Itzhak Shmulevich

Detection of fruit firmness by frequency analysis

High-value fresh agricultural products must maintain high quality standards and a predetermined shelf-life. Dynamic excitation and response sensing is an accepted method for the evaluation of fruit’s physical properties, quality, and shelf life. The purpose of the present study was to develop and evaluate a new nondestructive measuring technique of fruit firmness. The technique was based on mechanical impulse excitation, flexible piezoelectric film sensors and an FFT signal analysis method which was used to obtain the fruit’s resonance frequencies. Experiments with different geometrical configurations of the sensing elements, fruit mass, and impulse location were tested on three apple varieties. Results showed the potential of the new method to detect fruit firmness. The findings confirmed previous works on acoustical response of fruits and vegetables. The measuring technique was found to be simple, fast, and repeatable. Additional tests of large sample size and analysis by individual item are needed in order to develop reliable classification algorithms for various fruit species. Due to its simplicity, applications of the new technique may include on-line determination of firmness and shelf-life of fruit and vegetables.

Fourier Transform Infrared—Attenuated Total Reflection Nitrate Determination of Soil Pastes Using Principal Component Regression, Partial Least Squares, and Cross-Correlation

This paper investigates the use of Fourier transform infrared (FT-IR) attenuated total reflectance (ATR) spectroscopy as a fast and simple way for direct determination of nitrate concentration in soil pastes, which would assist precision fertilizer placement and reduce nitrate pollution. Eight types of soils are investigated, with nitrate concentrations ranging from 0 to 1000 ppm-N. The spectral region around the nitrate band (1300–1550 cm−1) is analyzed by (1) principal component regression (PCR), (2) partial least squares (PLS), and (3) cross-correlation with reference libraries that include spectra of pure ions and/or soils. The main obstacle to accurate nitrate measurement appears to be an interfering band present in calcareous soils. This band, which may be due to carbonate, is located around 1450 cm−1 and overlaps with the nitrate band centered around 1370 cm−1. For non-calcareous soils, and in particular for light sandy agricultural soils, PLS and cross-correlation with a reference library containing only spectra of ions in water give similar results (about 8 ppm-N on dry soil basis), while PCR leads to slightly poorer results. When calcareous soils are included in the analysis, the prediction errors are about twice as large. In this case, the best results are obtained using PLS, followed by PCR, while cross-correlation with reference libraries leads to poorer results.

PREDICTING SOIL-RIGID WHEEL PERFORMANCE USING DISTINCT ELEMENT METHODS

A two-dimensional discrete element model (DEM) for the interaction between a rigid wheel and soil is presented using PFC2D code. The soil particles are modeled by clumps of two discs. The contact model between the particles includes cohesion by a so-called softening model. The parameters of the model represent soil having a cone index (CI) of 200 kPa or 400 kPa. The model of the wheel is based on 30 grousers, spaced equally around a drum 200 mm in diameter and 100 mm in width. Dynamic simulations were performed with different combinations of drawbar force, vertical load, and soil conditions. The traction performance of the wheel was calculated, and the results were compared with known theories and reported test results. The simulation results show reasonably good correlation, quantitatively and qualitatively, with previously reported results and theories, and emphasize the ability of the DEM to simulate soil-wheel interaction for design purposes. Prediction of wheel performance as a function of slip for driven, self-propelled, and towed wheels is presented for different combinations of soil conditions and vertical loads. The ability to investigate soil deformation, stress distribution beneath the wheel, and the influence of slip on sinkage is shown. Contrary to the prediction of empirical theories, the simulations suggest that vertical load and soil CI have different influences on tractive performance; this point warrants further investigation. The model also predicts a different behavior of motion resistance and net traction at high slip rates compared with empirical and semi-empirical methods.

A new field single wheel tester

A new field single wheel testing device, as part of a field testing unit, was developed to perform traction tests on agricultural or cross country tires in the field. The tire testing device is mounted at the rear of a heavy wheeled tractor that also carries a unique soil property testing device at the front. The vertical, horizontal and side forces are measured inside a frame that holds the test wheel, while the torque is measured by a separate linkage system. The tire testing device is capable of testing tires up to 2 m in diameter; it can apply vertical force up to 50 kN, and torque up to 31 kNm.

Near infrared spectrometry of milk in its heterogeneous state.

Composition analysis by NIR spectrometry usually uses models that assume the sample to be homogeneous. However, agricultural fluid products are naturally heterogeneous, and in some cases of on-line sensing, it is very difficult to fulfill the homogeneity requirement, and some precautions are needed. The flow itself might create a non-uniform distribution of the measured ingredient concentrations across the cross-section of the flow. A modified discrete model was developed, which incorporates the concentration distribution of the ingredients. The effects of model parameters (number of layers and of iterations, valid ranges of absorbency and specular reflectance factors) were studied and evaluated. Samples of fresh raw milk were tested, in order to create a known distribution of the fat content in the sample, and were scanned by a NIR spectrometer. In the case of monotonic variation, along the sample, of the concentration of the measured ingredient (fat), the effect on the measured spectrum was similar to that of changes in the average concentration of a homogeneous sample. Comparison of the errors predicted by the model with the result of NIR measurements in heterogeneous conditions of fresh raw cows milk gave close correlation in their direction and their relative size. This created the basis for a technique to evaluate other fluids, in which the distribution of the concentration of the measured ingredient could be evaluated and incorporated in the model simulations.

