‎We consider four-dimensional lie groups equipped with‎ ‎left-invariant Lorentzian Einstein metrics‎, ‎and determine the harmonicity properties ‎of vector fields on these spaces‎. ‎In some cases‎, ‎all these vector fields are critical points for the energy functional ‎restricted to vector fields‎. ‎We also classify vector fields defining harmonic maps‎, ‎and calculate explicitly the energy of t...

In the first part of this paper, some theorems are given for a Riemannian manifold with semi-symmetric metric connection. In the second part of it, some special vector fields, for example, torse-forming vector fields, recurrent vector fields and concurrent vector fields are examined in this manifold. We obtain some properties of this manifold having the vectors mentioned above.

Background: Research project risks are uncertain contingent events or situations that, if transpire, will have positive or negative effects on objectives of a project. The Management of Health and Safety at Work (MHSW) Regulations 1999 require all employers and the self-employed persons to assess the risks from their work on anyone who may be affected by their activities. Risk assessment is the...

In the electromagnetic spectrum, structural damage to living tissues per unit of absorbed energy tends to increase with the decrease of a wavelength which is evident not only for ultraviolet and ionizing radiation but also for the infrared and visible light. By causing thermal damage after absorbing energies that would be harmless for radiofrequency electromagnetic fields (EMF), tissues are eve...

The produced electric and magnetic fields due to lightning strikes to mountainous ground are determined in this paper. For the sake of simplicity a cone-shaped ground with finite conductivity is assumed to represent a natural nonflat ground. By this assumption, we deal with an axillary symmetrical structure so we use the cylindrical 2D-FDTD to save the simulation memory and time, dramatically. ...

introduction: it has been reported that cardiovascular effects are among the possible health effects of being exposed to extremely low frequency electromagnetic fields (elf emss). material and methods: this study has been conducted to evaluate the long term effects of exposure to magnetic and electric fields on electrocardiogram signal changes. nine power transmission posts having different vol...

objective: radiochromic ebt3 film is a later generation of radiochromic films. the aim of this study is to compare ebt and ebt3 radiochromic films in radiotherapy fields of breast cancer. methods: a rando phantom was irradiated by a 6 mv siemens primus linac with medial and lateral fields of radiotherapy of breast cancer. dosimetry was performed in various points in the fields using ebt and ebt...