Minimum consumption and transitional dynamics in wealth distribution

This paper investigates the evolution of wealth distribution in a one sector growth model along its transition path. A key feature of the model is that a household's consumption cannot fall below a positive level each period. This requirement introduces a positive association between the intertemporal elasticity of substitution and household wealth. Households only differ in their initial holdings of capital. The model is calibrated to match some key statistics of the US economy. The level of inequality in the wealth distribution of our artificial economy has a n inverted Ushape. The level of wealth inequality and its evolution resembles that of the US economy. However, our model illustrates that the existence of a Kuznets curve is very sensitive tothe sources of growth: whether it is driven by productivity growth or capital accumulation. Additionally, our model predicts an upsurge in wealth inequality following the productivity slowdown in the 1970's

Performance Measurement Systems, Competitive Priorities, and Advanced Manufacturing Technologies: Some Evidence from the Aeronautical Sector

Purpose – When acquiring advanced manufacturing technologies (AMT), the greatest caution should be taken regarding the performance measurement system to be used: the decision regarding new investments should not be conditioned by the excessive use of financial indicators to the detriment of the strategic objectives that motivated the investments. It is intended to analyze the aeronautical sector, for which the purchase of AMT is qualifying criteria, with two intentions: first, to identify the performance measurement systems that are used, and second, to test their correspondence with the objectives that motivated the investments. Design/methodology/approach – A survey of the 20 plants in the population was conducted via a postal questionnaire plus a structured interview. The unit of analysis has been maintained through the triangulation of data sources. Findings – The findings suggest that both financial and non-financial indicators are used, with the latter gaining predominance over the former on some occasions, even though there is no clear correspondence between strategy and the measurement of performance. In the light of the findings, the question of what inspires a company’s performance measurement system is still open, especially in those cases where there is no explicit strategy. With regard to practical implications, what seems to be indispensable is an improvement in the determination of the critical variables that should be used to measure performance. Research limitations/implications – Being valuable for academics and practitioners, this contribution relies, rather, on the possibility of a logical extrapolation to circumstances where the findings might apply, and researchers can judge whether the particular findings would be valid. Originality/value – Provides new evidence on the adaptation of the make-up and combination of the type of performance measures currently used by plants in the aeronautical industry, one of the sectors in which technological innovation is of the utmost importance.Publicad

Analysis of orthogonal cutting of biocomposites

The use of 100% biodegradable composites in the industry is increasing significantly over the years, mainly due to their excellent properties as well as to the growing ecologic concern. However, after their manufacture, the composite pieces do not always have the final shape, requiring subsequent processing operations, usually drilling and trimming. The performance of cutting processes on fully biodegradable composites are often limited by induced damage as fraying and delamination. This type of phenomena is related, among others, with the cutting parameters and geometries of the tool. Orthogonal cutting is a simplified process that could help in the understanding of damage mechanisms, it is a well-known technique in traditional composites but its use in biocomposites is an almost unexplored field. This work focuses on flax/PLA 100% biodegradable woven composites. The specimens have been manufactured with different angles of orientation, ranging from 0° to 60°, being subjected to orthogonal cutting in a special machine developed for that purpose that allows to develop cutting tests with linear displacement at high speeds. Damage extension, failure modes, and cutting forces are analyzed allowing the extraction of important experimental information.Authors gratefully acknowledges the financial support to the Ministry of Economy and Competitiveness of Spain and FEDER program through the project DPI2017-89197-C2-1-R

Adopting and Implementing AMT: New Data on Key Factors from the Aeronautical Industry.

