A Review of Rail Research Relevant to the Case for Increased Rail Investment.

The purpose of this paper is to provide a review of rail transport research which has a bearing on the case of increased rail investment. The paper focuses on research which has been conducted on the demand for rail travel, both passenger and freight, rather than the supply side or new technology. The aim is to identify where we believe there to be significant gaps in knowledge and key areas in which further research is required are outlined. The paper deals with the following issues: the investment and funding mechanisms that currently exist for rail; the extent to which changes in the fare and service quality of rail affect the demand for rail travel and also the demand for air and road travel; the environmental and congestion benefits of diverting traffic from road and air to rail; and the links between rail investment and economic development. Where appropriate, the discussion considers inter-urban travel, suburban travel, light rail transit and freight transport separately

Influence of storage conditions on survival and sowing value of seed of tropical pasture grasses. 1. Longevity

To find ways of improving the sowing value of seed of tropical pasture grasses through attention to the storage environment used commercially, fresh seed lots of Panicum maximum, Brachiaria decumbens, Brachiaria humidicola, Setaria sphacelata and Chloris gayana were stored under different conditions and sampled periodically for laboratory, greenhouse and field testing. Comparisons were made between seed lots stored in bags of open weave in a cool-room at 10°C and 50% RH and in an open store-room at ambient temperature. Seed lots of P. maximum in moisture-proof packets at 5 different moisture contents between 7.3 and 12.9% were compared. One seed lot was also freezer-stored at −12°C. Part 1 reports their viability and dormancy loss. Viability loss of seed in woven bags in open storage was complete within 3 years while barely detectable in similar cool-stored seed. Rates of loss in sealed packets increased with moisture content at ambient temperatures. They were much higher in seed in woven bags at comparable average moisture contents, an effect attributed largely to spatial moisture content gradients. Cool storage temperatures and low seed moisture contents appeared to prolong dormancy, while freezer storage retained and even intensified it

Effects of electroplating on the mechanical properties of stereolithography and laser sintered parts

This paper provides a quantitative and qualitative assessment of the effects of electroplating on polymer parts made by stereolithography and laser sintering. A series of test samples were coated with copper and nickel with varying thickness. Thicker coatings (120μm) were reproduced with a repeatability that should not adversely affect the tolerances with which such parts may be produced given the tolerances of the initial rapid prototyping processes themselves. Thinner coatings (20μm) resulted in a smother surface finish than thicker coatings for stereolithography parts, however the converse was true for laser-sintered parts. Composite theory was used to predict that thicker coating would lead to higher Young’s modulus in parts and this was shown to be true in physical tests although the practical values were lower than the predicted values especially for thicker coatings. Physical tests also confirmed that thicker coatings increased UTS and impact energy but had a minimal effect on the ductility of parts

Mortality and Morbidity Following Endovascular Repair of Abdominal Aortic Aneurysms: Analysis of Two Single Centre Experiences

AbstractObjective to show how differences in anatomical and physiological risk factors can affect the outcome of endovascular repair of AAA by describing the experience of two centres with different selection policies. Methods one hundred and thirty-five patients (group I) were treated at Queen's Medical Centre (Nottingham, U.K.) using 101 in-house made and 34 manufactured stent-grafts. Median diameter, length and angulation of the proximal aneurysm neck were 26 mm, 27 mm, 40°, respectively. Seventy-six patients had ischaemic heart disease, 47 had left ventricular failure, median forced expiratory volume in one second (FEV1) was 83%, median creatinine was 100 μmol/l and median age was 72 years. Fifty patients (group II) were treated at Timone Hospital (Marseilles, France) using seven in-house made and 43 manufactured stent-grafts. Median diameter, length and angulation of the proximal aneurysm neck were 25 mm, 34 mm, 33°, respectively. Thirteen patients had ischaemic heart disease, two had left ventricular failure, median forced expiratory volume in one second was 101%, median creatinine was 108 μmol/l and mean age was 72 years. Results anatomical characteristics of the proximal neck were significantly worse in group I (p=0.02 for the three variables). Cardiac comorbidities were more frequent and mean FEV1 was lower in group I (p<0.0001 and p=0.001, respectively. Median aneurysm diameter was significantly greater in group I (65 mm) than in group II (53 mm) (p<0.001). Postoperative mortality was 9% and 0% in groups I and II respectively (p=0.03). The incidence of technical complications (groin wound complications and side branches endoleaks being excluded) was 20% and 0% in groups I and II, respectively (p=0.0006). Conclusion postoperative mortality and technical complication rates were significantly greater in group I than in group II, readily explained by poorer general condition and worse anatomical characteristics of the proximal neck in group I

