Testing for a unit root against ESTAR nonlinearity with a delay parameter greater than one.

In this paper, the tests of Kapetanios, Shin, and Snell (2003) and Bec, Ben Salem, and Carrasco (2004), which are designed to detect nonstationarity verses globally stationary exponential smooth transition autoregressive (ESTAR) nonlinearity, are extended to allow for a delay parameter, d, that is greater than one. Based on Monte Carlo simulations, it is shown that when the true delay parameter is greater than one, using the test with the correct value of d improves power almost uniformly compared to constraining the delay parameter to be unity. Using the tests when the delay parameter is not known and must be estimated is also addressed.Exponential smooth transition model, Unit roots, Monte Carlo simulations

Economic Evaluation of Positron Emission Tomography (PET) in Non Small Cell Lung Cancer (NSCLC), CHERE Working Paper 2007/6

Background: There are several perceived benefits from introducing positron emission tomography (PET) scanning into the staging of non small lung cancer (NSCLC). However, its greatest primary benefit is the role it can potential perform in reducing the number of unnecessary diagnostic examinations and futile surgeries. Objectives: To evaluate the economic impact and cost effectiveness of PET scanning in the management of potentially operable NSCLC patients using a cost-utility model. Methods: A literature review was conducted to find relevant studies and appropriate parameters to construct a decision model. Two strategies were compared. The first strategy was a conventional work up (CWU) consisting of an x-ray, a chest computer tomography (CT) scan and brochoscopy; the second strategy consisted of a CWU plus a whole body PET scan. These two strategies were applied to two sub-groups of NSCLC patients; those that had received a positive result on their CT scan and those that got a negative result on their CT scan. The cost-effectiveness of each strategy was dependent on a number of variables that were taken from a literature review. Costs were based on the Australian diagnostic related groups, a cost calculation for a chemotherapy course and values obtained from the literature. The life expectancy and utility scores were also taken from the literature and combined to create an incremental quality adjusted life year (QALY) value for PET for each of the patient groups. Results: The mean costs in CT negative and CT positive patients were lower in the CWU strategy, costing $A 20,427 and$A 23,578 per patient respectively compared to the PET strategy ($A 20,826 and$A 24,083 per patient respectively). The mean QALYs for both the CT positive and CT negative patients were higher in PET with 2.91 and 2.11 respectively compared to the CWU of 2.88 and 2.09. The incremental cost effectiveness ratio (ICER) for the CT negative strategy was $A 14,581 and$A 52,039 for the CT positive strategy. Conclusion: The PET strategy in CT negative and CT positive patients appears to be cost effective, however, there is much uncertainty surrounding this base result, particularly in CT positive patients.PET, non-small-cell lung cancer, economic evaluation

Lift distribution and velocity field measurements for a three-dimensional, steady blade/vortex interaction

A wind tunnel experiment simulating a steady three-dimensional helicopter rotor blade/vortex interaction is reported. The experimental configuration consisted of a vertical semispan vortex-generating wing, mounted upstream of a horizontal semispan rotor blade airfoil. A three-dimensional laser velocimeter was used to measure the velocity field in the region of the blade. Sectional lift coefficients were calculated by integrating the velocity field to obtain the bound vorticity. Total lift values, obtained by using an internal strain-gauge balance, verified the laser velocimeter data. Parametric variations of vortex strength, rotor blade angle of attack, and vortex position relative to the rotor blade were explored. These data are reported (with attention to experimental limitations) to provide a dataset for the validation of analytical work

Lorentz-transformation and Galileo-transformation Windows

We define Lorentz-transformation windows as windows that change the direction of transmitted light rays like a Lorentz transformation. Similarly, Galileo-transformation windows change the direction of transmitted light rays like a Galileo transformation. This light-ray-direction change distorts the scene seen through such a window in the same way in which the scene would be distorted in a photo taken with a camera moving through the scene. Lorentz-transformation windows can also undo the distortion of the scene when moving at relativistic velocity relative to it. For small angles between the direction of the light rays and the direction of the velocity, Galileo-transformation windows can be realised with relatively simple telescope windows, which consist of arrays of identical micro-telescopes

Development of a process envelope for friction stir welding of DH36 steel : a step change

Friction stir welding of steel presents an array of advantages across many industrial sectors compared to conventional fusion welding techniques. However, the fundamental knowledge of the friction stir welding process in relation to steel remains relatively limited. A microstructure and property evaluation of friction stir welded low alloy steel grade DH36 plate, commonly used in ship and marine applications has been undertaken. In this comprehensive study, plates of 2000 x 200 x 6 mm were butt welded together at varying rotational and traverse speeds. Samples were examined microscopically and by transverse tensile tests. In addition, the work was complemented by Charpy impact testing and micro-hardness testing in various regions of the weld. The study examined a wide range of process parameters; from this, a preliminary process parameter envelope has been developed and initial process parameter sets established that produce commercially attractive excellent quality welds through a substantial increase in the conventionally recognised weld traverse speed

