Search results

The knowledge over the performance of cutting fluids when applied under different machining conditions (such as distinct work material and cutting parameters) is critical in order to improve the efficiency of most machining operations. This paper is concerned with the performance of cutting fluids employed under two distinct machining operations involving aluminium alloys: drilling of AA 1050‐O aluminium applying cutting fluid as a mist and turning of AA 6262‐T6 aluminium alloy using cutting fluids (as a flood) with distinct extreme pressure additives (chlorine, sulphur and phosphor).

This work reports on a experimental study of the performance of cutting fluids when machining aluminium alloys.

The results indicated an increase in the flow rate of the mist led to lower feed forces but higher torque, power consumption and specific cutting pressure in the drilling operation (AA 1050‐O aluminium). The surface finish was not drastically affected by the cutting fluid flow rate. When turning AA 6162‐T6 aluminium alloy, in general, best results were observed using 10 per cent fluid concentration applied at the tool‐workpiece interface. The cutting fluid containing chlorine as extreme pressure additive produced lower cutting forces and better surface finish at high cutting speed and low feed rate and depth of cut.

The novel element of this paper is the use of minimal lubrication (drilling) and cutting fluids with distinct extreme pressure (turning).

The purpose of this paper is to study the tribological behavior and mechanism of water‐soluble bismuth dithiophosphate as the additive of water‐based cutting fluid in aluminum alloy tapping.

Comparable investigation has been made on the lubrication performance of bismuth dithiophosphate and sodium dithiophosphate in aluminum alloy tapping. The aluminum alloy‐machined surface finish was observed on scanning electron microscope. The films on the work‐piece‐machined surface and the tap tool working surface were analyzed by X‐ray photoelectron spectroscopy.

The results indicated that the water medium containing 1 wt% the prepared water‐soluble bismuth dithiophosphate exhibited better tapping efficiency than the liquid paraffin containing 2.5 wt% chlorinated paraffin and 2.5 wt% sulfurized olefin. The bismuth sulfide component in the reaction film on the tap working surface plays a leading role in elevating the tapping efficiency and improving the machined surface finish.

The paper is restricted to the lubrication performance of bismuth dithiophosphate as the water‐based cutting fluid additive in 2024 aluminum alloy tapping.

The test method adopted is very close to the machined method applied in industry. The test results show that the bismuth dithiophosphate can obviously improve the tapping efficiency and the machined surface finish. Thus, it can be applied to the aluminum alloy cutting in automotive and aviation.

An attempt has been made to identify the chemical reaction film sourced from bismuth element and dithiophosphate group on the work‐piece‐machined surface and the tool working surface and their contribution to enhancing the tapping efficiency and improving the machining surface finish. This is helpful to the designers and the practitioners of the additives of metalworking fluid.

The purpose of this paper is to investigate the performance of four cutting oils, two different vegetable‐based cutting fluids developed from refined sunflower oil and two commercial types (semi‐synthetic and mineral), for surface roughness during drilling of AISI 304 austenitic stainless steel with HSSE tool.

L₉ (3³) orthogonal array was used for the experiment plan. Spindle speed, feed rate and drilling depth were considered as machining parameters.

Results were evaluated statistically. Mathematical models based on cutting parameters were obtained from regression analyses to predict surface roughness. ANOVA was used to determine the effect of the cutting parameters on the surface roughness. The performance results were found to be better for vegetable‐based cutting oils than that of commercial ones.

The paper reports on the use of refined sunflower oil in drilling stainless steel.

The purpose of this paper is to identify and assess the perception of customers (students) about the services provided by Brazilian universities, through the identification of the attributes that impact on customer satisfaction and the dimensions or factors related to quality in services. This may generate a better management and seek more competitive edge in graduate courses.

The research method was developed in two phases: the first one is characterized by a qualitative and exploratory approach and the second one as a quantitative research of conclusive character. In the qualitative phase, in-depth interviews were implemented with a semi-structured approach. A survey was performed in the final phase and a multivariate statistical technique was used for the data analysis.

