Experimental and Statistical Parametric Optimisation of Surface Roughness and Machining Productivity by Lapping

The quality of surfaces machined by lapping depends on numerous variables, some of them controllable and others not. Their existence renders the task of selecting adequate working parameters and their values (set points) such as to obtain the desired response difficult. For this reason, this paper discusses the robust parameter design as an optimisation method for plane lapping. The paper presents the working equipment, the utilized methodology as well as the obtained experimental results. The output quantities selected for describing the lapped surface quality and the machining productivity, respectively, were roughness Ra and the height of the cut layer h

Optimization of the Lapping Process of Parts Made from X2 CrNiMo 17-12-2 Stainless Steel

Austenitic stainless steel with nickel and molybdenum content (X2 CrNiMo 17-12-2) is frequently used in the food, chemical, or nuclear industries, as well as in medical applications like endourology. Due to the high content of nickel and molybdenum in these steels, their machinability is difficult; however, the surface finishing by lapping of parts made from X2 CrNiMo 17-12-2 steel remains an issue to be addressed. The paper investigates the possibility of obtaining the smallest possible surface roughness based on the selection of an optimum combination of the main parameters that influence machining. The optimization of the machining system could be achieved by changing the setpoints of the four selected input factors (lap disk eccentricity, concentration of the abrasive paste, contact pressure, and duration of machining). Response surface methodology was applied to determine the combination of factor values that ensures the minimum roughness of the machined surface

APPLICATIONS OF PNEUMATIC MUSCLES DEVELOPED AT THE FESTO REGIONAL RESEARCH AND TRAINING CENTRE OF BRAŞOV

Compressed air is one of the most important sources of energy in industry, pneumatic actuations tending to hold an increasing share in the conception of modern industrial systems. At present, due to the development of new pneumatic components and systems assemblies of high complexity can be achieved, many of them with applicability in robotics. Such a component is the pneumatic muscle, increasingly deployed in actuation systems, particularly in the field of industrial robots. The paper presents some of the results of research conducted at the Festo Regional Research and Training Centre (FRRTC) at Transilvania University of Braşov

Linear pneumatic motors – a comparative study

The paper presents a comparative study of the performance of single-acting cylinders, diaphragm cylinders and pneumatic muscles, and offers users information that allows the selection of an optimum technical solution. Such a study was necessary, in view of the numerous papers on pneumatic muscle applications found in literature, that assert the superiority of pneumatic muscles over other pneumatic linear motors in relation to quantities like dimensions, mass, developed force or energy-to-mass ratios, however without offering concrete data

Comparison between two models of elbow rehabilitation equipment

International studies have revealed that using continuous passive motion (CPM) equipment as part of a rehabilitation program improves the recovery period and also diminishes the rehabilitation costs by about 50%. This explains the need for conceiving elbow joint rehabilitation equipment to help persons suffering from posttraumatic disabilities. In order to create the best model to meet the patients’ requirements this paper presents two constructive solutions of such equipment and a comparison between their designs. Both achieve the desired movements of the elbow joint: flexion-extension and pronation-supination and are actuated by pneumatic muscles, due to the multiple advantages of pneumatic actuation: low cost, compliance and favorable response to commands

The Rap–RapGAP complex: GTP hydrolysis without catalytic glutamine and arginine residues

The GTP-binding protein Rap1 regulates integrin-mediated and other cell adhesion processes. Unlike most other Ras-related proteins, it contains a threonine in switch II instead of a glutamine (Gln61 in Ras), a residue crucial for the GTPase reaction of most G proteins. Furthermore, unlike most other GTPase-activating proteins (GAPs) for small G proteins, which supply a catalytically important Arg-finger, no arginine residue of RapGAP makes a significant contribution to the GTPase reaction of Rap1. For a detailed understanding of the reaction mechanism, we have solved the structure of Rap1 in complex with Rap1GAP. It shows that the Thr61 of Rap is away from the active site and that an invariant asparagine of RapGAPs, the Asn-thumb, takes over the role of the cis-glutamine of Ras, Rho or Ran. The structure and biochemical data allow to further explain the mechanism and to define the important role of a conserved tyrosine. The structure and biochemical data furthermore show that the RapGAP homologous region of the tumour suppressor Tuberin is sufficient for catalysis on Rheb

Adding SMP support to fastpaths in an L4 microkernel

Fastpaths are a method of optimization which relies on treating the most commonly executed cases of certain functions in a privileged manner, such that behaviour is not modified, but execution time is reduced.Fastpaths play an important role on improving paravirtualization performance offered by an L4 microkernel.In this article we redesign two existing fastpaths in an L4 microkernel for the purpose of adding SMP support.We then put these fastpaths through a series of regression and performance tests to determine if the design is correct and what performance benefits we can expect by using them on a multiprocessor system

Optimizing Memory Usage in L4-Based Microkernel

Memory allocation is a critical aspect of any modern operating system kernel because it must run continuously for long periods of time, therefore memory leaks and inefficiency must be eliminated. This paper presents different memory management algorithms and their aplicability to an L4-based microkernel. We aim to reduce memory usage and increase the performance of allocation and deallocation of memory