INTRODUCTION The primary stability of dental implants is related to the bone in contact with the latter, and can be evaluated by resonance frequency analysis. MATERIAL AND METHODS Measurements were made in 133 implants (62 in the upper jaw and 71 in the mandible) of resonance frequency and insertion force to determine implant stability on the day of surgery, with an evaluation of its relation...

objective: to assess the stability changes as a reflection of early healing around roughened- surface implants in human by resonance frequency analysis (rfa). materials and methods: one hundred and fifty one iti sla implants were placed in either maxilla or mandible of 68 patients. bone type was classified into 4 groups according to lekholm and zarb index. rfa was used for direct implant stabil...

The issue of frequency stability of microgrids under islanded operation mode and mode transfer has attracted particular attention recently. In this paper, a cooperative frequency control method, which consists of a microgrid central control (MGCC) and microgrid local control (MGLC), is proposed to achieve a seamless transfer from grid-connected to islanded mode, and hence increase the frequency...

In this paper we develop computational techniques with enhanced accuracy for two frequency-weighted model reduction approaches, namely, balanced truncation, and singular perturbation approximation. New stability-enforcing choices of the frequency-weighted grammians can guarantee the stability of reduced models for two-sided frequency weights. Several numerical examples show the effectiveness of...

In this paper we develop computational techniques with enhanced accuracy for two frequency-weighted model reduction approaches, namely, balanced truncation, and singular perturbation approximation. New stability-enforcing choices of the frequency-weighted grammians can guarantee the stability of reduced models for two-sided frequency weights. Several numerical examples show the effectiveness of...

Power system blackouts have become a serious problem for electric utilities especially in recent years. Different forms of system instability have emerged in recent blackouts, such as voltage instability and frequency instability. To counteract each form of system instability, special algorithms have been designed in the protection system, e.g. Under Frequency Load Shedding (UFLS) and Under Vol...

This paper presents a low distortion signal generator with a frequency range from 0 to 10 kHz using the direct digital synthesis (DDS) method for ADC characterization. The results show that the maximum distortion in the whole frequency range is -80.37 dB, the frequency resolution is 1.421 nHz (with a 48-bits DDS chip), the stability in frequency is 25 μHz/Hz and the amplitude stability is 13 μV/V.

We characterize and compare the performance of various commercially available lasers in terms of their absolute frequency stability, lineshape and linewidth, and frequency noise. The frequency stability, linewidth and lineshape are evaluated using an ‘optical ruler’ – a carrier-envelope stabilized optical comb. The frequency noise is measured over an extended spectral range starting from 2 Hz. ...