Direct support and general support maintenance manual including repair parts and special tools list (including depot maintenance repair parts and special tools) for converter, telephone signal CV-1919A/G, (FSN 5805-229-5417).

Includes index.

Operator's, organizational, and direct support maintenance manual : converter, telephone signal CV-1918A(V)1/G (NSN 5805-00-504-9103), CV-1918A(V)2/G (NSN 5805-00-504-9107), CV-1918A(V)3/G (NSN 5805-00-137-7674).

"5 March 1984."

Operator's and organizational maintenance manual including repair parts and special tools lists for converter, telephone signal CV-1919A/G (FSN 5805-229-5417).

"November 1974."

Direct support and general support maintenance manual : converter, telephone signal CV-3478/TTC.

"18 April 1983."

General support maintenance manual : amplifier-converter AM-6879/URC (NSN 5820-01-070-1950).

Includes index.

Operator, organizational, DS, GS, and depot maintenance manual : Hewlett-Packard AC voltmeter AN/USM-265 (model 400EL02) NSN 6625-00-935-4294, ME-459 (model 400EL) NSN 6625-00-229-0457, ME-465 (model 400E) NSN 6625-00-995-7716.

"May 1967."

Opus polyhistoricon ac festivum, res totius pene orbis concinne complexum,

Ed. by H. von der Hardt.

Tractatus de legibus ac Deo legislatore, : in decem libros distributus. /

Includes indexes.

DC-DC Power Converters Featuring Wide-Bandgap Devices

This work focuses on the design of high-efficient DC-DC converters based on WBG power devices. The first objective is the development of an isolated bidirectional converter for the distribution network of future electrical aircrafts. A SiC-based Dual Active Bridge converter is designed and fabricated. Control strategies for individual and parallel operations are investigated and implemented into a FPGA platform. Experimental results on 1.2kW 270V/28V prototype are presented to confirm the proper behavior of the proposed solution. The second project belongs to the field of photovoltaic systems and aims to develop a three-port converter with multiple power elements interfacing capability. A GaN-based Triple Active Bridge has been designed, regarding both the controller and the hardware realization.

Seasonal growth of the crustose lichen Rhizocarpon geographicum (L.) DC. in South Gwynedd, Wales

Seasonal growth was studied in the slow-growing crustose lichen Rhizocarpon geographicum (L.) DC. in an area of South Gwynedd, Wales. Radial growth rate (RGR) of a sample of 20 thalli was measured in situ at three-month intervals over 51 months on a southeast-facing rock surface. There were five periods of significant growth: July-September of 1993, 1994 and 1995, in January-March of 1996, and in April-June of 1997. In four of these periods, growth coincided with a mean temperature maximum (Tmax) over a three-month period exceeding 15°C and three of the maxima with greater than 450 sunshine hours. Two of the growth maxima coincided with periods of total rainfall exceeding 300 mm and one with greater than 50 rain days in a three-month period. There were no significant linear correlations between RGR and the climatic variables measured. However, there were significant non-linear relationships between RGR and Tmax, the mean temperature minimum (Tmin), the total number of air and ground frosts and the number of rain days in a growth period, the relationship with Tmax being the most significant. Hence, in south Gwynedd, maximum growth of R. geographicum occurs in any season although the period July-September appears to be the most favourable. Relationships between growth and climatic variables were non-linear, temperature having the most significant influence on seasonal growth. ©2006 Balaban.

Variation in hypothallus width and the growth of the lichen Rhizocarpon geographicum (L.) DC.

Variations in hypothallus width were studied in relation to radial growth in the lichen Rhizocarpon geographicum (L.) DC. in South Gwynedd, Wales, UK. Variations were present both within and between thalli and in successive three-month growth periods, but there was no significant variation associated with thallus size. In individual thalli, there were increases and reductions in hypothallus width in successive three-month growth periods attributable to hypothallus growth and changes at the margin of the areolae. Total radial growth over 18 months was positively correlated with initial hypothallus width. These results suggest: 1) individual thalli of similar size vary considerably in hypothallus width, 2) fluctuations in the location of the margin of the areolae in successive three month periods is an important factor determining this variability, 3) hypothallus width predicts subsequent radial growth over 18 months, and 4) variation in hypothallus; width is a factor determining between thallus variability in radial growth rates in yellow-green species of Rhizocarpon.

