Adjustable Piston Research Articles

Reverse kinetostatic analysis and stiffness synthesis of a spatial tensegrity-based compliant mechanism

This paper presents an analysis of a spatial tensegrity-based mechanism. In this study, a moving body in space is joined to ground by seven compliant leg connectors. Each leg connector is comprised of a spring in series with an adjustable piston. The mechanism is said to be ‘tensegrity-based’ in that it is prestressed when at equilibrium due to compliant linear elements. Two problems are solved in this paper; the reverse kinetostatic analysis and stiffness synthesis problems. In the first problem, the values of the seven spring constants and free lengths are given and the lengths of the seven pistons are determined such that: (1) the top body is given at a desired pose; (2) the top body is at equilibrium while a specified external wrench is applied; and (3) the total potential energy stored in the seven springs equals some desired value. In the second problem, the seven spring constants and the lengths of the seven pistons are determined such that conditions (1) and (2) are met and also the instantaneous stiffness matrix of the top body equals a specified set of matrix values. The paper formulates the solutions of these problems. Numerical examples are also presented.

Ein realitätsnahes Kreislaufmodell zur Beurteilung der klinischen Anwendbarkeit von Duplex- und Farbdopplergeräten

To evaluate the accuracy and reliability of colour-coded Doppler devices (CCDD) for practical use, a circulatory phantom with in vivo characteristics was developed. The experimental design consists of a piston-diaphragm metering pump with an adjustable piston volume and frequency of stroke as well as silicone tubings with different elasticity and diameters comparable with cadaver arteries. Depending on physiological conditions, blood as a circulating fluid and the surrounding soft tissues of the artery near the Doppler probe should be employed. The transducer should be manually guided. Thus, comparable to physiological frequency spectral displays, different types of wave forms (e.g. monophasic, triphasic) were initiated to analyze the reliability of CCDDs for practical use.

Fluidized-bed receptor-affinity chromatography.

A multipurpose fluidized-bed receptor-affinity purification system based upon the biological recognition between an immobilized receptor and its soluble protein ligands is described. The fluidized affinity sorbent consists of a soluble form of interleukin-2 receptor chemically bonded to an aldehyde derivative of controlled pore glass beads, which have a pore diameter of 1000 A and a particle density of 1.2-1.3 g/mL. The fluidized-bed separation device used in this study consists of a specially designed column fitted at the inlet end with a perforated distributor plate covered with a screen and the top outlet with an adjustable piston. The fluidized-bed consisting of a loose gel matrix permits the unimpeded passage of cell debris and particulate matter, while the target protein is captured by the affinity beads. Purification of the humanized-anti-Tac monoclonal antibody is used as a model system to determine the operational parameters. Also, fluidized-bed receptor-affinity chromatography has been successfully employed in the purification of recombinant interleukin-2 and single chain anti-Tac(Fv)-Pseudomonas exotoxin immunotoxin from unclarified inclusion body extracts. Overall, fluidized-bed receptor-affinity chromatography is found to be a productive affinity method suitable for the purification of recombinant human interleukin-2 and related molecules.

Broad-band hydraulic vibrator

A hydraulic vibrator having an adjustable piston rod and a fixed piston rod to vary the cylinder volume for operation at different vibration frequencies. The adjustable piston rod is in threaded engagement with the fixed piston rod and has a piston head adjacent a piston head on the fixed piston rod. Rotation of the adjustable piston rod displaces the two piston heads, thereby varying the cylinder volume of the hydraulic vibrator.

Assessment of numerical computation of flow-properties in an axi-symmetric reversed flow furnace

Many practical applications of industrial furnaces require short, stabilized flames over a wide range of operating conditions. Others require high heat transfer from the flame to the furnace walls as in boilers. Conventionally, these requirements are achieved through controlling the flame length and its stability either by swirling the combustion air or using bluff body stabilizers to create a central recirculation zone. Another is by restricting the exit section of the furnace, thus causing an outer recirculation zone along the walls which leads to improved mixing and combustion. This paper demonstrates the extent to which the local flow properties and wall heat flux in an axi-symmetric reversed flow furnace can be controlled by furnace geometry, and the consequent effect on local temperature and combustion efficiency. The calculated results are obtained by solving the appropriate conservation equations. The procedure embodies a two-equation turbulence model, a combustion model which accounts for the effect of turbulent fluctuation and chemistry on the reaction, and a four-flux radiation model. The validity of these assumptions are assessed by comparisons with available experimental results. The calculations are performed in an axi-symmetric furnace fed by coaxial jets of butane gas and air at one end, while the other end is closed by an adjustable piston which allows for various furnace length to diameter ratios. The piston forces the products of combustion to reverse their direction and escape through the annular area between the burner and the furnace cylindrical walls. Comparisons which include mean axial velocity, mean gas temperature, and wall heat flux, illustrate the effect of the furnace length on its performance. They also indicate that the procedure qualitatively represents the measurements; and that the agreement is sufficiently close to justify the use of this method for furnace design purposes.

Water Flux and Electrical Potentials in Water‐Saturated Bentonite

AbstractElectrical potential, water flux, and hydraulic gradient were studied for saturated water flow through plugs of sodium bentonite at concentrations ranging from 11.5 to 35.1% clay. A special permeameter with an adjustable piston allowed measurements to be taken with a given mass of clay, but with successively lower clay concentrations as the piston was shifted out to increase the water content of the clay‐water mixture. At the lowest clay content, both electrical potential and water flux increased less than proportionally with increasing hydraulic gradient. This less‐than‐proportional behavior decreased as clay concentration increased, and, at 28.4% clay, proportional response to hydraulic gradient was obtained for both electrical potential and water flux. A less‐than‐proportional relationship between electrical potential and hydraulic gradient did not cause the water flux to increase more than proportionally with increasing hydraulic gradient, in contrast with what has been reported for nonswelling quartz powder and would be inferred from the classical double‐layer theory of streaming potential and electroosmotic flow. The relationship between electrical and hydraulic properties may thus be different for swelling porous media than for nonswelling media. The only indication of a more‐than‐proportional flux‐gradient relationship was found for a 35.1% clay concentration, in the form of a linear relationship displaced to the right from the origin to yield a positive gradient intercept and a negative water flux at zero hydraulic gradient.