Tesaf

Lo scritto analizza quali lezioni possono essere tratte da episodi di contaminazione derivante dai PFAS. Le sostanze chimiche immesse nelle matrici ambientali da parte della fabbrica Miteni in Veneto ci permettono di evidenziare come le autorità pubbliche hanno reagito, come hanno gestito la situazione e, di conseguenza, l'emergere di una crescente preoccupazione per un ambiente sano. Questo breve saggio riepiloga gli eventi, una storia di sottovalutazione degli effetti di questi inquinanti molto persistenti, al fine di ottenere degli ammonimenti utili per il futuro.

La contaminazione da PFAS, anche detti Forever Chemicals, impone un ripensamento delle tradizionali categorie e dell'usuale strumentario del diritto. Una sfida che ha già messo in luce una serie di contraddizioni insite nel nostro sistema sociale e normativo, evidenziando criticità e debolezze. Fra i numerosi aspetti che si potrebbero illustrare, ne spicca uno in particolare, ovvero la sussistenza di profonde asimmetrie di potere e di posizione tra le parti interessate ed intaccate. Asimmetrie informative legate alle modalità di comunicazione e ai destinatari delle informazioni riguardo effetti e portata della contaminazione; asimmetrie conoscitive, connesse al fenomeno della mancata divulgazione dei dati-sovente qualificati come dati aziendali confidenziali, relativi a produzione e gestione dei PFAS nonché agli impatti sulle matrici ambientali, da parte delle big corporations; asimmetrie di potere negoziale, riscontrabili in termini di posizione e ruolo nell'arena pubblica e nell'agenda pubblica, stante il peso specifico di attori, interlocutori e collaboratori; asimmetrie temporali, legate alle diverse proiezioni nel tempo e alla capacità di risposta o di rallentamento di azioni e reazioni; asimmetrie spaziali, dato che i confini geografici della contaminazione non sono chiaramente sovrapponibili ai confini amministrativi; asimmetrie organizzative e normative, come il tema dei limiti, della regolazione e della responsabilità per danno ambientale tristemente testimoniano.

A mathematical model was developed to correlate the four heat penetration parameters of 57 Stumbo’s tables (18,513 datasets) in canned food:g(the difference between the retort and the coldest point temperatures in the canned food at the end of the heating process),fh/U(the ratio of the heating rate index to the sterilizing value),z(the temperature change required for the thermal destruction curve to traverse one log cycle), andJcc, (the cooling lag factor). The quantitiesg,z, andJcc, are input variables for predictingfh/U, whilez,Jccandfh/Uare input variables for predicting the value ofg, which is necessary to calculate the heating process timeB, at constant retort temperature, using Ball’s formula. The process time calculated using thegvalue obtained from the mathematical model closely followed the time calculated from the tabulatedgvalues (root mean square of absolute errors RMS = 0.567 min, average absolute error = 0.421 min with a standard deviation SD = 0.380 min). Because the ...

In order to evaluate the effects of the variation of two factors of the working condition, the trajectory angle and the nozzle height from the ground, on the water distribution radial curve of a sprinkler, a mathematical model, able to elaborate with a very good accuracy the size spectrum of droplets generated by a nozzle starting from experimental water distribution radial curves, was used and applied in reversed form. In a previous paper, 37 dimensional droplet spectra were obtained, generated by four sprinklers under varying conditions of operating pressure and nozzle size, but with a single value of trajectory angle and a single value of the nozzle height from the ground level. The application of the mathematical model to the 37 dimensional spectra of the droplets has led to new water distribution radial curves on varying the trajectory angle and the nozzle height. The evaluation of these curves, along with original and experimental ones, has been made using the uniformity of distribution, by means of Christiansen's coefficient CU. Increasing values of pressure and nozzle size provide the best CU. This is applied to all heights of the nozzle from the ground and to almost all trajectory angle values. In all cases, different nozzle heights do not show significant differences in CU values. This also occurred in the comparison of three different trajectory angles, unless the larger diameter and lower height of the nozzle where the CU coefficient gets worse with decreasing the trajectory. The evaluation of the new water distribution radial curves was also made in relation to the produced radius of throw R (m), and it was found that R is positively influenced by all the variables involved. Considering this relationship, two monomial type equations (one for nozzle discharge up to 120 dm 3 /min and radius of throw less than 30 m and one for nozzle discharge above 120 dm 3 /min and higher throw radii) were found that can predict R compared to the discharge of the nozzle, the operating pressure, the trajectory angle, and the height of the nozzle from the ground level. The comparison between the calculated and actual values of R shows a relative error, for all sprinklers and all operating conditions, respectively equal to 6.9% in the first case and 4.1% in the second case.

