Information about vibration modes is needed during the planning of noise control measures on different parts of machinery. A visualization of vibration modes is a starting point and different methods can be used to visualize vibration modes. Some methods which incorporate an inverse calculation of surface velocity from the sound pressure on some boundary have already been proposed, among others. A direct inverse method based on the discretized Rayleigh integral was used in our work, to demonstrate that microphones should be placed close to the vibrating structure to provide an acoustic transfer matrix with a low condition number. It is demonstrated, that there is practically no need for the calculation of the inverse matrix if microphones are placed in a very near field of the vibrating structure. A single microphone placed in a very near field together with a reference vibration sensor provides sufficient information for producing the images of vibration modes. Analytical results, numerical results, FEM simulations and measurement results were used to prove that properties of the sound pressure in a very near field permit a cost effective visualization of the vibration modes.
COBISS.SI-ID: 13042203
Hospitals present complex indoor environment with various users, health hazards and specific activities. This paper classifies health hazards specific to the hospital environment (HE), defines their interactions and possible impacts on human health and summarizes recommendations for biological and chemical hazards. A detailed literature review clearly shows that there is no developed system or method for integral control of health hazards in HE. There is no appropriate technology available that would allow development of optimal thermal comfort conditions for individual users in HE. For integral control of physical hazards, an innovative low exergy (LowEx) system was designed and tested. The system enables individual control of thermal comfort parameters to meet the needs of various users in the same room. It enables the design of optional conditions for healthcare and treatment considering the different requirements of individual patients and thermally neutral zones for other users. The system application is presented in a model room for burns patient. The measured energy use was lower by 11–27% for space heating and by 32–73% for cooling, when using LowEx system as compared to the conventional system. Owning to its flexibility, the system can also be used for other potential users.
COBISS.SI-ID: 5988705
This paper deals with the mechanical properties of the double bass and double bass bow. The sound of the instrument, as well as the vibrations of the bow, were recorded while playing. The sound was recorded with a microphone, while a sensor, placed on the bow's stick, registered its vibrations. By observing these signals, from double bass and bow, the correlation between them was determined in order to explain the bow-string mechanism.
COBISS.SI-ID: 13267995
The purpose of this paper is the investigation of eddy currents induced in the axial-flux permanent-magnet machine housing by the leakage flux and the introduction of permanent magnets in the steady-state AC finite-element analysis and coupling their effects with the transient thermal analysis. The proposed approach is based on the finite-element method as well as on using the basic analytical equations. The approach was first applied in the magneto transient analyses. Because of the different physical transient-time constants, the steady-state AC analysis coupled with transient thermal should be used. The permanent magnets in the steady-state AC analysis coupled with the transient thermal analysis can be simulated by coils with an imposed current of a frequency depending on the number of pole pairs and rotation speed. Using any of the electrically conductive materials for the axial-flux inner slotless stator permanent-magnet machine housing should be avoided. The leakage flux induced by permanent magnets and spreading into the axial-flux permanent-machine housing is first defined by using the magneto-transient finite-element analysis and further used in the steady-state AC analysis coupled with the transient thermal analyses, all in 3D. Based on the results of these analyses, the temperature distribution in entire machine is calculated and compared with the measurement results.
COBISS.SI-ID: 10358356
Oxidative hair dyes are the most important hair dying products. Hairdressers are exposed to the allergens found in oxidative hair dyes during the process of applying dyes to the hair, when cutting freshly dyed hair, or as a consequence of prior contamination of the working environment. pphenylenediamine, toluene-2,5-diamine and its sulphate are the most common ingredients in oxidative hair dyes that cause allergic contact dermatitis in hairdressers. Cross-reactivity of p-phenylenediamine with para-amino benzoic acid, sulphonamides, sulphonylurea, dapsone, azo dyes, benzocaine, procaine, and black henna temporary tattoos is possible. Allergic contact dermatitis is classified as delayed-type hypersensitivity, according to Coombs and Gell. Skin changes typically appear on the hands after previous sensitization to causative allergens. Combined with the patients overall medical and work history and clinical picture, epicutaneous testing is the basic diagnostic procedure for confirming the diagnosis and identifying the causative allergens. The simplest and most effective measure for preventing the occurrence of allergic contact dermatitis in hairdressers is prevention. Preventive measures should be applied as early as in the beginning stage of vocational guidance for this profession. It is important to include health education in the process of professional training and to implement general technical safety measures, in order to reduce sensitization to allergens in hairdressing. Here, special emphasis must be given to the correct use of protective gloves. Legislation must limit the concentration of allergenic substances in hair dyes, based on their potential hazards documented by scientific research.
COBISS.SI-ID: 30677977