No description available.

No description available.

The evolution of the landscape of Vestfirđir, made almost entirely of volcanic rocks, is traced from the lilocene, when the oldest rocks formed, through the Pliocene and Pleistocene. Volcanic activity ceased first in the north western part leaving a basalt plateau with occasional large volcanoes protruding. Fluvial erosion, guided by a westerly dip of the plateau and tectonic lineaments, left a well developed drainage pattern there by the rime volcanic activity ceased in the southeast. The snowline fluctuated widely during the Plio-Pleistocene. Cirque and valley glaciations were very effective in sculpturing the landscape where the preglacial relief was greatest, in the northwest. Ice sheet glaciations affected the whole peninsula and offshore areas with linear erosion dominant in the northwest and areal scouring elsewhere. The glacial geomorphology of Dyrafjorour and northern Arnarfjorour is mapped. The highest marine limit is in the Nupur area, about 110 m, and shorelines and marine limits higher than 70 m are at 7 other localities at least. At least' two stages of glacial readvances are recognized: The Tjaldanes stage occurred when sea level was between 11 and 22 m and is probably of "Younger Dryas" age; later a readvance occurred in the cirques in the area. On the basis of evidence on cirque distribution, cirque elevation, zeolite zonation, distribution of glacial erosional landscapes, glacial history, marine limits, ice cap profiles and shelf moraine a model of maximum glaciations of Vestfir6ir is proposed: The whole of Vestfir6ir and the surrounding shelf areas was completely ice covered with no ice free areas. Such a stage of glaciation, the Latragrunn stage, probably prevailed in the Vestfiroir area during the last glaciation.

No description available.

The increase in strength of gold-nickel brazed joints, with increasing joint gap is explained by considering the mode of failure of the joints. Failure occurs in an apparently semi-brittle manner by crack initiation and propagation. Crack propagation is considered to be the controlling factor in joints brazed at 970°C. On raising the brazing temperature to 1000°C the controlling factor changes to one of crack initiation. This is the result of changes in the braze alloy microstructure due to pick up of small amounts of alloying elements from the steel. The effects of alloying between braze material and steel, on the joint microstructure, are considered and a corner of the gold-nickel-silicon ternary is calculated, silicon having been found to have a large effect on the joint microstructure.

The thesis presents the findings of a programme of research into the design and performance of variable displacement axial piston pumps of the swashplate type with integral controls. The work is principally concerned with developing a systematic design and performance prediction method for use at the design stage. The method developed outlines stage by stage the problems which arise and give guidance on the decisions which have to be made during the design process. Existing theory and technological data is integrated in the method and is augmented by the author's own contributions in the area of force analysis and contact stresses in the cylinder bores. Graphical optimisation methods are employed and the effects of manufacturing tolerances and .pump working ranges are investigated. The effectiveness of the method is demonstrated by designing a pump to the same specification as that of an existing industrial pump and by making a critical comparison of the two designs. Various regions of power loss are identified and equations derived for estimating these losses. The equations are developed and integrated into a performance prediction method which is novel in that unlike any known method, pump performance can be predicted without the need to test a similar pump. Using data readily available at the design stage the method is used to compare the performance of the existing pump with predicted values. Close agreement is claimed as an indication of the reliability of the method. The thesis gives an account of the historical development of the axial piston pump, a survey of published work on design and performance and a description of axial piston pumps and hydrostatic transmissions. Also included is an analytical treatment for the frequency response of servo controlled pumps by manual and electrohydraulic control.

No description available.

The factors affecting the distribution of surge-type glaciers and the causes of the surge mechanism are not fully understood. Statistical analyses of glaciers in Svalbard have been used to identify characteristics which are related to surging. Field experiments were undertaken on Bjuvbreen, a small surge-type glacier in central Spitsbergen, to determine the dynamics and hydrology of the glacier during its quiescent phase. The probability that a glacier in the Svalbard sample population was surge-type was 36·4%. The probability varied spatially within the sample area. Glaciers resting on sedimentary tocks had a greater probability of being surge-type compared to those overlying igneous or metamorphic rocks. The probability of surging was also increased in glaciers with a two-layered thermal structure as indicated by radio echo sounding. Geometrical characteristics such as slope, orientation, curvature and the presence of tributaries were not related to surge-type behaviour, although long glaciers had a greater chance of being surge-type. Certain aspects of Kamb's and Fowler's theories of surging were not supported by the statistical analysis. Despite the associations between surging and certain characteristics, no single factor fully explained the observed geographical distribution of surge-type glaciers in Svalbard. Bjuvbreen is a small surge-type in its quiescent phase. Changes in the geometry of the glacier are occurring relatively slowly. This slow rate of change is a function the low accumulation rates on Svalbard glaciers. On the basis of a simple model, the next surge of Bjuvbreen is predicted to occur between .2022- 2055, indicating a comparatively long quiescent period of -90-130 years. Bjuvbreen is comprised of two dynamically distinct zones which are separated by a large bulge. The lower portion of the glacier is inactive and stagnating, in contrast to the active ice up.:.glacier from the bulge. The observed velocity of the active region was compared with various hydrological characteristics of the glacier. The inferred behaviour of water within the glacier seems to have some, although limited, influence on the ice motion. A spatially restricted drainage system is the probable reason for this limited influence of hydrology on glacier velocity.

No description available.

No description available.