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For almost as long as the electricity distribution industry itself has existed, so also has the idea of utilising the transmission grid, be it over a wide area or on a local basis, for the transmission of 'intelligence'. This might be in the form of voice transmissions, or for the purposes of monitoring or controlling electrical devices attached to the network. This thesis specifically concerns itself with the potential applications of power-line-carrier (PLC) communications technology within the field of industrial plant/equipment control, as it is within this field that the author works. We look at the entire subject area of industrial control, starting from a historical viewpoint, and consider the special needs and requirements that a proposed PLC solution must offer for this application, especially based on the noise conditions likely to be experienced on a `real' power line. A proposal is made for a `Power Bus', intended for use within certain areas of industrial control, and decisions are made based on the projected link response times for such applications. The experimental phase of the research is practical in nature and consists of a raft of tests and evaluations of the performance of power line modem technologies, under controlled and repeatable noise conditions. To complement these results, further tests are carried out under `real world' conditions, within an actual factory environment. Based on the results of all of these tests, the suitability of a PLC solution for this type of industrial control application is considered. The Thesis concludes with a look at recent developments in, as well as the future of, Power Line Communication techniques.

Fluid-borne noise is one of the main components of hydraulic noise. Its attenuation may have a significant effect on the cost of hydraulic systems. Standard passive silencers and dampers can be useful in reducing it in certain frequency ranges; however, these tend to be heavy, bulky and expensive. Active control algorithms, which are a comparatively recent means of reducing fluid-borne noise, can be applied to overcome this compromise. The work presented in this thesis is the development of some active control algorithms utilized in a simple hydraulic system to cancel a number of harmonic orders of fluid-borne noise generated by a servo valve or a real pump. To realize cancellation the filtered reference least mean square (FXLMS) adaptive control method is mainly presented. Furthermore, a fast response servo valve is applied as an actuator to generate a proper anti-noise flow signal in real-time. For simplicity, an off-line identification method for the secondary path is applied in the time invariant working condition. Moreover, ripple reflection from both ends of the hydraulic circuit can produce different effects under different working conditions. In order to execute the cancellation without any prior information about the dynamics of hydraulic systems, the on-line secondary path identification method is discussed. However, in this algorithm an auxiliary white-noise signal applied to an on-line method may contribute to residual noise and an extra computation burden may be added to the whole control system. The performance of these control algorithms is firstly investigated via simulation in a hydraulic pipe model and the real-time application on a test rig using a servo valve as a noise source. Finally, these schemes are realized in a simple hydraulic system with a real pump noise source. The fluid-borne noise can be attenuated by about 20 dB in normal working conditions.

Typescript Includes bibliographical references

Seed piece to plant transmission of the potato late blight pathogen, Phytophthora infestans, occurred with isolates of the clonal lineages US-8 in Oregon and US-11 in Washington in field trials. Average transmission rate across potato cultivars was 0.5 and 2.4% with US-8, and 0.8 and 1.0% with US-11 in 1999 and 2000, respectively. Transmission rate with US-8 was 2.3% for Russet Burbank (RB) in 1999 and 1.7, 0.7, 4.3, 7.6 and 0.5% for Bannock, Bzura, Ranger, Russet Norkotah (RN), and Umatilla, respectively, in 2000. Transmission rate with US-11 in 1999 was 0.5, 4.9 and 1.4% for RB, RN, and Shepody, respectively, and 1.7% for RB in 2000. Seedborne inoculum of both clonal lineages significantly affected stand establishment and plant vigor. With US-8, final emergence, emergence rate, and aerial biomass of cvs Kennebec, RB, RN, and Shepody were significantly lower than Bzura in 1999, whereas in 2000, these same responses in Chieftain, Bannock, Ranger, and Shepody were significantly lower than Bzura, Umatilla and RN. With US-11, these same response variables were significantly lower in Kennebec, RN and Shepody compared to Bzura and RB in 1999, and were significantly lower in Bannock, Chieftain, Ranger and Shepody compared to RB and Umatilla in 2000. Plant growth responses of cvs RB and RN grown from seed pieces infected with US-8 or US-11 were evaluated in greenhouse trials. RN was equally susceptible to both clonal lineages whereas RB was more resistant than RN to seedborne inoculum of US-11. Compared to RN its final emergence was higher, emergence rate was faster, aerial biomass was greater, and seed piece decay was lower. US-8 was more aggressive than US-11 on RB. US-8 caused a greater reduction in final emergence, emergence rate, and aerial biomass, and a greater increase in seed piece decay. The two clonal lineages were similar in their aggressiveness on RN. This is the first report of cultivar*clonal lineage*inoculum density interactions for plant growth responses of potato grown from seed pieces infected with P. infestans. / Graduation date: 2002

Powassan (POW) virus, the cause of human encephalitis in the northeastern U.S. and Canada, is transmitted by tick bite. Since the geographic and host distribution patterns of Ixodes dammini Spielman, et al, 1979 and POW virus overlap, the potential of this tick species to transmit POW virus was explored. Transmission experiments were conducted with hamsters and rabbits which fed immature and adult ticks, respectively, from a POW-free colony. Oral infection rates in larvae and nymphs fed on POW-infected hamsters were 10% and 40%, respectively; in females fed on POW-infected rabbits, 57%. Transstadial transmission rates for nymphs exposed to POW virus as larvae, adults exposed as larvae, and adults exposed as nymphs, were 9.5%, 10% and 54%, respectively. Evidence of transovarial transmission was acquired when 2 clean hamsters feeding F$ sb2$ larvae and nymphs originally exposed to virus in the F$ sb1$ nymphal stage seroconverted to POW virus with hemagglutination inhibition titers of 80 and 5120, respectively, on week 4 post-tick-drop-off. The transovarial transmission rate was 16.6%. All developmental stages were able to transmit POW virus orally to clean hosts regardless of when the ticks were originally exposed to virus. / These results indicate that I. dammini is a competent vector of POW virus under experimental conditions. Field studies are necessary to determine if the same holds true under natural conditions.