowing biologists to devise complex interaction protocols that are impossible to manage otherwise. The manipulation does not damage the viability of the cells, so that this approach could be a unique extension to the techniques already available to biologists.
How dynamic ranges (DRs) of single stages are combined together in a sensor acquisition chain are shown. This is a key feature in sensor design, since it shows a simple way to understand how and ...where the DR has been enhanced or deteriorated along the chain. The relationship devised is applicable to any kind of transducing processes such as the mechanical one as implemented by micro- and nano-electro-mechanical devices.
•A non-invasive soil moisture sensing based on combining dielectric spectroscopy with multivariate analysis is proposed.•Gain and phase spectra are tested on river sand, LECA and silty clay loam ...soils.•Estimation of moisture content (%) for both non-layered and layered soils id demonstated.•PLS regression shows R2 up to 0.989 for river sand gain (RMSE=0.8%).•NPLS regression increases the accuracy of the prediction for all types of soil.
In this paper, we demonstrate the effectiveness of multivariate analysis to increase the performance and reliability of a novel method for a non-invasive sensing approach for measuring gravimetric soil moisture. Unlike time and frequency domain spectrometers, as well as impedance sensors, where probes should be inserted into the terrain, the proposed approach simply uses a waveguide faced to the soil surface. An open-ended waveguide spectrometer system was developed to acquire “gain” and “phase” spectra, related to received and transmitted signals, in the 1.5–2.7GHz range from river sand, lightweight expanded clay aggregate (LECA) and silty clay loam soil samples. For each soil type, predictive models of the moisture (%) were obtained and discussed by using multivariate tools (Principal Component Analysis, Partial Least Square Regression and N-dimensional Partial Least Square Regression). The potentiality of the measurement technique was explored for both non-layered (homogeneous moisture) and layered (two layers with different, homogeneous moisture) soils. In validation tests, R2 values up to 0.989 (RMSE=0.8%, river sand gain) were observed for single layer test. For double layer test, R2 values up to 0.977 (RMSE=1.4%, LECA gain, top layer) and 0.962 (RMSE=1.9%, LECA gain, bottom layer) were obtained. A better accuracy was achieved with N-PLS combining “gain” and “phase” spectra: R2 values increase up to 0.991 (RMSE=0.9%, LECA samples). The measurement results demonstrate that the non-invasive waveguide-based spectrometry together with the multivariate analysis is able to assess different moisture contents, with a high level of accuracy, both for non-layered and layered samples of soil with homogenous moisture.
•Gain and phase signals were acquired on soil samples from 1.0 GHz to 2.7 GHz.•Silty clay loam soil, river sand and lightweight expanded clay aggregate samples were assessed.•Kernel-based orthogonal ...projections to latent structures algorithms (K-OPLS) were explored.•Multivariate prediction models of the soil moisture content (%) were set up and discussed.•Respect to PLS.K-OPLS allows to greatly improve the accuracy independently on the kind of soil.
In this paper we will show the boosting performance of nonlinear machine learning techniques applied to a novel soil moisture sensing approach. A probe consisting in a transmitting and a receiving dipole antenna was set up to indirect assess the moisture content (%) of three different types of soils (silty clay loam, river sand and lightweight expanded clay aggregate, LECA). Gain and phase signals acquired in the 1.0 GHz – 2.7 GHz frequency range were used to built predictive models based on linear PLS regression and on nonlinear Kernel-based orthogonal projections to latent structures (K-OPLS) algorithms. K-OPLS algorithm slightly increased the accuracy of the models built on the gain response on specific kind of soils with respect to classical linear PLS. However, the predictability increases significantly in the case where the models are built starting from a matrix containing all the considered soil samples (silty clay loam + river sand + LECA) achieving R2 = 0.971 (RMSE = 1.4%) when using K-OPLS non-linear model with respect to R2 = 0.513 (RMSE = 6.1%) obtained using linear PLS. Therefore, K-OPLS algorithm appears to give a significant improvement to modelling data where nonlinear behaviours occur.
•A vector impedance analyser based on delta-sigma conversion.•i) low-power, ii) high-integration, iii) multi-parameter and iv) high-accuracy.•4-Core prototype on a 3 × 6-cm PCB board: power <500 mW; ...mean uncertainty <0.14%.•Indirect estimate of TDS deviates from reference value by less than 1.2%.
