The effect of prior austenite grain size on the transformation behaviour of C-Mn-Ni weld metal

The influence of prior austenite grain size on the transformation behaviour and microstructural development of C-Mn-Ni weld metals was investigated. It was found that increasing the grain size depressed the start temperature of grain-boundary ferrite and slightly increased the acicular ferrite start temperature. The microstructural products also changed from a boundary-dominated effect in the small grain sizes, to an intragranular-dominated effect in the large grain sizes, and at the same time, the morphology of the acicular ferrite was seen to change to a larger aspect ratio.     

A conceptual spacecraft radioisotope thermoelectric and heating unit (RTHU)

Spacecraft venturing to the outer planets and beyond—or onto the planetary surface where available solar energy is reduced—benefit from the longevity and consistency of electrical and thermal energy derived from radioisotope energy sources. A review of likely mission requirements and concept studies of small electrical generating units (<10 W_e) reveals a potential opportunity for a unit with an electrical output of around 1 W_e that can also supply some heat to the spacecraft to aid thermal control: a radioisotope thermoelectric and heating unit. This power requirement cannot be achieved with current US space‐qualified modular radioisotope fuel assemblies. Additionally, new European programmes consider ²⁴¹Am fuel to be much more cost effective than ²³⁸Pu. Taken together, these factors provide the rationale for taking a relatively ‘clean‐sheet’ approach to design of a radioisotope thermoelectric and heating unit fuelled with ²⁴¹Am. In this paper, initial requirements and performance targets for such a unit are developed, a simple concept design and thermal model is presented and the performance and mass are estimated. The results suggest that units generating 1–2 W_e may achieve a specific power of around 0.7–0.9 W_e kg^?1 without the thermal inputs to spacecraft becoming impractically large. Such units can use a bismuth telluride thermoelectric material, which is commercially applied in terrestrial applications and is therefore likely to incur lower cost and development risk than more specialised compounds. This study may form the basis of a more detailed design effort. Copyright © 2011 John Wiley & Sons, Ltd.     

Solubility of TiO2 in ZrO2

The solubility of TiO₂ in tetragonal ZrO₂ is 13.8±0.3 mol% ui 1300°C, 14.9±0.2 mol% at 1400°C, and 16.1±0.2 mol% at 1500°C. These solid solutions transform to metastable monoclinic solid solutions without compositional change on cooling to room temperature.     

Spectroscopic sensor techniques applicable to real-time biodiesel determination

The term biodiesel refers to the Fatty Acid Alkyl Esters (FAAE) derived from vegetable, animal or waste oil feedstocks. This alternative fuel is increasingly becoming a significant part of the transport sector with over 10 million tonnes sold in the EU in 2007. Currently a small amount of biodiesel (presently 3.5% in the UK) is present in diesel fuel but this could rise to up to 30% in the medium term. As biodiesel is not one chemical compound but an amalgamation of different FAAE, the physical properties of the diesel fuel are not only dependent on the amount of biodiesel in the diesel fuel (blend level) but also on the fatty acid profile of the biodiesel. In this paper we report on an initial study to assess a range of current techniques which could be used in the future as a basis to determine blend level in unknown samples of diesel and gain further information on the fatty acid profile of the biodiesel in the blend. The three techniques applied were FT-IR spectroscopy, refractive index and UV-Vis spectroscopy.     

Issues in the assimilation of the sources of a trace gas by inverse modelling

The problem of reconstructing the (otherwise unknown) source and sink field of a tracer in a fluid is studied by developing and testing a simple tracer transport model of a single-level global atmosphere and a dynamic data assimilation system. The source/sink field (taken to be constant over a 10-day assimilation window) and initial tracer field are analysed together by assimilating imperfect tracer observations over the window.Experiments show that useful information about the source/sink field may be determined from relatively few observations when the initial tracer field is known very accurately a-priori, even when a-priori source/sink information is biased (the source/sink a-priori is set to zero). In this case each observation provides information about the source/sink field at positions upstream and the assimilation of many observations together can reasonably determine the location and strength of a test source.     

Conformation and ion-channeling activity of a 27-residue peptide modeled on the single-transmembrane segment of the IsK (minK) protein

IsK (minK) protein, in concert with another channel protein KVLQT1, mediates a distinct, slowly activating, voltage-gated potassium current across certain mammalian cell membranes. Site-directed mutational studies have led to the proposal that the single transmembrane segment of IsK participates in the pore of the potassium channel [Takumi, T. (1993) News Physiol. Sci. 8, 175-178]. We present functional and structural studies of a short peptide (K27) with primary structure NH2-1KLEALYILMVLGFFGFFTLGIMLSYI27R-COOH, corresponding to the transmembrane segment of IsK (residues 42-68). When K27 was incorporated, at low concentrations, into phosphatidylethanolamine, black-lipid membranes, single-channel activity was observed, with no strong ion selectivity. IR measurements reveal the peptide has a predominantly helical conformation in the membrane. The atomic resolution structure of the helix has been established by high-resolution 1H NMR spectroscopy studies. These studies were carried out in a solvent comprising 86% v/v 1,1,1,3,3,3-hexafluoro-isopropanol-14% v/v water, in which the IR spectrum of the peptide was found to be very similar to that observed in the bilayer. The NMR studies have established that residues 1-3 are disordered, while residues 4-27 have an alpha-helical conformation, the helix being looser near the termini and more stable in the central region of the molecule. The length (2. 6 nm) of the hydrophobic segment of the helix, residues 7-23, matches the span of the hydrocarbon chains (2.3 +/- 0.25 nm) of fully hydrated bilayers of phosphatidylcholine lipid mixture from egg yolk. The side chains on the helix surface are predominantly hydrophobic, consistent with a transmembrane location of the helix. The ion-channeling activity is believed to stem from long-lived aggregates of these helices. The aggregation is mediated by the pi-pi stacking of phenylalanine aromatic rings of adjacent helices and favorable interactions of the opposing aliphatic-like side chains, such as leucine and methionine, with the lipid chains of the bilayer. This mechanism is in keeping with site-directed mutational studies which suggest that the transmembrane segment of IsK is an integral part of the pore of the potassium channel and has a similar disposition to that in the peptide model system.     

Image Theory Results for the Mutual Impedance of Crossing Earth Return Circuits

Suitable engineering expressions for the mutual impedance of crossing earth return circuits are derived by employing finitely conducting earth image theory techniques. It is shown that the image theory and previously derived analytical results, which are rather complicated, are in excellent agreement.     

DESIGN AND APPLICATION OF A DEHUMIDIFIER DRYER FOR DRYING PINE CONES AND POLLEN CATKINS

A critical issue for the plantation forest industry is the preservation and control of genetic material in order to facilitate the fertilisation process. This is best achieved by drying at low temperature and low humidity prior to extraction of seeds and pollen. For example, freshly picked green cones of Pinus radiata are best dried at 25°C, 20% relative humidity to avoid thermal damage and to prevent mould formation. Similar conditions are required for drying pollen catkins. These conditions can be met efficiently and reliably by the use of a dehumidifier dryer. This paper describes the design of such a drying system, including a review of the dehumidifier and the kiln design parameters necessary to achieve the required drying conditions. Performance data and commercial operating experience are also presented and analysed. The system is effective and reliable, and has increased both the speed of drying and the quality of the product.