The objective of this paper is to take a greater in-depth look at which factors might be considered to be key to the performance of investments made in advanced manufacturing technologies (AMT), given their supposed positive effects, and on the influence that the time these factors are taken into account during the adoption and implementation process can have on that relationship. It provides a specially devised empirical analysis in the aeronautical sector in the south of Spain. A survey of the 20 plants in the population was conducted via a postal questionnaire between July 1999 and April 2001, with a structured interview being held at a later date. The testing of hypotheses was performed by applying the t-test to independent samples. The results show that the only factor that has a clear and positive effect on performance is the training of personnel. It can also be seen that a lack of strategic planning contributes to dampening the effects of investments. These results may be of some help to management staff and public administrators in charge of promoting the process of technological innovation, by indicating actions that need to be taken in order to successfully adopt and implement AMT.

Sustainable high-speed finishing turning of haynes 282 using carbide tools in dry conditions

Nickel-based superalloys exhibit an exceptional combination of corrosion resistance, enhanced mechanical properties at high temperatures, and thermal stability. The mechanical behavior of nickel-based superalloys depends on the grain size and the precipitation state after aging. Haynes 282 was developed in order to improve the creep behavior, formability, and strain-age cracking of the other commonly used nickel-based superalloys. Nevertheless, taking into account the interest of the industry in the machinability of Haynes 282 because of its great mechanical properties, which is not found in other superalloys like Inconel 718 or Waspaloy, more research on this alloy is necessary. Cutting tools suffer extreme thermomechanical loading because of the high pressure and temperature localized in the cutting zone. The consequence is material adhesion during machining and strong abrasion due to the hard carbides included in the material. The main recommendations for finishing turning in Haynes 282 include the use of carbide tools, low cutting speeds, low depth of pass, and the use of cutting fluids. However, because of the growing interest in sustainable processes and cost reduction, dry machining is considered to be one of the best techniques for material removal. During the machining of Haynes 282, at both the finishing and roughing turning, cemented carbide inserts are most commonly used and are recommended all over the industry. This paper deals with the machining of Haynes 282 by means of coated carbide tools cutting fluids (dry condition). Different cutting speeds and feeds were tested to quantify the cutting forces, quality of surface, wear progression, and end of tool life. Tool life values similar to those obtained with a lubricant under similar conditions in other studies have been obtained for the most favorable conditions in dry environments.This research was funded by the Ministry of Economy, Industry, and Competitiveness, and the FEDER program, grant number DPI2017-89197-C2-1-R

Finishing Turning of Ni Superalloy Haynes 282

Nickel-based superalloys are widely used in the aeronautical industry, especially in components requiring excellent corrosion resistance, enhanced thermal fatigue properties, and thermal stability. Haynes 282 is a nickel-based superalloy that was developed to improve the low weldability, formability, and creep strength of other gamma'-strengthened Ni superalloys. Despite the industrial interest in Haynes 282, there is a lack of research that is focused on this alloy. Moreover, it is difficult to find studies dealing with the machinability of Haynes 282. Although Haynes 282 is considered an alloy with improved formability when compared with other nickel alloys, its machining performance should be analyzed. High pressure and temperature localized in the cutting zone, the abrasion generated by the hard carbides included in the material, and the tendency toward adhesion during machining are phenomena that generate extreme thermomechanical loading on the tool during the cutting process. Excessive wear results in reduced tool life, leading to frequent tool change, low productivity, and a high consumption of energy; consequentially, there are increased costs. With regard to tool materials, cemented carbide tools are widely used in different applications, and carbide is a recommended cutting material for turning Haynes 282, for both finishing and roughing operations. This work focuses on the finishing turning of Haynes 282 using coated carbide tools with conventional coolant. Machining forces, surface roughness, tool wear, and tool life were quantified for different cutting speeds and feeds.This research was funded by the Ministry of Economy, Industry and Competitiveness and the FEDER program, grant number DPI2014-56137-C2-2-R

High-pressure cooling in finishing turning of haynes 282 using carbide tools: Haynes 282 and inconel 718 comparison

