Chainsaws generate high level vibrations and noise during work. No matter what type of the drive (electric, combustion) they exceed the per-missible levels defined for a standard eight-hour working day. The intensity of a vibro-acoustic impact on chainsaw operators depends on many factors. One of them is the type of the drive. This is due to significant differences in saw design (inter alia characteristics of the drive, rotational speeds - quasi-constant for an electric drive and variable for a combustion one). For chain-saws of the same or similar power and different types of the drive the levels of vibrations and noise may vary. The paper compares the noise levels and frequency weighted vibration accelerations for different types of the drive. The tests were performed with the same interchangeable cutting set (guide bar, cutting chain). The repeatability of the cutting process was ensured. The test results may be helpful when choosing the tool.

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In the process of post-production testing of rolling bearings, quality classification and/or qualification of finished products as good and defective is performed. In view of mass production, bearing testing should be carried out within a short period of time. Vibroacoustic (VA) processes are widely used for post-production testing. Parameterization of bearing vibrations is largely determined by stabilization of lubrication conditions and VA processes, which to some extent depend on temperature. The article presents the results of temperature measurements carried out during the testing of a set of new tapered roller bearings. On their basis, an attempt was made to estimate the value of rms values of bearing vibration accelerations. This is based on the known relationships between the temperature and viscosity of the oil as well as the relationship between viscosity and acceleration of the bearing vibrations. The estimated acceleration values were verified experimentally. The time after which the temperature of a bearing is stabilized was also determined. The paper also shows the influence of a lubricant on these processes, mainly its kinematic viscosity.

This paper concerns the asymptotics of certain parabolic-elliptic chemotaxisconsumption systems with logistic growth and constant concentration of chemoattractant on the boundary. First we prove that in two dimensional bounded domains there exists a unique global classical solution which is uniformly bounded in time, and then we show that if the concentration of chemoattractant on the boundary is sufficiently low then the solution converges to the positive steady state as time goes to infinity.

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