Investigating mechanical anisotropy and end-of-vector effect in laser-sintered nylon parts

A study investigating the effects of part-build orientation in the laser sintering process is presented. The investigation uses tensile, flexural, and compression testing methods to assess the changes in the mechanical properties of laser-sintered nylon-12 parts. The test parts were built in the x, y, and z orientations with the x axis parallel to the direction of the laser scanning, the y axis perpendicular to the direction laser of scanning, and the z axis in the direction of powder layers. The results from the tests show that the build orientation of the parts has an effect on the mechanical properties produced. The tensile tests show a maximum difference of 16 per cent and 11.2 per cent in strength and modulus respectively for parts built in the x, y, and z axes. The flexural tests show a 9.4 per cent and 7 per cent maximum difference in strength and modulus respectively for the parts produced in the x, y, and z axes. For the compressive tests, there is a 3.4 per cent and 13.4 per cent maximum difference in strength and modulus respectively for the parts produced in the x, y, and z axes. A statistical analysis of the results obtained highlights the presence of anisotropy in tensile and compression parts owing to their build orientation in the laser sintering machine. The test parts built in the x axis orientation showed the highest strength and modulus values while the parts built in the z axis orientation showed poor strength and modulus values. However, this is not the case for the flexural test parts, which show the highest strength and modulus values are from those built in the y axis orientation. Analysis has shown that this is due to the end-of-vector effect, which is most prominent in the y axis orientation. This effect should always be considered during laser sintering, when mechanical integrity is vital

Layer thickness and draft angle selection for stereolithography injection mould tooling

The introduction of rapid prototyping has allowed engineers and designers to generate physical models of required parts very early on in the design and development phase. Further to this, the use of stereolithography (SL) cavities as a rapid tooling method has allowed plastic prototype parts to be produced in their most common production manner -- by injection moulding. The process is best suited to small production runs where the high costs of conventionally machined tooling is prohibitive. One of the major drawbacks of the SL injectionmoulding process is the susceptibility of the tools to premature failure. SL tools may break under the force exerted by part ejection when the friction between a moulding and a core is greater than the tensile strength of the core, resulting in tensile failure. Very few justified recommendations exist about the choice of mould design variables that can lower the part ejection force experienced and reduce the risk of SL tool failure. This research investigates the ejection forces resulting from SL injection moulding tools which are identical in all respects except for their build layer thickness and incorporated draft angles in an attempt to identify appropriate evidence for recommendations with respect to these design variables and SL injection moulding. The results show that adjustment of draft angle results in a change of part ejection force as a reasonably linear relationship. An adjustment of the build layer thickness results in a change in part ejection force as a more non-linear relationship. The adjustment of build layer thickness had a greater effect on ejection force than the adjustment of draft angle. The results also show that the surface roughness of all tools remains unchanged after moulding a number of parts in polypropylene. A mathematical model was used in an attempt to predict ejection forces according to the moulding material used. This model reflected the experimental results in terms of relative values but not in absolute values, which may be due to inappropriate specific values used in their calculation. Finite element analysis (FEA) was used in an attempt to identify the factors involved in the ejection process. Results indicate that the effect of draft angle on ejection force is due to elastic deformation of the surface roughness. A fact borne out by the lack of damage to the surface after ejection