Design of the optimized and downsized axial fan for the air carrier orchard sprayers

The new vineyard and orchard installations are made with a high intensity of plants per hectare and therefore with a reduced distance between the rows. The tractors and the air carrier sprayers for plant protection, must therefore have smaller width. In consequence, a method of design of axial fans for the air carrier sprayer, to get a small diameter without losing the performance required by the agrochemical applications, must also be studied. The new method was found by imposing a law of Compound Vortex for the tangential component of absolute air speed. In consequence the equations for: the axial component of the absolute air velocity, the flow rate, the total specific energy and the invariance of the lift coefficient versus the radius, were found. Then, the method consists in the solution of the system of these four equations to determine the fan design parameters. This new method allows to obtain a reduction of the external diameter of the fan by a factor of 0.8 and a reduction of the lift coefficient because imposed constant vs. the radius. Therefore the new method may allow to further increase the total specific energy. Finally, there was no significant difference between the average speed, relative to airfoils, of the new method (Compound Vortex) and of the traditional method one (Free Vortex) and then there are no downgrades in the fluid dynamic efficiency

The check problem of food thermal processes: A mathematical solution

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\u2019s 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\u2019s values of fh/U, provided the following statistical indices: a mean relative error MRE=1.18\ub12.11%, a mean absolute error MAE=1.61\ub111.7 and a determination coefficient R2=0.991, better than ANN models. The mathematical procedure, quickly usable also with a spreadsheet, replaces the 57 Stumbo\u2019s tables and 18512 data sets in the Ball formula method

A mathematical solution for food thermal process design

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\ub0C 64 z 64111\ub0C , fh/U 65 0.3 and 0.4 64 Jcc 64 2 ) using two polynomials (second and third equation) obtained with articulated multiple regressions starting from the Stumbo's datasets. A comparison between the calculated value of g and desired Stumbo's values of g provided the following values: a determination coefficient R2=0.9999, a mean relative error MRE=0.85\ub10.91% and a mean absolute error MAE=0.06\ub0\ub10.09\ub0C (0.11\ub0\ub10.16\ub0F). The results obtained by applying the mathematical procedure of this work, namely the g values using the three equations and the process time B using Ball's formula, closely followed the process time calculated from tabulated Stumbo's g values (root mean square of absolute errors RMS=0.393 min, average absolute error=0.259 min with a standard deviation SD=0.296 min). The high accuracy and simplicity of the procedure proposed here, make it useful in the development of mathematical algorithms for calculating and controlling, by computer, of food thermal processes. These algorithms replace the 57 look-up tables and 18,513 data sets needed in the Stumbo formula method. As such, this work offers a computerized formula method as an alternative to existing computerized numerical methods for this purpose

Local human capital, segregation by skill, and skill-specific employment growth

Labour markets in most highly developed countries are marked by rising levels of skill segregation in the production process and increasing inequalities in skill-specific employment prospects. The local skill structure is frequently regarded as a major cause for regional growth disparities. There are several studies investigating the influence of the local human capital endowment on qualification-specific wages levels. Furthermore, theoretical studies suggest that skill segregation might matter for the polarisation of wages and employment. However, analyses on regional employment growth by different skill levels are still scarce and empirical evidence on the effects of skill segregation on qualification-specific employment is completely lacking. This paper investigates the effects of the local skill composition and skill segregation in the production process on qualification-specific employment growth in West German regions. This study provides first evidence for negative effects of skill segregation on low-skilled employment growth. Furthermore, the results show that a large share of local high-skilled employment does not foster further regional concentration of human capital but positively affects the employment prospects of less skilled workers. --regional employment growth,low-skilled employment,skill segregation