The results echoed in a set of 40 analyzed attributes (variables), distributed in six dimensions of quality in services, in the graduate courses (second cycle) of administration, which could serve as a basis for orienting other Brazilian universities.

The data analysis did not include crossed techniques that could have enriched the analysis process. Another limitation that can be pointed out is the fact of having only adopted a factor analysis method to identify the dimensions of service quality that influence customer satisfaction (students). In addition, data collection was cross-sectional, which does not allow any change verification of the respondents’ perception.

Taking into account the current scenario of increased competition between the Brazilian universities to attract and retain students, the knowledge of student’s preferences and the dimensions of quality service can effectively contribute in the development of strategies and actions for an effective graduate programs management (second cycle), and for their consolidation in the Brazilian market.

The development of more adequate courses, in terms of level of quality and relevancy.

The identification of the attributes that represent the quality dimensions, related to the services provided, can assist any Brazilian university to prioritize its strategies and actions and to contribute to excellence in education. In addition, it may encourage customer retention (students) and consolidate its market position. Moreover, the study can contribute as a source of empirical data for transferability and benchmark strategies in other contexts for Brazilian universities.

This paper aims to explore the optimization process involved in the aircraft maintenance allocation and packing problem. The aircraft industry misses a part of the optimization potential while developing maintenance plans. This research provides the modeling foundation for the missing part considering the failure behavior of components, costs involved with all maintenance tasks and opportunity costs.

The study models the cost-effectiveness of support against the availability to come up with an optimization problem. The mathematical problem was solved with an exact algorithm. Experiments were performed with real field and synthetically generated data, to validate the correctness of the model and its potential to provide more accurate and better engineered maintenance plans.

The solution procedure provided excellent results by enhancing the overall arrangement of the tasks, resulting in higher availability rates and a substantial decrease in total maintenance costs. In terms of situational awareness, it provides the user with the flexibility to better manage resource constraints while still achieving optimal results.

This is an innovative research providing a state-of-the-art mathematical model and an algorithm for efficiently solving a task allocation and packing problem by incorporating components’ due flight time, failure probability, task relationships, smart allocation of common preparation tasks, operational profile and resource limitations.

This chapter examines the barriers to reentry for justice involved young people in the US and Australia from the perspectives of the 44 Australian and 14 US stakeholders who work with them. The interviews were analyzed using inductive content analysis to identify key internal and external barriers. Results suggest a need for improvement in the areas of collaboration among systems, family engagement, and student self-determination. The discussion focuses on the similarities and differences in the barriers that exist across nations and systems. Implications for future research, practice, and policy are included to improve transition services and supports for juvenile justice involved youth.

According to the market timing theory, firms try to take advantage of windows of opportunity to raise capital by exploiting temporary cost fluctuations of alternative financing sources. In this context, the main objective of this paper is to examine the influence and persistence of market timing in the financing decisions of Brazilian firms that launched IPOs in the period from 2001 to 2011.

We analyze the influence of past market values on the capital structure of these firms, based on the main models proposed by Baker and Wurgler (2002), adapted to reflect the characteristics of Brazilian firms’ financial statements.

We find evidence of market timing, but this behavior is not sufficiently persistent in the period studied to the point of determining these firms’ capital structure. We believe the fact that Brazilian companies rarely carried out follow-on primary equity issues after floating their capital in the period analyzed, due to the presence of more advantageous financing sources (particularly from the national development bank, BNDES), explains the results. Therefore, Brazilian firms appear to be pay heed to different funding sources, in search of windows of opportunity, to guide their financing decisions and determine their capital structures.

The Brazilian capital market has been developing intensely in recent years, making it increasingly relevant to analyze the financing and investment decisions of the country’s listed companies. The Brazilian literature on capital structure is extensive, but few works have addressed the issue of market timing.