High-Frequency and Very-High-Frequency (HF & VHF) Above-Ground Electromagnetic Impedance Measurements

A New High Frequency Grid Impedance Estimation Technique for the Frequency Range of 2 to150 kHz

Grid impedance estimation is used in many power system applications such as grid connected renewable energy systems and power quality analysis of smart grids. The grid impedance estimation techniques based on signal injection uses Ohm’s law for the estimation. In these methods, one or several signal(s) is (are) injected to Point of Common Coupling (PCC). Then the current through and voltage of ...

A comparison of High Frequency (HF) and Ultra High Frequency (UHF) Options

Modeling the Antenna Configuration of a Digital Very-High Frequency (VHF) Direction Finding System

The U.S. Coast Guard Academy (USCGA) has developed a prototype Digital Very High Frequency super-heterodyne Direction Finding system (DVHF-DF) in support of the U.S. Coast Guard's National Distress Response System Modernization Project (NDRSMP). This receiver, which processes four independent channels of in-phase (I) and quadrature (Q) data, offers significant advantages over more conventional ...

Plant Responses to High Frequency Electromagnetic Fields

High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume rati...

High-frequency oscillatory ventilation on shaky ground.

We thought it was impossible. Physiological principles maintained that ventilation at tidal volumes less than the anatomical deadspace should be ineffective (i.e., inspired air not reaching the alveolae). Data from a 1980 study dispelled that myth, showing unequivocally that ventilation with tidal volumes as small as 20 to 30 ml in dogs, a mere fraction of the anatomical deadspace, could mainta...