Hybrid cam mechanisms

This paper investigates the problem of driving a machine with several reciprocating heavy inertias. The drive should also realize some programmable flexibility of the motion, so that the operation of the machine, e,g., synchronization between different motions and duration of standstills, can easily be modified. The use of a single servomotor for every motion is not the best solution, since it does not allow for energy recuperation. This means that the installed servomotor power will be much higher than the required net peak power for the machine as a whole. The presented solution, however, reduces the servomotor peak torque and power by one order of magnitude, and makes energy transfer between the motions possible. The hybrid cam mechanism consists of a hybrid drive, which is a combination of a servomotor, a constant velocity motor and a cam follower mechanism. The operation principle exploits the nonlinear characteristics of the cam to add flexibility at low cost of energy. The hybrid solution is particularly successful for motions involving high peak acceleration. In addition, the concept can be used to reject disturbances. Simulations show the performance of the hybrid cam mechanism.     

Accurate determination of the mean relative humidity in controlled climates at high humidities (new method)

The measurement of the relative humidity (RH) at high levels to the desired accuracy is still a problem, especially for levels above 90% RH. The reasons for this are:

• i The accuracy of the standard apparatus is lower at high RH than at moderate and low RH;
• ii The need for accurate measurement of the RH in moisture controlled rooms is greater at high RH than at lower RH, because for moisture sensitive products, such as fibreboard boxes and certain horticultural products, the influence of a minor deviation in RH on the properties of these products is considerably greater at high RH than at moderate and low RH.

     

Initial stages of tin electrodeposition from sulfate baths in the presence of gluconate

Tin electrodeposition in its initial stages in acid sulfate/gluconate baths was studied with varying tin and gluconate concentrations using potential-controlled electrochemical techniques. The deposit morphology was observed by scanning electron microscopy (SEM). A comparison with tin electrodeposition from acid sulfate baths in the absence of gluconate was also carried out. Use of a highly acidic bath leads to nonuniform deposits, even in the presence of gluconate; at pH 4 deposits are uniform, brilliant and suitable for finishing applications. Tin crystallites have a well defined morphology which depends on bath agitation conditions. In the absence of agitation, the crystallites have the same tetragonal shape as in a sulfate bath without gluconate.     

Elongational viscosity of microbead suspensions

A ‘tubeless syphon’ was used as an elongational viscometer for the purpose of measuring elongational viscosities of glass bead suspensions in dilute polymer solutions. It was found that while the shear viscosities increased, the elongational viscosities decreased very sharply with increasing bead concentration. The conclusions from the present data are then compared with the observed changes in the elastic properties of two phase molten polymer systems. A double shift procedure has been successfully adopted to correlate the experimental data.     

Non-markovian diffusion processes in polymers and a stretched exponential relaxation constitutive equation

Non-Markovian diffusion transport in polymers was studied. Applying the results of various researchers, a stretched exponential relaxation function was obtained and a linear viscoelastic constitutive equation formulated. Frequency dependent material functions, obtained from this constitutive equation were studied and the results successfully compared with experimental data for polyethylene oxide solutions. Sorption kinetics in a polymeric film were also studied. © 1994 John Wiley & Sons, Inc.     

Acid cleaning and passivation of power plant condensers and desalination plants

Experiences of acid cleaning and passivation treatments of copper alloy tubes are described. The suitability of corrosion monitoring to follow each step of such operation is demonstrated.     

Polymerization of 2-phenyl-aziridine

Summary The ring-opening polymerization of 2-phenyl aziridine was studied with several catalyst systems: boron trifluoride etherate, chlorhydric acid, perchloric acid, dimethyl sulfate and methyl triflate. The corresponding polyamine was obtained as a pale yellow solid with a number average molecular weight around 2,000–3,000.A kinetic study is discussed in the case of perchloric acid and methyl triflate.