An improved switching converter model

The nonlinear modeling and analysis of dc-dc converters in the continuous mode and discontinuous mode was done by averaging and discrete sampling techniques. A model was developed by combining these two techniques. This model, the discrete average model, accurately predicts the envelope of the output voltage and is easy to implement in circuit and state variable forms. The proposed model is shown to be dependent on the type of duty cycle control. The proper selection of the power stage model, between average and discrete average, is largely a function of the error processor in the feedback loop. The accuracy of the measurement data taken by a conventional technique is affected by the conditions at which the data is collected

Compression of encrypted digital holograms using artificial neural networks

An important aspect of security and defense is information gathering, dissemination, processing,and analysis. Central to this is the encryption and decryption of messages for storage and transmission. Although public-key cryptosystems are the state of the art currently, there is a place for private-key systems in cases where hardware implementation permits very high through puts. Optical implementation is a candidate for this. Optics has some very promising scalability advantages over purely electronic systems as, in principle, the size of the key can be increased without increasing the encryption or decryption time..

Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4x4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively

Summary of meteorological observation taken at Hobart during part of the year 1882

Summary of meteorological observation taken at Hobart during part of the year 1882 by Commander J Shortt, R.N., Government Observer. Latitude, 42 degrees South Longitude, 147 degrees East. Height of Observatory above mean sea level, 130ft. Barometer corrected to 32 degrees Fahrenheit, and reduced to mean sea level

Meteorological observations and rainfall tables for the year 1883

Summary of meteorological observation taken at Hobart during part of the year 1883 by Commander J Shortt, R.N., Government Observer. Latitude, 42 degrees South Longitude, 147 degrees East. Height of Observatory above mean sea level, 130ft. Barometer corrected to 32 degrees Fahrenheit, and reduced to mean sea level. Also including rainfall in various locations across Tasmania and table of rainfall at lighthouse

Summary of observations on earthquake phenomena made in Tasmania during 1883 and 1884

During the last eighteen months Tasmania has been visited by so many earthquake shocks, that general interest has been excited and favourable opportunities afforded for studying some of the phenomena connected with them. It is hoped that interest in these observations may be thus stimulated, so that any shocks which occur in the future may be more carefully observed and recorded, and we may hope that in time many of the questions which remain for solution may be satisfactorily answered, and others on which one has to speak with great caution may be completely established. The great interest, indeed, of our earthquakes, in a scientific point of view, is the occurrence of such a large number of slight shocks close together in a country where they were previously very rare. In the month of February, 1884, nearly one hundred shocks and tremors were felt at St. Mary's, and in some months of 1883 and 1884 this number has been exceeded. Similarly numerous are the reports from Gould's Country and Moorina, so that since April 12, 1883, when the first shock was recorded at Gould's Country, over one thousand distinct shocks have been felt, besides many which must have passed unnoticed

Summary of Meteorological observations taken at Hobart for 1884

Summary of Meteorological observations taken at Hobart for 1884. Includes mean results for the year 1884, rainfall in Tasmania, epitome of results of Meteorological observations at the various stations, mean and extreme results for the year, rainfall, including number of days that rain fell during the year and distance from the sea coast of the various stations.Table of rainfall at lighthouses for the year 1884. Latitude, 42 degrees 43’25” S. : Longitude, 147 degrees 28’ 6” E.: Height of observatory above sea level, 190 feet. Barometer corrected to 32 degrees Fahrenheit and reduced to sea leve

Notes on the possible oscillation of levels of land and sea in Tasmania during recent years

During the years 1883, 1884, 1885, and l886, or immediately prior to the eruption at Tarawera, this island, and the South-Eastern portion of the mainland of Australia, were frequently shaken by earth tremors; and as such disturbances are often known to be associated with local changes of sea and land, it appeared to me to be of great importance to ascertain whether any recent change could be traced along the coast-line of this island. The exception, however, is of peculiar interest, as it affords us some information, so far as the locality is concerned, in which this fixed tide mark occurs. The tide mark here referred to is situated on the North side of the "Isle of the Dead," which lies off Point Puer, Port Arthur. This mark was cut in the rock broad arrow form, on the 1st July, 1841, by the then Deputy-Assistant Commissary-General, Mr. Lempriere. The aim was to establish a permanent mark at the zero point, or general mean level of the sea, as determined by the tidal observations which Mr. Lempriere had conducted with perseverance and exactness

Earthquake phenomena in Tasmania.

Since last November when I read a former paper on earthquake shocks and tremors, and tp to the present time there has been a considerable decrease both in the number and intensity of the shocks, excepting that of May 13th. Includes table of the severest shocks, November, 1884 to November, 1885