The aim of this study is to evaluate the impact of factors such as cutting speed, feed rate, and depth of cut on surface roughness and Material Removed Rate (MRR) when machining in dry face milling AISI 1040 steel with coated carbide inserts GC1030 using the response surface methodology (RSM). For this purpose, a number of machining experiments based on statistical three-factor and three-level factorial experiment designs, completed (L27) with a statistical analysis of variance (ANOVA), were performed in order to develop mathematical models and to identify the significant factors of these technological parameters. Multi-objective optimization procedure for minimizing Ra, Ry and Rz and maximizing MRR using desirability approach has been also implementented. The current study was also carried out to investigate the tool life of the inserts. The models found the relationship between the cutting parameters (Vc, fz and ap) and the studied technological parameters. It has been found that the cutting speed was the most affecting surface roughness which is due to the geometry of the insert which has a scraping edge and enables to obtain low roughness even at important feed rate, followed by the feed rate and the depth of cut at the end. The optimal combination of cutting parameters were cutting speed of 314 m/min, feed rate of 0.16 mm/tooth and depth of cut of 0.6 mm with a composite desirability of 0.924.
Inconel 718 is among difficult to machine materials because of its abrasiveness and high strength even at high temperature. This alloy is mainly used in aircraft and aerospace industries. Therefore, it is very important to reveal and evaluate cutting tools behavior during machining of this kind of alloy. The experimental study presented in this research work has been carried out in order to elucidate surface roughness and productivity mathematical models during turning of Inconel 718 superalloy (35 HRC) with SiC Whisker ceramic tool at various cutting parameters (depth of cut, feed rate, cutting speed and radius nose). A small central composite design (SCCD) including 16 basics runs replicated three times (48 runs), was adopted and graphically evaluated using Fraction of design space (FDS) graph, completed by a statistical analysis of variance (ANOVA). Mathematical models for surface roughness and productivity were developed and normality was improved using the Box-Cox transformation. Results show that surface roughness criterion Ra was mainly influenced by cutting speed, radius nose and feed rate, and that the depth of cut had major effect on productivity. Finally, ranges of optimized cutting conditions were proposed for serial industrial production. Industrial benefit was illustrated in terms of high surface quality accompanied with high productivity. Indeed, results show that the use of optimal cutting condition had an industrial benefit to 46.9 % as an improvement in surface quality Ra and 160.54 % in productivity MRR.
Reflecting investor expectations, most prior corporate governance research attempt to find a relationship between boards of directors’ composition and firm financial performance. Specifically, we try to examine the relationship between the boards’ size, board independence, CEO duality and gender diversity and two measurements of performance in listed companies in CAC 40, namely return on assets (ROA) and return of equities (ROE). We found evidence provide that board characteristics were positively correlated to the firm’ performance. However, our results show a significant association between ROE, ROA and the board of directors’ composition. We find significant negative association between financial information and equity-based management compensation. On the other hand, the presence of independent directors on the board seems to affect, positively, the level of financial performance of CAC 40 firms. Likewise, the stewardship theory assumption, the CEO duality is very high and is significantly associated with a higher level of firm performance. The results show that there was a significant relationship between board gender diversity and firm performance from our samples CAC 40 companies. In addition, we find significant negative impact of leverage on the financial performance for CAC 40 firms.
This paper examines the relationship between trade credit and bank loan during the financial crisis using annual data on Tunisian exporting companies over the period 2005- 2011. Results based on 2SLS regression have shown that trade credit and bank credit were simultaneously determined and maintained a complementary effect before 2008 financial crisis. On the other side, the substitution effect has been detected between the two sources of short term financing during 2008 financial crisis. Finally, companies rely more on bank loan after the financial crisis because bankers are able to cover financial need of their customers.
Most recent studies are based on benchmarking analysis allowing the measure of company efficiency relatively to a reference performance. Benchmarking is a helpful tool to analyze and promote efficiency in insurance companies. The fast development of X-efficiency notion makes traditional performance measures (ROA, ROE, etc.) obsolete. Indeed, various methods have been used, various input-output measures have been proposed and various research fields have been explored in insurance company investigation. So, after reviewing most known efficiency concepts and their definitions, this section explores the literature review of two principal points of discussion: the first point is focused on the different used techniques to measure efficiency, including the developed approaches to define inputs, outputs and their prices. The second point represents an overview of efficiency investigations in insurance industry.
The aim of this paper is to explore the determinants of Portfolio Choice under the investors, professionals and academics’ perception. We introduce an approach based on cognitive mapping technique with a series of semi-directive interviews. Among a sample of 30 Tunisian individuals, we propose tow different frameworks: a mean-variance framework and a behavioral framework. Each framework is oriented to capture the effect of some concepts as proposed by the mean-variance portfolio theory and the behavioral portfolio theory on the portfolio choice decision. The originality of this research paper is guaranteed since it traits the behavioral portfolio choice in emergent markets. In the best of our knowledge this is the first study in the Tunisian context that explores such area of research. Ours results show that the Tunisian investors behave as it prescribed by the behavioral portfolio theory. They use some concepts proposed by the rational mean-variance theory of portfolio choice but they are affected by their emotions and some others cognitive bias when constructing and managing they portfolio of assets.
This research examines the determinants of firms’ investment introducing a behavioral perspective that has received little attention in corporate finance literature. The following central hypothesis emerges from a set of recently developed theories: Investment decisions are influenced not only by their fundamentals but also depend on some other factors. One factor is the biasness of any CEO to their investment, biasness depends on the cognition and emotions, because some leaders use them as heuristic for the investment decision instead of fundamentals. This paper shows how CEO emotional bias (optimism, loss aversion and overconfidence) affects the investment decisions. The proposed model of this paper uses Bayesian Network Method to examine this relationship. Emotional bias has been measured by means of a questionnaire comprising several items. As for the selected sample, it has been composed of some 100 Tunisian executives. Our results have revealed that the behavioral analysis of investment decision implies leader affected by behavioral biases (optimism, loss aversion, and overconfidence) adjusts its investment choices based on their ability to assess alternatives (optimism and overconfidence) and risk perception (loss aversion) to create of shareholder value and ensure its place at the head of the management team.
The idea of this paper is to determine the mental models of actors in the firm with respect to the stakeholder approach of corporate governance. The use of the cognitive map to view these diagrams to show the ways of thinking and conceptualization of the stakeholder approach. The paper takes a corporate governance perspective, discusses stakeholder model. It takes also a cognitive mapping technique.
This study deals with appreciating the role of both governance system and executives cognitive and attitudinal aspects in the innovation decision-making. After discussing the theoretical relationship between board independence and CEOs attitude and behavior, we are advancing an empirical model testing the correlation between the managers’ attitude and behavior towards innovation and his psychological commitment level. The CEOs commitment bias and attitude constituent were measured using questionnaire. The data analysis was performed using the Bayesian network method on 220 Tunisian executives. Empirical results confirm the theoretical prediction and shows that processing with persuasive mechanism does not have an effective role on the alignment of the manager’s attitude and behavior in key tasks such innovation decision. CEOs authentic behavior was more related to an important manager involvement in this behavior rather than to persuasive effort committed by outside directors to make him contract this action. CEOs attitude and behavior towards innovation are shown related to commitment link “manager-task” and suggests that the board of directors plays no role in the CEOs discretion management. We argue that persuasive approach is not a sufficient path in behavior and interests alignment; yet, it should be applied with the commitment approach for understanding manager decision-making.