Hopping transport on a fractal: ac conductivity of porous silicon

We have measured the frequency dependence of the conductivity and the dielectric constant of various samples of porous Si in the regime 1 Hz-100 kHz at different temperatures. The conductivity data exhibit a strong frequency dependence. When normalized to the dc conductivity, our data obey a universal scaling law, with a well-defined crossover, in which the real part of the conductivity sigma' changes from an sqrt(omega) dependence to being proportional to omega. We explain this in terms of activated hopping in a fractal network. The low-frequency regime is governed by the fractal properties of porous Si, whereas the high-frequency dispersion comes from a broad distribution of activation energies. Calculations using the effective-medium approximation for activated hopping on a percolating lattice give fair agreement with the data.

Two way power flow using GTO thyristors

Two-way power flow is nothing new and has been in practical use using line commutated converters for at least 50 years. With these types of converters, reversal of power flow can be achieved by increasing the firing angle of the devices beyond 90 degrees thus producing a negative DC voltage. Line commutated converters have several known disadvantages including: the direct current cannot be reversed, the power factor decreases when the firing angle increases and the harmonics are high on the line current. To tackle the above problems a forced commutated converter can be used. The power factor can be unity and the harmonics can be reduced. Many researchers have used PWM with different control techniques to serve the above purposes. In each converter arm, they used a forced commutated device with an antiparallel diode. Under the rectification mode of operation the current path is preponderantly through the diodes and under the inverter operation the current flows preponderantly through the forced commutated devices. Although their results were encouraging and gave a unity power factor with nearly sinusoidal current, the main disadvantage was that there were difficulties in controlling the power factor when the system is needed to operate at lagging or leading power factor. In this work, a new idea was introduced by connecting two GTOs antiparallel instead of a diode and a GTO. A single phase system using two GTO converters which are connected in series was built. One converter operates as a rectifier and the other converter operates as an inverter. In the case of the inversion mode and in each inverter arm one GTO is operated as a diode simply by switching it always on and the other antiparallel GTO is operated as a normal device to carry the inverter current. In case of the rectification mode, in each arm one GTO is always off and the other GTP is operated as a controlled device. The main advantage is that the system can be operated at lagging or leading power factor.

Carbohydrates in the hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC

Carbohydrate concentrations in the marginal hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC. were measured in north Wales, U.K. using gas chromatography. Ribitol, arabitol, and mannitol were the most abundant carbohydrates while a- glucose ß-glucose, fructose, sucrose, and trehalose were present in smaller amounts. The concentrations of arabitol, ribitol, mannitol, fructose, and a-glucose were greater in the areolae while the concentration of trehalose was greater in the hypothallus. Concentrations of carbohydrates varied little between sample days. Concentrations of polyols in the hypothallus were not correlated with those in the areolae. These results suggest: 1) the hypothallus has a lower demand for carbohydrates than the areolae or there is limited transport from areolae to hypothallus, 2) increased trehalose in the non-lichenised hypothallus may be an adaptation to withstand stress and desiccation, and 3) polyols are partitioned differently in the hypothallus and areolae.

A converter compensator for power factor control in 3-phase induction machines

The advent of the harmonic neutralised shunt Converter Compensator as a practical means of reactive power compensation in power transmission systems has cleared ground for wider application of this type of equipment. An experimental 24-pulse voltage sourced convector has been successfully applied in controlling the terminal power factor of a 1.5kW, 240V three phase cage rotor induction motor, whose winding has been used in place of the usual phase shifting transformers. To achieve this, modifications have been made to the conventional stator winding of the induction machine. These include an unconventional phase spread and facilitation of compensator connections to selected tapping points between stator coils to give a three phase winding with a twelve phase connection to the twenty four pulse converter. Theoretical and experimental assessments of the impact of these modifications and attachment of the compensator have shown that there is a slight reduction in the torque developed at a given slip and in the combined system efficiency. There is also an increase in the noise level, also a consequence of the harmonics. The stator leakage inductance gave inadequate coupling reactance between the converter and the effective voltage source, necessitating the use of external inductors in each of the twelve phases. The terminal power factor is fully controllable when the induction machine is used either as a motor or as a generator.