Spaced Rings Research Articles

Compression ratio and leakage through stages in turbomolecular pumps

The presence of leaks through the stages of a turbomolecular pump affects its actual compression ratio. The measured compression ratios are in many instances much lower than calculated ones if this effect is not considered in the calculation. A theoretical evaluation is done for the effect of the leakage from high pressure stages to the low pressure stages. A simple model is developed to calculate the decrease in the compression ratio caused by leakage. Two cases are studied in detail, referring to a particular design of the pump: (1) the conductance in the region between the envelope of the pump and the spacer rings is much larger than the conductance between two adjacent spacer rings; (2) the conductance between two adjacent spacer rings is much larger than the conductance in the region between the envelope of the pump and the spacer rings. In the latter case, compression ratios might be very close to the maximum (without leakage). Above considerations show a way to improve compression ratios in turbomolecular pumps. Finally an experimental verification has been performed, the calculated configurations have been tested, and the experimental and theoretical results are compared.

A Search in the Infrared to Microwave for Astroengineering Activity

Huge space power plants (Dyson Spheres) utilizing most of a star's energy should be detectable as infrared or microwave sources. A recent far infrared all-sky survey has revealed many sources with a spectrum peaking on this region which is characteristic of the thermal emission of the hypothetical Dyson spheres. The possibility of confusing them with thick circumstellar dust shells around evolved red giant stars is discussed. Microwave detection of cool extended Dyson Spheres by all-sky surveys searching for microwave background fluctuations is also considered.

Side bridge geometry after quick-freezing of stimulated and unstimulated frog skeletal muscle fibers

Quick-freezing allows the structural analysis of timed perturbations of morphology. We are presenting preliminary results concerning the feasibility of studying directly the side bridge geometry of actin-myosin interactions within the time course of a twitch in single intact frog skeletal muscle fibers, both by freeze-substitution and freeze-fracture after quick-freezing, and following various time intervals between stimulation and impact of the fibers on a liquid He-cooled copper block.Materials and Methods. The quick-freezing device was a "Slammer"(Polaron) for which the electronics had been redesigned; they are capable, in combination with a Grass S48 stimulator, of any stimulation interval between 0 and 1 sec prior to freezing, including tetanus. The actual elapsed time between stimulation and freezing is recorded with a digital clock. Single intact tendonto- tendon frog skeletal muscle fibers (semitendinosus of r. temporaria) or toe muscle bundles (r.pipiens) were isolated by sharp dissection and placed between coextensive Pt stimulation wires on blackened 2% agarose, the height of which on the specimen holder was adjusted appropriately with respect to a spacer ring both, to calibrate the impact time and to prevent smashing of the fibers.

Disk-shaped heat-pipe oven used for lithium excited-state lifetime measurements

A metal-vapor spectroscopic oven based on the heat-pipe principle has been constructed in which the heated stainless steel wicks are mounted on disks spaced closely compared with their radii and in which the window is a glass spacer ring separating the disks and permitting optical access to the active volume. The device has been successfully operated using both sodium and lithium as the working fluid. The lithium 4s2S1/2 and 5s2S1/2 radiative lifetimes were measured with this device, yielding values of 56 ± 1.7 and 99 ± 9 nsec, respectively.

回転体部品を基本構成要素とする機構・構造の自動設計システムの開発

A conversational CAD system for the design of mechanical assembly such as a lens unit system consisting of the rotational symmetry parts, for example, barrel, spacer ring, thread ring etc., is developed. The system has the following functions; display of assembly drawing, supporting creation and judgement by the designer, display of parts drawing, modification of the shape of parts, addition of new parts, automated initial designing. The function of display of assembly drawing is realized by 2-dimensional treatment of rotational symmetry component with additional non-rotational symme-try component. In the system, the parts shape is ex-pressed by figure component and state component. Furthermore, in order to recognize mutual relation of parts, the connecting type is grouped into two types. A new method which recognize the connection of the parts, using the function of the interference check, is developed. The method is called virtual displacement method.

General discussion

In order to analyse quantitatively the images obtained by using the Radiation Dynamics Super X, 8 MeV linear accelerator, Rolls-Royce have developed a system of close-range X-ray photogrammetry. In order to study the behaviour of components in motion, it is necessary to provide a flow of images from which specific events may be identified in a qualitative manner to allow a radiograph to be made for detailed measurement purposes. The use of real-time video techniques also allows the speed of an event or the rate of flexure of components to be determined, giving an indication of the nature of the force creating the movement. This may, for instance, be a thermal growth which may be slow or a pressure force which is likely to be more rapid in change. By using the Super X in the stroboscopic mode linked to engine speed, it is possible to identify eccentricity of compressor spacer rings. The video then allows the determination of the time when the ring becomes free and eccentric.

Some Thoughts on Dyson Spheres

According to Dyson (1960), Malthusian pressures may have led extra-terrestrial civilizations to utilize significant fractions of the energy output from their stars or the total amount of matter in their planetary systems in their search for living space. This would have been achieved by constructing from a large number of independently orbiting colonies, an artificial biosphere surrounding their star. Biospheres of this nature are known as Dyson spheres. If enough matter is available to construct an optically thick Dyson sphere the result of such astroengineering activity, as far as observations from the earth are concerned, would be a point source of infra-red radiation which peaks in the 10 micron range. If not enough matter is available to completely block the stars’ light the result would be anomalous infra-red emission accompanying the visible radiation (Dyson 1960).

Sintered spacer rings for cotton picking machines

Sintered spacer rings for cotton picking machines