The objective of this work was to investigate the brake specific fuel consumption (BSFC) of the engine, installed in an agricultural tractor, fueled before with diesel oil (B0) and then with biodiesel (B100). This was done both vs. the engine speed, which vs. engine load. To understand the influence of the fuel heating value and the brake thermal efficiency (BTE), a mathematical modeling of the BTE vs. engine speed and engine torque was developed. The bench tests on the engine, fueled with the two fuels (B0 and B100), allowed to point out that on average, the BTE of the engine was unchanged in the comparison between the two fuels, while the average BSFC was 19% higher with the B100, consistent with the lower heating value of B100 (-17.2%). However, the power output of the engine with the B100 was not reduced by the same amount, but with an average value of 11%, as there was a partial recovery due to the slight increase in the fuel consumption rate. The fitting of the mathematical model to the engine, fuelled with the two fuels (B0 and B100), allowed to draw the diagrams of the calculated BTE and BSFC contours for both fuels, with a good accuracy represented by a mean relative error of 2.1±2.2% (B0) and 2.0±1.5% (B100). Finally, the comparison of the previous results, allowed to highlight the points of the engine speed-torque plane where the biodiesel BTE was different than that of diesel oil BTE. It emerged that the engine fuelled with B100 had a higher BTE at low load and speed, but lower than that of B0 at high speed due to reduced inclination to evaporate compared to diesel oil, which is critical when the speed increases and the time available for combustion is reduced.

A mathematical model was developed to get an equation of the decrease of air velocity crossing the canopy of tree crops during pesticide application using air carrier orchard sprayers. The utility of such a model rises from the need for an aid to understand the experimental results of several authors, who agree with the opinion that air jet velocity greatly affects environmental pollution from pesticides. Further, probably in the future it will arise the demand to implement the equation of air velocity decay in self-adjustment systems of the fan installed on orchard sprayers to limit spray drift. Based on momentum theorem applied under three assumptions, a differential equation was found and its integration lead to a closed solution that can easily be implemented in a PLC for the self-adjustment system to develop. The integral equation thus obtained, together with the assumptions made, was submitted to on-field verification on three crops (peach, vine and apple). The results show a ...

With the aim of energy saving in cold storage in Italy, an integrated system (Total Energy System - TES) was considered for production of cold air, obtained by assembling compression system, absorption system and cogeneration unit (CHP) fuelled with methane-gas, in two different plant solutions: 1) TES consisting of the CHP, mechanically coupled with the compression refrigerating machine and thermically with the absorption system both designed to cool the air in the store rooms; 2) TES* characterized by the CHP, mechanically coupled with the compression refrigerating machine, designed to cool the air in the store rooms, and thermically with the absorption system designed to cool the air in a pre-refrigeration plant. A mathematical modeling and a consequent computer simulation of the behavior of both integrated system (TES and TES*) and both related conventional systems (CES consisting of a compression machine to cool the air in the store rooms and CES* characterized by two compressi...

For red wines, the phase of maceration is fundamental as it affects important features such as colour, aroma and flavour. For wines for everyday consumption these features must provide an easily drinkable product with a good quality basis that is consistent over time. In recent years two methods of maceration seem to guarantee these objectives better than others, while also allowing good work organization and automation: hot maceration and pneumo-carbonic pumping over. These techniques have been evaluated in a large winery, defining their production potential, labour requirements, energy consumptions and economic costs. Chemical and sensory evaluations were carried out on wines produced from grapes with the same characteristics.

A new mathematical procedure was developed to correlate g (the difference between the retort and the coldest point temperatures in canned food at the end of the heating process), fh/U (the ratio of the heating rate index to the sterilizing value), z (the temperature change required for the thermal destruction curve to traverse one log cycle) and Jcc (the cooling lag factor). These are the four heat penetration parameters of 57 Stumbo’s tables (18,513 datasets) in canned food. The quantities fh/U, z and Jcc are input variables to determine the g values, which is used in Ball's formula to calculate the heating process time B at constant retort temperature. The new procedure was based on three equations; the first was obtained by the inversion of the function that expresses the process lethality, F, and hence the fh/U parameter. However, the inversion was possible for a sub-domain of the function. The inverse function g=g(fh/U, z, Jcc) was then extended to the entire domain (10°C&l...

With the aim to gain a better understanding of the phenomenon of drift occurring during spray application of agrochemicals to agricultural crops, a laboratory testing was carried out using a wind tunnel under controlled environmental conditions (wind, temperature and relative humidity RH). Spray drift was measured with wind velocity of 1, 3 and 5 m/s and RH of 30, 50 and 70%. Under medium to high wind velocities the effect of RH was negligible. These results suggested to work out a simplified mathematical modelling by assuming the absence of droplets evaporation by means of closed solutions of the equations of the droplets motion. The main result of the mathematical model is the removal of the droplets smaller than about 80 μm from the spray produced by the nozzles.

An analytical approach to correlate the travel distance of the drops from the irrigation sprinkler with the drops water volume was studied.Such approach was used along with a simplified ballistic model, able to define the trajectories of the drops produced by the nozzle of the sprinklers, to develop a rapid and simple method to obtain sprinkler drop-size spectrum from the water distribution radial curves.

