Pneumatic Power Source Research Articles

Classification et indications des dispositifs d’assistance cardiaque mécanique

Mechanical cardiac support represents a large spectrum of devices, differing by the duration of assistance, the support or replacement of the heart, the mono or bi ventricular assistance, the paracorporal or implantable positioning, the pulsed or continuous flow, the pneumatic or electric power source. We can distinguish: 1) the ECMO/ECLS systems (extracorporeal membrane oxygenation–extracorporeal life support) systems of peripheral extracorporeal circulation, accessible at patient bedside, that benefited from technological developments allowing longer assistance and therefore more indications; 2) the ventricular assist devices (VADs) that comprise pneumatic ventricles (mono- or biventricular, extra- or paracorporal), implantable left-VAD (pulsed-flow electromechanical ventricles and continuous-flow axial pumps), total artificial hearts (partially or totally implantable) and percutaneous left-VAD (available in the catheterization laboratory, still in the development stage). Partial or total mechanical cardiac support, although used in routine for 20 years, remains a technology seldom used outside the operating room. This slow diffusion is due to the small number of indications (end-stage heart failure and different heart failures considered as reversible), but also to its extreme complexity and to the alternative offered by heart transplantation. However, this situation is changing with the decreasing availability of organs and with the improvements of devices.

On a methodology for discrete–continuous scheduling

Discrete–continuous problems of scheduling nonpreemptable jobs on parallel machines are considered. The problems arise e.g. when jobs are assigned to multiple parallel processors driven by a common electric, hydraulic or pneumatic power source. Existing models have assumed job processing rates as a function of the number of jobs currently being processed, or equivalently the number of machines currently in operation. In this paper a more general model is proposed in which processing rates of a job assigned to a machine depend on the amount of a continuous, i.e. continuously divisible resource (e.g. power) allotted to this job at a time. Thus the problem consists of two interrelated subproblems: (i) to sequence jobs on machines, and (ii) to allocate the continuous resource among jobs already sequenced. We provide a comprehensive analysis of the problem. This includes properties of optimal schedules, efficiently (in particular analytically) solvable cases, formulations of the possibly simplest mathematical programming problems for finding optimal schedules in the general case, heuristics and the worst-case analysis. Although our objective function in this paper is to minimize makespan of a set of independent jobs, the presented methodology can be applied to other criteria, precedence-related jobs, and many resource types (apart from, or instead of machines).

Vibration of Pressurized Cylinders : Warren, C.H.; Barbin, A.R. Army Missile Command, Redstone Arsenal, Alabama (United States), AD- A199 191/8/GAR, 20 pp. (Jan. 1988)

Abstract : A study was conducted of the effects of internal pressure and media on the vibration of small cylindrical pressure vessels. Utilizing approximate expressions for elastic potential and kinetic energies of the cylinder-fluid system, LaGrange's equation was applied and an expression developed for predicting the frequency of vibration as a function of the pressure and density of the fluid for axial wave factors wavelength = M OI R/L 0.03 and number of circumferential waves n > 2. End conditions are empirically included in the measured zero-pressure frequency . A series of experiments on a small cylinder of the type used as pneumatic power sources on missiles confirmed the predictions over a range of pressure 0-34 MPA, with helium and nitrogen gases. A technique of nondestructive pressure measurements is proposed based on the results of this study.

Parallel Machine Scheduling: Processing Rates Dependent on Number of Jobs in Operation

We treat the class of n job − m machine scheduling problems with job processing times dependent on the number of jobs being simultaneously processed in the system at any point in time. Such systems occur when jobs are assigned to multiple parallel processors driven by a common power source. In situations typical of hydraulic and pneumatic power sources the level of power delivered to each processor is inversely proportional to the number of processors simultaneously at work. Aside from the variable processing rate assumptions, the remaining assumptions on the structure of the system conform to those of the standard identical parallel processor problem without job preemption. Although the standard n job − m machine problem is NP-hard with respect to a makespan measure, this is not the case when our seemingly complicating variable processing rate function, typical of hydraulic power sources, is included. In this case our main results are exceedingly simple. The makespan is found to be independent of the job-machine assignment, and the flowtime is minimized using one out of m processors. When other job processing rate functions or constant switch-over times are considered, then solving the problem becomes increasingly difficult, and the use of multiple processors is recommended. This paper concludes with a description of a real-world problem (scheduling the refueling of navy boats) which motivated this research.

Automated Tumor Extraction Device for Neurological Surgery

Various types of pneumatically driven devices have been used in craniotomy procedures for opening the skull. By contrast, except for some limited cases where a rotating cutter has been used to remove tumors from the central nervous system, only hand tools are commonly used for tumor or tissue removal. A pneumatically-activated probe cutter has been designed for the neurosurgical removal of nervous-system tumors and diseased tissue. The handheld probe-cutter utilizes concentric needles, one reciprocating inside the other. A scalpel-sharp edge on the tip of the inner needle moves in a shearing motion past a stationary port on one side near the distal end of the outer needle. The driving force for the reciprocating motion of the inner needle is provided by a pneumatic power source.

An Automated Tumor Resection Device for Neurological Surgery

Abstract A pneumatically activated cutting probe has been designed for the neurosurgical removal of nervous system tumors or diseased tissue. The hand-held probe is formed of concentric slender tubes, one reciprocating inside the other. A scalpelsharp edge on the tip of the inner tube moves in a shear motion past a stationary port on one side near the distal end of the outer tube. The reciprocating motion of the inner tube is provided by a pneumatic power source housed in a separate control console.

An automated tumor resection device for neurological surgery.

A pneumatically activated cutting probe has been designed for the neurosurgical removal of nervous system tumors or diseased tissue. The hand-held probe is formed of concentric slender tubes, one reciprocating inside the other. A scalpel-sharp edge on the tip of the inner tube moves in a shear motion past a stationary port on one side near the distal end of the outer tube. The reciprocating motion of the inner tube is provided by a pneumatic power source housed in a separate control console.