Comparison between friction stir and submerged arc welding applied to joining DH36 and E36 shipbuilding steel

With the impending development of FSW tools for steel with useful lifetimes, attention has turned to the mechanical properties of the welds that can be made in a range of industrially significant steels. This work reports on a comparative study undertaken to examine the use of friction stir and submerged arc welding on DH36 and E36 shipbuilding steels. The study made an assessment of the distortion induced in fabricating plates by the two welding techniques, and provides initial comparative data on weld tensile strength, toughness and fatigue life. In each case, friction stir welding was shown to outperform submerged arc welding

A comparison between single sided friction stir welded and submerged arc welded DH36 steel thin plate

The adoption of the friction stir welding (FSW) process into the shipbuilding industry is being considered as a medium term issue. Currently the data on friction stir welded mild steels tends to be fragmented, with critical areas being short on specific data e.g. toughness. The work described has been put in place to directly compare friction stir welded and submerged arc welded thin plate. The plate thicknesses used were 4, 6 and 8mm thick DH36 grade steel, which are commonly used in the construction of vessels such and destroyers, frigates corvettes and offshore patrol vessels. Friction stir welding was carried out using the currently best established parameters for a single sided process and this was compared against Submerged Arc Welding (SAW) over the same thickness range. Distortion was found to be lower in friction stir welded steel, but the 4mm thick was still showing significant distortion. No issues were identified with weld metal strength, and toughness at -20OC was found to be comparable but more uniform across the weld area than with the submerged arc welded material. Microstructural observations have been linked to hardness, toughness and fatigue test data. The fatigue data includes the observation of preferential crack initiation relative to the trailing/leading side of the welding process. An assessment on the feasibility of the process in a shipbuilding environment will be included based on the data presented

A comparison between single sided and double sided friction stir welded 8mm thick DH36 steel plate

As part of an ongoing process to fully evaluate the potential for friction stir welding (FSW) to be used in the shipbuilding industry, a comparison has been made between two variants of the process. 8mm thick DH36 steel plate was friction stir welded using a single sided and a double sided process. An assessment of the processes was made to report on the resultant distortion behaviour, hardness, yield strength, toughness and microstructure. As a further comparison, additional work on 8mm thick submerged arc welded (SAW) DH36 plate has been included as the current shipbuilding benchmark. The overall process feasibility will be assessed including the issue of the requirement to rotate the workpiece through 180° to complete the second side of the double sided process

Friction stir welding of thin DH36 steel plate

A series of 4, 6 and 8 mm DH36 steel welds were produced using optimum conditions for friction stir welding (FSW). Comparator welds in the same thickness from the same plates were produced using a single sided single pass process submerged arc welds (SAW). This work was carried out to evaluate the mechanical properties of FSW material with a view to its possible application in a shipbuilding production process route. Overall, the performance of the FSW material was superior to the SAW comparators. Areas such as distortion and fatigue were particularly positive in the FSW material. An 8 mm thick plate was also produced using two FSW passes, one from either side, and it was found to have superior toughness and fatigue performance when compared to the single sided 8 mm FSW material. Some of these benefits are thought to have originated from the internal overlap zone between the two passes

The use of magnetic fields to create high-speed plasma jets for spacecraft propulsion

The aim of the work reported in this thesis has been to explore arrangements of magnetic fields and electric currents to create novel plasma thrusters that are more efficient and less complex than existing designs. Two original devices are discussed, firstly a thruster that uses a magnetic nozzle in combination with a High Power Impulse Magnetron Sputtering source (HiPIMS) to produce a jet of copper plasma and secondly, a thruster that uses the phenomena of magnetic reconnection that occurs between opposing magnetic fields in a plasma to produce a plasma jet. While HiPIMS has been normally employed to create thin films, the use of a solenoidal magnetic field to accelerate and focus the ions produced by that source has not been previously investigated as a means of creating a thruster. The HiPIMS thruster has a specific impulse (Isp) of 1543s. Magnetic reconnection has been studied for decades by geophysicists and by astronomers. Despite that effort, so far there has been little interest in exploiting the phenomena as a means of producing high-speed plasmas in a thruster despite the evidence of jets in those environments. A thruster consisting of two slit coaxial tubes of copper was constructed. Evidence for the occurrence of magnetic connection was fourfold. (1) A significant electron current that coincided with the rise of the magnetic field that was followed by a large ion current. (2) Ion currents were found to increase as the plasma became less collisional. (3) Ions with energies greater than 130 eV corresponding to a speed of 2.50 x 104 m/s and an Isp of 2550s were detected. (4) The ratio between the estimated speed of ions flowing into the diffusion layer (350m/s) and the measured speed of the out-flowing ions (2.50 x 104 m/s) was approximately 68. The physics indicates that such a thruster could have a basic energy efficiency of 50%