Despite the interest of industry in nickel-based superalloys and its main features (high temperatures resistance, hardness, low thermal conductivity, among others), even today they are still materials that are difficult to cut. Cutting tools withstand both high pressures and temperatures highly localized at the cutting area because of the elevated work hardening of the alloy and the problems for the cutting fluid to access the region, with the consequent strong tool wear. The use of cutting fluids at high pressures improves coolant access and heat removal. This paper analyzed the machining of Haynes 282 alloy by means of coated carbide tools under high-pressure cutting fluids at finishing conditions. Tests were developed at different cutting speeds and feeds quantifying the machining forces, surface roughness, tool wear, and tool life. Values of 45.9 min and Ra between 2 µm and 1 µm were obtained in this study for tool life and roughness, respectively, for the combination of cutting speed 50 m/min and feed 0.1 mm/rev. Likewise, a comparative analysis is included with the results obtained in previous works developed by the authors relating to the finishing turning of Haynes 282 and Inconel 718 under conventional pressure cooling. The comparative analysis with Inconel 718 is included in the study due to its importance within the nickel base superalloys being widely used in industry and widely analyzed in scientific literature.The authors gratefully acknowledge the funding support received from the Spanish Ministry of Science and Innovation and the FEDER program for funding the projects PID2020-112628RA-I00, PID2020-118480RB-C22 and PDC2021-121368-C21

Experimental analysis of the influence of drill point angle and wear on the drilling of woven CFRPs

This paper focuses on the effect of the drill geometry on the drilling of woven Carbon Fiber Reinforced Polymer composite (CFRPs). Although different geometrical effects can be considered in drilling CFRPs, the present work focuses on the influence of point angle and wear because they are the important factors influencing hole quality and machining forces. Surface quality was evaluated in terms of delamination and superficial defects. Three different point angles were tested representative of the geometries commonly used in the industry. Two wear modes were considered, being representative of the wear patterns commonly observed when drilling CFRPs: flank wear and honed cutting edge. It was found that the crossed influence of the point angle and wear were significant to the thrust force. Delamination at the hole entry and exit showed opposite trends with the change of geometry. Also, cutting parameters were checked showing the feed's dominant influence on surface damage.This work was supported by the Ministry of Economy and Competitiveness of Spain under the project DPI2011-25999Publicad

Experimental and numerical analysis of the influence of drill point angle when drilling biocomposites

Biocomposites are promising materials for traditional composites replacement in specific applications due to their interesting properties and sustainability. Although the composite components are manufactured near net shape, some machining operations, commonly drilling, are commonly required prior to mechanical joining of the components. Tool geometry, mainly the point angle of the drill, strongly affects the performance of the drilling process of composites in terms of machining induced damage. The aim of this work is analyzing the influence of the point angle of the drill on the damage generated during drilling of 100% biodegradable composite, using both numerical and experimental approaches. The novelty of the work relies on the lack of studies of drilling 100% biodegradable composites. The influence of the point angle on the thrust forces and hence in the machining induced damage was demonstrated.The authors acknowledge the financial support to the Ministry of Economy and Competitiveness of Spain and FEDER program through the projects DPI2017-89197-C2-1-R and DPI2017-89197-C2-2-R

La percepción de los estudiantes universitarios en la medida de la competencia docente: validación de una escala

El propósito de este estudio consiste en desarrollar y validar la medida de un constructo de competencia docente universitaria, utilizando un cuestionario de opinión de los estudiantes, con 30 ítems. En la muestra han participado 374 estudiantes de tres departamentos de la Universidad de Costa Rica, Sede de Guanacaste, cuyo mayor grupo está representado por estudiantes de primer ingreso (39,4%), con una edad media de 19,9 años. Para validar el constructo propuesto se han aplicado los modelos de ecuaciones estructurales a seis factores de competencia docente universitaria, identificados como: organización, evaluación, presentación, entusiasmo, interacción y valoración global del estudiante. Las universidades interesadas en la innovación pueden utilizar estos factores para desarrollar planes de formación y mejora de sus docente