Return to Investment in Human Capital and Policy of Labour Market: Empirical Analysis Of Developing Countries

AbstractOur objective in this paper is to examine the relation which exists between education and the policy of labour market. In order to calculate the profitability of the investment in the human capital we adopt the theory of the human capital and the hypothesis of the labour market segmentation. This paper summarizes in theory, the evaluation in the rate of profitability compared to education considering the individuals. In segmented and competitor labour market, the rise of the level of education generates a rise of the rates of unemployment and the manufacturing units proceed to use the level of education like a quantitative index of employment.To evaluate the rate of cost on the investment in the human capital, we applied the econometric method using the available resources on several levels in the education system, which affects consequently on the supply of labour in the labour market

QUASI NORMS INTEGRAL INEQUALITIES RELATED TO LAPLACE TRANSFORMATION

In [4], the authors have proved the theorems 2.4 and 2.5 related to some integral inequalities via the Laplace transformation with the parameter p > 1. Inthis manuscript, we propose new extension for integral inequalities related to Laplace transformation with two parameters p ; q and using the weight functions w; φ. We deduce some new inequalities linked to the Laplace transformation

Role of the interphase in the interfacial flow stability of multilayer coextrusion of compatible polymers

International audienceThe role of interphase triggered from interdiffusion process at neighboring layers on controlling the interfacial flow instability of multilayer coextrusion have been highlighted in this study using a compatible bilayer system. The polymers used are based on poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF). The interdiffusion kinetics and the rheological and geometrical properties of the generated interphase have been modelized in real experimental conditions of the coextrusion process. Polymer chain orientation in coextrusion process was demonstrated to decelerate the interdiffusion coefficient. Furthermore, the interfacial shear stress was able to promote mixing and homogenizing process at the vicinity of the interface, which favors the development of the interphase. The convective mixing was evidenced by performing a pre-shear mode on PMMA/PVDF multilayer structures. The rheological and morphological properties of the interphase are related to a lot of parameters like contact time, processing temperature, interfacial shear stress and compatibility of the polymers, etc. Some key classical decisive parameters concerning the interfacial instability phenomena such as viscosity ratio, thickness ratio and elasticity ratio, etc. were highlighted during the coextrusion process. These key factors which are significant for the interfacial stability of coextrusion of incompatible multilayered polymers seem not that important for the studied compatible systems. The coextrusion of PMMA/PVDF compatible bilayers appears to be more stable. This would be attributable to the presence of the interphase generated from interdiffusion and favored from convective mixing. The interfacial flow instability of coextrusion can be reduced (or even eliminated) despite of the very high viscosity ratio and elasticity ratio of PMMA versus PVDF, especially at low temperatures. Overall, apart from the classical mechanical parameters, we have demonstrated that the creation of diffuse interphase that favors the homogenization should be taken into consideration as an important factor to remove the interfacial instability properties

Reactive Functionalized Multilayer Polymers in a Coextrusion Process: Experimental and Theoretical Investigations of Interfacial Instabilities

International audienceCoextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances regarding the stability of compatible and incompatible polymers have, during the last decades, been made using a mechanical approach. However, few research efforts have been dedicated to the physicochemical affinity between the neighboring layers. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers. Polyamide (PA6)/polyethylene grafted with glycidyl methacrylate (PE-GMA) was used as a reactive system and PE/PA6 as a non reactive one. Two grades of polyamide (PA6) were used in order to change the viscosity and elasticity ratios between PE (or PE-GMA) and PA6. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to an interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. According to rheological investigations from previous work, an experimental strategy was here formulated to optimize the process by listing the parameters that controlled the stability of the reactive multilayer flows. Plastic films with two layers were coextruded in symmetrical and asymmetrical configurations in which PA6 was the middle layer. Indeed, for reactive multilayered systems, the interfacial flow instability could be reduced or eliminated, for instance, by (i) increasing the residence time or temperature in the coextrusion bloc (for T above the reaction temperature T = 240°C), and (ii) reducing the total extrusion flow rate. The reaction rate/compatibilization played a major role that must be taken into account. Furthermore, the role of the viscosity ratio, elasticity ratio, and layer ratio of the stability of the interface were also investigated coupling to the physicochemical affinity. The results show that it is necessary to obtain links between the classic factors that are introduced in the evaluation of the theoretical, given by linear stability analysis/longwave asymptotic investigations, and its corresponding experimental stability charts. Hence, based on this analysis, guide-lines for a stable coextrusion of reactive functionalized polymers can be provided

Compounding and processing of biodegradable materials based on PLA for packaging applications: In greening the 21st century materials world.

Poly(lactic acid) is a well known polymer for more than 20 years in the biomedical fieldsapplications. Today, according to rising prices of oil and massive consumption of fossil resource,this biodegradable aliphatic polyester is on the way to be a wide used commodity polymer.Moreover PLA is as a “green plastic” because it is synthesized from annually renewable resources.In many ways similar to poly(ethylene terephtalate) such as rigidity, transparency, crystallizationkinetics and food contact ability, it fulfills the packaging industry requirements for most of the rigidobjects. But for applications like hot food packages, soft films and stretch blow bottles for examplesome properties of PLA have to be improved like heat deflection temperature (HDT), impactstiffness and gas barrier properties. There are many ways reported in literature today to improvethese properties. In order to compare it with other well known polymers, figure 1 representsthermal properties of PLA and these polymers. The aim of the work deals to identify actualweaknesses of commercial grades of PLA. Secondly, to present pertinent ways to improve PLA‟sproperties have been identified according to chosen process and final properties wished. This studyis composed of three main items. In a first time, a bibliographical study is necessary to identify thedifferent ways to improve PLA‟s properties used by researchers and industrials in literature. Themost significant ways will be describe here. Then PLA compound (PLA with additives or PLAcopolymers for examples) will be synthesized in conditions closed to industrial conditions studyingcrystallisation kinetic and rheological properties. In this step thermal, physico-chemical andmechanical properties of products synthesized will be characterized. At the end of this study thebest ways of improving PLA‟s behavior will be presented and describe

Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

A reactive rotational molding (RRM) process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6). Sodium caprolactamate (C10) and caprolactam magnesium bromide (C1) were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) was used as an activator. The kinetics of the anionic polymerization of !-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation

Bolytrope orders

Bolytropes are bounded subsets of an affine building that consist of all points that have distance at most $r$ from some polytrope. We prove that the points of a bolytrope describe the set of all invariant lattices of a bolytrope order, generalizing the correspondence between polytropes and graduated orders.Comment: Minor revisions according to referee's suggestions. To appear in International Journal of Number Theor

Reshoring Process of Manufacturing Process in the UK: An Emergent Theory Perspective.

Purpose: The aim of this research is to examine the reshoring process by shedding light on the drivers, barriers, decision-making and implementation phase. Current theoretical explanations of reshoring have not adequately considered the dynamics of the phenomenon. This research aim is to theoretically explain reshoring through the perspective of the emergent theory that takes into consideration the dynamic environment in which the reshoring process occurs. Practically, the research aim is to provide a conceptual framework that includes information about the reshoring steps and decision-making, and how to apply each step in a dynamic environment. This conceptual framework’s main purpose is to assist and support reshoring managerial decisions to relocate back to the UK successfully by adopting a flexible approach consistent with the dynamic environment. Design/methodology/approach – The research deploys mixed methods. The quantitative research was conducted using a survey that obtained 113 complete responses from UK reshored manufacturing. The qualitative research collected data from 10 interviewees through semi-structured in-depth interviews. The quantitative data was analysed using SPSS26 and descriptive statistics. The qualitative data was analysed using thematic analysis and NVIVO. Findings – The findings of the research suggest that reshoring drivers, barriers, decision-making and implementation is a dynamic process. The drivers and barriers emerge from the business environment unpredictability, and therefore should be identified based on a flexible reshoring approach, which is able to consider, add, and eliminate factors accordingly with the environmental uncertainties. The decision-making and implementation process emerges from the dynamic drivers and barriers and occurs in an unpredictable environment. This makes the decision making- phases highly dynamic. Thus, this research proposes this phase should be based on a flexible approach characterised by a looping process, not sequential (Mintzberg et al., 1976). Contribution – First, the research sheds light on the dynamics of the reshoring process, and the importance of formulating a reshoring strategy that takes into consideration the uncertainties of the environment. Second, the analysis revealed a UK perspective of the drivers and barriers of reshoring. The study contributes to extending the factors related to the drivers and barriers to a larger set. New findings concerning driver factors are the government support for reshoring, legal issues, and the “made-in-effect”. For the barriers, the study shows novel findings – which are: the lack of availability of factories and lands for manufacturing, legal issues, and psychological challenges. The new findings have been explained and discussed in the context of the UK economy and market. Concerning the decision-making and implementation phase, the study contributes to an in-depth explanation by providing the steps of these phases and by empirically explaining what happens in each phase. Third, this study contributes to forming a theoretical explanation of the reshoring process dynamics based on emergent theory (Mintzberg et al., 1976). The reshoring process, grounded upon emergent theory, is a dynamic phenomenon that requires an emergent strategy. The emergent strategy is characterized by management’s ability to continuously adjust and adapt to environment unpredictibilities and uncertainties (Mintzberg & Waters, 1985). This is done through continuous cycles of decision making until the reshoring is achieved (Mintzberg & Waters, 1985). The strength of this theory is that it considers the risks and opportunities of the environment in which the reshoring occurs (Mintzberg & Waters, 1985). Fourth, this research proposes an empirically and theory-based conceptual framework of the reshoring process to support future decision-makers with their reshoring strategies. This conceptual framework is the first to have the complete phases of reshoring, which are the drivers, barriers, decision-making and implementation. In the conceptual framework, the reshoring process phases are explained through a step-by-step guide to support reshoring decision-makers. Thus, the research contributes to a practical understanding of the process of reshoring through a dynamic lens by explaining each phase and its steps set in an unpredictable environment. Originality/value – The literature is missing a theoretical understanding of the reshoring process. This research provides a theoretical explanation of the reshoring process from a dynamical lens based on the emergent theory. New empirical findings from a UK perspective have been explained and discussed that are important for future reshoring decision-makers. Moreover, the theory-based conceptual framework is the first to include a step-by-step flexible practice approach that includes all the reshoring phases

Tropical invariants for binary quintics and reduction types of Picard curves

In this paper, we express the reduction types of Picard curves in terms of tropical invariants associated to binary quintics. These invariants are connected to Picard modular forms using recent work by Cl{\'e}ry and van der Geer. We furthermore give a general framework for tropical invariants associated to group actions on arbitrary varieties. The previous problem fits in this general framework by mapping the space of binary forms to symmetrized versions of the Deligne--Mumford compactification $\bar{M}_{0,n}$. We conjecture that the techniques introduced here can be used to find tropical invariants for binary forms of any degree