Distributed measurements are important in many application fields, from environment to biomedicine. In both cases, the sensor nodes employed in the measurement network have to satisfy many requirements; among them, the most important ones are: i) low power consumption, ii) miniaturization, iii) adequate accuracy, and iv) capability of multi-parameter measurement. This paper presents a Vector Impedance Analyser (VIA) architecture that satisfies these main requirements. The architecture is specifically devised to be interfaced with an array of impedimetric sensors for environmental applications, such as distributed water monitoring, or for mobile-Health/wearable biomedical devices. The proposed architecture is based on delta-sigma digital-to-analogue (D/A) conversion for the generation of the low-noise excitation and on band-pass delta-sigma analogue-to-digital (A/D) conversion for the low-power and high-accuracy acquisition of the impedimetric sensor response. The proposed combination of delta-sigma D/A and A/D conversion allows to i) implement many measurement cores in a single silicon chip with reduced dimensions, ii) achieve a fair accuracy/power trade-off, and iii) tune the operative frequency in real time so as to span the target portion of the frequency domain.
A prototype of the VIA is implemented in a 3 × 6-cm PCB board to investigate the potentialities of the architecture. The low-noise analogue circuits of the architecture are implemented in an Application Specific Integrated Circuit (ASIC), while part of the digital circuits are implemented on a commercial microcontroller for better testability purposes. The prototype embeds four independent cores to allow real-time multi-parameter measurement. To prove the performance of the proposed VIA, the prototype is characterized in terms of noise (input-referred noise between 20 mΩ and 70 mΩ in 10-Hz bandwidth, i.e. from 25 to 92 ppm of the full scale), accuracy (average uncertainty of 0.14% of the full scale for the magnitude and 0.72° for the argument, accounting for the limited accuracy of the reference instrument used for calibration), and power consumption (approximately 125 mW per-core including the power consumption of the microcontroller and the ancillary circuits used for power management and communication). The multi-parameter measurement capability is demonstrated by the realistic case-study of estimating the concentration of total dissolved solids in a potassium chloride (KCl) solution by means of direct concurrent measurements of conductivity and temperature.
The spinning-current technique is the state-of-the-art method for offset cancellation in Hall-effect probe. This technique achieves the best results in terms of offset reduction but limits the ...acquisition bandwidth to less than 1 MHz; therefore, it precludes the use of purely Hall-effect sensors in broadband current measurement. We present the X-Hall probe, a DC bias approach combined with an octagonal 8-contact morphology of the Hall-effect probe, which overcomes the bandwidth limitations of spinning-current-operated Hall sensors while reducing the offset. A prototype of the X-Hall probe is realized in CMOS-like technology and can potentially achieve a bandwidth wider than 40 MHz with an acceptable residual offset.
•Architecture and related operation for low-noise broadband digital picoammeter.•The architecture overcomes conventional noise-performance/bandwidth trade-off.•Study of time-variance in periodically ...reset measurement architectures.•Compact and low-cost picoammeter prototype.•Low noise (⩽4fA/√Hz) broadband (⩾100kHz) current measurements.
A low-noise (⩽4fA/√Hz), broadband (⩾100kHz) compact architecture and related operation solutions are proposed for portable and low-cost time-domain acquisition of currents with effective resolution in the order of 1pA and below. The front-end architecture is based on an integrating-differentiating scheme to achieve the optimal performance in terms of input-referred equivalent noise, but it overcomes the typical noise/bandwidth trade-off by making the sampling frequency of the A/D conversion independent from the rate at which the analog front-end is reset. In order to strongly mitigate the main drawback, i.e., the introduction in the system of an inherent time-variance, a Track-and-Hold circuit synchronized with the reset is exploited.
For validation purposes, a dual-channel prototype was implemented in a low-cost CMOS technology. The prototype is characterized by standard figures of merit and is experimentally validated by two simple case studies, which are typical of practical applications.
Presents a lab-on-a-chip for electronic manipulation and detection of microorganisms based on the use of closed dielectrophoretic (DEP) cages combined with impedance sensing. A printed circuit board ...(PCB) prototype has been used to trap, concentrate, and quantify polystyrene micro-beads in agreement with CAD simulations. The experiment was successfully repeated with S. cerevisiae. The results prove the effectiveness of the approach for particle manipulation and detection without the need for external optical components nor chemical labeling. With the proposed approach, particle concentration may be increased on-chip of more than three orders of magnitude, correspondingly boosting the detection sensitivity.
This paper presents a self-powered energy harvesting circuit based on synchronous charge extraction with a single shared inductor for power conversion from arrays of independent piezoelectric ...transducers. The number of handled elements can be easily increased at the expense of few additional components and without affecting performance. The energy harvesting circuit was characterized with three 0.5 × 12.7 × 31.8 mm 3 piezoelectric cantilevers subject to different types of vibrations. Throughout all operating conditions, the circuit was able to extract the maximum power independently from every transducer. Compared to passive energy harvesting interfaces, the output power is significantly higher, with worst-case increases ranging from +75% to +184%. The circuit starts up passively and is based on ultralow power active control, which consumes during operation at 3 V a fraction of the extra harvested power as low as 10 μW per source. As part of the best tradeoff between harvested and intrinsic power, an overall energy efficiency up to 74% was achieved.
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