A review of the current understanding and technology of powder mixed electrical discharge machining (PMEDM)
This paper reviews the current understanding of powder mixed electrical discharge machining (PMEDM), highlighting particularly the mechanisms proposed for PMEDM under the influence of additive of powders in the dielectric fluids. Generally, the mirror surface phenomenon in PMEDM can be explained by the enlarged gap widths which can expand the discharge channel and thereby reduce the electrical power density since lower power density can yield large and shallow craters that evenly distributed on the machined surface. Moreover, the increment of the inter electrodes distance will limit the capacitive effect and enable a small surface roughness even in a large area. Another possible mechanism, multi-discharge model was also presented in this paper. More investigations on the fundamental mechanism in power mixed EDM are highly desirable since it has not been understood clearly. In this paper, the traditional and some recent development technology for PMEDM is also reviewed. Historically, PMEDM was invented to improve the surface quality of the machined components. Nowadays, some new applications of this technology, such as micro machining, rough machining and surface modification were proposed; some novel variations that based on power mixed EDM, such as PMEDM combined with ultrasonic or abrasive, powder mixed near-dry EDM and powder mixed electrical chemical discharge machining (ECDM) were also developed.
Characteristics of plasma channel in powder-mixed EDM based on monopulse discharge
Electrical discharge machining (EDM) was developed over 70 years ago, but the knowledge of plasma channels that form during this process remain understudied. Therefore, this study systematically investigated the breakdown process and impedance characteristics of plasma channels through singe-pulse discharge experiments. The influence of discharge current and gap distance on the breakdown process and impedance characteristics of plasma channels was also analyzed. The results of this work can contribute to the existing body of knowledge of the physical nature of EDM.
Anaesthetic aspects of bronchial fistula.
SINCE the term bronchial fistula can, from the practical point of view, be applied to any abnormal connection between the inside of the intrathoracic respiratory system and the outside, it includes a very wide assortment of cases. Fistulae vary in their acuteness and duration from a few minutes up to thirty years or more (Huizinga and Smelt, 1950), and in their consequences from the rapidly fatal to the almost insignificant. Although the anaesthetic management of these cases falls mainly within the province of those working in specialized units, any anaesthetist may be caught unawares from time to time. Quite apart from this consideration the subject is well worth discussing because of its intrinsic interest and because it has probably called for as much anaesthetic ingenuity and resourcefulness as any other subject within the specialty.