To calculate the sterilizing value U, and hence, the microbial lethality F in thermal processes of the canned food, starting from the knowledge of heating time B, a mathematical modeling was carried out. Therefore it's useful to verify the desired microbial destruction (check problem) and it was obtained by reversing the mathematical approach carried out in a previous work [23] for the design problem, namely to calculate the retort heating time B, starting from a desired lethality F and, hence from the fh/U parameter. A comparison between the predicted fh/U, related to the lethality F calculated with the mathematical model of the present work and the desired Stumbo's values of fh/U, provided the following statistical indices: a mean relative error MRE=1.18±2.11%, a mean absolute error MAE=1.61±11.7 and a determination coefficient R 2 =0.991, better than ANN models. The mathematical procedure, quickly usable also with a spreadsheet, replaces the 57 Stumbo's tables and 18512 data sets in the Ball formula method.

A theoretical model that could be useful for investigating the performance of ground vehicles using acceleration tests was developed. The model takes into account all of the forces acting on a moving vehicle to give a description of its kinematics: the rolling friction of the propulsion devices, their slip on the soil, aerodynamic resistance, road slope and traction developed by the engine. In the methodology of applying the model, the experimental data collected during acceleration tests on a flat and sloping road from a standing start to reach a given distance or a stated speed are used to determine the average efficiency of the transmission of three tractors with different equipment (a mechanical full-powershift drive and two different hydro-mechanical continuouslyvariable ratio transmissions e CVT). The same model was also used to predict tractor performance during other acceleration tests. The results of the CVT tests suggest that there probably is an influence of the transmission architecture that takes precedence over the general type of the transmission.

The performance of a 118-kW tractor fuelled by pure biodiesel was monitored during a long-term field experiment with approximately 800 h of engine function. The objective was to demonstrate that B100, a pure biodiesel fuel, is a viable alternative to traditional diesel oil in terms of long-term mechanical reliability. A bench test on the new engine, performed by attaching a test stand to the power takeoff of the tractor, showed an expected reduction in power (-9%) and torque (-7%) and an increase in specific consumption (+13%) when biodiesel was used as a complete substitute to diesel oil. Furthermore, with the same setup, the exhaust gas had a Bosch smoke index equal to 50% of the value for the same engine fuelled with diesel oil. After these initial tests, the tractor was set up for normal field operations, in which both the engine curves and lubricant quality were periodically monitored. These surveys indicated no significant reduction in engine performance; however, the lubricant was consequently diluted and contaminated by biodiesel, which caused the lubricant properties to considerably worsen. However, on the basis of the chemical-physical analysis, reducing the oil change interval from 200 h (manufacturer's indications for the engine when operating with diesel oil) to 100 h would compensate for this progressive quality decline. At the end of the trials, the engine was disassembled to check the condition of its components; wear and lacquer-like coating phenomena were observed, and their levels were acceptable. The obtained results demonstrated that B100 can effectively substitute for diesel oil in a standard compression-ignition engine: the power change is not perceptible during normal operation of a tractor, and no particular problem will arise in the engine during its life if the lubricant is changed every 100 h.

The classical theory of the precoat filtration with body-feed suggests the Carman equation obtained by integration of the Darcy ODE with constant pressure. Hereinafter the equation obtained in Part I by mean a mathematical modelling of the precoat filtration with body-feed in more realistic conditions of variable pressure was recalled and an experimental validation was done. A pilot filter equipped with a small centrifugal pump was used. The experimental results of the curve of filtrate volume vs. filtration time were compared both with the new equation curve and the Carman equation curve. In the specific conditions of laboratory testing, the estimation error in the filtration time with the new equation is-3.7%, while the estimation error with the classical Carman equation is-21.6%. But with higher permeability conditions of the filtration layer the error with Carman equation can greatly increase, as it was contemplate in Part I. The precoat filtration with body-feed must be followed by the filter cleaning. The research of an optimization of the filtration-cleaning cycle using the classic theory 7368 Dario Friso and Lucia Bortolini of filtration, and therefore the Carman equation, leads to the well known condition to have equal both filtration time and cleaning time. With the proposal of the new equation, in this work a new modelling of the cycle optimization was elaborated. It provided a ratio between filtration time and cleaning time always greater than 1 with values also up to 16 for the higher permeability of the filtering layer (reduced c  ). Therefore, the use of the previous optimization with a rate equal 1 is unacceptable with higher permeability, leading to a substantial halving of the filter productivity.

The centrifugation process for the separation and/or the clarification of food and chemical liquids, requires complex and expensive machines called centrifugal separator. For example, the insertion of an expensive gear-box between the electric motor and the body of the separator and a longer starting time (about 10 min) are required. In an attempt to solve these two problems, in this work, the use of a modern multi-phase motor supplied by a variable-frequency drive (VFD) and without the gear-box has been considered. About the starting phase and the corresponding unsteady-state condition, a dynamic analysis of the traditional system, in comparison to the proposed one, was conducted. Thus, the starting time for the two cases was compared. The system with variable-frequency drive (VFD) presented a lower time (-16%) compared to the traditional one. This reduction of the starting time was found to be greater if the motor allows a starting phase with overload (-42%). Furthermore, through the equations obtained from the dynamic analysis, the starting time has been correlated with the rated power of the motor. By maintaining the high starting time in about 10 min, the equations give a halving of rated power of motor + VFD overloaded, compared to the traditional system, with a further advantage on the reduction of investment costs.