Multi-input Multi-output Farm-level Cost Function: A Comparison of Least Squares and Entropy Estimators

We introduce a modification of the quadratic-Leontieff multi-output cost function that is particularly suitable for the data of the Farm Accountancy Data Network. We present least squares and entropy estimates of that function and compare their results for a sample of crop farms. Our results are encouraging for the use of entropy estimators in cases in which farms are not assumed to share the same technology. Our approach can be seen as an extension of the Positive Mathematical Programming approach (Howitt, 1995). The extension consists in an explicit specification of inputs in the cost function and in the possibility of modeling several farms simultaneously.cost function, least squares estimator, entropy estimator, heterogeneity, Farm Management, C3, D61, Q12,

New Developments in Agricultural Policy Modelling and Consequences for Managing the Policy Analysis Systems

Last decade, the importance of multifunctionality and environmental issues in agricultural policies has been growing. This shift in scope of agricultural policy instruments implies an adjustment of the conventional ex-ante policy analysis systems. New requirements on input and output parameters will be needed. The objective of this paper is to show how the input/output management can be improved. Focus is on how the information management by the system can enhance the policy analysis and decision making and facilitate information flow and social support from the stakeholder debate.policy impact analysis, joint production, farmers' behaviour, knowledge flow Organisation, Agricultural and Food Policy, C8, Q18,

Review : Auto-oxidation of aliphatic polyamides

The literature on oxidation kinetics of polyamides and model compounds has been reviewed in order to try to extract suitable information for non-empirical kinetic modeling. Polyamide characteristics are systematically compared to polyolefin ones, these latter being more extensively studied. From kinetic analysis point of view, it is shown that oxidation attacks predominantly a amino methylenes of which C eH bond is considerably weaker than the other methylenes. As a result, propagation by H abstraction is considerably faster in polyamides than in polyethylene for instance. Termination by radical combination is also very fast. Another cause of PA oxidizability is the instability of a amino hydroperoxides linked to the inductive effect of nitrogen. This instability is responsible for many key features of oxidation kinetics especially the absence of induction period. The main stable oxidation products are imides resulting from disproportionation processes meanwhile chain scissions resulting from rearrangements of a amino alkyls by b-scission are also significant process although their yield appears lower than in polyolefins

Molecular and macromolecular structure changes in polyamide 11 during thermal oxidation

The present article reports a study of thermal oxidation of unstabilized polyamide 11 films at several temperatures (90–165 °C) under atmospheric pressure and under various oxygen pressures (up to 1.6 MPa) at 110 °C. The chemical structure changes are monitored by IR spectroscopy (carbonyl groups) and UV–visible spectrophotometry (yellowing). Molar mass changes are determined by size exclusion chromatography (SEC). By investigating the influence of oxygen pressure it is clearly shown that reactions involving P° radicals other than O2 addition cannot be neglected under atmospheric pressure. Under the conditions of this study limited to relatively low oxidation levels, IR and UV measurements indicate that carbonyl groups and chromophores responsible for yellowing have the same relative yield whatever the temperature and oxygen pressure. SEC measurements highlight the significant predominance of random chain scissions over crosslinking events. Crosslinking only appears after an induction time, presumably because it involves reactions between primary oxidation products. The ratio of carbonyl groups over chain scissions is about 7.5 at low conversion and about 2.5 at high conversion, showing that α amino alkoxy radicals are mainly transformed into imides without chain scission

Effects of a flat rate introduction: shifts in farm activity and impact on farmers' income

Current thoughts on CAP changes, e.g. the "Health Check", emphasize the necessity to move away from payments based on historical receipts towards a "flatter rate" system. The aim of current research is to simulate the impact of a flat rate system (equal payments per hectare of cultivated land) compared to the current historical system (payments based on individual historic entitlements). Impact on production and income of arable, dairy and cattle farms of two different flat rate scenario's, is assessed with a farm-based sector model for Flanders. The model maximizes income at farm level, calibrated to observed farming behavior in 2001-2003. Farm data can be selected by farm type, size and region, simulations could be run for specific sub sectors, size classes or regions. In the two simulated flat rate scenario's subsectors will gain subsidies at the expense of other subsectors. However, farms can compensate a substantial part of their income loss by changing activity choice.Positive Mathematical Programming, farm model, Common Agricultural Policy, Payment Entitlements., Agricultural and Food Policy, Agricultural Finance, Farm Management, Research Methods/ Statistical Methods,

Investigation of polyamide 11 embrittlement during oxidative degradation

Embrittlement processes occurring during thermal oxidation are investigated for stabilized and unstabilized polyamide 11 samples differing by their thicknesses and initial molar masses. Tensile tests were carried out in the temperature range between room temperature and 110 °C in order to investigate the influence of mechanical testing temperature on the embrittlement coordinates. In the same time, molar mass and crystalline morphology are monitored by size exclusion chromatography (SEC) and DSC/SAXS measurements respectively. The experimental results point out the existence of a critical molar mass for ductile-brittle transition M′c about 10 kg mol−1, independent of sample initial molar mass or stabilization, but depending on tensile testing temperature. However, even if oxidation chain scissions are shown to be clearly responsible for the loss of mechanical properties at failure, the structure-property relationships governing ductile-brittle transition require a mixed criterion involving molar mass and crystalline morphology, especially the interlamellar distance. For this purpose, specific molar mass – crystalline morphology relationships are investigate

Thermal stabilization of polyamide 11 by phenolic antioxidants

This paper addresses the effect of hindered phenols (mainly Irganox 1098 with a few comparisons with other phenolic antioxidants) on the stabilization of polyamide 11 aged at several temperatures (90–165 °C). The effect of several phenol concentrations (up to about 0.4%) on kinetic curves for imide build-up, yellowing, and molar mass changes (in association with embrittlement) was investigated. Phenols significantly contribute to yellowing, even at low imide concentrations. When they are used at high concentrations, a post-polycondensation reaction becomes predominant at earlier exposure times, thus increasing molar mass and significantly delaying embrittlement

Quantification of hindered phenols in polyamide 11 during thermal aging

Polyamide 11 films stabilized by Irganox® 1098, Irganox® 1010 or Irganox® 245 were subjected to thermal oxidation at 110°C. The residual phenol content was assessed by comparing three analytical methods:high performance liquid chromatography (HPLC), determination of the Oxidation Induction Time (OIT)and Onset Oxidation Temperature (OOT) by thermal analyses. Both OIT and OOT are reliable for virgin PA11 after a relevant calibration by HPLC measurement. In the case of oxidized samples, OOT measurements have the benefits of being more easily interpretable than OIT and less time-consuming than HPLC measurements.CIFR

Multi-input Multi-output Farm-level Cost Function: A Comparison of Least Squares and Entropy Estimators

We introduce a modification of the quadratic-Leontieff multi-output cost function that is particularly suitable for the data of the Farm Accountancy Data Network. We present least squares and entropy estimates of that function and compare their results for a sample of crop farms. Our results are encouraging for the use of entropy estimators in cases in which farms are not assumed to share the same technology. Our approach can be seen as an extension of the Positive Mathematical Programming approach (Howitt, 1995). The extension consists in an explicit specification of inputs in the cost function and in the possibility of modeling several farms simultaneously