The effect of velocity on rigid wheel performance

Abstract A simulation model to predict the effect of velocity on rigid-wheel performance for off-road terrain was examined. The soil–wheel simulation model is based on determining the forces acting on a wheel in steady state conditions. The stress distribution at the interface was analyzed from the instantaneous equilibrium between wheel and soil elements. The soil was presented by its reaction to penetration and shear. The simulation model describes the effect of wheel velocity on the soil–wheel interaction performances such as: wheel sinkage, wheel slip, net tractive ratio, gross traction ratio, tractive efficiency and motion resistance ratio. Simulation results from several soil-wheel configurations corroborate that the effect of velocity should be considered. It was found that wheel performance such as net tractive ratio and tractive efficiency, increases with increasing velocity. Both, relative wheel sinkage and relative free rolling wheel force ratio, decrease as velocity increases. The suggested model improves the performance prediction of off-road operating vehicles and can be used for applications such as controlling and improving off-road vehicle performance.

Determination of Soil Nitrate and Water Content Using Attenuated Total Reflectance Spectroscopy

Direct determination of nitrate and soil moisture can significantly improve N-application management and thus reduce N-derived environmental pollution related to agriculture. Several studies have shown that Fourier transform infrared attenuated total reflectance (FT-IR/ATR) spectroscopy could be used to estimate the nitrate content of standardized soil pastes. Paste standardization appeared to be the main obstacle to in situ application of this approach, and the present study shows how FT-IR/ATR can be used to estimate both water content and nitrate concentration of field soil samples. Water content and nitrate concentration are determined sequentially using two subsamples of the initial soil sample. An a priori determined amount of highly concentrated nitrate solution is added to the first subsample and the ATR spectrum of this paste is used to estimate the sample water content. It is then possible to calculate the amount of water that should be added to the second subsample so that the resulting paste is very close to the ideal standard paste. Nitrate concentration, mg [N]/kg [dry soil], is estimated using the FT-IR/ATR spectrum of this second paste. Results are presented for a laboratory experiment with four agricultural soils, as well as for a field trial with a calcareous soil. For water content, the determination errors range from 0.01 to 0.02 g [water]/g [dry soil]. For nitrate concentration, the errors for three of the soils range from 5.9 to 8.4 mg [N]/kg [dry soil], while for the fourth, calcareous clay soil, the determination error is 13.6 mg [N]/kg [dry soil]. The determination errors obtained for the field trial are similar to the ones obtained for a similar soil under laboratory conditions, which shows the potential usefulness of the approach for improving N-application management and reducing environmental pollution.

Processing techniques for ethanol production from sweet sorghum.

Abstract Several processing techniques for producing ethanol from sweet sorghum were investigated. Fermenting chopped stalks yielded more ethanol than shredded sorghum or juice. Leaf removal prior to fermentation yielded slightly more ethanol than solids removal before fermentation.

Prediction of Soil-Bulldozer Blade Interaction Using Discrete Element Method

Modeling the interaction between soil and a tillage implement, such as a bulldozer blade, is a complex task, involving many factors, such as ground layout, soil strength, soil buildup in front of the tool, soil flow, and cracks that may occur in the soil during blade work. The discrete element method (DEM) is a numerical tool designed to model granular materials. Soil, and particularly sandy soil, may be described as a granular material. Therefore, DEM seems to be a promising tool for modeling the interaction between a blade and soil. The model parameters are usually set using a trial-and-error process, as there is no robust theory for determining the soil parameters of the model. This article suggests a method for determining the parameters for the DEM model and simulates the soil-blade interaction of cohesionless soil, as a case study, using a 2D DEM program (PFC2D). The method is based on the interlocking property of the particles. The maximum error of the parameters obtained by the method compared with the actual soil parameters was 22.8%. Selecting the optimum spring constant between the particles may reduce the error. Two-dimensional simulations were performed of a bulldozer blade moving in a particle medium, working at different blade angles and depths, and in different soil parameters. Comparing the simulations with the prediction results using McKyess calculation model, the DEM model predicted an average draft force 7.2% greater than, and an average vertical force 1.7% less than, the forces predicted by McKyess approach. The failure line was defined in the simulation according to the differences in particle velocities; the results fit the prediction of the failure line according to McKyess approach. The contribution of this article lies in the use of DEM as a qualitative and quantitative predictive simulation tool.

Tire footprint characteristics as a function of soil properties and tire operations

The main objective of the following presentation is to examine the possibility of predicting agricultural tire footprint parameters under different operational conditions. The experimental part of the research involved the operation of two agricultural transport tires on two soils, under variations of tire load, inflation pressures and soil moisture contents. Results obtained show that tire footprint parameters, such as contact area, length, width and sinkage, can be reliably predicted using multifactorial linear and total regressions, within the range of recommended tire loads, inflation pressures and soil moisture contents around the plastic limit.