Naval submarines and surface ships are regularly subjected to a treatment called &quotdeperming&quot that seeks to design the vessel???s permanent magnetisation for optimal magnetic camouflage. A scaled model of a magnetic treatment facility (MTF) has been established as a valid system to simulate deperming and used to investigate various aspects of the deperm process including: magnetic anisotropy and demagnetising fields as factors in the physical modelling of magnetism in whole vessels; a comparison of current and alternative deperm procedures; the application of theoretical models of bulk magnetisation to calculate deperm outcomes in the physical model and in actual vessels. A &quotlaboratory MTF&quot was constructed to imitate the applied field geometry at a naval MTF. The system was calibrated and it was determined that the laboratory MTF could make magnetic measurements on a CU200T-G steel bar sample with an equivalent accuracy (error = ??5%) to that of standard magnetometric equipment. Experiments were conducted with emphasis on a holistic approach to modelling the deperm process and describing magnetisation changes in whole objects. The importance of the magnetic anisotropic changes to steel with cold rolling was confirmed. In CU200T-G steel sheet the initial susceptibility (ci) was found to increase by a factor of 3 ??0.1 in the rolling direction, from a value of ~ 110 in the un-rolled steel sheet (thickness dependent). ci in the rolled sheet transverse to the rolling direction was decreased by a factor of 0.94 ??0.09 to ci in the un-rolled sheet steel. Previous studies on hull steel have neglected to account for this transformation through cold work. The demonstration on mild steel here is expected to have an analogy in the final state of the hull sheet steel as it resides in a submarine pressure hull. Future studies either on hull material or on modelling whole vessels should include the same or similar magnetic anisotropic properties in the steel(s) under investigation. Hollow circular tubes made from CA2S-E and CU200T-G steel sheet were selected as models for vessels. It was shown that these steel tubes were a good choice in this regard: minimising the complexity of the experiment whilst maintaining the validity of a deperm simulation. During a deperm there was an excellent qualitative likeness in the permanent longitudinal magnetisation (PLM) for the steel tubes to PLM in both a submarine and a surface vessel. Permanent vertical magnetisation (PVM) deperm results from the tubes displayed a close qualitative match with PVM in a submarine but not in a surface vessel. A theoretical treatment for demagnetisation factors (Nd) in hollow ellipsoids was used in conjunction with a geometrical approximation to calculate Nd for finite hollow objects of revolution. Subsequent theoretical calculations correlated well with experimental results for measured effective ci (ceff) in hollow circular CU200T-G steel tubes of various lengths and aspect ratios. Using an estimate of 100 as ci for submarine hull steel, the same analysis produces Nd for the axial and transaxial directions in a submarine equal to 5.97??10-3 and 0.0142 respectively. Three items for potential improvement were identified in the current deperm protocol used on naval vessels (Flash-D): redundancy in the protocol; the duration of the deperm and a theoretical basis for predicting the final magnetisation or changes in magnetisation during a deperm. Simulations of a novel &quotanhysteretic deperm&quot method, designed to combat these issues, compared favourably to the Flash-D protocol. The standard deviation (s) of the final PVM from 30 Flash-D deperms on steel tubes was 206 A/m; for the final PVM from 30 anhysteretic deperms of the same duration, this was 60 A/m. The s for the final PLM for Flash-D and anhysteretic deperms of the same duration were 416 A/m and 670 A/m respectively. The conclusion is that adopting the anhysteretic deperm on actual vessels would improve the reliability of the PVM outcome. Though the procedure would demand the same duration as Flash-D, there is the advantage of saving time by not having to repeat deperms to obtain the desired result. Additionally the anhysteretic deperm is considerably more amenable to theoretical analysis. A modified version of Langevin???s equation was used to predict the final PLM and PVM results for anhysteretic deperms and to provide a useful analysis of the anhysteretic processes in the Flash-D procedure. Using a Preisach analysis of hysteresis, a mathematical description of bulk magnetic changes that occur to a specific object, within a deperm, has been developed. Theoretical calculations of PLM in a steel tube during and after both types of deperm are in excellent agreement with experimental data. The same theoretical approach was also used to retrospectively model PLM results from previous Flash-D deperms on a submarine with equal success. With this analysis it is proposed that anhysteretic deperm outcomes could be predicted a priori. The influence of magnetic cargo on hull magnetisation was demonstrated to be of significance during and after deperming. &quotSympathetic deperming&quot occurs where a magnetic source is located close to the hull during a deperm. It was found that a vessel or model vessel hull could still be demagnetised even when they contain magnetic cargo that would normally resist the direct application of the same magnetic fields. This was explained using the principles of demagnetising fields and anhysteretic magnetisation. A possible explanation was provided for a PVM measurement anomaly common to the model and vessel deperm results. From measurement, alternating longitudinal applied fields apparently induce corresponding changes in the PVM. This effect could be explained by the depermed object being offset longitudinally from the position expected by the measurement system. This offset could be estimated using an analysis of the changes to PLM and PVM after a longitudinal applied field. The offset displacements calculated for the vessels were too small to be verified experimentally (&gt 0.1m), but the predicted offset for the steel tubes coincided with the limit of precision for their placement in the laboratory MTF = 0.5mm The aim of this work was to look at the deperm process with reference to a system that demonstrated qualitative similarities to deperms on actual vessels. The laboratory MTF is a unique facility, permitting a useful practical analysis of deperming based on sound magnetostatic measurements The experimental and theoretical results gained here have direct application to future deperms on naval vessels with particular reference to submarines.