Local human capital, segregation by skill, and skill-specific employment growth

"Labour markets in most highly developed countries are marked by rising levels of skill segregation in the production process and increasing inequalities in skill-specific employment prospects. Local human capital has a likely effect on skill specific productivity levels and employment growth. Furthermore, theoretical studies suggest that skill segregation might matter for the polarisation of wages and employment. There are several studies investigating the influence of the local human capital endowment on qualification-specific wages levels. However, analyses on regional employment growth by different skill levels are still scarce and empirical evidence on the effects of skill segregation on qualification-specific employment is completely lacking. This paper investigates the effects of the local skill composition and skill segregation in the production process on qualification-specific employment growth in West German regions. This study provides first evidence for negative effects of skill segregation on low-skilled employment growth. Furthermore, the results show that a large share of local high-skilled employment does not foster further regional concentration of human capital but positively affects the employment prospects of less skilled workers." (Author's abstract, IAB-Doku) ((en))Humankapital, lokale Ökonomie, Beschäftigungsentwicklung, Lohnhöhe, Qualifikationsniveau, Niedrigqualifizierte, Hochqualifizierte, Kompetenz, Segregation, regionaler Arbeitsmarkt, Westdeutschland, Bundesrepublik Deutschland

Mathematical modelling and experimental assessment of agrochemical drift using a wind tunnel

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 \u3bcm from the spray produced by the nozzles

Precoat filtration with body-feed and variable pressure. Part II: Experimental tests and optimization of filtration cycles

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 re-called 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 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 . 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

Blending Words & Numbers: Towards a Framework for Combining Quantitative and Qualitative Strategies for Organizational Research

Blending qualitative and quantitative research methods is widely propagatedas a strategy for both quality control and enrichment of organizationresearch. This has been recognized in the organization literature for morethan twenty years. However, during the last decade the progress in thepractice of research has not been altogether impressive. Ambiguity is one ofthe key problems in this respect. This paper tries to clarify the discussion onblended methods, by (1) clarifying concepts used to describe blendeddesign, (2) inventoririzing and categorizing the different forms and objectivesof blended design, and (3) developing a provisional framework. The studydeparts from the research practice, the sequences of action in concretestudies. The focus is on research as a process, rather than on specificmethods. Finally, the paper suggest some directions for a developmentprogram for blending methods.economics of technology ;

Exact Real Arithmetic with Perturbation Analysis and Proof of Correctness

In this article, we consider a simple representation for real numbers and propose top-down procedures to approximate various algebraic and transcendental operations with arbitrary precision. Detailed algorithms and proofs are provided to guarantee the correctness of the approximations. Moreover, we develop and apply a perturbation analysis method to show that our approximation procedures only recompute expressions when unavoidable. In the last decade, various theories have been developed and implemented to realize real computations with arbitrary precision. Proof of correctness for existing approaches typically consider basic algebraic operations, whereas detailed arguments about transcendental operations are not available. Another important observation is that in each approach some expressions might require iterative computations to guarantee the desired precision. However, no formal reasoning is provided to prove that such iterative calculations are essential in the approximation procedures. In our approximations of real functions, we explicitly relate the precision of the inputs to the guaranteed precision of the output, provide full proofs and a precise analysis of the necessity of iterations

Regional income inequality and convergence processes in the EU-25

This paper deals with the development of disparities in regional per capita GDP and convergence processes in the enlarged EU. A cross-section of 861 regions is analysed for the period from 1995 to 2003. Firstly, we apply Theil's index of inequality in order to show the development of between- and within-country disparities. Secondly, we conduct a formal Ø-convergence analysis, taking into account the effects of spatial dependence and controlling for national effects. The analyses show that poorer regions mainly situated in the European periphery have tended to grow faster than the relatively rich regions in the centre of Europe. However, the convergence process has been driven mainly by national factors. In the course of this process, regional disparities within the new member countries have actually increased. Furthermore, we find that spatial growth spillovers lose relevance when crossing a national border. Thus, border impediments still matter for the intensity of economic cross-border integration in the EU. --regional inequality,convergence,EU-25,regional interactions,spatial econometrics