Diabetic retinopathy is an eye disease that causes blindness amongst many people with diabetes if left untreated. When the eye is affected, various changes in the blood vessels occur. To be able to observe these changes over time, images of the back of the eye called retinograms are acquired. Automated analysis of retinograms becomes important as the number of people afflicted with diabetes increases worldwide. A diabetic retinopathy detection system should be able to analyse retinograms, interpret them and record the changes over time. The methods associated with blood vessel detection in retinograms have a common drawback which is that small vessels that have low contrast are normally missed out during detection. Evaluation of these methods is commonly carried out using a technique which has the drawback of having a bias towards the detection of thick vessels. In this thesis a retinal vessel detection method is proposed which is capable of detecting blood vessels of different width, length and orientation in the back of the eye. The state-of-the-art method proves to be comparable to the existing methods applied to the same images used in this project. When applied for segmenting the whole vessel network, it achieves an area under the ROC curve (Az) of 0.960(±0.0021)599 compared to the best result of 0.9722 obtained via another method. When applied for vessel centreline detection, it achieves an Az of 0.977(±0.0013)66 which is higher than the best method with an Az of 0.967(±0.0017). These results are obtained using an evaluation method proposed in this project that eliminates the drawback of current evaluation methods hence removes the bias towards the detection of thick vessels.

Maritime is a very competitive industry in global market. In addition to political, economic and prosperity, container carriers have to confront oil prices and climate. It gets high risk and uncertainty in operation. The threat of oversupply of capacity will affect the operation and development of container carriers. Costs is aggravated on container carriers due to they brought too many new vessels when previous boom but economic declined soon. Fleet deployment is a big issue when making operational strategies and plans. Container carriers have to plan how to purchase and lease vessels. People said that the proportion of owned container vessels of Europe container carriers is lower than Asia container carriers. Europe container carries may not spend too much cost to purchase container vessels so it would be more flexible to lease container vessels and able to deploy container vessels in/out of route and create brand new service more mobility. For this reason, operating performance is better than Asia container carriers. This study is base on secondary data from Alphaliner, Containerisation International and American Shipper database and periodical in 2007 and 2008: net profit, total revenue, the numbers of owned, leased and operated container vessels. The 15 major container carriers are divided into three segments: Asia-Chinese, Asia-Non-Chinese and Non-Asia container carriers. The General Linear Mode is practiced on these to find out if any impact or correlation from the proportion of owned container vessel to performance. The conclusions of this study are as following. 1. It¡¦s no correlation between the proportion of owned container vessels and net profit and total revenue in 2007 and 2008 2. The proportion of owned container vessels can not be fixed at a value 3. The proportion of owned container vessels is dynamic, may not be operated by container carriers.

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Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

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The micromechanisms by which ductile fracture extended from a pre-existing crack was experimentally observed for two classes of forged SA 508 pressure vessel steel. The micromechanisms were related to the measured values of fracture toughness characterised by the resistance to crack initiation and growth. This comparison was only possible with the aid of an accurate fracture resistance test technique which could determine the crack growth toughness from a single specimen. An unloading compliance test system was developed and was used for the construction of crack growth resistance curves. Microstructural parameters determined from a specimen were related to the toughness measured on that specimen and this proved invaluable in isolating the controlling parameters. The effect of orientation and location on the toughness of the materials was assessed. The crack growth resistance was sensitive to the orientation of the crack with respect to the maximum hot working direction and the bands of segregation associated with elongated manganese sulphide inclusions. The toughness was high when the crack plane was perpendicular to the segregation bands and low when the crack plane was parallel with the bands. The location of the crack-tip through the thickness of the forging had a minor effect on the crack growth resistance. A limited study of test temperature, strength level and isothermal ageing was undertaken. Testing within the dynamic strain ageing regime of temperature had a marked effect and reduced the crack growth resistance to below the value at room temperature. Increasing the strength level of one steel by re-heat treating had no effect on the crack growth resistance. Subsequent isothermal ageing treatments also had no effect on the resistance curves. The magnitude and extent of void formation around growing cracks was studied and related to the applied loading. The size, shape and distribution of inclusions was characterised for the materials and orientations used in the fracture tests. Correlations between inclusion parameters and toughness revealed the important microstructural parameters controlling initiation and crack growth. Simple models for initiation and crack growth resistance were developed which take the controlling parameters into account. These models are shown to agree reasonably well with some experimental data.

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The R6 procedure is used for the prevention and prediction of crack behaviour and other defects in the reactor pressure vessel(RPV). The RPV material is an upper-bainitic, low alloy steel structure, which deforms inhomogeneously when yielding. The current codes that are used to design and calculate the fracture, within an RPV, assume that the material yields continuously as the size of the L¨uders strain is less than 2%. However, the work of Wenman et al[1] has shown that the inclusion of a L¨uders band during calculations can reduce the residual stress in a material, when compared to standard work-hardening models and, consequently, reduces the amount of conservatism. The objective of the research was to determine whether Wenman’s finding could be generalised and therefore initiate a re-evaluation of R6 procedure, when looking into materials that yield discontinuously. This required further investigation into L¨uders bands, such as using failure assessment diagrams (FADs). The findings from FADs showed that at the temperature range for an RPV steel at -155±C for different micro-structures (assuming that the material deforms homogeneously), this reduced the amount of conservatism. However, at fracture toughness values more representative of room temperature behaviour, the converse was true. That is, assuming a discontinuous yield point reduced the amount of conservatism. It was also shown that the tempered martensite structure could be used as an alternative to the current upper bainitic, low alloy steel that is used in RPVs. Further insight is gained into the nature of a L¨uders band, by developing a theoretical model that showed explicit relations between L¨uders strain and the mean free-path(ferrite path), dislocation density and the grain-size. It was also shown that an explicit relation between the L¨uders strain and carbon content was possible from known data, which a new parameter Á was derived, and is the derivative of the work-hardening exponent with respect to the lower yield stress.