Massive stars form in the dense optically thick cores of molecular clouds throughout the Galaxy. They actively participate in the heating of these molecular clouds and also in enriching the interstellar medium with heavy elements. Stellar winds may contribute to change the original cloud structure by in uencing nearby low mass star formation, or even by triggering the formation of new stars. Despite the fact that massive star formation is manifest throughout the Galaxy, the mechanisms involved in their formation are poorly understood. The coincidence of methanol masers and ultracompact (UC) HII regions with young massive stars, indicates their eectiveness in tracing the earliest stages of high-mass stellar evolution. This thesis concentrates on a multiwavelength study of massive star formation regions. The cornerstone of this thesis is a (sub)millimetre study of methanol maser and UC HII sources associated with massive star formation regions. The 15m Swedish ESO Submillimetre Telescope (SEST) and the 15m James Clerk Maxwell Telescope (JCMT) were used to survey continuum emission at 1.2mm and 450 & 850 m, respectively. The 1.2-mm continuum emission observations were undertaken with the SEST IMaging Bolometer Array (SIMBA) toward star-forming complexes associated with methanol maser and/or radio continuum sources. This survey detected emission toward all of the methanol maser and UC HII regions targeted, and revealed evidence of a handful of these tracers lying within the elds mapped without millimetre continuum emission. Interestingly, the SIMBA survey also revealed evidence of sources devoid of traditional star formation tracers (methanol/OH maser, UC HII regions, IRAS sources), detected solely from their millimetre continuum emission. These `mm-only' sources prompted a follow-up study with the JCMT. The 450 and 850m observations of mm-only cores discovered in the SIMBA survey, utilised the Submillimetre Common User Bolometer Array (SCUBA) on the JCMT, which detected submillimetre continuum emission toward 97 per cent of sources targeted. The SCUBA instrument also resolved a number of SIMBA sources into multiple components, and found evidence of submillimetre sources devoid of SIMBA emission. The (sub)millimetre data from the SIMBA and SCUBA surveys enabled study of the dust properties of the cores, and in particular the dust grain emissivity index , which is of order 2 for the sample. Spectral energy distribution (SED) diagrams were drawn for the SIMBA sources, employing MSX and IRAS data where possible. Eight parameters are reported for each of the sources in the sample: luminosity, temperature, mass, H2 number density (nH2 ), surface density (), radius, distance and luminosity-tomass ratio (L/M). These data show that the mm-only cores are of comparable mass to sources harbouring a methanol maser and/or radio continuum source, but are smaller, cooler, less luminous, with smaller luminosity-to-mass ratios, than these sources. This prompts the suggestion that the mm-only core is an example of the earliest stages of massive star formation prior to the onset of methanol maser emission. The mm-only sample was identied as comprising two populations, which are distinguished by temperature. The cool-mm sources are distinct from the warm-mm sources as well as from those sources with a methanol maser and/or a radio continuum source for all parameters tested but for the mass and in some instances the radius. The warm-mm on the other hand are similar to those sources with a methanol maser site and/or an UC HII region for all parameters tested. The cool-mm sources are less luminous, with lower luminosity-to-mass ratios, as well as higher H2 number and surface densities. This prompts hypotheses to be drawn regarding the nature of these two mm-only populations. The warm-mm sources are possible precursors to the methanol maser and are thus indicative of the earliest stages of massive star formation, whilst the cool-mm sources are possible examples of `failed' cores that will remain starless. It is, however, not yet clear which of these mm-only populations are forming massive stars and further work to test these hypotheses is required.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

Thesis (M. SC.)--Carleton University, 1974. / Also available in electronic format on the Internet.

Thesis (M. SC.)--Carleton University, 1977. / Also available in electronic format on the Internet.

Thesis (M.SC.) - Carleton University, 1977. / Also available in electronic format on the Internet.

Thesis (M. SC.)--Carleton University, 1978. / Also available in electronic format on the Internet.

Thesis (M. SC.)--Carleton University, 1978. / Also available in electronic format on the Internet.

Thesis (M.SC.) - Carleton University, 1978. / Also available in electronic format on the Internet.