Ionization coefficients and breakdown voltages of cycloparaffin vapours

Townsend primary ionization coefficients have been measured and breakdown voltages deduced for cyeclopentane and eyclohexane vapours up to their respective saturation vapour pressure. corresponding to 46  E/p₀  20OO V cm^-1 torr^-1 at 0^°C and voltages up to 400KV. The Townsend relation α/p_o = A exp (—Bp0/E) is found to be obeyed over α/po range of 300 to 1 and the constants A and B are deduced. This allows the paraffin gases and vapours to be correctly categorized. Large electron avalanches exceeding exp (αd) = 10⁸ have once more been observed.     

Microwave breakdown voltages in hydrogen from DC data

The general microwave breakdown characteristic in hydrogen is obtained from the DC dependence of the ionization coefficient and electron mean energy on the reduced electric field, using the basic equations of motion of electrons in a high frequency electric field. Excellent agreement is obtained between the calculated characteristic and experimental values from the literature. With the aid of the derived effective reduced electric field concept, specific breakdown characteristics are then obtained for given microwave cavities. These also agree well with experimental results except well below the Paschen minimum, confirming the validity of the concept. The subject is presented as a self-contained entity and its analogy with an applied crossed magnetic field is emphasized. A direct comparison between the microwave and the DC Paschen formula is made.     

Electrical ionization and breakdown in gaseous ethylene derivatives and in isoprene

Townsend primary and secondary ionization coefficients have been measured and sparking voltages deduced for di- and tri-methyl ethylene and for isoprene over a pressure range of 2 to 200 Torr and a parallel plate gap distance up to 1 cm yielding derived sparking voltages in excess of 500 000 V. The Townsend equation for ionization is found to be closely obeyed by the gases and vapours and the Townsend constants have been derived. A detailed analysis of the experimental results shows that progressive methyl substitution around the ethylene double bond influeneces the electrical characteristics less markedly than straight chain substitution, in line with further electrical data taken from other sources on hydrocarbons.     

Dynamic Stability Analysis of Linear Time-varying Systems via an Extended Modal Identification Approach

The problem of linear time-varying(LTV) system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ‘‘frozen-time' assumption are not able to determine the dynamic stability of LTV systems.Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system's stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam experimental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides a new way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.