U-shaped Enclosure Research Articles

1D virtual force field algorithm for reflexive local path planning of mobile robots

A one-dimensional (1D) virtual force field (VFF) algorithm for real-time reflexive local path planning of mobile robots is proposed. The 1D-VFF is composed of the virtual steering, obstacle and integrated force fields (IFFs). The steering force field (SFF) is generated by the local or global goal position. This SFF leads a mobile robot to the goal. The obstacle force field (OFF) is created by the raw data of a range measurement sensor (RMS). By this OFF, a mobile robot avoids obstacles. The IFF is produced by combining the steering and OFFs in which weights between 0 and 1 are multiplied. Through this IFF, a final steering command by which a mobile robot reaches a goal by avoiding obstacles is generated. Various simulations compare the performance of the proposed 1D-VFF with the weighted virtual tangential vector (WVTV), which is the recently suggested local path planning method to overcome the U-shaped enclosure problem.

Magnetohydrodynamic Natural Convection of Nanofluids in U-shaped Enclosures

This article presents the results of a numerical study of laminar natural convection in a U-shaped enclosure that is filled with a water-Cu nanofluid and is under the influence of a horizontal magnetic field. A computational domain was defined and a numerical scheme based on the control volume formulation using the SIMPLE algorithm was developed. The convection-diffusion terms were discretized using a power-law scheme. The effects of the Rayleigh number, the solid volume fraction, the Hartmann number, and the enclosure aspect ratio on the heat transfer performance of the enclosure were examined. The thermal performance of the enclosure was found to be a function of the enclosure aspect ratio. The results also showed that the heat transfer rate increased with an increase of the Rayleigh number and the solid volume fraction, but it decreased with an increase of the Hartmann number.

Open-Type Magnetically Shielded Room Using Only Canceling Coil Without a Ferromagnetic Wall for Magnetic Resonance Imaging

In order to improve amenities for patients in hospitals, a new open type of magnetically shielded room (MSR) for magnetic resonance imaging (MRI), which uses only canceling coils without a ferromagnetic wall, has been developed. The device was designed by three-dimensional magnetic field analysis and experimentally investigated using an actual MRI of 1.5 T. First, a coil and ferromagnetic material were modeled on an actual MRI, so that the distribution of the leakage magnetic flux vectors was in agreement with that measured. Second, the optimal shaped canceling coil, a saddle-shaped coil which can reduce the leakage flux from the edge plane to the side plane of the room, was designed using the modeled MRI, and realized. The effectiveness of this coil for shielding and its influence on MRI imaging were confirmed experimentally using an actual MRI. In addition, an optimal U-shaped enclosure that can sufficiently shield the leakage flux generated by the coil itself was designed; its effectiveness was confirmed experimentally by using an actual canceling coil.

An Elastomeric Micrometering System for the Controlled Administration of Drugs

Abstract When drugs are infused, it is often necessary to minimize the volume of fluid delivered. Fluid delivery rates of 1 cm3/h or less are frequently desirable; however, the accurate metering of fluids at such low flow rates to the human body has been difficult to accomplish. The metering devices most commonly used to control flow rate from a constant-pressure source have been micrometer valves, clamped tubes, capillaries, and porous plugs. Each of these devices has specific disadvantages : micrometer valves are expensive and bulky, clamped tubes are not stable for long-term infusion and present a hazard of greatly fluctuating flow rates, capillary tubes are subject to particle blockage and are not adjustable, and porous plugs suffer from lack of adjustability. Recently a valve made of extruded silicone rubber rod with axial holes was reported to yield stable flow rates; it was adjusted by placement in a plastic clamp. A new low-infusion-rate metering system has been developed to overcome the above deficiencies. This system consists of axially aligned polyurethane fibers contained within the lumen of a length of silicone rubber tubing. The fibers fill the lumen to the extent that they are subjected to a compressive hoop stress by the tubing. The assembly represents two elastomeric materials in states of strain, exerting equal and opposite stresses on each other. The elastomeric tubular assembly is contained in a rigid, adjustable, U-shaped enclosure that controls the deformation of the assembly. While other elastomeric materials would be suitable for the elastomeric valving system, we report here on our experience with polyurethane fibers and silicone rubber tubing. These materials were selected for their expected compatibility with most aqueous drugs and their availability.